214 
ADULTERATION OF POTASSA BY SODA. 
I say induced me to pursue this subject still' further, and 
with this view I had recourse to tartaric acid. 
I expected to find, in the property which bitartrate of 
potassa possesses, of dissolving only with considerable diffi- 
culty in water, the most convenient means for founding a 
process of testing potassa, on the employment of this acid ; 
for it must be foreseen, that if to a sample of potassa con- 
taining soda, be added the proportion of tartaric acid 
precisely necessary for converting the two alkalis into 
bicarbonates, the bitartrate of soda, in presence of a suffi- 
cient quantity of the solvent, should remain in solution 
on account of its greater solubility, and the bitartrate 
of potassa should be precipitated, under the form of a 
crystalline powder, either in greater part or entirely, 
when all the liquors employed have been previously satu- 
rated with bitartrate of potassa at the ordinary tempera- 
ture : this deposit might then easily be measured. 
In order to make a trial of this theoretical supposition, it 
was necessary first to solve the following question — " Hoiv 
much bitartrate of soda is dissolved in a solution of bitar- 
trate of potassa, at the ordinary temperature?" 
In order to solve this question, I put into 240 grains of a 
solution of bitartrate of potassa, completely saturated at the 
ordinary temperature, crystallised bitartrate of soda, until 
the last portion added remained undissolved, after the mix- 
ture had been well stirred — 13.6 grains of bitartrate of soda 
were dissolved. Consequently, 100 parts of concentrated 
solution of bitartrate of potassa dissolve 5.6 parts of bitar- 
trate of soda, or, to dissolve 1 part of the latter salt, 17.8 
parts of the saturated solution of the bitartrate of potassa 
are required. If, therefore, 100 grains, for example, of an- 
hydrous carbonate of soda be converted into 35S.1 of bitar- 
trate of soda, by the necessary quantity of tartaric acid, 
6,394 grains of solution of bitartrate of potassa, completely 
saturated, at the ordinary temperature, are required for 
holding in solution the bitartrate of soda formed. 
