96 On the Defnite Proportions m which the [Fkb. 



Hydrogen 3-951 



Carbon 36'167 



Oxygen 53-882 



100-000 

 The true capacity of saturation of this acid is then 11-976, 

 instead of 1 r94 given by experiment. It follows from this, that 

 in the neutral tartrates the carbon of the acid is combined with li 

 volume of oxygen, including the oxygen of the base. I have not 

 been able to obtain a subtartrate of lead. 



Let us now examine the result of the analysis of this acid made 

 by Thcnard and Gay-Lussac. They found it composed of hydrogen 

 6-629, carbon 24-05, oxygen 69-321 ; but they employed tartrate 

 of lime, in which they supposed 77*577 of tartaric acid. That is 

 to say, that they paid no attention to the water of combination of 

 the citrate of lime. To find the quantity of this water 1 made the 

 following experiments. 



I dissolved neutral tartrate of potash in water, and precipitated it 

 by muriate of lime ; the neutrality was not altered. Hence it fol- 

 lows, that 100 tartaric acid saturate a quantity of lime containing 

 1 1-976 of oxygen ; that is to say, equal to that in the potash sepa- 

 rated from the tartaric acid. I burnt 100 parts of this tartrate of 

 lirae in a platinum crucible, till the lime was reduced to a caustic 

 state. To be quite sure of getting rid of all the carbonic acid, I 

 allowed the lime to unite with a little water, and exposed it again 

 to a strong heat; its weight was not altered. It weighed 21-64 

 parts, and dissolved in diluted muriatic acid without the smallest 

 disengagement of gas. 21*64 parts of lime require for saturation 

 50-55 of tartaric acid ; hence it follows, that tartrate of lime is 

 composed of 



Tartaric acid 50-55 



Lime 21-64 



Water of combination 27*81 



100-00 



But 21-64 of lime contain 6-094 of oxygen, and 27 '81 of 

 water, 24-54. Now 6094 X 4 = 24-376 ; "that is to say, that 

 thajsalt contains a quantity of water of combination, the oxygen in 

 which is four times' that in the lime. It follows from this, that 

 what Thcnard and Gay-Lussac considered as 100 tartaric acid, was 

 in fact a mixture of 65-46 of acid with 34-54 of water. If we 

 subtract this proportion of water from their result, we obtain tar- 

 taric acid composed of 



Hydrogen 3-912 



Carbon 36-888 



Oxygen 59-200 



100*000 

 which agi-ees perfectly with the result of my experiments. 



