Dr. Thomson on Oxalic Acid. 65 
succeeded in separating the whole of the lime without using 
any sensible excess of oxalic acid. 
558 grains of the acid solution were employed, a quan- 
tity which is equivalent to 58.3 grains of the crystallized 
acid. 
2. The oxalate of lime, after being well washed and drained, 
and exposed for a week to the open air, at a temperature of 
about 6>o°, weighed 7b grains ; but upon being left on the sand 
bath for some hours in a temperature between 200° and 300°, 
its weight was reduced to 72 grains. 
3. These 72 grains of dry oxalate of lime were put into an 
open platinum crucible, and gradually heated to redness. By 
these means they were reduced to 49.5 grains, which proved 
to be carbonate of lime. The crucible was now exposed to 
a violent heat in a forge. Nothing remained but a quantity of 
pure lime weighing 27 grains. 
4. From this experiment we learn, that 72 grains of dry 
oxalate of lime contain 27 grains of lime. Of consequence, 
the oxalic acid in this compound must be 45 grains. But the 
weight of crystallized oxalic acid actually used was 58.3 grains, 
a quantity which exceeds the whole acid in the oxalate by 
33.3 grains. These 13.3 grains are the amount of the water of 
crystallization, which either did not unite with the salt, or was 
driven off by the subsequent exposure to heat. Hence crystal- 
lized oxalic acid is composed of 
Real acid - - 45. 
Water - - 13.3 
MDCCCVIII. 
K 
58.3 
