The last days of the year are always super colorful, especially when it comes to fireworks. But how do all these different colors work? This is not about short-lived colored flames, which can be created by holding the appropriate salts in a Bunsen burner flame. Examples are copper (II) chloride (or alternatively a mixture of copper (II) sulfate and ammonium chloride) for the well-known blue-green “copper flame”. This page is more about pyrotechnic mixtures that burn slowly and exhibit the colored flame for a long time.
Despite the unclear origin and despite possible infringement of copyright rights, the recipes should be published so that they are not forgotten. Reading them is also instructive for another reason: the recipes show clearly how the experimental side of chemistry lessons has changed significantly over the past due to chemicals that are now banned in chemistry lessons.
Mix 54% potassium chlorate, 16% sulfur, 30% anhydrous soda.
There are several mixing options for this:
a) 48% ammonium picrate, 52% barium nitrate.
b) 25% ammonium picrate, 67% barium nitrate, 8% sulfur.
c) 73% potassium chlorate, 17% sulfur, 10% boric acid.
d) 76% barium nitrate, 20% sulfur, 3% charcoal powder, 1% shellac powder.
e) 67% barium nitrate, 11% potassium chlorate, 22% shellac powder.
f) 36% potassium chlorate, 40% barium nitrate, 24% sulfur.
There are also several possible combinations for this:
a) 10% potassium chlorate, 24% sulfur, 2% charcoal, 64% strontium nitrate.
b) 40% potassium chlorate, 20% sulfur, 3% charcoal, 37% strontium nitrate.
c) 46% strontium nitrate, 54% ammonium picrate.
d) Rose red: 23% calcium chloride anhydrous, 61% potassium chlorate, 16% sulfur.
e) Pink: 61% potassium chlorate, 16% sulfur, 23% calcium carbonate (real chalk).
60% potassium chlorate, 15% sulfur, 13% calcined anhydrous potassium aluminum alum, 12% copper (II) carbonate or copper (II) chloride.
60% potassium chlorate, 16% sulfur, 12% calcined anhydrous potassium aluminum alum, 12% potassium carbonate.
Demonstration of colorful pyrotechnic mixtures
The substances mentioned include a number of chemicals that are no longer permitted today, including ammonium picrate, which is now a banned explosive. Therefore, each mixture must be checked for compliance with modern regulations on a case-by-case basis before being used.
All substances must be dry. You may have to dry them in a desiccator. Mix the finely divided powders using a beaker. Under no circumstances should the substances be mechanically crushed or even ground in a mortar after mixing. There is a risk of self-ignition!
Work in the fume hood or outside, as harmful gases (e.g. sulfur dioxide) and dusts are produced during combustion.
The mixtures are placed on a fireproof base and lighted with a fuse or a match. You can also make large matches yourself. In any case, do not use the usual short household matches as the flames can hit quite high.
More colorful fires
Of course, you can also use mixtures of flammable liquids and corresponding additives, which burn off with a brightly colored flame.
Alcoholic mixtures with colorful flames
A porcelain dish is filled with 50 ml of denatured alcohol (F) and about 1 g of calcium nitrate is added. Mix as well as possible, heat the solution / suspension and ignite the hot mixture. An orange-red flame burns over the solution.
If you take strontium nitrate instead of the calcium salt, you get an intensely red flame. You can also take lithium nitrate (red). With sodium carbonate the flame becomes deep yellow. Copper (II) chloride produces a blue-green flame color. These alcoholic mixtures also include the boric acid esters (green).