Google Books
On some Compounds of Chrome. By M. Grouvelle. From the Annales De Chimie Et De Physique. Acid Chromate of Potash.

The acid chromate of potash is anhydrous: I obtained it by digesting the neutral chromate of potash with nitric acid, separating from the first crop of crystals all those of nitre, and then re-dissolving and again crystallizing the chromate.

When this salt is strongly calcined it melts, and passes to the state of neutral chromate, giving up half its acid, which is decomposed, and leaving an oxyd of chrome crystallised in brilliant green scales. The neutral chromate thus obtained was analysed by a solution of sulphurous ous acid, which changed it instanteously into sulphate of potash, sulphate and sulphite of chrome. The metallic oxyd was precipitated by ammonia, and the sulphate of potash evaporated. The super-chromate, therefore, contains twice as much acid as the neutral chromate, and is composed of

Chromic acid (two atoms) 68.346

Potash (one atom) 31.154

Hope this helps. How this effects shotgun barrels is beyond me.

Pete

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