EJlmate of Utenfils and Men for the Work of vefiniiig Saltp:tre, ' 25 



Thefc waters are therefore very drfferent in their nature. The water of the wafliings i« 

 really a mother water. It muft be collected in veflcls, and treated with potafh by the 

 known procefles. It mud be evaporated to 66 degrees (or 1,848 fp. gr.), taking out the 

 jnuriate of foda as it falls. This folution is to be faturated with 2 or 3 per cent, of potaQi, 

 then fuffered to fettle, decanted and poured into cryfiallizing veffels, where 20 per cent, 

 of water is to be added to keep the whole of the muriate of foda fufpended. 



The waters which are thus obtained by treatment of the mother water, niay be mixed 

 ■with the water of the firft cryftallization. From thefc the marine fait may be feparated 

 by fimplc evaporation ; and the nitrate of potafli, which they hold in folution, may be 

 :aftcrwards obtained bv cooling. 



The fmall quantity of water made ufe of to wafli and whiten the refined faltpetre, con- 

 tains nothing but the nitrate of potafli : it may therefore be ufed in the folution of the 

 faltpetre when taken from the tubs. 



From this defcription it follows, that a manufadtory for the fpeedy refining of faltpetre 

 ought to be provided with (i) mallets or rammers for pounding the faltpetre, (2) tubs for 

 wafliing, {3) a boiler for folution, (4) a cryftall'zing veflel of copper or lead, in which 

 the faltpetre is to be obtained by cooling, (5) balkets to drain the cryftals, (6) a wooden 

 cafe or hopper for the laft wafliing and draining the faltpetre, (7) fcales and weights for 

 weighing, (8) hydrometers and thermometers to afcertaiii denfities and temperatures, 

 (9) rakes to agitate the liquor in the cryftallizing veflel, (10) flcimmers to take out the 

 cryft:als and convey them to the baflcets, ( 1 1 ) fyphons or hand-pumps to empty the boilers. 



The number and dimenfions of tRefe fevcral articles mufl: vary according to the quantity 

 of faltpetre intended to be refined. 



If it be propofed to refine ten thoufand weight of crude faltpetre per day, the requifite 

 men and utenfils may be determined as follows : 



Part of the ground near the magazine may be difpofed for conveniently breaking and 

 pounding the faltpetre. 



This ground-fiiould be paved with large flat fl;ones very uniformly, or with thick pieces 

 of wood. Mallets fimilar to thofe ufed in pulverizing gypfum may be applied to this ufe. 

 Two men are fufiicient to weigh and pound the faltpetre, and flow it in the magazine. 



As the three wafhings require two days, and each tub can hold only five or fix hundred 

 pounds of faltpetre, it would require twenty days to refine ten thoufand weight (with one tub). 



Thefe tubs are two feet and a half in height, and the fame in diameter. They muft be 

 very well made, in order that the water of the wafliing may not leak out. ^ They are to be 

 placed folidly on a plane flightly inclined, of fuch a material as fliall not imbibe the water 

 which may be fpilt during the operation, but tranfmit it to a refervoir placed at the 

 extremity of the row of tubs, ■ - 



Twenty of thefe tubs mufl: be difpofed in two parallel lines ; the planes on which they 

 arefet may incline towards each other, and form, by their union, the gutter or cavtty for 

 tranfmittlng into the common refervoir fuch waters as may efcape. Thefe tubs are per- 

 forated at the diftance of two inches from the bottom. 1 he aperture is clofed by a fpigot* 



Four men may be appropriated to the wafhing of the faltpetre. It is a part of their 



duty to convey the" faltpetre from the magazine, to the tubs, and from the tubs-lo the boiler. 



Vol. II.— Afril 1798. E J 



