204 
ADULTERATION OF POTASSA BY SODA. 
The chloride of platinum and potassium, after having been 
washed, is maintained at a very gentle heat, until several 
weighings show that it loses no more in weight. The quan- 
tity of chloride of platinum and potassium obtained, serves 
for calculating that of the potassa or chloride of potassium. 
One part of chloride of platinum and potassium corresponds 
to 0.19334 of potassa, or 0.30565 of chloride of potassium. 
Finally, the quantity of chloride of sodium is found by sub- 
tracting the quantity of chloride of potassium found from 
the total weight of the two metallic chloride?, and the quan- 
tity of soda is then deduced by calculation. One part of 
chloride of sodium corresponds to 0.53289 of soda. 
This process is not at all applicable to the object in ques- 
tion : in the first place, on account of its expense ; and in 
the next place, because it requires an experienced chemist; 
and also because almost all kinds of potassa contain chloride 
of potassium or chloride of sodium, or else both chlorides 
at once, and a more or less inaccurate result must then be 
obtained, according to the proportion of the two metallic 
chlorides contained in potassa, if care have not been taken 
previously to ascertain their quantity, that they may not be 
reckoned in the second instance. 
I have said sufficient to show that this process of separa- 
tion, however valuable it may be, is not very applicable to 
the object in question. 
Another process of separating potassa from soda has 
been indicated by Serullas. It is based on the property of 
perchloric acid, of giving with potassa a compound very 
sparingly, soluble in water and insoluble in alcohol, and 
with soda on the contrary — a compound very soluble in 
water, as well as in the strongest alcohol. The operation 
is ordinarily performed by adding an excess of perchloric 
acid to the solution containing the salts of potassa and soda, 
and cautiously evaporating the mixture, almost to dryness. 
The mass obtained is then treated by alcohol, which dis. 
solves the perchlorate of soda, with the acid which was 
previously combined with the two alkalis, in the case when 
