183 On the Dejinile JProportions in which the [March, 



evaporated is not decomposed, and, being mixed with the gas, it is 

 not deposited in the water, but is carried probably in the form of gas 

 into the tubes and pneumatic trough. In consequence of this cir- 

 cumstance, the analysis of this acid always gave a loss too great to 

 be ascribed to oxygen. I thought at first that my analyses of the 

 benzoates were inaccurate ; but having repeated them with the 

 same result, it became obvious that the cause of the anomaly must 

 be something different. After having made analytical experiments 

 on benzoic acid in a free state, and in that of benzoate and sub- 

 benzoate, I found that the loss diminished in proportion as the acid 

 was more strongly retained by the base ; so that the subbenzoates 

 gave a less loss than the other salts. This induced me to examine 

 vvhether there was really an evaporation of undecomposed acid 

 during the experiments. 1 observed that the vessels through which 

 the gas had passed, and in which it remained, had diminished in 

 transparency, though not very remarkably. As these experiments 

 were mostly made in the very severe winter of 1813-14, it happened 

 sometimes that the temperature of the mercury in the trough was 

 at 3^ or at zero. On this account a greater quantity of the acid had 

 been deposited in the part of the tube which entered the mercury, 

 where 1 found sufficient to be collected and examined. It possessed 

 the characters of benzoic acid ; but its odour was a little empyreu- 

 matic. 



The analysis of a quantity of subbenzoate of lead, containing 

 C'317 of acid, gave 0'1414 water and 0"8645 carbonic acid. Hence 

 the acid is composed of 



Hydrogen 5- 1 6 



Carbon 74*4 1 



Qxygen'. 20-43 



100-00 



The most simple ratio in which these bodies can be combined is' 

 30 + 12 H + 15 C, or (which conaes to the same thing) 

 O + 3 H -f- 5 C. By turning these volumes into numbers we 

 have the composition of the acid per cent, as follows : — 



Hydrogen 5-27 



Carbon 74-71 



Oxygen , , 20-02 



100-00 



Now G-GO X 8 = 20 07. Hence it follows that the analysis of 

 the subbenzoate has given an exact result ; while neither the ben- 

 zoate nor fused benzoic acid ever gave more than 4'8 hydrogen and 

 70 carbon. 



9. lanmn from Nntgalls. — I prepared a cold infusion of nnt- 

 galls in water, which I mixed with ammonia till it ceased to act as 

 3n acid. 1 then added a little of the infusion not mixed with 



