MANUFACTURE OF SULPHATE OF POTASH. 
343 
Manufacture of Sulphate of Potash. — The solution of sulphate 
of potash, resulting from the decomposition of the neutral tartrate 
of potash by sulphate of lime, as above mentioned, is run into 
sheet-iron boilers placed over a coke oven, in which it is concen- 
trated to a certain extent, and is then drawn off into suitable ves- 
sels of iron, or wood lined with lead, in which the evaporation is 
completed by means of steam from the boiler in which the weaker 
liquors are evaporated, the steam thus generated being made to 
traverse coils of lead or iron pipe placed in the solution. The 
sulphate of potash crystallizes as soon as the liquor has acquired a 
certain density, and falling to the bottom of the vessel, or becom- 
ing attached to its sides, is readily fished out by means of strain- 
ers; and its superfluous moisture having been allowed to drain out, 
it is packed in a somewhat damp state in casks ready for sale. In 
this process the spare heat of the coke oven is made available, and 
as the complete evaporation of the solution is accomplished by the 
agency of the steam from the boiler, the greatest possibly econo- 
my is thus effected as regards fuel. This process is, of course, 
applicable to a variety of other purposes where large quantities of 
weak liquors have to be evaporated, and where a market can be 
obtained for the coke manufactured. The principal consumers of 
this impure sulphate of potash are the manufacturers of prussiate 
of potash : it has also been applicable as manure. 
Pure sulphate of potash may be obtained by dissolving the 
impure salt, digesting it with animal charcoal, filtering and re- 
crystallizing. 
Bisulphate of potash may also be obtained by heating the im- 
pure salt with the requisite excess of sulphuric acid, and proceed- 
ing as above. 
Mr. A. J. Phillips read a paper a few days since at the Chemi- 
cal Society on a double salt of sulphate of potash and lime, dis- 
covered by him to exist in the deposit from the sulphate of potash 
in liquors in the boilers before mentioned. As this paper will no 
doubt appear in the Quarterly Journal of the proceedings of the 
Chemical Society, we will confine ourselves to simply mentioning 
the constitution of this double salt as furnished by two analyses of 
Mr. Phillips: 
