1834.] On the method of extracting Saltpetre. 184 



parts of the solution by weight, 85 parts consist of water, and 15 

 parts of salt. 



The material containing the Saltpetre having- been brought to a 

 fine powder, is to be placed in large wooden troughs having holes 

 cut at intervals along one of their long sides, and closed with wood- 

 en pegs. Water is then to be sprinkled over the earth, till it over- 

 flows and remains above it about 1 decimitre (nearly 4 inches) and 

 left till next morning, when the plugs are to be removed, and the 

 water allowed to flow into a reservoir prepared for it. 



Place the Areonietre in this solution and if it marks 15 degrees or 

 upwards the solution may be set aside to be evaporated, if under 15 

 degrees, this water, together with that which results from the fur- 

 *jier washing of the first trough, is to be used in washing the earth 

 in the second trough. 



Although it is necessary in the first operation, that the water 

 should remain upon the earth for about 10 hours, in the subsequent 

 washings two hours will be sufficient, or the plugs may be removed 

 altogether. 



Water is to be sprinkled as before over the earth in the first 

 trough, till that which flows from the apertures, marks only J of a 

 degree by the Areometre, when the earth may be removed from the 

 trough, and replaced with fresh earth, to be treated as before, or to 

 receive the waters from the second trough, if found to be so feeble as 

 to require it. 



River or rain water ought to be used for these washings in prefer- 

 ence to well water. 



On the treatment of the Saltpetre water, by potasse — or hy 

 Sulphate of potasse, or by ashes. 



Nitrate of potasse is never found alone but mixed with muriate of 

 soda, earthy parts and frequently also by sulphates— from the result 

 of much experience, we may consider the saltpetre materials as con- 

 taining, about 10 per cent nitrate of potasse — 70 per cent nitrous 

 earth, 15 per cent muriate of soda, and 5 per cent of earthy muri- 

 ates — so that taking 100 Kilogrammes of the water obtained from 

 washing the saltpetre earth, which marks 15 degrees by the Areo- 

 metre (indicating that the solution contains 15 Kilogrammes of salts) 

 there is only 12 Kilogrammes of nitrate of potasse — and earthy ni- 

 trates ; or about IJ nitrate of potasse —and 10 J earthy nitrates. 



It is this latter portion of earthy nitrates which it is necessary to 

 decompose and to convert into nitrate of potass. 



