Part 390

PYROGALLIC ACID STAINS, TO REMOVE, FROM THE SKIN: See Cleaning Preparations and Methods and Photography.

PYROCATECHIN DEVELOPER: See Photography.

«Pyrotechnics»

«FIREWORKS.»

The chief chemical process is, of course, oxidation. Oxidation may be produced by the atmosphere, but in many cases this is not enough, and then the pyrotechnist must employ his knowledge of chemistry in selecting oxidizing agents.

The chief of these oxidizing agents are chlorates and nitrates, the effect of which is to promote the continuance of combustion when it is once started. They are specially useful, owing to their solid non-hygroscopic nature. Then ingredients are needed to prevent the too speedy action of the oxidizing agents, to regulate the process of combustion, such as calomel, sand, and sulphate of potash. Thirdly, there are the active ingredients that produce the desired effect, prominent among which are substances that in contact with flame impart some special color to it. Brilliancy and brightness are imparted by steel, zinc, and copper {609} filings. Other substances employed are lampblack with gunpowder, and, for theatre purposes, lycopodium.

Fireworks may be classified under four heads, viz.:

1. Single fireworks.

2. Terrestrial fireworks, which are placed upon the ground and the fire issues direct from the surface.

3. Atmospheric fireworks, which begin their display in the air.

4. Aquatic fireworks, in which oxidation is so intense that they produce a flame under water.

«Rockets.»—First and foremost among atmospheric fireworks are rockets, made in different sizes, each requiring a slightly different percentage composition. A good formula is

Sulphur 1 part Carbon, wood 2 parts Niter 4 parts Meal powder 1 part

Meal powder is a fine black or brown dust, which acts as a diluent.

«Roman Candles.»—Roman candles are somewhat after the same principle. An average formula is:

Sulphur 4 parts Carbon 3 parts Niter 8 parts

«Pin Wheels.»—These are also similar in composition to the preceding. The formula for the basis is

Sulphur 5 parts Niter 9 parts Meal powder 15 parts Color as desired.

«Bengal Lights.»—Bengal lights have the disadvantage of being poisonous. A typical preparation can be made according to this formula:

Realgar 1 part Black antimony 5 parts Red lead 1 part Sulphur 3 parts Niter 14 parts

«COLORED FIRES.»

The compounds should be ignited in a small pill box resting on a plate. All the ingredients must be dried and powdered separately, and then lightly mixed on a sheet of paper. Always bear in mind that sulphur and chlorate of potassium explode violently if rubbed together.

«Smokeless Vari-Colored Fire.»—First take barytes or strontium, and bring to a glowing heat in a suitable dish, remove from the fire, and add the shellac. The latter (unpowdered) will melt at once, and can then be intimately mixed with the barytes or strontium by means of a spatula. After cooling, pulverize. One may also add about 2 1⁠/⁠2 per cent of powdered magnesium to increase the effect. Take for instance 4 parts of barytes or strontium and 1 part of shellac.

The following salts, if finely powdered and burned in an iron ladle with a little spirits, will communicate to the flame their peculiar colors.

Potassium nitrate or sodium chlorate, yellow.

Potassium chlorate, violet.

Calcium chloride, orange.

Strontium nitrate, red.