268 Researches respecting the radical of Benzoic Acid. 



The variation of the composition of benzoic acid, thus obtained, 

 from that which Berzelius found by the analysis of the benzoate of 

 lead, caused us at first to mistrust our own analysis. Upon nearer 

 inspection however, we found it necessary to admit, that the cause of 

 the difference between the two analyses should be sought in the com- 

 position of the salt analyzed by Berzelius. We therefore undertook 

 the analysis of the acid united to a base, and chose the benzoate of 

 silver because of the facility with which it is obtained pure and crys- 

 tallized, and because the oxide of silver shews but little disposition to 



form compounds. 



Neutral nitrate of silver mixed with an alkaline benzoate in solu- 

 tion, gave a thick white precipitate, which by warmth became crys- 

 talline, and completely dissolved in a greater quantity of boiling wa- 

 ter. By cooling the solution, oxide of silver was deposited in long' . 

 shining crystals, which by drying under the air pump, neither lost 

 their lustre, nor diminished in weight. 



By heating in a porcelain crucible, this salt melts, puffs up, and af- 

 ter the deposited charcoal is consumed, leaves very white metallic: 

 silver. In this manner we determined the atomic weight of the acid. 



I. 0.391 gramme of benzoate of silver left 0.1 S4 of metallic silver. 

 II. 0.436 " of the same gave 0.205. 



According to these numbers, the composition of the salt is, 



I. II. 



Oxid of silver, . 50.56 . 50.52 



Benzoic acid, . 49.44 . 49.48 



And the atomic weight of the acid as the mean of both analyse?, 

 is 142.039. 



We now submitted the salt of silver to ignition with oxide of cop- 

 per, and obtained from 0.600 grammes of the salt, 0.797 grammes of 

 carbonic acid, and 0.122 of water. 



The composition of the acid, as deduced from these numbers, con- 

 sists in 100 parts of 



Carbon, 



Hydrogen, 

 Oxygen, 



74.378 



4.5b7 



21.055 



Calculating from the atomic weight already found, we obtain, 



14 atoms carbon, . 107.0118 . 74.43 



10 " hydrogen, . 6.2397 . 4.34 



3 " oxygen, .. 30.000 . 21.23 



143.2515 100.00 



