208 ADULTERATION OF POTASSA BY SODA. 
All these considerations show the difficulties which the 
solution of the problem entails. 
I then asked myself whether it would not be possible to 
effect a separation by converting the alkaline carbonates 
of the potassa to be examined into bicarbonates, and then 
separating by means of a solution of bicarbonate of soda, 
completely saturated at the ordinary temperature, the bicar- 
bonate of soda formed from the bicarbonate of potassa ; for, 
on one hand, a saturated solution of salt cannot naturally 
dissolve more of the same salt at the same temperature, 
whilst, on the other hand, it might be expected that the 
solution of bicarbonate of soda would dissolve not only the 
bicarbonate of potassa, but also the accidental impurities of 
the potassa, such as the chloride of potassium, the chloride 
of sodium, the sulphate of potassa, &c, and would leave 
only the bicarbonate of soda rising from the simple carbo- 
nate of soda contained in the potassa, and which would ena- 
ble the quantity of this carbonate to be readily calculated. 
In order to ascertain whether this idea was practically 
executable, I wished first to convince myself of the solu- 
bility of sulphate of potassa, chloride of potassium, and 
chloride of sodium, (the ordinary impurities of potassa) as 
well as of bicarbonate of potassa in a solution of bicarbo- 
nate of soda : I weighed with this object four times 1,000 
grains of a solution completely saturated at 54.5°F., of car- 
bonate of soda, and I added to them these four salts by 
grains, until they were no longer dissolved. When the 
last grain added remained at the bottom of the vessel 
without being dissolved, after the liquor had been care- 
fully stirred, and at a temperature of £4.5° F., I found that 
there was dissolved in 100 parts of the solution of bicarbo- 
nate of soda — 
Bicarbonate of potassa - - - 245 grains 
Sulphate of potassa - - - - ISO " 
Chloride of potassium - - - 285 " 
" sodium - - - - 75 " 
