ON SULPHATE OP POTASH. 
31 
When two salts, having different acids and bases, are mixed 
in solution, a partial decomposition of each is frequently ef- 
fected, so that four salts instead of two will be present. Some 
Chemists, as Berthollet, have considered that this partition 
of acids and bases takes place in all cases where salts in so- 
lution are mixed ; but of this there is no sufficient evidence. 
Changes of color and changes of solubility are almost the 
only means we have of determining the point ; so that every 
fresh observation, with reference to these effects, is so far of 
importance. 
That decompositions are effected in sulphate of potash, as 
well as in other salts, in opposition to what is conceived to 
be the prevailing power of affinity, is certain. Thus, on di- 
gesting sulphate of potash in nitric acid, with a slight degree 
of heat, nitrate of potash is obtained ; and yet sulphuric acid, 
under other circumstances, expels nitric acid from its com- 
bination with potash. Hydrochloric acid is also capable of 
decomposing sulphate of potash ; and even tartaric acid, if 
added to a concentrated solution of sulphate of potash, is pre- 
cipitated in the form of bitartrate of potash. In these cases 
the decomposition is only partial ; so also is that which takes 
place on adding carbonate of soda to sulphate of potash. In 
the latter case, sulphate of soda and carbonate of potash are 
formed to a certain extent ; and as sulphate of soda is more 
soluble than sulphate of potash, the solution of the latter will 
be promoted by the admixture of carbonate of soda, in pro- 
portion to the greater solubility of the newly-formed salts, 
and to the extent to which double decomposition takes place. 
London Pharm. Journal. 
