1821.] Atomic Weight of various Metals and Acids. 145 



Bismuth g.QO 



Tin. 7-25 



Antimony 5.5 



Mercury 25-0 



Arsenious acid 6-75 



Boracic acid 2*75 



Oxalic acid 9-0 



Tartaric acid 9-5 



Citric acid 9-5 



Benzoic acid 15-00 



Succinic acid 6-25 



Acetic acid 8-5 1 



Now all these atomic weights (as has been the case with all 

 those determined before) are not only multiples of 0-125, the 

 atomic weight of hydrogen ; but of 0-25 = the double of that 

 atomic weight. 



Four of these bodies ; viz. 



Oxalic acid, Citric acid, 



Tartaric acid, Acetic acid, 



appear to contain water of crystallization, of which, however, 

 they cannot be deprived completely without undergoing decom- 

 position. This water, or at least a portion of it, they retain 

 even when combined with bases. Thus when oxalic acid is 

 combined with lime, and merely dried in the open air, or at a 

 temperature of 100°, it retains the half of its water; but it may 

 be deprived of the whole of its water by the action of a stronger 

 heat ; yet the acid is not decomposed, for it may afterwards be 

 separated from the lime, and exhibited in its usual crystallized 

 state. Tartaric and citric acid, when they are united to oxide of 

 lead, and the saline compound is dried at the temperature of 

 100°, are completely deprived of their water. On the contrary, 

 I have been unable to deprive acetic acid of its water, when 

 combined with any other base, except soda. 



It would appear from this, that when these acids unite to 

 bases, a certain portion of their water may be separated from 

 them; so that their equivalent number, when they enter into 

 combination, may be represented as follows : 



Oxalic acid 4.5 



Tartaric acid 8-375 



Citric acid , 7-25 



Acetic acid 6-25 ? 



These weights are all multiples of 0-125. They are all multi- 

 ples of 0-25, except the number for tartaric acid, which evidently 

 contains an odd number of atoms of hydrogen. I entertain 

 some doubts at present whether we should consider the crystals 

 w flu sc acids, or the proportions in which they combine with 



Me u< Series, vol. n. l 



