Choosing the chemicals to start with

On this page, a guideline for which chemicals to purchase is given. Especially, when you start with a home lab, it may be difficult to determine, which chemicals you need first. Chemicals are quite expensive, so, especially when budget is limited, it is wise to think things over, before buying.

Another important thing is not to buy too much of chemicals. Many aqueous chemistry experiments can be done on a micro scale with less than 100 mg of chemicals and volumes of no more than a few ml. This makes experimenting less expensive and produces small amounts of waste. Only if one wants to demonstrate something to a larger group, larger quantities may be needed, but for private experimenting, using larger quantities does not add any other dimension to the experiments. Of all the chemicals, except the acids, 100 grams frequently is more than enough. Even with 50 grams hundreds of experiments can be done. For the common mineral acids, it is best to start with 1 liter for each acid.

For dry chemical experiments, it also is wise to work with sub-gram quantities. This makes these experiments much safer and if something gets out of control, then the consequences usually are not that bad with such small quantities.

Below follows an overview of chemicals, which are most interesting to start with. There is no need, to buy all of these chemicals at once. For all chemicals, mentioned below, you will need a few hundreds of dollars, even if only purchased at 50 gram quantities. My own experience is that building up a home lab over the course of many years is more rewarding. One can best choose a certain theme (e.g. halogen chemistry or transition metal chemistry) to start with and explore that theme.

Separation of properties of chemicals

When purchasing chemicals, it is important to buy the ones, which only have a single main property. Many inorganic chemicals are more or less ionic and consist of a cation/anion pair. An example is sodium chloride, consisting of Na⁺ ions and Cl^– ions. Of such ionic compounds, the properties are determined by both the cation and the anion. Frequently, inorganic chemicals are such, that either just the cation or just the anion has a specific property and the counter-ion is just a charge balance, not taking part in any interesting reaction, for which the chemical is intended. Such a non-reactive ion is called a spectator ion.

Fortunately, there are some cations, which in practice have no effect and always are spectator ions in practical situations. For anions the situation is somewhat different and there is not a single anion, which safely can be regarded as spectator ion in all cases.

• Cations, which can safely be regarded as non-reactive in all practical cases are Na⁺ and K⁺. To a lesser extent, ammonium ions, NH₄⁺, also can be regarded as non-reactive, but only in neutral to acidic environments and in the absence of very strong oxidizers and nitrites.
• Common anions, used as spectator ion are sulfate, SO₄^2-, nitrate, NO₃^–, and chloride, Cl^–. Sulfate is the least reactive of these and in many experiments, this can be used as a safe non-interfering spectator ion. Nitrate can sometimes interfere as a strong oxidizer, especially at very low pH and at higher concentrations. Chloride frequently also is a true spectator ion, but in the presence of strong oxidizers, it may be oxidized to chlorine, which is strongly interfering. In many coordination chemistry experiments, chloride also may be strongly interfering.

When a compound is purchased, because of its anionic properties (e.g. dichromate, permanganate), then the cation should be a non-reactive one like sodium or potassium. When a compound is purchased, because of its cationic properties (e.g. copper (II), hydroxylamine), then a safe choice frequently is to buy the sulfate. Sometimes chlorides or nitrates also are suitable.

This separation of properties really is important. Imagine that you want to study the properties of permanganate ion, but the only permanganate available in your home lab is silver permanganate (a commercially available compound, although probably not for the general public). When you dissolve this compound in water, then you always have the properties of silver ions interfering (e.g. formation of precipitates with chlorides). For this reason, it really is preferable to have sodium permanganate or potassium permanganate. These let you study the properties of permanganate ion without interference of other ions. If you really want to study the specific properties of a combination of silver ions and permanganate ions, then you always have the option to dissolve for example silver nitrate and potassium permanganate in a single solution. The potassium and nitrate ions, will be just spectator ions in most of your experiments.

So as rules of thumb:

• When you purchase a compound because of the properties of its anionic part, then choose the sodium or potassium salt, whichever is cheaper or easiest to obtain. If this is not possible, then the ammonium salt is the second-best alternative.
• When you purchase a compound because of the properties of its cationic part (mostly a metal salt), then choose the sulfate or the nitrate, whichever is cheaper or easiest to obtain. For some experiments, in which strong reductors are involved, such as metallic zinc, the chloride may be more suitable. Nitrate and sulfate can be reduced by very strong reductors. This may cause interference (a possible interference is formation of black sulfide or nitride precipitates with some metal ions).
• For many experiments, where a slight alkalinity of the anion is no problem, the acetate also is a very good choice. Acetate is resistant, both to oxidation and reduction and at low pH, it is converted to acetic acid, which hardly has any coordinating properties. At high pH, acetate may be interfering, due to complex formation.

Acids and bases

Many experiments require the use of an acid or a base. The ideal situation would be to have an acid, which is strong and which has no other property, besides being acidic. The same holds for bases.

Unfortunately there is not a single acid, which is just acidic and has no other relevant properties. For this reason, even a simple home lab should have a choice between strong acids. If no suitable strong acids are available, many interesting experiments simply are not possible. If possible, try to obtain the following acids:

• hydrochloric acid, 30% HCl
• nitric acid, 50% HNO₃
• sulphuric acid, 96% H₂SO₄

Hydrochloric acid has slight reducing properties, which only becomes a problem in combination with strong oxidizers like permanganate and persulfate. For many experiments this is not a problem. The chloride anion, however, also has quite strong coordinating properties. With many metals (e.g. copper, cobalt, iron) it forms colored complexes, which may affect the outcome of certain experiments.

Nitric acid is a strong oxidizer when it is at moderate to high concentration.  Dilute nitric acid (approximately 1 M or less), however, is a very good approximation of the ideal acid without other properties. Nitrate ion is only very weakly coordinating in most situations. So, dilute nitric acid is a good choice for many experiments, where hydrochloric acid causes interference from the chloride ions.

For most chemical experiments, requiring an acidic environment, sulphuric acid probably is the most versatile. This acid is non-reducing and non-oxidizing, even at fairly high concentration and in most situations, the sulfate counter ion also is non-coordinating. Only with some metals, such as lead, silver, barium and calcium, the use of sulphuric acid may be a problem, due to formation of a precipitate of the metal salt. When sulphuric acid needs to be diluted, always add acid to water slowly, while constantly stirring, never pour water on the acid.

For many experiments, a relatively safe and suitable alternative for dilute sulphuric acid is sodium bisulfate, NaHSO₄. The sodium ions and extra sulfate ions do not interfere in most experiments. It is strongly advised to buy a pound or two of this compound, which is available as pH-minus for swimming pools. It can also be ordered and shipped from many photography raw chemical suppliers.

With bases, the situation is more simple. Either sodium hydroxide or potassium hydroxide is suitable. Both of these give the strong base OH ^–. The cations Na⁺ or K⁺ generally do not interfere. Both bases are soluble in water very well. For the majority of the chemical experiments, requiring a strong base, the drain openers, based on 98 - 99% NaOH are a suitable and cheap source of a strong base.

Oxidizers

Many interesting experiments involve the oxidation of one or more compounds. It is best to have a set of oxidizers, ranging from mildly oxidizing to strongly oxidizing. It is best if both the oxidizer and the reduced species are colorless in aqueous solution, otherwise the color of the oxidizer or its reduced species may mask the results of the experiment or at least the color will interfere. Oxidizers like potassium permanganate and potassium dichromate, which are quite common, are not suitable as the main oxidizers for a home lab, due to their strong colors. The following compounds constitute a reasonable set of suitable oxidizers:

• Potassium persulfate or sodium persulfate (if not available, then ammonium persulfate can most times be used as well). Both the oxidizer and its reaction product are colorless. It acts as a good oxidizer for all pH. This is a really clean oxidizer, without all kinds of side reactions. It also is a very strong oxidizer, although sometimes its reactions are somewhat sluggish and a little heating may be required.
• Hydrogen peroxide is a good oxidizer, both at high and low pH. Surprisingly, this also can act as reductor. It however, frequently has many side-reactions, such as simple decomposition, but also complex formation and peroxo-compound formation.
• Potassium chlorate or sodium chlorate (the latter is more suitable for aqueous chemistry, due to its greater solubility). This only is a good oxidizer in acidic environments. Does not work cleanly in the presence of high concentrations of chloride, due to formation of deep yellow chlorine dioxide and chlorine. Aqueous chemistry of chlorates is somewhat sluggish and frequently needs some heating.
• Bleach, also known as solution of sodium hypochlorite. This is a light yellow liquid and its reaction products are colorless or light green. In acidic media, this evolves chlorine gas. Be careful. Oxidation with bleach is not always clean, especially oxidation of organic compounds frequently is accompanied with chlorinating side reactions.

In a starting home lab, it is sufficient to have these oxidizers. Potassium nitrate and potassium perchlorate are not suitable as oxidizers in aqueous chemistry, due to the very low speed of the reactions of these compounds at any pH larger than 0. For dry chemical experiments or pyrotechnics experiments, these oxidizers, however can be quite useful.

Reductors

For reductors, it also is best if they are colorless and the reaction product also is colorless. In aqueous chemistry, the number of strong soluble and colorless reductors is quite limited. Most reductors, mentioned here, are only mild reductors. The only strong reductor is zinc, which however is not colorless and soluble, but which does have a colorless and soluble reaction product.

• Sodium sulfite, anhydrous, is a nice reductor, which is completely colorless. This reductor is moderately strong. In acidic media, the pungent gas sulphur dioxide is formed, which also is a fairly strong reductor and which dissolves in water quite well. All these properties make this one of the most versatile reductors for aqueous chemistry experiments. This reductor, however, works best in acidic media.
• Sodium thiosulfate is colorless and is a mild reductor at near neutral pH. At low pH, this is not suitable, due to decomposition of the thiosulfate ion and formation of a finely divided precipitate of elementary sulphur, which strongly interferes with many experiments. Thiosulfate hence is much less versatile than sulfite.
• Zinc metal is a very strong reductor. For many experiments, this is the only alternative for situations, where a strong reductor is needed. If fine filings or coarse powder is used, then this works quite well with some shaking. Any excess zinc metal quickly settles at the bottom and does not really interfere.
• Organic compounds (e.g. ethanol, glucose, formic acid) sometimes also can be used as suitable reductors, but in practice their use is limited.

Besides the reductors, mentioned above, there are a few more, such as magnesium and aluminium. Especially magnesium is too reactive to be useful as aqueous reductor. In acidic media it quickly reacts with the acid, forming hydrogen gas, such that only a small amount of reductive power is made available for the reaction with any compound in the water. Other strong reductors, such as photographic developers also are not suitable. The reaction products often are intensely colored polymeric species, which also are strongly coordinating to most metal ions.

There is a strong reductor, suitable for aqueous chemistry at high pH. This is sodium borohydride. This compound, however, is quite expensive and not without risk. This is not a compound to start with, but for the more experienced home chemist, this may be a valuable addition to the home lab. It is available from a few raw chemical photography suppliers.

Halogens

The halogens chlorine, bromine and iodine are an interesting group of elements to experiment with. These elements form interesting colorful gaseous compounds at low to medium temperatures and are quite reactive. With an oxidizer like bleach or hydrogen peroxide, halogens can be prepared easily at the home.

Interesting compounds of the halogens are:

• sodium chloride
• bleach
• potassium chlorate or sodium chlorate
• potassium bromide
• potassium iodide
• iodine

Elementary chlorine and bromine can be prepared, but should not be stored. Iodine can be stored well, but it is wise to store this in a small tightly capped container, wrapped in tissue paper, which is placed in a larger tightly capped container. The problem with iodine is its volatility. Iodine vapor stains everything with a strong brown color. Hence the need to store this in a double container with tissue paper around the smaller container.

Iodine and its compounds are quite expensive. However, you only need at most a few tens of grams of these compounds. Bromides are fairly cheap and chlorine compounds also are quite cheap.

Transition metals and some ligands

The transition metals are among the most interesting for the amateur chemist. These metals form many colorful compounds and can be used in a large number of interesting experiments. Even up to now, there still is a lot to discover about the chemistry of these metals, also for the home chemist. For a starting home chemist, the following compounds are definitely worth the cost:

• vanadium pentoxide
• chrome alum
• potassium dichromate
• potassium permanganate
• ferric chloride
• ferrous sulfate, better: ferrous ammonium sulfate
• ferric sulfate, better: ferric ammonium sulfate
• iron powder
• cobalt sulfate or cobalt carbonate
• nickel sulfate or nickel carbonate
• copper sulfate
• silver nitrate
• molybdenum oxide

All compounds, mentioned above, can be obtained fairly easily in most parts of the world. For the more advanced home chemist, the following can be added to this list.

• titanium powder
• sodium tungstate
• tetrachloroauric acid, also known as 'gold chloride'
• palladium chloride
• potassium tetrachloroplatinate (II), also known as potassium chloroplatinite

The transition metals have an interesting coordination chemistry and redox chemistry. Interesting ligands to start with for the transition metals are:

• ammonia
• hydrogen peroxide
• citrate, available as citric acid, but also as sodium citrate
• acetate, available as acetic acid, but also as sodium acetate
• tartrate, available as tartaric acid, but also as sodium potassium tartrate.
• EDTA, preferably as tetrasodium EDTA
• concentrated chloride and bromide
• photographic developers like hydroquinone and metol
• sulfite, available as sodium sulfite
• thiosulfate, available as sodium thiosulfate
• thiocyanate, available as the sodium salt or potassium salt.

An interesting aspect of coordination chemistry is the relation between pH and the complexes formed. With the set of chemicals, mentioned in this section on transition metals, there is a really endless variation of possibilities, which can be explored deeply.

Miscellaneous chemicals

Finally, there are some chemicals, which are a nice addition to the home lab at low cost. These can be used for precipitation reactions, redox reactions and sometimes also in coordination reactions. When starting a home lab, it is suggested to have these chemicals available soon.

• sodium carbonate
• sodium bicarbonate
• alum
• potassium ferrocyanide
• potassium ferricyanide
• borax
• sodium perborate
• sodium sulfide
• sodium nitrite
• ethanol (colorless denatured is suitable)
• methanol
• ligroin
• acetone
• acetic acid (28% or 80%)

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