1833.] On the Manufacture of Saltpetre. 25 
to the practice of the operator, the fire is stayed, and the liquor remov- 
ed to large shallow earthen dishes (which are used instead of crystal- 
lizing coolers), placed in rows, and sunk to the brim in soft earth. At 
the end of about 30 hours, the process of crystallization is finished. The 
crystals of saltpetre are taken out of the coolers, and put into baskets to 
drain, after which they are removed to the store-house, ready for sale. 
During the operation of boiling, it occasionally happens that too much 
heat has been used, and the pots are in danger of boiling over. To 
prevent this, the operator has a very simple remedy, which our more 
scientific operators might not be ashamed to take a lesson from—a bunch 
of dry jungle grass is fixed at a right angle, to the end of a stick; this 
is dipped into the liquor, and held up over the pot, and the liquor, which 
it had absorbed, falls down in a shower (cooled by the air) into the 
vessel it had been taken from. The temperature being thus reduced, 
the evaporation proceeds more steadily, and the accidental boiling over 
is prevented. The mother liquor, remaining after the crystals of saltpetre 
have been removed, is returned to the evaporating pots, and mixed with 
a fresh portion of the liquor from the filters, for a second boiling, and 
crystallization. The extraneous salts, such as sulphate and muriate of 
soda, which the filtered liquor from the earth always contains, are partly 
found at the bottom of the pots, (the muriate of soda in particular,) and 
partly in the mother liquor, remaining after the process of crystallization. 
But to separate them more effectually, the manufacturer passes the li- 
quor from the boilers through a piece of coarse cloth, placed in a basket ; 
and when the liquor has drained through, the greater part of the ex- 
traneous salts are found on the cloth. To do this effectually, it is ne- 
cessary, that the liquor should be at the boiling point, otherwise the 
saltpetre liquor would not leave the sulphates and muriates, but would 
form an anhydrous mass. 
The muriate of soda, or common salt, is rendered more pure by a sub- 
sequent boiling. It is then called by the natives pakwa nimak, and 
is sold in the bazars as an article for culinary purposes. The remaining 
extraneous salts—sulphate of soda, nitrate of lime, &c. are returned to 
the earth, to undergoa change by decomposition against another season. 
The nitrate of lime is decomposed by the carbonate of potass, which the 
vegetable ashes, used in the process, contain. When solutions of these 
salts come in contact with each other, a mutual decomposition takes 
place. The nitric acid of the lime combines with the potass, and the 
carbonic acid of the potass combines with the lime. Thus two new salts 
are formed, viz. nitrate of potass (saltpetre), and carbonate of lime. In 
this manner, the old earth, which has already produced saltpetre, is re- 
generated, and rendered productive against other seasons. The native 
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