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A. Preparation of grough from natural saltpetre.

“Take white, clean, bright (natural) saltpetre ad lib., and two new (earthen) jars. Put the saltpetre into one of them, and add some water. Put the jar on a gentle fire until it gets warm” (and the saltpetre dissolves. Skim off) “the scum that rises” (and) “throw it away. Stir up the fire until the liquid becomes quite clear. Then pour it into the other jar in such a way that no scum remains attached to it. Place this jar on a low fire until the contents begin to coagulate. Then take it off the fire, and beat (the crystals) gently.”

F. Use of wood-ash, animal charcoal, &c.

“Take dry willow wood, burn it, and plunge it into water according to the recipe for its incineration. Take three parts by weight of the saltpetre” (just obtained), “and the third of a part of the wood-ash, which has been carefully pulverised, and put the mixture into a jar—if made of brass, so much the better.”

B. Boiling the solution of grough saltpetre.

“Add water and apply heat, until the ashes and saltpetre no longer adhere together. Beware of sparks.”

The original is as follows:—41