30 
ON SULPHATE OP POTASH. 
The state of aggregation of sulphate of potash appears 
to influence its solution very considerably. 
Exp. 5. — On adding one part of sulphate of potash in 
crystals to fourteen parts of water, kept at a temperature 
of 60°, the solution was not effected in three days, although 
the vial was frequently agitated ; and it was found necessary 
to add two more parts of water to complete the solution. 
This fact will probably account for the statement of some 
Chemists, that sulphate of potash requires sixteen parts of 
water for its solution. 
Exp. 6. — Considerably more sulphate of potash, in powder. 
was added to distilled water, than the latter was capable of 
dissolving. After keeping the mixture for several hours at 
60°, the solution was found to contain one part of salt to 9.5 
parts of water. This very nearly accords with Gay-Lussac's 
statement. 
The difference between the results in Exp. 1 and Exp. 6 
appears to arise from the fact, that the particles of which the 
powdered sulphate of potash consists, are not all of equal di- 
mensions. On adding a portion of this powder to water, as 
in Exp. 1, the smaller particles are first dissolved, and when 
the solution has nearly attained its point of saturation, the 
solvent power of the liquid becomes incapable of overcoming 
the molecular attraction of the remaining particles. This so- 
lution, however, although incapable of dissolving the larger 
particles, would still take up a farther quantity of the salt in 
a state of minuter division, as occurs in Exp. 6. 
There can be no doubt, I presume, that the increased so- 
lubility of sulphate of potash when mixed with sesquicar- 
bonate of soda, arises from the partial decomposition of these 
two salts, which is quite in accordance with what occurs in 
many analogous cases. Thus, it has been found, as noticed 
by Mr. Richard Phillips, that sulphate of barytes may be de- 
composed by carbonate of potash. Sulphate of strontian is 
also subject to a similar decomposition. 
