The mixture, that is inherently dangerous, due to it's high sensitivity or instability, is called a Deathmix. One should realize, which chemicals are compatible with each other, before mixing anything. Even certain combinations in some known, especially older formulas, may be defined as death mixes.
Important! The scratches of plastic hardware, especially ball milling jars, will store traces of chemicals. This applies also to the ball milling media. You must have enough application-specific hardware to make sure, that even traces of incompatible chemicals may not interact.
Disclaimer: Following information does not imply any mixture as "safe".
Potassium permanganate with any fuel
Potassium permanganate is exceedingly dangerous if mixed with any fuel. Prevention: DO NOT PURCHASE POTASSIUM PERMANGANATE.
Red phosphorus with any oxidizer
Red phosphorus is exceedingly dangerous mixed with any oxidizer. Prevention: DO NOT PURCHASE RED PHOSPHORUS.
Chlorates with ammonium salts
Ammonium of ammonium chloride, will react with alkali metal chlorate forming ammonium chlorate and alkali metal chloride. Ammonium chlorate can DETONATE of minimum friction, or even of no reason at all. Ammonium for the reaction may also be generated at the reduction of nitrates, please see below. Some known formulas exhibit both nitrate and a chlorate, so avoid them! Prevention: NEVER MIX AMMONIUM SALTS OR ANY NITRATES, WITH CHLORATES.
Chlorates with sulfur
Finely powdered sulfur will react with the oxygen of the air, forming sulfur dioxide. Sulfur dioxide reacts further with moisture to form sulphurous acid, which eventually reacts with chlorate forming chloric acid. Chloric acid makes mixture unstable, and is even capable of igniting sulfur at room temperature. Prevention: NEVER MIX CHLORATE WITH SULFUR.
Chlorates with sulfides (arsenic, antimony, other)
All mixtures containing chlorates with sulfides, are highly sensitive to the heat, shock and friction. There are much safer and less toxic fuels available. Prevention: NEVER MIX CHLORATES WITH SULFIDES.
The following combinations of chemicals can be problematic due to chemical reactions that are likely to render the compositon useless. As such, they may not be true death mixes, but it is good to be aware of them. Some, like the Aluminium - nitrate reaction could in extreme cases cause ignitions to occur, but they are some of the most widely used compositions, for example, almost all glitter stars, and provided that the conditions are not extreme, the risk of ignition is quite acceptable. As such they would more accurately be called incompatible, or potentially incompatible.
Chlorates with metal powders
All mixtures containing chlorates with metal powders, are sensitive to the heat, shock and friction. There are always safer perchlorate versions available for these mixtures. Prevention: THINK TWICE BEFORE MIXING CHLORATES WITH METAL POWDERS.
Flitter aluminum with alkaline nitrate and water
In alkaline aqueous conditions, aluminum powder reacts with water forming hydrogen. Hydrogen, in its free-radical form, is capable of reducing metal nitrate to the corresponding amide. The amide will react further with moisture, to form ammonia and metal hydroxide, thus making the mixture even more basic. In the reaction, much heat is generated. Prevention: MINIMISE WATER USED. KEEP OUT OF SUN AND HEAT. AVOID USING VERY REACTIVE ALUMINIUM WITH NITRATES AND WATER. USE SMALL PERCENTAGE OF BORIC ACID.
Magnalium or fine aluminum with nitrates
All mixtures containing nitrates with these metals, are more sensitive to the heat, shock and friction than their safer perchlorate versions. Also, there is a risk of nitrate reducing reaction as above. Prevention: AVOID MIXING NITRATES WITH THESE METALS. USE SMALL PERCENTAGE OF POTASSIUM DICHROMATE WITH MAGNALIUM. WITH ALUMINUM, USE SMALL PERCENTAGE OF BORIC ACID. DO NOT STORE FOR A LONG PERIOD OF TIME.
Magnesium with water
Magnesium reacts with water or with moisture, forming magnesium hydroxide, hydrogen gas and heat. Prevention: NEVER MIX WATER WITH MAGNESIUM. ALWAYS COAT MAGNESIUM WITH POTASSIUM DICHROMATE OR LINSEED OIL.
Magnalium or fine aluminum with water
Magnesium in magnalium, reacts with water forming magnesium hydroxide, hydrogen gas and heat. Magnalium is somewhat less reactive than magnesium alone. This applies also to aluminum, when it's particle size is small. The danger is cumulative with nitrates, see above. Prevention: AVOID MIXING WATER WITH THESE METALS. USE SMALL PERCENTAGE OF POTASSIUM DICHROMATE WITH MAGNALIUM. WITH ALUMINUM, USE SMALL PERCENTAGE OF BORIC ACID.
Unprotected magnesium, magnalium with ammonium perchlorate
Moisture will react with magnesium forming magnesium hydroxide. Magnesium hydroxide will react further with ammonium perchlorate, forming ammonia and magnesium perchlorate. Magnesium perchlorate is hygroscopic, and will draw more moisture from air. The reaction of anhydrous magnesium perchlorate with moisture generates heat. Linseed oil does not protect magnesium/magnalium from ammonium perchlorate! Prevention: ALWAYS COAT MAGNESIUM/MAGNALIUM WITH POTASSIUM DICHROMATE. POWDERED DICHROMATE ADDED TO THE COMPOSITION WILL NOT PREVENT THE REACTION.
Copper or zinc with ammonium perchlorate
Copper or zinc reacts with AP as magnesium/magnalium, but to lesser extent. Some strobe compositions exhibit this combination. (Potassium dichromate uncertain->see discussion). Prevention: CHECK pH FOR NEUTRAL. NEVER USE WATER BINDER. USE IMMEDIATELY AFTER MIXING.
Magnesium, magnalium with boric acid
Boric acid passivates aluminum, but attacks magnesium and magnalium. So to say, magnesium and magnalium can not be stabilized by acid buffer. Prevention: NEVER MIX BORIC ACID WITH MAGNESIUM OR MAGNALIUM.
Nitrates with ammonium perchlorate
Some nitrates react with ammonium perchlorate forming ammonium nitrate and the corresponding perchlorate. Ammonium nitrate is hygroscopic, and will draw moisture from the air. With metal, it will pose dangers as discussed above, and will at least lead into ignition problems. Prevention: KEEP POTASSIUM NITRATE SEPARATE FROM AMMONIUM PERCHLORATE MIXES. IF USED WITHIN A STAR, FOR EXAMPLE, SEPARATE WITH SEVERAL MILLIMETERS OF POTASSIUM PERCHLORATE BUFFER, BOUND IN NITROCELLULOSE.
Unprotected iron powder with water
Iron corrodes easily in damp conditions, and many firework chemicals, such as Potassium nitrate, greatly speed up this reaction. Prevention: COAT IRON POWDER WITH LINSEED OIL, WAX OR STEARIN. USE AS LITTLE AS WATER WITH ETANOL AS NECESSARY, WET COMP ONLY AS NECESSARY. DO NOT STORE COMPS WITH UNPROTECTED IRON FOR A LONG PERIOD OF TIME.
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