144 Dr. Thomson's Experiments to determine the [Aug. 



loss of some of it, about 16 grs. of shreds of platinum were put 

 into the phial. 



It is obvious that 6-75 grs. anhydrous carbonate of soda are 

 composed of 



Grains. 



Soda 4-00 



Carbonic acid 2-75 



6-75 



"Now as 4 represents the weight of an atom of soda, it is 

 obvious .that the weight of the acetate of soda obtained by dis- 

 solving 6 - 75 grs. of carbonate of soda in acetic acid, and then 

 drying the salt, diminished by 4, must represent the weight of 

 an atom of acetic acid. Now in the two successful trials which 

 1 made, the acetate of soda weighed exactly 10-2-5 grains ; and 

 10-25 — 4 = 6*25; consequently I consider 6*25 as represent- 

 ing the true weight of an atom of acetic acid. 



It may be worth while to relate the attempt which I made to 

 deprive acetate of lime of the whole of its water, though that 

 attempt was unsuccessful. 6-25 grains of calcareous spar were 

 dissolved in acetic acid in a silver crucible, the solution was 

 evaporated to dryness in a very moderate temperature, and the 

 dry salt was left for 12 hours exposed to the open air in the 

 laboratory. The weight of the salt was 1 1-36" grs. It was now 

 exposed to the temperature of 450° for four hours. By this 

 treatment, the weight was reduced to 10-22 grs. ; and no further 

 . diminution of weight was produced, though the same tempera- 

 ture was kept up for many hours. 



Now it is obvious from the experiments above related with 

 acetate of soda that if the acetate of lime had been completely 

 deprived of its water, its weight would have been 9-75 grs. ; for 

 it must have consisted of 



Lime 3*5 



Acetic acid 6*25 



9-75 



The water in the salt when it was gently evaporated to dry- 

 ness was 1-61 gr. or nearly an atom and a half. I was not able 

 at the temperature of 450° to drive off the whole water; what 

 remained must have weighed 0*47 gr. or rather more than the 

 third of an atom. 



The preceding experiments, which I have detailed as briefly 

 as possible, though sufficiently minutely, I trust, to put it in the 

 power of others so inclined to repeat them and verify their accu- 

 racy, lead to the conclusion that the different bodies treated of,- 

 when in a separate and insulated state, have atomic weights 

 represented by the following numbers : 



