KNO3 in Adelaide, or sufficient replacement.

[kahlzun]

I've been meaning to try my hand at making some rocket candy, and am having serious difficulties locating potassium nitrate in Adelaide.

None of the usual 'stump remover' products seem to be available here.

Does anyone know of any major retailers that stock the product, or an equivalent substance I could use for the oxidiser which is available?

Cheers,

Sam

[Streetwind]

Online ordering is an option. Look for "food grade" potassium nitrate. This means it can be used for curing meat with no health concerns (provided you do the curing right), indicating 100% pure KNO3 and nothing else. If it's good enough for human consumption*, it's good enough for making rocket fuel Chemistry and science supply stores as well as commercial food processing suppliers may carry it. But also keep in mind that some meat curing products are mixtures of KNO3 with other compounds, for flavor. Look closely at what is offered.

Failing that, KNO3 synthesis is possible with household materials to >99% purity, if you are patient and diligent (it'll be a day's work to do it properly). It will require some less controlled chemical substances, including distilled water, absolute alcohol, water softener and fertilizer. Note that you will be dealing with the salt of an aggressive mineral acid - while it shouldn't actually become seriously acidic in this form, it's always a good idea to use protection, guarantee perfect ventilation and offer due respect.

* please do not eat pure potassium nitrate, it is not good for you. You will regret it all the way to the hospital and during your stay there too.

Edited December 19, 2014 by Streetwind

[lajoswinkler]

Potassium nitrate is not acidic. It's a salf of a strong base and strong acid just like NaCl is. K⁺ and NO₃^- do not hydrolize so it won't corrode your skin any more than table salt - by retaining water and drying your tissues if you sleep in a bag of it.

It is an oxidizer at higher temperatures sufficient to melt it, but any liquid that hot will burn you. It really isn't dangerous unless you sprinkle it over your house and set the carpet on fire.

If you buy food grade meat curing salt, you'll get something like 98% NaCl and 2% KNO₃. It's an expensive source, so be careful what you buy.

eBay offers decent quantities, but don't go for reagent grade because that's expensive, too. Food grade 99% KNO₃ or technical grade is just fine.

There are no substitutes for this salt in rocketry. Ammonium equivalent is unstable and yields poor I_sp, and other stuff like perchlorates are chronic poisons, extremely reactive, and very expensive.

You could try with powdered zinc and sulfur if you manage to find them at a reasonable price, but that yields excess, noxious SO₂.

[QuesoExplosivo]

Ask on www.sciencemadness.org/talk/. There are Australian members who might know.