131?.] Elements of Organic Nature are comlincd. 95 



of citric acid, and cannot take place in other circumstances. The 

 conrposition of citric acid may then be expressed by this formula, 

 H -h C + O. . 



My expectation of being able to illustrate the composition of this 

 ecid by the examination of a suhcitrate of lead was disappointed, 

 by the property which the neutral citrate has ot dissolvi:'g in am- 

 monia, and of forming a triple suit, from which the ammonia could 

 not he driven otr even in a vacuum. 



Thenard and Gay-Lussac, in their experiments on citric acid, 

 obtained as a result C"33 Ijydrogen, 33*81i carbon, 55)859 oxygen. 

 This result differs very much from mine. Th.?ir analysis of the 

 citrate of lime employed by them shows that verv little water of 

 combination remained in the salt. Besides, a correction for the 

 water of combination remaining in the salt would only increase 

 the difference between our results. I am unable to divine the cause 

 of this difference. 



2. Tartaric acid, — 100 parts of tartrate of lead analysed by 

 combustion, left G2*5 of oxide of lead in one experiment, and 

 62'48 in another. This differs but little from my old experiments 

 in wjjich I found 622 per cent, of oxide of lead in this salt. It is 

 composed then of 



Tartaric acid 37*5 100 



Oxide of lead 62-5 167 



100-0 

 But 167 of oxide of lead contain 11*94 of oxygen. In one of 

 my old experiments I found that 100 of tartaric acid are neutralized 

 by 70-4 of potash, in which there are 11*93 oxygen. I have shown 

 likewise in tiicse experiments, that tartaric acid must contain five 

 times as much oxygen as the base by vvhieh it is saturated. 



1~- of tartrate of lead, equivalent to 0*5 of tartaric acid, pro- 

 duced in different experiments from 0*161 to O-JGJ of water, equi- 

 valent to from 3*79 to 3 SO7 per cent, of the weight of the acid of 

 hydrogen.. In the same experiments I obtained from 0-654 to 

 0*661 of carbonic acid, equivalent to from 35*36 to 35*98 per 

 cent of the weight of the acid of carbon. The acid is then com- 

 posed of 



Hydrogen 3*807 



Carbon 35*980 



Oxygen 60*213 



1 00*000 

 But 11*94 X 5 = 59*7. If we examine tlic ratio of these num- 

 bers, we find that the liydrogcn is to the oxygen :: C6 : ICOO; that 

 is to say, that there is a volume of eacli. 'I'he 'arbon constitutes 

 ■J of a volume. But if the oxygen is in reality five volumes, it is 

 combined with five volumes of iiydrogcn and four volumes of car- 

 bun. Supposing then tartaric acid a compound of 5 11 -j- 4 C -f 

 i O, calculation givei its composition as follcv.-s: — 



