The stabilization of an unstable powder

If the stability of the powder does not deviate greatly from the required standard, it may be improved by soaking it in an alcoholic solution of diphenylamine. 

For this purpose the powder is put into cylinders, filled with a diphenylamine solution, sealed and left to stand for several days. The concentration of diphenylamine must be such that its total amount is no higher than 0.5-1.0% of the weight of the powder. 

Some methods recommend the use of an alcoholic solution with a small addition of ether, e.g. one part of ether per five parts of alcohol. The ether causes part of the nitrocellulose to swell and facilitates the penetration of the diphenylamine solution into the strips or tubes. It should not be used in such an amount as to cause the nitrocellulose to dissolve. 

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