185 On the method of extract wg Saltpetre, [April 



For this purpose the potass of commerce, or sulphate of potass, 

 or simply ashes may be used. 



The mt thod of employing the potass, consists in dissolving' it 

 in double its weight of water, and in this state to mix it well with 

 the saltpetre water — this gives place on the spot to 'a separation of 

 the earthy bases from their combinations replaced by the potass, 

 and produces a precipitate, which when the operation of agitating 

 or stirring the solution ceases, deposits at the bottom of the pan. 



The quantity of potass required to be used may as a general rule 

 be estimated at one third of the number of degrees indicated by the 

 Areometre, as it is better to use too little than too much — thus for 

 instance if the saltpetre water marks by the Areometre 15 degrees ; 

 a vessel containing 400 Kilogrammes of this water will require 5 per' 

 cent or 20 Kilogrammes of potass, and so on according to the de- 

 gree indicated by the Areometre. 



Oyi the decomposition of the earthy nitrates, by the Sulphate of 

 potasse, as practised at the Manufactory of Saltpetre at Mont- 

 pellier, by M. Berard. 



The Sulphate of potass which is frequently to be procured at a 

 very small price results principally from the combustion of a mixture 

 of Sulphur and Saltpetre, in the fabrication of Sulphuric acid, that 

 which is obtained by other means is generally extremely pure and is 

 sold to advantage to chemists &c. 



Having procured a sufficient quantity of sulphate of Potass to fill 

 several pans or troughs, it is to be broken or pounded, and thrown 

 into pans with a mixture of wood ashes, heaped up above the sur- 

 face of the pan, and left a short time till the acid is absorbed. 

 Water is then to be sprinkled by little at a time over it, until the 

 water overflows the surface, and allowed to rest for a few hours, 

 when the cock near the bottom is to be opened, and the water al- 

 lowed to flow from it into a reservoir. 



This water will at first be discoloured and cloudy, but will in a 

 short time become clear, and when tested by the Areometre will 

 mark about 20 degrees. 



The matter cor.tamed in the pans will have fallen considerably, 

 and ought to be filled up with fresh materials, and the washing with 

 water continued as before, to obtain as much of the salt as possible. 

 If the water flowing from the pans when tested by the Areometre is 

 found to be too feeble, it must be used to wash another pan, till it 

 acquires a density of about 20 degrees. 



