98 EFFLORESCING PROPERTIES 
It is sometimes a desideratum to ascertain if 
and to what amount muriate of potash (an article 
much used in the manufacture of alum) is adul- 
terated with muriate of soda. The means which 
would hitherto be used to accomplish that ob- 
ject are tedious. If, however, a solution of a 
sample of the kind in question be treated with 
sulphate of ammonia till all the muriate of the 
fixed alkali is converted into sulphate, and the 
resulting mixture be evaporated to dryness, and 
calcined till all the ammoniacal salt is dissipated, 
the residue will be the anhydrous sulphate of 
the alkali of the sample: and by placing it under 
an exhausted receiver along with a vessel of 
water we shall be able to ascertain whether it is 
entirely sulphate of potash or a mixture of that 
salt with sulphate of soda :—if it is all sulphate 
of potash it will gain no permanent weight how- 
ever long the experiment is continued, since 
water is not a constituent part of the crystals of 
that sulphate; but if there is any sulphate of 
soda present it will gain weight till that portion 
becomes of the same constitution as it is of when 
it exists in the crystallized state. 
