52 



Mean, 62.0106, ±: .0096 

 Or, corrected, 62.0016 



Now, applying to these mean results the atomic weights 

 already found for oxygen and silver, we get the following 

 values for carbon : 



From the acetate C = 12.0306, ± .0047 



" tartrate " = 12,0356, i .0064 



" racemate "= 12.0413, ± .0063 



" malate " = 12.0408, zb .0054 



General mean " = 12.0363, zb .0028 



Now these results, although remarkably concordant, are by 

 no means unimpeachable. They involve two possible sources 

 of constant error, namely, impurit}^ of material and the vol- 

 atility of the silver. These objections have both been raised 

 by Stas, who found that the silver tartrate, prepared as Liebig 

 and Redtenbacher prepared it, always carried traces of the 

 nitrate, and that he, by the ignition of that salt, could not 

 get results at all agreeing with theirs. In the case of the 

 acetate a similar impurity would lower the percentage of 

 silver, and thus both sources of error would reinforce each 

 other and make the atomic weight of carbon come out too 

 high. With the three other salts the two sources of error 

 act in opposite directions, although the volatility of the 

 silver is probably far greater in its influence than the im- 

 purity. Even if we had no other data relating to the atomic 

 weight of carbon, it would be clear from these facts that 

 the results obtained by Liebig and Redtenbacher must be 

 decidedly in excess of the true figure. 



A different method of dealing with organic silver salts 

 was adopted by Maumene,* in 1846, for the purpose of estab- 



* Ann. d. Chim. et d. Phys., (3,) 18, 41. 



