1834.] On the method of extracting Saltpetre. 186 



It only remains to fill a deep pan or boiler, three parts full with 

 Saltpetre water, and to throw upon it one fifth -J- by weight of the 

 water obtained as abovementioned, the solution is then to be well 

 mixed, and left to settle, when it is to be drawn off from the sur- 

 face, leaving the sediment. 



The expense of this operation is a very small matter, compared to 

 the quantity of nitrate of potass recovered which would otherwise 

 be lost — and the saltpetre will be obtained of a fine white colour. 



On the decomposition of the earthly nitrates by means of ashes. 



Troughs the same as are required to wash the saltpetre earth, or 

 wine barrels with double bottoms pierced with small holes, may be 

 used for this purpose. 



A small quantity of long straw is to be placed between the two 

 bottoms, and also over the false bottom, covered by a piece of coarse 

 flannel or serge. 



Having prepared fresh wood ashes, by passing them through a 

 sieve to separate the charcoal, they are to be moistened with water 

 very equally, so that when taken in the hand ihey may form in 

 lumps, in this state they are to be spread over the flannel, in the 

 first instance to the depth of six centimetres, (about 2| inches) and 

 pressed down lightly at first, and afterwards more strongly by a fiat 

 beater, continue to add fresh layers of ashes pressed down as before- 

 mentioned, until the trough or cask, is about half full, the surface 

 being levelled each time with a trowel. It is necessary to place over 

 the trough in which the ashes are placed a hurdle, or basket with 

 some straw in it, to prevent the loss of water. 



All that is necessary then, is, to pass the Saltpetre wa^er through 

 the ashes, in the proportion of fifteen measures of water, for one of 

 ashes. After which the ashes which remain may be mixed with 

 fresh saltpetre earth, to disengage by washing any saltpetre remain- 

 ing in them. 



If the use of ashes does not altogether supercede the employment 

 of potass, still they will assist, and diminish the quantity of alkali 

 required to be used, according to the proportion of alkali, contained 

 in the ashes. 



To ascertain the quality of the ashes to be used, take about 25 

 lbs. of them, and wash with water, till no salt remains in the ashes ; 

 filter this water, and then evaporate it to dryness in an iron pan, 

 taking care to remove the different salts which may precipitate, 

 during the operation, and to constantly stir the salts at the time of 

 desiccation^ in order that they may not adhere to the bottom of the 



