Donivan & Maggiora

A Chemistry Primer

For Jewelers and Metalsmiths

By John Donivan

The science of chemistry is about what the Universe is made of, and how that works on a level of tangible matter and beyond. This writing is an attempt to make it understandable on an everyday level. I’m going to try to keep it as non-technical as possible – the fundamentals are not really that complicated. I’m not going to repeat the same things: Wear goggles, do this, don’t do that. My goal is not to say How, but to generate an understanding of Why.

ELEMENTS AND ATOMS

The building blocks of matter in the world of chemistry are atoms. As of this writing there are 117 elements, of which about 40 or 50 are useful on a daily basis. Modern theory is more detailed and complex, but the analogy that an atom resembles the solar system – electrons revolving around a nucleus – works just fine for this purpose. The atom is the smallest thing there can be without getting into subatomic particles. 

Subatomic particles are essentially parts of atoms. There are different numbers of particles in different atoms, and each of those different atoms is an Element, the most fundamental thing of matter for our purposes. It’s likely useful to know one of the fundamental things about atoms and elements, that is that each one has an “atomic number”. The atomic number of hydrogen is #1, helium is #2, carbon is #6, and silver is #47. The atomic number represents the number of protons in the nucleus – add a proton, get a new element. And that, in an atom of neutral charge, the number of electrons in orbit will equal the number of protons. Just a little deeper theory, there. Maybe more than 100 electrons can be orbiting the nucleus, but they are, in this basic theory, arranged in what are called “shells”. Think of each shell as the orbit of a different planet, containing 8 or more electrons. The only important thing to know for us is how many electrons there are orbiting in the very outer shell of any given atom. The elements or atoms that we use on a daily basis want to have eight electrons orbiting out there in order to be stable. That number is 2 for hydrogen and helium, and more for the heavy elements. Most atoms have fewer than eight, and they roam around trying to find a way to make it a full eight. It’s useful to think of it as pegs and holes or tinker toys. In fact, molecular models are made in just such a way. There are three groups of elements: Metals, Metalloids and Non-Metals. In general, Metals approach having the full eight electrons – generally five, six or seven, and you could think of the empty spaces as the “Holes”. Non-metals have one or two or three extra electrons to give, and you could think of them as the “Pegs”. This is all background, because the basic concept is what it’s all about – how chemistry works. A simple example would be sodium and chlorine. Sodium has 7 electrons orbiting, and chlorine has 1. When they meet, the chlorine shares the one electron with the sodium, and the sodium shares the seven with the chlorine – they both think they have eight electrons orbiting and are happy as clams. And we get Sodium Chloride, or table salt. Carbon has four, oxygen has two, so two oxygens match up with one carbon and we get CO2, or carbon dioxide. In terms of everyday, practical chemistry it’s really not necessary to understand all about the particles and charges and math. The above discussion is called “Valence” – the amount of electrons missing, or the amount extra. So a valence of +2 (two electrons missing) and a valence of -2 (two lone “extra” electrons) will combine with each other one-to-one. A valence of +1 and -2 will combine two-to-one, etc. Modern Chemical Valence Theory is greatly more complicated, but all it really does is analyze the above concepts in much greater detail. In lay terms, this is just how uncomplicated it really is. One atom says, “Hey, I’ve got an empty spot.” Another says, “I have an extra that will go there.” And a chemical compound is born. Also simply enough, those two or more atoms combined together are what we call a “molecule”. And if you see a formula or chemical shorthand, the letters are the atoms, and the numbers are how many. So H2O – water - is two hydrogens and one oxygen. H2O2 – hydrogen peroxide – is two hydrogens and two oxygens. CH4 – methane – is one carbon and four hydrogens.

MOLARITY AND MOLALITY

I’m putting this mostly because some might wonder what it means when you are buying reagents. Without getting real technical (Avogadro’s constant….). Each element has an atomic weight, which is in the periodic chart. One Mole of a substance is that quantity of a substance whose mass in grams is the same as its formula weight. Iron has an atomic weight of 55.845. Therefore one mole of iron is 55.845 grams. Molarity is that weight per liter of solution. Molality is that weight per kilogram of solvent. If you want to know what a mole of sulfuric acid is, that is H2SO4. So, you get the atomic weight of hydrogen, sulfur and oxygen, multiply the hydrogen times two (H2), and the oxygen times 4 (O4), and there’s only one sulfur. Add them all up and that will be one mole of sulfuric acid. The reason for this is partly to have a standard for chemists. Deeper than that is that theoretically one mole of carbon and one mole of nitrogen have the same number of atoms. That’s dependent on the accuracy of measurement, of course. If you see a reagent that is 1 M, that’s a one molar solution. If it is 1 m, that’s a one molal solution. I’ll point out that in the metric system one milliliter of water = one cubic centimeter = one gram (of water) at 4 deg. C. So a liter (of water) weighs a kilogram – it’s just that there’s an advantage to weighing things as opposed to using volume, sometimes.

REACTIVITY

Fluorine is the smallest atom of the halogens, and is the most reactive of all elements. (Water will burn in fluorine gas, along with almost everything else) Then comes chlorine, bromine and iodine. Astatine is not something most of us will ever hear about. (A little tidbit I didn’t know before my research – astatine is highly radioactive, and is formed as a byproduct of the natural decay of uranium. It is considered the rarest naturally occurring element on Earth, and they figure there’s no more than about a teaspoon full on the whole Earth at any given time – now THAT”S rare!) As the atoms get bigger, their reactivity tends to diminish. Fluorine is violently reactive; iodine in some form is put on wounds at times. The fundamental thing to understand is that the more reactive elements will steal or grab other ions from less reactive elements. If you have an iodine salt and introduce fluorine, that will in the end become a fluoride salt, because the fluorine is more reactive and will take the combinant ions away from the iodide. The reasons for this involve activation energy, transition states and overcoming the potential barrier – again, all stuff you don’t need to know unless you just want to. However, the elements on the left side of the periodic chart are “electropositive” – that’s the metals and other things. The right side is “electronegative” – that’s the gases, sulfur and others. Those are big words, but it’s just the positive and negative that matters. A positive will attract a negative and repel another positive, just like a magnet does, though it’s not strictly “magnetism”. And that’s why you’ll rarely see iron and sodium combined and many others, because those are both electropositive. It can be done and IS done, but it isn’t easy, chemically.

By and large it is the reactive elements that do the work in chemistry. That is hydrogen, nitrogen, oxygen, sulfur and phosphorus, the halogens, and the reactive metals calcium, sodium and potassium. All of the elements react with each other in various ways, but those are nearly always involved somehow. There’s also carbon, which I’ll get into later. In addition to those, some elements form “polyatomic ions”, generally known as radicals, which behave as though they are a single atom. Thus, when sulfur and oxygen hook up in certain ways, it forms a radical known as sulfate – SO4. Other radicals are nitrate, ammonium, carbonate, and others. These all can behave as though they were individual atoms in reactions. So the sulfate radical might be split from it’s calcium partner in some reaction, but the sulfate will remain sulfate – it won’t be split. The punch line of all of this is that more reactive atoms will “overcome” less reactive atoms. So, if you take sodium chloride, and put it with fluorine under certain conditions, the more reactive fluorine will “steal” the sodium from the chlorine and form sodium fluoride. This is most important, because it’s how most reactions work, how metals are extracted from ores, and many other things. If you have silver sulfide, and you can get something to take the sulfide away, it will leave you with silver. Iron ore is usually iron oxide. If you simply use carbon to combine with the oxygen (called extracting by reduction), you’ll get carbon dioxide and iron. Exploring those reactions is fascinating, but here I just want to get the basic idea across: most simple reactions occur because a more reactive element takes something from a less reactive element, and new compounds are formed in the process. Finally, the “Noble” ones – the noble gases and the noble metals, are called such because they have the full eight electrons already. Helium (which has 2), argon, neon, etc., and also the platinum group metals, are already full, and so are disinclined to react with anything else.

If I have hopefully piqued anyone’s interest in this portion, I would urge you to study the periodic chart. It’s a most ingenious thing – it’s not just some graphical diagram, it’s actually a map whereby one can find all of these things with ease, if they know how.

DISSOCIATION

We tend to take water for granted, but it’s a unique and fascinating substance. One of the things is does is that when one puts some other compounds into it, they dissociate. Another term for this is “ionization”. Table salt, sodium chloride, is a white powder. When you dissolve it in water, the atoms (in essence) split apart and become charged particles, like they were before they combined. So the Na (sodium) becomes Na+, and the Cl (Chlorine) becomes Cl-. The salt “ionizes” or becomes an “ionic solution”. This also has huge importance. When you dissolve two compounds in water, it is the ions that do the combining and recombining. In electroplating we put a - anode and a + cathode into an ionized solution. When we turn on the power, the positive ions go to the negative terminal, and vice versa with the negative. If the solution happens to contain gold, then the Au+ ions will migrate to the negative terminal, and an object connected to the terminal will become gold plated. Sodium and aluminum are so reactive that the usual methods of extracting them don’t work, and they are done by the electrolysis of molten ores. If you melt sodium chloride, put in electrodes, and turn on the power, you will get elemental sodium at the negative pole, and elemental chlorine at the positive pole. In fact, elemental aluminum wasn’t extracted commercially until this process was perfected, and is used to this day to get the metal from ore.

OXIDATION AND REDUCTION – REDOX REACTIONS

The technical definitions of oxidation and reduction are extremely complicated, because they cover a wide spectrum of reactions. Simply, Oxidation describes the loss of electrons by a molecule, atom or ion. Reduction describes the gain of electrons by a molecule, atom or ion. Even beyond that, redox reactions more properly refer to a change in the oxidation number. Even more than that, in organic chemistry you get into “stepwise” reactions, redox cycling, photosynthesis, sugars, and all sorts of things. For our purposes, though, you don’t need to know any of that stuff, unless you just want to. When iron combines with oxygen, it forms iron oxide, commonly called rust. It has “oxidized” and oxygen is the “oxidizing agent”. When you put that iron oxide in a blast furnace with coke, the carbon in the coke combines with the oxygen forming carbon monoxide and leaving behind iron. The iron oxide is “reduced”, and coke/carbon is the “reducing agent”. The important thing to understand is just the principal of it. When you put sulfur with silver, the silver tarnishes, and you have “oxidized” it, even though the oxidizing agent is sulfur. If you get some substance that takes that sulfur away from the silver again, you will have “reduced” the silver sulfide. The main oxidizing agents in inorganic chemistry are oxygen, sulfur and the halogens (bromine, chlorine, fluorine), and some compounds that mostly have an extra oxygen lying around – peroxides, permanganates, chromates and such. Probably the only reducing agent most people will use in real life is carbon. Other ones, though, are electropositive metals – lithium, sodium, iron, magnesium, zinc…. Mostly this is just a fundamental part of chemistry to understand, and also to realize that when a metal has oxidized, maybe it’s not oxygen that did it, and that if it can be reduced, the process can be reversed.

ACIDS AND BASES AND SALTS

The modern theory of acids and bases is about being a proton donor or acceptor (Bronsted-Lowry). The old definition is that an acid lowers the ph of water, and a base raises it, which is fine for us. An acid in the everyday world is hydrogen bonded to something (It forms the “Hydronium” ion in water – HO3), and a base is something bonded to the “hydroxyl” radical, which is OH. The most important thing to understand is one of the most important tools in all of chemistry: An acid and a base combine to form a salt and water. So, this can be shown as a general chemical formula, where R1 is “Any”, and R2 is “Another “any”: H R1 (acid) + R2 OH (base) --> R1 R2 (salt) + HOH. HOH is of course properly written as H2O. If you mix hydrochloric acid – HCl, with sodium hydroxide – NaOH, the sodium and the chlorine match up, forming sodium chloride, and the H and the OH match up, forming water and you will have salt water in the end. About 50% or something of the things we use are one of these three things, and the rest are mostly going to be oxides, sulfides or the like, or organics. Ammonium chloride is formed from ammonium hydroxide (“ammonia”) and hydrochloric acid, sodium chloride, potassium nitrate, sodium fluoride; all of these are salts – the product of mixing an acid and a base. If it says sulfate, nitrate, phosphate or carbonate, among other things, it’s a salt.

Bases are little used in metalwork. Ammonia, which is really ammonium hydroxide, is used for cleaning, so it may as well be soap, for our purposes. In fact, what it does, and also sodium hydroxide (lye) is called “saponification”. They turn fats into soap, which I’ll get into below. The reason lye or ammonia feels soapy between your fingers (a characteristic of a base), is because it is – and the soap it’s making is from the fat in your skin. One way to remove fired enamel is to submerge the piece in molten lye for 12 hours in a kiln (The tiniest bit of water will cause it to explode!!) – Not something I’m going to hang around for, frankly.

Acids, on the other hand, are used frequently in metals, largely because they will dissolve them. There are two types of acids: Strong Acids, and Weak Acids (There’s also superacids, but if you ever encounter one, likely you’ll wish you hadn’t). Although there’s some correlation between “strong acid” and “corrosive”, what it actually refers to is the degree of ionization (see, there was another reason to learn that...) Strong acids dissociate into their ions fairly completely, weak acids much less or hardly at all. Boric acid is one that dissociates almost not at all. The well-known mineral acids are all strong acids. Hydrochloric, sulfuric and nitric acids are all strong acids. Perchloric is the strongest (besides, again, superacids), but that’s another thing you just don’t want to be around. Hydrofluoric acid is a weak acid, acetic acid also, as are many others. I’m going to discuss chemical safety shortly, which is tied to acids, too. In practice, sulfuric acid has little use in jewelry making, which is to say non-ferrous metals (ferrous = iron, and the symbol for iron is Fe). It’s used to remove flux after soldering and not a lot more, at least not that I’ve ever encountered. It attacks iron, aluminum, zinc, manganese and nickel. Sodium bisulfate is Sparex and other things – toilet bowl cleaner, etc. When dissolved in water it dissociates also, and the hydrogen from the water and the sulfate make a nice, safe alternative to true sulfuric acid for pickle. (It’s also buffered, which is neither here nor there). Since most of the oxides of our metals are “basic oxides”, meaning that can behave as weak bases in some circumstances, pickle is usually effective in removing them. The main acid in jewelry is nitric acid, HNO3; the reason being that it dissolves copper and silver for refining, etching and other purposes. Hydrochloric acid is handy for dissolving iron and steel, zinc, tin and lead when the occasion arises. I’ll use it to strip the plating off of nuts and bolts before brazing on them, for instance. Aqua regia is a mixture of nitric and hydrochloric acids, and is used to dissolve gold and platinum group metals. The reactions of aqua regia are pretty interesting, I won’t go into it here, but I’d invite you to explore it elsewhere. Since you all know how it works now, I’ll point out that when you dissolve lead into hydrochloric acid, you get lead chloride, and so with tin and the rest – it’s really not that complicated. The reactions of nitric acid are more complicated, but you still also get copper nitrate or silver nitrate. If you etch a lot of silver with nitric acid, you end up with a silver nitrate solution. Since chloride is more reactive than the nitrate, if you pour sodium chloride solution into it, the chloride will “grab” the silver, making silver chloride, which, being insoluble in water, will precipitate (“snow”) out of the solution. Simple, huh?

Nitric Acid: HNO3 - When you put a drop of most acids on metals, it generates hydrogen gas. Because nitric acid is such a powerful oxidizer, it doesn’t do that, and forms salts in a higher oxidized state, usually what that means is, “Not what you might expect from an acid.” Although it dissolves all non-precious metals, the fact that it is unstable and tends to put off nitrogen oxides mean that I’d save it for the ones the other acids don’t touch – copper and silver.

Hydrochloric acid: HCl – Hydrochloric acid is considered the least hazardous of the common mineral acids – that’s not to say it’s “safe” – it’s still very powerful. It is stable; it forms mostly non-toxic and non-reactive chlorides. It’s probably the most useful everyday acid, although it doesn’t dissolve copper or silver. It does dissolve iron, lead, tin, zinc and other metals you might encounter. Instead of getting nitrogen oxides in the process, it produces hydrogen gas, which is flammable but non-toxic. One of the most important industrial uses for it is in organic chemistry.

Hydrofluoric acid: HF – HF is not much used in jewelry until one gets to enameling, where it’s ability to dissolve silica (silicon dioxide), the main component of glass, becomes extremely useful. It is also used at times to dissolve investment from platinum castings. I have written this entire treatise in my own words, up until now. At this point, though, I’m going to paste a passage about HF:

>Symptoms of skin exposure to dilute HF are not felt immediately, but exposure of less than 10% of the body to it can be fatal, even with immediate medical treatment. Highly concentrated solutions may lead to acute hypocalcemia, followed by cardiac arrest and death, and will usually be fatal in as little as 2% body exposure (about the size of the sole of the foot). This substance is extremely toxic and has the capacity to kill upon exposure rather than simply damage skin and eyes. It should be handled with extreme care, beyond that given to hydrochloric, sulfuric, or other mineral acids.

Due to low dissociation constant, HF can penetrate tissues quickly like a small non-polar particle {JD – it goes through the skin like a sieve}. Hydrofluoric acid which comes into direct contact with the fingers can severely damage or destroy the tissue underneath the nail without causing any damage to the nail itself. It is this ability to cause little harm to outer tissues but considerable harm to inner tissues which can produce dangerous delays in treatment of hydrofluoric acid exposure. Once the pain starts, it is out of proportion to the burns produced. Patients often describe the feeling as if they have struck their fingers with a hammer. HF that penetrates under the skin causes later development of painful ulcers, which heal slowly.

Solutions of less than 20% HF can produce pain and redness with delay up to 24 hours after skin exposure. 20 to 50% HF produces pain and redness within 8 hours, and solutions of more than 50% produce immediate burning, redness and blister formation. Contact of the skin with the anhydrous liquid produces severe burns.

In the body, hydrofluoric acid reacts with the ubiquitous ions of calcium and magnesium and so can disable tissues and organs whose proper function depends on these metal ions. Exposure to hydrofluoric acid may not be initially painful, and symptoms may not occur until several hours later, when the acid begins to react with calcium in the bones. Under most circumstances, hydrofluoric acid exposure results in severe or even lethal damage to the heart, liver, kidneys, and nerves. Initial treatment to hydrofluoric acid exposure usually involves applying calcium gluconate gel to the exposed areas. If exposure is high, or too much time has passed, a calcium gluconate solution may be injected directly into a local artery or surrounding tissues. In all cases, hydrofluoric acid exposure requires immediate professional medical attention. If coming in contact with human skin or bone the acid can severely burn and then decompose the bone, potentially necessitating amputation of the affected limb/s.

The highest concentration of HF in air that can be tolerated by a human for 1 minute is 100 mg/m3. This causes a definite sensation of pain on the skin, a definite sour taste, and some degree of eye and respiratory irritation. If the air contains 50 mg/m3, the sour taste is apparent and there is irritation of the eyes and nose, but no pain is sensed on the skin. The concentration of 26 mg/m3 can be tolerated for several minutes, but the sour taste becomes evident after a short time, and there is mild pain in the nose and eyes. The American Conference of Governmental Industrial Hygienists has adopted 2 mg/m3 as the threshold limit for hydrogen fluoride. This comes to about 3 ppm (parts per million). Inhalational exposure to concentrated HF for as little as 5 minutes is usually fatal, producing death within 2-10 hours.<

You are better off not having it on the premises unless you have a specific reason for it.

CYANIDE

There are some elements that just don’t belong together, although they can be made to join, and two of those are carbon and nitrogen, unless it’s organic, below. Cyanide is the product of the union of carbon and nitrogen. It is the other thing, besides aqua regia, that dissolves gold, and is used for plating solutions and other things I won’t elaborate on. It is intensely poisonous in any form. One drop on a cut in your finger can make you seriously ill and can kill you. A drop in your eye can “kill” your eye, blinding you. I recommend that people don’t possess or use it in concentrated form unless they have a really, really good reason. It comes in lumps, called “eggs”, because if you were to sniff a bit of powder while scooping it out you’d be dead in minutes. Don’t ever crush an egg or do anything like that unless you have big-time safety precautions in place. It’s not paranoia, it’s just not something to fool around with – you’ll only get one mistake. (In case you’re wondering, it’s a potent enzyme inhibitor, and it binds with the protein Cytochrome c oxidase, which prevents its function and causes chemical suffocation of cells. Carbon monoxide does the same.) Despite its hazards, it’s an important industrial chemical, being used largely in the plastics industry – and other organic applications. Cyanide is an important “ligand”, which is why is does what it does with gold.

METALS

If you look at the periodic chart -http://www.webelements.com/webelements/index.html is a good place for that.

You’ll see that the left hand side is metals, and the right side is non-metals. Group one and two on the left are metals like sodium, calcium, magnesium, strontium, barium. These metals tend to be very straightforward – they’ll have a valence of one or two, and combine accordingly. Groups three through twelve (though group 12 is disputed), which includes most of the metals we use, are called “transition metals”. There are 40 of them. Some important properties they share are: They tend to form colored compounds (for paint, glass, etc.), they can have a variety of oxidation states, except for copper and gold they are silvery-blue at room temperature, and they can form complexes. Most important of those here is the oxidation states. The reasons why are extremely complicated, but the transition metals can form various oxides. There is only one oxide of silicon – silicon dioxide or beach sand. There are 16 known oxides of iron. Because of the arrangement of the electron shells they are able to bond in a greater variety of ways than most atoms. This is something else that you don’t need to know in detail unless you just want to. What it does mean, though, is that is what ferric and ferrous, cupric and cuprous, stannic and stannous means, and also iron I, iron II, etc. – those are different oxidation states, and different compounds, too. The ability to form complexes is what minerals and things are: copper iron arsenic permanganate and the like (again, I just made that up as an example). This article is not going to address the physical properties of metals, because it’s about chemistry. But here’s a few chemical tidbits about jewelry related metals, but there’s not a lot to say because by and large they’re not very reactive:

Iron: Fe Melting point 1538 C, 2800 F. I’m including iron in this because it’s use by everybody, every day. Pure iron is actually fairly soft, and also fairly reactive, by metals standards. Introducing carbon in fairly large amounts (2%-4%) gives cast iron. Carbon steel has .4% - 1.5%. In the case of steel, more is not better, carbon wise. Then of course there are alloy steels, which have small quantities of other metals added. It is the alloying component in blue or purple gold, aluminum being another – I have no experience with that, though. Iron III chloride or ferric chloride is an etchant for copper based metals. It does that because it’s a Lewis Acid, by the way.

Copper: Cu Melting Point 1084.62 C, 1984.32 F. Copper is closely related chemically to silver and gold, which is a big reason why it alloys so easily and just seems to belong. Copper is a trace element in the human diet, but beyond that it is a moderately toxic metal. You should avoid ingesting it, whether it’s in solution or inhaling dust. About one ounce of copper sulfate can be lethal in humans. Copper is mostly used in jewelry either on it’s own or as an alloy. It’s main solvent in practice is nitric acid. The other place you’ll find it is in a huge variety of minerals, because it’s salts tend to be blue and green. It’s a fairly reactive metal, and oxidizes quickly when exposed to air, forming the black copper II oxide, which is cupric, and the reddish copper I oxide, which is cuprous. Cupric oxide is the principal one, though, and it’s classified as an irritant and is fairly toxic, especially by inhalation. It can cause metal fume fever, which I’ll address below.

Pewter Sn (tin) Melting point (tin) 231.93 C, 449.47 F. Pewter is a generic name for what is essentially tin. Copper is added as a hardener at times. There was a time when lead was also added, but since pewter is often used for food related utensils, that practice has all but ended. It may contain antimony or bismuth, too. It is easily attacked by hydrochloric acid.

Silver: Ag Melting point 961.78 C, 1763.2 F. Probably the most extraordinary thing about silver is that it has the highest electrical and thermal conductivity of any metal – copper is second. And that silver halides are photosensitive, which is what gives us photographic film. Silver itself is not toxic, but most of it’s salts are. It forms silver oxide almost exclusively, and that’s not very stable – acids, light and heat will break it down. The “oxidation” that people think of is actually silver sulfide formed from sulfur in the air or on purpose with a chemical.

Gold: Au Melting Point 1064.18 C, 1947.52 F. There’s not a lot to say about gold, chemically. It only reacts (that is, pure gold) with chlorine, fluorine, aqua regia and cyanide. Again, this article doesn’t address physical properties – those are in every jewelry book ever published. Most of the issues involved with oxidation and such with gold are related to the alloys involved, and mostly that’s going to be copper related, as described above.

Platinum Group: The six platinum group metals are ruthenium Ru, rhodium Rh, palladium Pd, osmium Os, iridium Ir and platinum Pt. They are all resistant or highly resistant to combining with anything. Iridium is the most corrosion resistant metal known, for instance. Osmium is considered to be the densest metal known, with iridium second, and I’ve heard it has an odor from it’s oxide. Again, chemically there’s not a lot to say. Some of these are soluble or slightly so in aqua regia, half are not. Palladium is the most reactive of the bunch, though it still doesn’t form an oxide until 800c temperature. But it does react with hydrochloric, sulfuric and nitric acids. Ruthenium only reacts with hot halogens. The melting points can be quite high: Platinum 1763.3 C, 3214.9 F. Palladium 1554.9 C, 2830.82 F. Ruthenium 2334 C, 4233 F. Rhodium 1964 C, 3567 F. Osmium 3033 C, 5491 F. Iridium 2446 C, 4435 F.

ALLOYS

When I first wrote this paper, I dodged the topic of alloying. Part of that is because it is a whole field in itself. Another reason is because I’m not sure it’s really chemistry at all, though certainly it’s related. The first thing to understand is that metals are always monatomic. There are two atoms in an oxygen molecule – that which we breathe in the air is actually O2. The hydrogen that industry uses is also H2. Metals don’t do that, there is always only a single atom, making it monatomic. Two of the basic things in life and chemistry are mixtures and solutions. A mixture is a mechanical thing. When you put flour and salt together in a bowl, you’ve made a mixture. It’s just a mechanical blend, nothing chemical or atomic is happening. When you put table salt into water, you will make a solution. A solution is called a “homogenous mixture”, meaning that the solution, although there is no reaction taking place, has it’s own properties. The salt in the water is unchanged, chemically, as is the water, but now there is a thing called “salt water”, which has properties different from either of the ingredients. By the way, the water is the “solvent” and the salt is the “solute”. Even though there is no real reaction going on, there is something going on. The atoms are now ions, and they are grouping around each other in various ways that is more akin to a crystalline structure. There is again a whole field devoted to this stuff, and how each solution behaves will depend on the contents. Solids can dissolve in liquids, gases can dissolve in liquids or solids (soda water is carbon dioxide dissolved in water), and solids can dissolve in solids. Obviously in order for a solid to dissolve in a solid they must first be melted - a crushed solid mixed with another is a simple mixture, not a solution. Such a thing is called a “solid solution”. Without getting too technical (short-range order, long range order, Hume-Rothery rules, Vegard’s law…..), metals in a liquid state are in a random order. As the metal cools and solidifies, the atoms arrange themselves into a crystalline lattice – a regular arrangement of atoms held together by the forces present in the atoms themselves – again, that can get real technical real fast. It’s important to understand that this arrangement and force is not the same as a chemical reaction – the material is not changing, it’s just arranging it’s atoms. What you end up with is a 3-dimensional checkerboard, though the shape of it will differ with different materials. Metals can do this partly because they are monatomic, by the way. In a pure metal, that’s pretty much what happens. In a simple binary alloy, there are two kinds of atoms – one of each metal. If the atoms are of a similar size, a “substitutional alloy” is formed. A similar lattice will form, but the atoms of each metal will alternate positions depending on their properties. It will still be a similar lattice, though. If one atom is smaller than the others, you will get an “interstitial alloy”, and the small atoms will pack between the larger atoms. Think large balls an small balls in an ordered arrangement. One example of an interstitial alloy is that of carbon in iron to form austenite, one of the components of steel. It is most important to remember that this is not a chemical reaction. The atoms are not bonded in the same way as a reaction; they are more just “arranged” in a certain pattern, which has physical properties. You could say that just as we have “salt water” which boils at a certain point and freezes at some point, so we have “copper zinc” (brass) which has it’s own properties. Yet the copper is still copper and the zinc is still zinc.

To a large degree it is whether an alloy is substitutional or interstitial, how many metals or different atoms are present and what proportion of each that will determine it’s properties. Interstitial alloys will be tough, rigid and hard. Substitutional alloys will be more resilient and flexible. Again, there are so many combinations that any curiosity on that should be directed towards metallurgy itself.

That’s as far as I’m going to go on that. From here arises the question of what happens with different proportions, tertiary alloys, order-disorder transformations, and equilibrium diagrams. But the concept is still the same – that just becomes the science of metallurgy.

One of the Hume-Rothery rules is called the “Chemical Affinity Factor.” Condensed, it says that the greater the affinity of two metals, that is that they have similar electropositivity, the more likely they will dissolve into each other. The more dissimilar they are, the more likely they are to form intermetallic compounds. Intermetallic compounds are true compounds coming from the actual reaction of two metals. They are not really pertinent here – gold and aluminum is one (called “purple plague” in the semiconductor industry), and bad welding creates them, too.

A metal is an element, and as such has a definite melting point that is unchanging. An alloy is different, and there is usually a range of temperature in which it melts. The temperature at which it begins to melt is the solidus. The temperature at which it is completely molten is the liquidus. Conversely, the liquidus is the point at which freezing begins when cooling, and the solidus is the point at which it is completely solid. Some binary alloys have a certain proportion that gives a eutectic alloy, meaning the solidus and liquidus are the same. Binary phase diagrams chart all of these things, if you’re interested.

I will sum this section up by saying that, for the practical jewelry maker, most of the above is interesting but unnecessary to know on an everyday basis. That’s one reason I omitted it originally. The fact that sterling silver is a solid solution has no bearing on how to bend it into a ring, and many people I hear talking about eutectic alloys seem more interested in us knowing that they know what it means. Again, it is interesting, but unless you work in a refinery’s lab it’s unlikely you’ll miss the information.

CADMIUM

Since there are solders and things that contain it in our industry, this is the second time I’m simply going to paste some words to listen to:

Acute exposure to cadmium fumes may cause flu like symptoms including chills, fever, and muscle ache. Symptoms may resolve after a week if there is no respiratory damage. More severe exposures can cause tracheo-bronchitis, pneumonitis, and pulmonary edema. Symptoms of inflammation may start hours after the exposure and include cough, dryness and irritation of the nose and throat, headache, dizziness, weakness, fever, chills, and chest pain.

Inhaling cadmium-laden dust quickly leads to respiratory tract and kidney problems which can be fatal (often from renal failure). Ingestion of any significant amount of cadmium causes immediate poisoning and damage to the liver and the kidneys. Compounds containing cadmium are also carcinogenic.

The bones become soft (osteomalacia), lose bone mass and become weaker (osteoporosis). This causes the pain in the joints and the back, and also increases the risk of fractures. In extreme cases of cadmium poisoning, the mere body weight causes a fracture.

The kidneys lose their function to remove acids from the blood in proximal renal tubular dysfunction. The kidney damage inflicted by cadmium poisoning is irreversible and does not heal over time. The proximal renal tubular dysfunction creates low phosphate levels in the blood (hypophosphatemia), causing muscle weakness and sometimes coma. The dysfunction also causes gout, a form of arthritis due to the accumulation of uric acid crystals in the joints because of high acidity of the blood (hyperuricemia). Another side effect is increased levels of chloride in the blood (hyperchloremia). The kidneys can also shrink up to 30%.

Other patients lose their sense of smell (anosmia).

I don’t use it in my shop. If you do, treat it very carefully!

MERCURY

It took centuries for the dangers of mercury poisoning to become clear, but at this time they ARE clear. Mercury is a liquid at room temperature, one of five elements that are so (cesium, francium, gallium and bromine are the others). This is of course because of ambient temperature. One of the trick things people do with cryogenics is to pour mercury into a cardboard box submerged in liquid nitrogen and put a stick into it, and then after a few minutes take it out and hammer nails with it. Temperature is infinitely relative – if we lived on Venus there would be 20 liquid elements and water would be a gas. It has been traditionally used because of it’s alloying properties – it forms what are called “amalgams”, which are simply alloys, but their properties are so unique that they have their own name. Mercury will “grab” gold out of the dirt in a gold pan, and it will also release that gold if it’s heated, which is how fire-gilding was done. Since a person in a workshop would have to be nuts to have anything to do with mercury, I’ll just address the reasons why. Mercury (along with lead) is a potent neurotoxin, meaning it affects the nervous system, of which the brain is most prominent. It is rather poorly absorbed through the digestive tract, moderately absorbed through the skin, and readily absorbed and extremely toxic as vapors in the lungs. Symptoms include loss of memory, slurred speech, dizziness, mental retardation, liver and kidney disease, only some of which is reversible or treatable. Virtually all compounds of mercury are poisonous to some degree – the organic compounds especially so. One famous example was Professor Karen Wetterhahn, a specialist in toxic metal exposure. She spilled two drops of a certain organic mercury compound, a particularly powerful neurotoxin, on her finger on a latex glove, and some months later died of mercury poisoning. Mercury, along with lead, cadmium and others, is called a “cumulative heavy metal poison.” The body cannot process and eliminate them as fast as they might be introduced. Since there are alternative methods to do pretty much everything in the jewelry world that mercury might be used for, it’s foolhardy to use it in the modern world. Again I quote: Minamata disease, sometimes referred to as Chisso-Minamata disease, is a neurological syndrome caused by severe mercury poisoning. Symptoms include ataxia, numbness in the hands and feet, general muscle weakness, narrowing of the field of vision and damage to hearing and speech. In extreme cases, insanity, paralysis, coma and death follow within weeks of the onset of symptoms. A congenital form of the disease can also affect fetuses in the womb.

METAL FUME FEVER

The resource I consulted on this said that it’s related to exposure to zinc oxide or magnesium oxide, which is not the whole truth. Copper and many others can also cause it. I had a bout once from exposure to cadmium. Nobody really knows what it is – an immune system reaction is one idea. Symptoms are flu-like: Fever, chills, fatigue, aching joints. Also a sweet or metallic taste in the mouth and a very dry, irritated throat. It’s unpleasant, but not really that bad – if you stop the exposure. If you don’t stop the exposure it can lead to long-term illness: bronchitis, pneumonia, pulmonary edema, bone damage. If you should get any of these symptoms from working with metals, especially fumes from heating them, stop what you’re doing and do it some other way. Understand that it’s METAL FUME fever – it comes from the actual metal and the oxides produced at high temperatures. It’s not from fluxes or gases in the process, though those can conceivably cause their own problems.

GETTING ALONG WITH CHEMICALS

The living body is a chemical factory. Most of the things called “chemicals” – salts and solutions for patinas and the like, are not terribly hazardous, though they all should be handled with care. If you ingested many of them you’d likely feel ill for a few days, and get over it, unless it was a massive quantity. Boric acid has a hazard rating comparable to table salt, for instance, though it’s listed as a hazard. They aren’t all that simple, though.

In chemistry, although even a chemist might say, “I have an acid burn”, it’s not the same as combustion. What chemicals do is react with the chemistry of your body. As I said before, bases react with fats to create soap. If you have an unfortunate encounter with lye, what it does is turn whatever it touches into soap. That’s not a good thing. Sulfuric acid is intensely hydroscopic – it has this aching hunger to take on water, and it will take the hydrogen and oxygen out of hydrocarbons to do it, leaving carbon behind. The free ions in acids are intensely reactive, too. To understand nitric acid, you have to understand nitrates. Nitrogen and oxygen also don’t really belong together, in a way, and they are tough to combine and easy to break apart, chemically. The reason that nitrate fertilizer makes a good home-made bomb (no secret) is because when they do break apart not just oxygen is released but oxygen IONS – oxygen with a kick, just looking to combine with something. I’m not an expert of nitrogen oxides, but in lay terms this is what makes nitric acid so dangerous. It’s not just an acid, though it is a potent acid. It’s also an oxidizer. The heat, oxides, and oxygen from a reaction can create fires, though that’s unlikely in a jewelry shop. Even though I know some things about it, the reactions of nitric acid are much more complex than most if not all other mineral acids – another reason to treat it with respect. If you want to know more, I’d suggest you look into it farther. You should be aware that there are many oxides of nitrogen – nitrous, nitric, dinotrogen trioxide, and others and nitrous oxide is the only one humans can be around. The red nitrogen dioxide (nitric oxide + water vapor = NO2) you might see coming off is the gas that becomes nitric acid when dissolved in water. That is, like the water in your lungs and nose and eyes. Nitric acid’s varied properties make it extremely useful for many things – don’t argue with it though, it’ll bite you. 

Before I move on, though, a word about oxygen. The oxygen in our atmosphere is actually two oxygen atoms bonded together - O2. The two halogens that are most encountered in everyday chemistry are chlorine (chloride) and fluorine (fluoride). They are arguably the two most reactive elements of all. Probably a single atom of oxygen is next in line, though hydrogen is in there, too. When you see a chemical that starts with “per”, as in peroxide, or ends in “ate”, as in permanganate, or “hypo”, as in hypochlorite (household bleach) that means it has an extra oxygen beyond what it might, and that means that that extra oxygen is probably easily dislodged. That makes it an oxidizer, and those are potent things. The peroxide you buy in the drug store is 3%. High percentage hydrogen peroxide is used instead of liquid oxygen in missiles, it’s that potent.

Nitric acid is technically an aqueous solution of nitric oxide. Ammonium hydroxide, which most people simply call “ammonia”, is a solution of ammonia gas in water. Just be aware that when you heat it, the gas will come out of solution, and that’s not a good thing to be around. Ammonia is not ~deadly~ poisonous, like cyanide, but it is quite poisonous. Two other things that are gases dissolved in water are hydrochloric acid and hydrofluoric acid – heating them or otherwise abusing them can release voluminous quantities of acid gas – the kind that dissolves in your eyes to become hydrochloric acid again. All of the strong acids, and even the weak ones, are hydroscopic – they want to take on water. And that reaction is what’s called exothermic – it generates heat in the process. If you should pour water into concentrated sulfuric acid it will generate so much heat so quickly that it will effectively explode, probably in your face. Doing the same thing with hydrochloric will do the same thing, except you’ll also get the gas cloud from hell. My brother’s a scientist who once worked at White Sands on missiles. Every once in a while the radio would crackle, “Hey, there’s a BFRC coming your way!!”, which meant “Get the hell out of there”. A BFRC was a Big F----ing Red Cloud – nitric oxide from some incident involving fuming nitric acid. A word about hydrofluoric acid. It’s a weak acid, as explained above. I recently read about a glass worker who put a drop on his finger just to convince himself that it wasn’t so corrosive, walked across the room to the sink, rinsed it off and said, “See?” While it is true that it doesn’t have that sizzle and pop of the others, the problem is that hydrogen fluoride, the gas which becomes the acid in water, is incompatible with human flesh. It will aggressively combine with almost everything in the universe. The only compounds I know of that have been formed with the noble gases are with fluorine. While it’s not maybe technically true, I’d say it’s useful to say, “No, it’s not such a dangerous acid. It IS an incredibly dangerous and destructive poison or substance, though.” Meaning it’s not the acidity of it, it’s just the stuff itself. You may not even know it’s there, but it will destroy everything in it’s path. People I know in the chip industry get a little shudder in their bones when it’s mentioned and say, “No, I’m not around HF”, and smile like they’re happy to see the sunshine. It may seem tame at first glance, but it’s not.

So, I’ve tried to lay out some of how it all works together. You should understand by now that if you mix hydrochloric acid with ammonia because you think you’re getting a double kick, what you’re really doing is neutralizing them both and making ammonium chloride and water. The problem, and the danger, is that there are 117 elements, and they can combine in billions of ways. There are many things you can do with chemistry that make new, harmless compounds, but there are many that do not, and it’s good to know the difference. If you get sodium fluoride, which is an unassuming white powder they put in toothpaste in tiny quantities, and pour concentrated sulfuric acid on it, you’ll get hydrogen fluoride, because the fluoride is so reactive. That’s hydrofluoric acid gas, and you might want to vacate the premises. The same thing happens with what we call “cyanide”. The solid form is usually sodium cyanide, and pouring acid on it generates hydrogen cyanide, which we call cyanide gas, and you might want to vacate the premises. This is why it’s so useful, and really pretty easy, to be able to make predictions. “If I put this sulfate with this chloride, the chloride is more reactive, and will take control.” Nobody’s going to be a real chemist from reading this article (and neither am I a “Real” chemist), but hopefully some will “Get It.”

ENVIRONMENTAL TOXICITY

As I said before, the body is a chemical factory, and chemicals affect it. People think of something as “poison”, and it is. What it really does can be described chemically, though, if someone has taken the trouble to explore it in history. One of the big theories of environmental cancer, especially, is that the body at times can’t tell what a chemical is. Cadmium poisoning is thought to be from it replacing zinc in certain enzymes – the body thinks it’s zinc, which it resembles, but it’s not. This especially applies to complex hydrocarbons in the body, wherein the body thinks it’s getting some needed enzyme or something, but it’s actually an industrial solvent or plastic that chemically resembles the enzyme. The result is like eating sand – it fills your stomach but you starve to death – or worse, mutations and all that other bad stuff. As far as I know this whole idea as it relates to cancer is a pretty well accepted theory, but only that. This means that it’s best to take precautions around any chemicals that are anywhere out of the ordinary. It’s paranoid to wear a bio suit to handle table salt, but it’s prudent to take reasonable precautions when handling more exotic solvents, working with plastics and resins, and heavy metals. Photo etching is a process that uses some pretty potent chemicals, for example. Someone might get a good lungful of some aromatic hydrocarbon, feel sick for an hour and recover but discover worse things even years later. I’m not going to advocate people going overboard with safety – we still need to live and work with common substances. But think before you open that reagent, too.

PLASTER

When you see a chemical formula for something, and it is CaSO4•2H2O, the •2H2O part means that there are molecules of water actually bonded intact to the molecule. That’s called a “hydrated molecule”. It’s not like a solution, the water is a part of the molecule itself. The hydrated calcium sulfate that the above means is gypsum, which is a glassy hard mineral. Opal, among many others, is also a hydrated molecule, as is emerald. If you take gypsum and heat it in a kiln to 150C – beyond just the boiling point of water, it will drive off the water molecules, leaving plain calcium sulfate. If you put that in a container and mix water with it, it will take up the water again, rebind it to the CaSO4 molecule, and form gypsum again, except this time it will be a mud and you can pour it and mold it. Understand that in all of these things, it’s a chemical reaction. If you mix dirt with water and get mud, you’ll have to wait until the water evaporates to get a hard block. With plaster, the water is bonding with the molecule, and when that happens it becomes hard gypsum again very quickly, and nothing can stop it. That is Plaster of Paris – just plain old plaster. I will confess that I don’t know the formulas for refractory (high-temperature) plasters, and they are pretty much trade secrets. But they are still plaster in essence. Cement and mortars are very similar – the water is burned off and then when it gets replaced by the user, you have cement – mix it with sand and aggregate and you have concrete. Cement in particular is much too complicated to lay out here, though, and it’s not necessary anyway. But it acts on the same principal as plaster, by and large; it’s just a complex mix, and solid solutions, and cross-linking molecules and such. It’s almost not much different from what an alloy does when it freezes, in a way.

CARBON

Carbon is unique. Carbon is special. It’s also this sooty black stuff. Carbon is unique because it has exactly four electrons in the outer shell – one half of what it wants. It’s also able to make “covalent bonds”, which simply means that it can “share” a bond. It can give and take at the same time. That’s oversimplified, but I’m just going to touch on the subject here – a certain knowledge of organic chemistry is useful, more is unnecessary in jewelry. Many elements come in different forms – white and red phosphorus, for instance. Look up “allotropes” for more on that. Carbon is no different. If you imagine carbon schematically as a “c” with four lines coming off of it, north, south east and west, it will become clear. Let us say that another carbon atom bonds with each one of those lines, and another, and another and another, in three dimensions. What we’ll have is some sort of 3 dimensional grid, with carbons and lines in between each one of them. What we’ll also have is a diamond crystal in about the most efficient arrangement of atoms imaginable. That’s mostly why diamond is what it is – the hardest substance on earth and other things. If you take three carbons in a row, bonded together, and put an oxygen at one end, and some nitrogen on the other end, and a few hydrogens, you’ll be into organic chemistry. It’s the unique ability of carbon to form long strings and circles with a huge variety of other things connected around the outside that makes it so versatile and useful. You can get a hugely complicated molecule with a valence of +1 and connect it to another hugely complicated molecule with a valence of -1, and they will bond in theory at that one single spot and become something even more. The ability to form long strings, strong, linked molecules and the rest is the whole field of “Polymerization”, and that’s what epoxy and plastics is about, among many others. I’ve heard it said that a nylon thread is a single molecule, three feet long. I’m not sure that’s exactly true, but it’s partially so, I think.

Very quickly, organic chemistry is about what is called “Functional Groups”, which are similar to the radicals I mentioned before, like the sulfate ion. Functional groups are the alcohols, aldehydes, alkanes, alkenes, alkynes, amines, amides, ketones, benzenes, pyridines…… Well, you get the idea. So Methyl Ethyl Ketone is a methyl group, an ethyl group and a ketone group, bonded together. It’s not necessary to know more than that, but it’s handy to just know the structure of it. Using the proper procedures, chemists combine an aldehyde with an isocyanate (I made that up…), say, and come up with some new arcane substance. It’s also like tinker toys, but the toys are complex and there’s more of them, and the combinations are infinite.

POLYMERS

So, let’s take the automobile. Say, a Volkswagen. It’s composed of about 10,000 parts – however many. So, let’s suppose that you’re standing on a hill overlooking the VW plant, and below you is the parking lot, with 1000 identical cars waiting to be shipped, row upon row. If you somehow tied each car to the next one, that would be a pretty good illustration of a polymer. Polymers are built from monomers. In our case each car is a monomer, and the whole is a polymer. People tend to think of polymers as man made, and at this point most of them are. But DNA is a polymer, as is amber, shellac and cellulose. Proteins and nucleic acids are, also. To give you some idea of how seemingly small things can radically change the results: polyethylene is a polymer of ethylene, which is a gas. Polystyrene is a polymer of styrene, which is a liquid. Polypropylene is a polymer of propylene, also a gas. The main polymer most people deal with, aside from the plastics, is epoxy resin. Fiberglass is also some sort of epoxy resin with glass fibers. That’s just two liquids that, when mixed together, form a polymer on the spot. In fact, one of the ingredients, Epichlorohydrin, is made from propylene.

ISOMERS

Isomers have little if anything to do with jewelry, but since they are an important concept, I’ll just touch on them. Carbon, graphite and diamond are what are called “allotropic” varieties of carbon. They have different physical forms, but they are all elemental carbon. An isomer is conceptually similar, though it applies to molecules, not atoms. If you have a large molecule, say C20H40, which is, again, just made-up. Those sixty atoms can arrange themselves in a long row, or in a circular pattern, or with ten in the center and another circle around them, or some squarish, 3-dimensional matrix. Each of those molecules will exhibit different properties, often radically so, and if we dub my made-up molecule “blueane”, then each one is an isomer of Blueane. I don’t “speak the language” of it myself, but when you see an organic compound called 2, 4, D or something, that is identifying the isomer.  The 2, the 4, and the D all identify where some of the key elements of the molecular structure are bonding.  As in, “The main molecule is bonded at the #2 carbon, and the secondary one is at the #4 carbon.”  That’s made-up again, but that’s conceptually what those numbers and letters are for in chemicals.

ESTERS

This also has nothing to do with jewelry, but since it’s a huge family of organic compounds, I’ll mention it just for general knowledge. In simple terms – even too simple, maybe – an ester is a combination of an acid and an alcohol. This involves certain processes and usually a catalyst. You can’t just pour them together and get an ester. They’re interesting because they are the tastes and smells of the world. Butyl ester is banana, for one, although there are many. These are the artificial flavorings and things in food, though they also occur naturally. There are thousands of alcohols and thousands of acids, not just the household things we use – so there are countless combinations.

ALCOHOLS AND SOLVENTS

An alcohol is technically a hydroxyl group (-OH) bonded to the carbon atom of an alkyl group. There are three types of alcohols – primary, secondary and tertiary. Methanol and ethanol are the two most important primary alcohols, isopropyl is a secondary alcohol. There are thousands of alcohols in the universe, but only these three probably mean much to most people. Methanol is the simplest alcohol, ethanol is the next simplest. Basically there’s not a lot to know except that they make good solvents for certain things – boric acid in jewelry. Besides the fact that it’s nice to be able to burn off the solvent, boric acid is also insoluble in cold water – it is somewhat soluble in hot water. Denatured alcohol is ethanol with some things added to make it undrinkable. Sometimes it’s methanol, but not always, because if people drink it anyway the methanol will get them. There are other various additives used. By the way, methanol in itself is not poisonous. When the body metabolizes it in the same way as ethanol, instead of just burning it, it creates formic acid and formaldehyde, both of which ARE poisonous. And if you dunk a hot piece into methanol, it will give off formaldehyde in small quantities, too Isopropyl alcohol is an isomer of propanol, and it can be oxidized to form acetone, which is a ketone. It IS alcohol, but in some respects for our purposes, such as a solvent, it’s not really quite the same.

Acetone is the simplest ketone. A ketone is just a thing, like “an alcohol”, there’s “a ketone”. Mostly it’s used as a solvent in the everyday world – it’s an important chemical, as are all of these, in industry. Acetone can create health problems if fumes are inhaled in quantity, and it can cause eye damage. It is also formed naturally in the body in small quantities. One of the signs of diabetes is an elevated level of acetone in the body. Other than that one of the nice things about it is it’s low toxicity, though it’s offset a little by it’s high flammability. Acetone is used in acetylene tanks to dissolve the acetylene gas. Be aware that it is highly useful in the plastics industry – it’s one of the precursors of epoxy resin, for instance. Thus it will dissolve a great many plastics, including vinyl tile on your floor. It would be wise to test for this before dunking some piece into it. We use it a lot to wipe away epoxy before it sets up, among many other things.

The word for the ability of things to dissolve into each other is “miscibility”. All three of the above are mutually miscible in water to any degree. You might think that’s always true, but it’s not. One of the useful things about solvents, and especially acetone, is as a “transitional” solvent. Use the acetone to dissolve some non water soluble substance, and then use water to wash away the acetone solution. This is a fairly common practice.

DICHLOROMETHANE

Otherwise known as methylene chloride or the brand name “Attack”, is widely used as a solvent for plastics. It is a chlorocarbon, none of which are good for you, though dichloromethane is considered among the safest. It’s used to dissolve cured epoxy resins, and it’s also the active ingredient in paint strippers. While it’s not intensely dangerous, it is dangerous. It’s non-flammable, but extremely volatile, and inhalation can lead to carbon monoxide poisoning, as it metabolizes into carbon monoxide. It can strip the fats out of your skin, leading to burns, but most importantly it’s a suspected carcinogen and a known mutagen, meaning it can create mutations in fetuses. By the way, it’s also the stuff in Christmas “Bubble lights”.

WAXES

After I put this paper out, it was suggested that I add waxes to it. I will freely confess that I know little about the chemistry of wax, so this section is the product of research – don’t think I’m a wax expert if you see me. The term wax original comes from beeswax, and it’s a generic term which now means something that possesses properties similar to beeswax. Waxes are lipids, which are the triglycerides, which includes fatty acids. Generally they are esters (see above) of some alcohol and some fatty acid. There are a great many waxes, and they come under categories: Animal and insect, which includes beeswax, shellac, spermaceti and lanolin. Vegetable waxes: Bayberry, Carnuba, Candelilla, Castor Wax and Jojoba, among others. Mineral waxes: Ceresin, Montan, Ozocerite and Peat waxes. Petroleum waxes: Paraffin (long-chain alkane – another relative of methane) and microcrystalline wax. And synthetics: Polyethylene waxes, esterified waxes, polymerized olefins (an alkene). From the standpoint of jewelry waxes, if you want to know more I’d suggest that you talk to the reps from the wax companies about what waxes they use. They are going to be proprietary formulas – I know I’ve heard Carvex is a blend of wax and plastic, though I’m sure the “plastic” is more like a synthetic wax. Everyone needs to remember that paraffin is not a wax in the same sense as the others, though it’s classified as a wax. The most significant difference being that’s it’s highly flammable. If you do a lost wax casting with it, it won’t just burn out, it will catch fire.

SOAP AND DETERGENTS

Soap is made by a process called saponification. When we put an alkali with a fat, it makes soap, basically. In a schematic way, and actually fairly literally, the soap molecule has two ends. One end is attracted to polar molecules, such as water. The other end is attracted to nonpolar molecules, such as fats and greases. You could think of it as a magnet with north-south poles, and water is north and fat is south, though that’s not technically true, just a mental image. So when you put soap on grease, the nonpolar side bonds with the grease. Then when you add water, the polar side bonds with the water, and up comes the grease. Think of it as a mediator. Since there are many alkalis, and any number of oils and fats, the ability to make different soaps – toothpaste is soap, essentially – is endless. The word detergent actually has a few meanings – soap and even water have a detergent quality. There are also what are essentially synthetic soaps that are called detergents. They have the same polar/nonpolar quality that makes them cleaning agents. Surfactants are substances that reduce the surface tension of water, which is another subject in it’s details, but that allows the water to be “wetter”. Surfactants are also known as wetting agents. All of the commercial detergents and many soaps are blends of soaps or synthetic detergents, surfactants, maybe some oxidizers (peroxides, hypochlorites), enzymes to dissolve proteins, water softeners, substances to adjust the pH, and maybe something to enhance or control foaming. Not to mention color, perfume and viscosity. But the essential quality – the ability to let us dissolve fats with a water base, is the same.

VULCANIZATION

Uncured, natural rubber is a natural polymer. However, as it comes it’s a thick white liquid, and it breaks down quickly into a gooey mess. A polymer is, as I’ve said, a long chain of molecules, often billions of atoms long. In the case of rubber, the analogy is more of a plate of spaghetti than of a nice neat parking lot full of monomers – a little mixed metaphor, but you get the idea. If those chains can be “cross linked”, then we’ll have something. One of the first things to realize is that most plastics are “thermoplastic”. Thermoplastic materials can be melted, and set hard when they cool. Rubbers are “thermoset” materials – they set by heat, and then afterwards if they are heated they won’t melt, they’ll burn. That’s one of the distinguishing characteristics of rubber vs. plastic, in fact. They are also “elastomers”, which is a 50 cent word for “They’re stretchy”. When you buy rubber for vulcanizing, it’s actually a mixture of compounds – these are again proprietary formulas, and I’m only talking about the theory, here. The critical ingredient in most rubber is sulfur. Along the molecule of rubber are spots that are called “cure sites” or spots where sulfur can bond to them. During vulcanizing the eight membered ring of sulfur breaks down into smaller parts with varying numbers of sulfur atoms, which are quite reactive. Those atoms migrate to a cure site, and chains of sulfur atoms grow until they reach another cure site on another rubber molecule, “cross linking” them. The number of sulfur atoms in the cross link determine the final properties of the rubber: fewer atoms give less flexibility and greater heat resistance, more give greater flexibility and less heat resistance. This cross linking in effect turns our plate of spaghetti into a chain link fence – strong, durable, stable and resilient. The process is also entirely irreversible. And by the way, even though there is some evidence that ancient people used the process in some way, we can thank Charles Goodyear for inventing the modern process of sulfur vulcanization, even though he never made any money off of it, poor man.

3D PRINTING

New as I add this to our refreshed website. 3D printing has swept across the jewelry industry in recent years. At this point we could call it ubiquitous…… Home, inexpensive 3D printing – usually the one called FDM – uses thermoplastics. Spools of plastic (much of which is made from corn, as I understand it) that melt to become the shape. Plastic bottles and most computer cases are thermoplastics. Melt them and mold them.

3D printing in jewelry – jewelry CASTING, that is – requires resins that burn out cleanly so they can produce clean castings.

Resins for 3D printing are “cured” using UV light and as they are exposed it creates polymers where the light strikes. The resin becomes a plastic when exposed to the UV light.

The entire topic of how to do 3D printing is more than just chemistry and far beyond the scope of this paper.

FLAMMABLE GASES

METHANE is the most basic hydrocarbon, CH4, and the simplest alkane. It’s interesting on the level of the formation of the universe and it’s relationship to life, but we won’t go there right now. It is the major component of natural gas; it’s non-toxic though any gas that displaces oxygen in the atmosphere is considered asphyxiating. For those interested, here’s the combustion of methane: Upon heating it forms the methyl radical CH3, which combines with oxygen to form formaldehyde. The formaldehyde gives a formyl radical HCO, which gives carbon monoxide. A left-behind hydrogen oxidizes, forming water, and then the carbon monoxide oxidizes, forming CO2, both of which release heat. And here you thought it “just burned”!! That’s what real chemists do, is figure out this stuff.

BUTANE is an alkane, which means it’s related to methanol. It’s formula is long and unnecessary, so I won’t write it out. It is toxic to some degree, and can create drowsiness and other effects. When it burns it doesn’t do the methane thing, it just burns. It combines with oxygen to form CO2. There are actually several butanes, but they’re all flammable gases.

PROPANE is also an alkane, also burns simply and is a very efficient fuel. It’s also non-toxic, heavier than air, and is the component of LPG – liquefied petroleum gas, though that is often a mixture with butane and others.

ACETYLENE is the simplest alkyne hydrocarbon. In fact it is somewhat of a gateway to a whole family of molecules in the same way methane is for alkanes. It does not occur naturally. It’s also quite unstable and volatile. It is toxic in the way most of these can be. 80% of the acetylene in the world is used for chemical synthesis; the remaining 20% is used as a fuel. It’s an important chemical in plastics manufacture.

JUST A WORD

When wondering if some organic thing is really bad to be around, I use what I’ve seen as a guideline. That is that “ethyls” are often more benign, we drink ethyl alcohol, and the like. “Methyls” are not so benign, we don’t put hardly any of them in our bodies, and some are really nasty. Now, there are plenty of ethyl- chemicals that will put you in the ground – do NOT take this to mean “Ethyl is safe” - it just seems to me that the methyls are less forgiving to human flesh. All I’m saying is, if it’s an ethyl-whatever, be careful with it. If it’s a methyl-whatever, be even more careful.

THE WRAP UP

I know quite a lot about chemistry. I know so much, in fact, that I have no illusions that I am anything approaching a real chemist. Although I knew a great deal of what I wrote here already, you can be sure that I had plenty of reference in several spots. The idea was to get a broad view of how things work, and much of this I just can’t recite off the top of my head. Why chemistry? First of all, in jewelry we use it more often than most industries that aren’t IN chemistry. More importantly to me, and I think many others, is its relationship to the field of Materials Science, which I’ve never taken formally. In general, it asks the question, “Why is sulfur sulfur? Why is copper red? Why is carbon, which has the atomic number 6, a black solid with the properties it has, and nitrogen, which is 7 and right next to carbon, a gas with the properties it has? This extends to everything else, too – metals, alloys, plastics, nature, DNA, how the brain works, why fire is fire. It is literally the stuff of life and the world around us. This little paper represents a grain of sand on the beach. Just about every word that I have written can be researched deeper, and in many cases MUCH deeper. I didn’t see much point in writing very deeply about the gases – if you’re inclined to go exploring enthalpy, well, have at it. Modern Chemical Valence Theory is closely tied to quantum mechanics, acid-base theory makes what I wrote look like kindergarten. And organic chemistry just goes on forever. So if I have awakened some interest in some readers, I would invite you to look further – there are many resources for Chemistry online – just search for it. And I used Wikipedia fairly extensively in writing this – it’s a great resource.