The Amateur Chemist

Synthesis of Strontium Nitrate

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Strontium nitrate is an inorganic compound with the formula Sr(NO3)2. This colorless solid is used as a colorant in pyrotechnics and is also used as an oxidizer in pyrotechnics. It gives off a brilliant red color. A well-known example is in flares.

Formula: Sr(NO3)2 

Molar mass: 211.63 g/mol 

Density: 2.99 g/cm³ 

Boiling point: 645° C (1,193° F) 

Melting point: 570° C (1,058° F)

Sr(CO3) + 2HNO3 -->  Sr(NO3)2 + H2CO3

H2CO3 --> H2O + CO2

Actually making it is very simple. Just mix 45 grams of strontium carbonate, 100mL of water, and 40mL of concentrated 70% (15.6M) nitric acid and then boil down until it's dry.  If the reaction is too vigorous, you can always dilute the acid down even more with some more water. You will just have to boil it down longer. If you use nitric acid of unknown concentration, just add strontium carbonate until it stops fizzing. If the carbonate you are using is impure, or especially if it is pottery grade, you will want to filter it after you react all of the carbonate. Pottery grade strontium nitrate is usually contaminated with some barium salts and even some sulfur. If you want to make it even more pure (I would do this, unless you are specifically using it for pyrotechnic purposes), you should recrystalize it at least once, perhaps even more if you feel like it.

Luckily, strontium nitrate is extremely stable to moderate heating, unlike other nitrates, so you can boil it without fear of accidentally destroying it or causing an explosion (like in ammonium nitrate).  Once you boil it dry, store it in an airtight container.  Strontium nitrate itself isn't that hygroscopic. It is when you buy the cheap fireworks grade stuff that contains hygroscopic strontium chloride as an impurity that you have to worry about it. However, you can never be too safe.

You can test your strontium nitrate by dissolving some in methanol or some other kind of alcohol. Then light this alcohol on fire and you should see a bright red flame. You can go to this website for some info on making homemade flares. One composition that is simple is 69% Strontium Nitrate, 13% Sulfur, and 10% sawdust.  There are many other compositions as well.  Thanks goes to nurdrage (an awesome YouTube channel), sciencemadness, and to pyroguide, for the procedure and the compositions.

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