Recrystallization and/or refining of sulphur. Sulphur is dissolved in hot toluene, and on cooling down, nice needle-like crystals of sulphur are formed.

Allotropes of selenium. In this experiment, some black/grey selenium is dissolved in nitric acid and the solution of selenous acid then is reduced with a solution of a sulfite. This results in formation of a red precipitate of selenium. This red selenium is another allotrope of selenium. In the same experiment, some pieces of zinc are plated with a thin layer of selenium.

Poly cation species of tellurium, selenium and sulphur. A comparison is made of what happens when tellurium, selenium and sulphur are added to concentrated sulphuric acid and heated. Tellurium and selenium form remarkable and really uncommon cationic species. Sulphur does not react with sulphuric acid, but in oleum the element sulphur also gives a remarkable cationic species.

Colorful properties of halogen complexes of tellurium in oxidation state +4. At very low pH, tellurium in oxidation state +4 forms remarkable compounds with the halide ions. The heavier the halogen, the more stable the complex and the more intense the color. All of these complexes, however, are very prone to hydrolysis in aqueous solution.

Tutorial for making a miniature electrolysis cell for chlorate production. This is not really an experiment, it is a description of how one can setup a nice small electrolysis cell, suitable for making chlorates from chlorides. The good working of this cell is demonstrated for making potassium chlorate and cesium chlorate.

Colored gases - chlorine and chlorine dioxide . Two experiments are performed. In one of them, chlorine gas is made from dilute hydrochloric acid and calcium hypochlorite. In the other, chlorine dioxide is made from sodium chlorate and concentrated hydrochloric acid. The chlorine dioxide has a really intense yellow color.

Violent 'combustion' of acetylene in chlorine gas . Acetylene gas, made from reacting water with calcium carbide (a.k.a. 'carbid) is bubbled into an erlenmeyer, filled with chlorine gas. This results in violent explosions inside the erlenmeyer. Spectacular, but also somewhat scary.

Red chemiluminiscence with chlorine swimming pool chemicals. Hydrogen peroxide (30%) is added to some solid swimming pool chemicals. This gives a clearly visible red chemiluminiscence. This experiment is particularly interesting, when done in a dark room.

Reaction between bromine/chlorine and phosphorus . When red phosphorus is immersed in an atmosphere of bromine vapor or chlorine gas, then it ignites and keeps burning in the bromine vapor or chlorine gas.

Example of interhalogen compounds . Iodine and chlorine react with each other and form so-called interhalogen compounds, iodine monochloride and iodine trichloride. The dry iodine monochloride does not react with magnesium, but when it is wetted a little, then a violent reaction starts.

Reaction between bromine and aluminium . When a small piece of aluminium is put in liquid bromine, then after some induction period, a very violent reaction starts, with fire and brilliant sparks.

Preparation of polyhalide salt of potassium. Potassium iodate reacts with concentrated hydrochloric acid, giving chlorine gas. From the solution, long needles of potassium tetrachloroiodate(III) can be isolated. This is an example of a polyhalide salt.

A polyhalide compound of rubidium. Rubidium is known to form polyhalide compounds fairly easily, more so than the lighter alkali metals (see experiment above). In this experiment such a compound is prepared. During the preparation a beautiful crystalline precipitate is formed.

Oscillating reaction with bromate. This is the classical Belousov-Zhabotinsky reaction, an oscillating reaction. Although it is well-known, it remains one of the most beautiful and remarkable demonstrations. The reaction, shown in this page, is based on the oxidation of malonic acid with bromate ions, with manganese(II/III) or cerium(III/IV) as a catalyst.

Synthesis of potassium bromate. Potassium bromate can be synthesized fairly easily from the easy to obtain potassium bromide by means of electrolysis, especially, when a tiny amount of a chromate or dichromate is added. This makes an interesting and hard to obtain energetic chemical accessible for a large group of home chemists.

Bromine from OTC compounds. Bromine is prepared from standard swimming pool chemicals. Only a very small amount of chromate or dichromate is needed, but this can be made easily as well (no need to isolate and purify this).

Synthesis and isolation of phosphorus tribromide . Phosphorus tribromide is prepared by means of careful addition of red phosphorus to bromine. By means of distillation the product is purified.

Synthesis of potassium periodate. Potassium periodate is prepared by leading chlorine gas through a solution of potassium iodate and potassium hydroxide. Some acid is used to precipitate all of the periodate as the very sparingly metaperiodate.

Synthesis of sodium orthoperiodate. Sodium orthoperiodate is prepared by leading chlorine gas through a solution of sodium iodide and sodium hydroxide. The nice thing of this synthesis is that it allows one to make periodate without needing access to any special chemicals besides the easy to obtain sodium iodide.

Delayed self-ignition of mix of periodic acid and red phosphorus. Some red phosphorus and periodic acid are mixed. After a while, this mix suddenly self-ignites and a plume of fire and smoke is produced.

Ammonium halates, unstable compounds . Ammonium bromate and ammonium iodate are prepared and it is demonstrated how easily and violently they decompose on slight heating. This is a nice and fairly spectacular experiment, but it should not be scaled up.

Formation of dense smoke from bromine and ammonia . Ammonia gas and bromine vapor react with each other, giving dense smoke of ammonium bromide. In this experiment, some bromine vapor is poured into an erlenmeyer, containing dilute ammonia gas. The result is stunning.

Colored smoke -- purple and yellow. This is a surprising experiment. A mix of potassium periodate and ammonium thiocyanate is ignited. Initially, the smoke, produced from the burning mix, is purple, but this smoke quickly turns golden yellow.

Reaction between molten nitrite and iodate. Some potassium hydrogen diiodate (double salt of potassium iodate and iodic acid) is mixed with sodium nitrite and the mix is heated. This gives a mix of nitrogen dioxide and iodine vapor. This mix has a beautiful color.

Decomposition of iodoform. A small amount of iodoform is heated in a test tube, and it is shown how this decomposes, giving purple vapor of iodine.

Reaction in gas phase. Nitrogen monoxide and oxygen are prepared and mixed by setting up an apparatus with two glass bottles. As soon as the gases mix, a deep brown gas is formed.

Fun with red cabbage. Red cabbage juice is treated with solutions of different pH. Surprising colors can be obtained in this way, much more than the well-known pink/rose to violet/blue colors, which one knows from the kitchen.

Electrolysis of water -- detonating gas. Water is decomposed by means of electrolysis of a dilute sulphuric acid solution. The resulting gases are mixed and the impressive explosive power of this gas mix is demonstrated.

Precision electrolysis of acetate and formiate. Acetate and formiate are electrolysed and based on the observations in this experiment, the net reactions are derived. A demonstration of what can be achieved with a combination of careful observation and reasoning.

Dehydration and oxidation of sugar by concentrated sulphuric acid. This is a spectacular experiment, in which sugar is charred by concentrated sulphuric acid and a lot of black foam, smoke and noise is produced.

Conversion of red phosphorus to white phosphorus . This is a write-up on how one can convert red phosphorus to white phosphorus. The process described here is suitable for making a few grams of white phosphorus per batch.

Color of the flame of burning gases. Different gases are collected in a test tube, sucked in a syringe, and then ignited. Many different flame colors can be obtained from different gases. Some flame colors are remarkable, such as pink/rose and grey.

Explosive properties of chlorine dioxide . The brightly colored chlorine dioxide gas is prepared and ignited. This results in a nice and quite spectacular decompositon reaction.

Explosion of chlorine dioxide, initiated by presence of ammonia . Another experiment, which demonstrates the danger of chlorine dioxide. This experiment shows how chlorine dioxide can be brought to explosion, simply by adding a few drops of household ammonia.

Barking dog reaction . Nitrous oxide is mixed with carbon disulfide vapor and this mix is ignited. This results in a very spectacular reaction with bright light and an impressive barking noise.

Preparation and properties of ammonium periodate. A simple experiment, in which ammonium (meta)periodate is made. This compound explodes when it is heated.

Violent reaction between hydrazine and periodate. In this experiment it is demonstrated that hydrazine and periodate react extremely violently and so much heat is produced that iodine escapes as vapor, even from aqueous solutions!

Explanation of what happens when hard water is heated. This experiment is a nice and safe demonstration and explanation of what happens when hard water is boiled.

Reactivity of different oxohalogenate ions. Several oxohalogenate compounds are added to a concentrated solution of hydrazine dihydrochloride. In many cases this leads to a reaction, some of them being very violent. A comparison is made of the reactivity of the different oxohalogenate ions at room temperature.

Self-ignition of phosphine in chlorine gas . In this experiment some phosphine is prepared, and the gas is bubbled in an atmosphere of chlorine, resulting in self-ignition of the gas and contraction of gas volume. This demonstrates the high reactivity of chlorine but also the high reactivity of phosphine. This is a remarkable and spectacular experiment, which makes a good demo.

Less common aspects of selenium chemistry . The element selenium has some interesting properties in combination with sulfide and bromide. It can form strongly colored species, which are stable in aqueous solution and can be studied without the need of exotic solvents.

Formation of a self-igniting gas from fine sand powder and magnesium . Magnesium metal and finely powdered sand are reacted to form magnesium silicide, which in contact with dilute acids produces self-igniting silane gas. This is a spectacular, but somewhat dangerous experiment.

Formation of cationic iodine species in oleum. Iodine is dissolved in oleum and the formation of a blue cationic species is demonstrated. Iodine is brought to oxidation state +½, which is very special for iodine.

Preparation of tin(IV) iodide, a volatile covalent compound. Tin and iodine are made to react in a suitable solvent for iodine. Under these conditions the interesting compound tin(IV) iodide is formed, which can easily be isolated. Some properties of this compound are shown.

Violent decomposition of hydrazine perchlorate and fairy-like sparkles. A small quantity of hydrazine perchlorate is prepared and this compound is heated, leading to a peculiar fairy-like sparkling when heating is not too strong and violent deflagration on stronger heating.

Violent decomposition of an organic perchlorate salt. A perchlorate salt of a basic organic amine is prepared and it is shown how this salt decomposes violently when it is ignited.

Timed explosive reaction. Hydroxylamine and bromate, when mixed with each other at high concentration, do not react immediately. There is a lead time of tens of seconds, and after that lead time there is a sudden very fast reaction, which only takes milliseconds.

Concentrating and purification of ammonia. Ordinary household ammonia is concentrated and purified by heating the liquid, driving out the gas and leading that gas through distilled water. This process can be used to make very pure ammonia at a higher concentration than the plain household ammonia.