OF ARTS AND SCIENCES. 869 



An experiment of Mulder* deserves notice here, as showing the 

 possible existence of a cause of error in the processes made use of 

 both by Rose and Dumas. Mulder dissolved 1 gramme of silver 

 and 0.13 gr. of antimony in nitric acid, added 5 gr. of tartaric acid 

 to retain the antimony in solution, and then determined the silver by 

 precipitation with a standard solution of salt. He obtained 999.125 

 instead of 1,000, while a similar experiment without the antimony and 

 tartaric acid gave precisely 1,000 silver. Upon what this difference of 

 nearly 0.9 milligr. depended was not ascertained. It is not impossible 

 that a trace of tartrate of silver may be precipitated with the chloride ; 

 and if this be so, the chlorine would be estimated too high, whether 

 determined volumetrically, as in the case of Dumas, or by weight, as 

 was done by Rose ; and the atomic weight would consequently be 

 found too low. 



It appears from the foregoing remarks that recent investigations 

 may be considered as having led essentially to two different numbers 

 for the atomic weight of antimony. That of these numbers, the one, 

 120, was first deduced by Schneider, and is supported by a single 

 analysis of Professor Rose. That the other, 122.34 is the result of 

 my own observations, subsequently confirmed by the works of Dumas 

 and of Kessler, of which the first differs only by a few decimals from, 

 and the second agrees precisely with, the equivalent previously ob- 

 tained by me. I have given the reasons which cause me to doubt the 

 correctness of the equivalent assigned by Schneider ; I cannot think 

 that thi'ee experimenters, working independently of each other and 

 using different processes, would arrive at results so nearly identical, 

 were these results very far removed from the truth. 



Five hundred and th.ird meeting. 



January 29, 1862. — Statute Meeting. 



The President in the chair. 



The Corresponding Secretary read a letter of acknowledg- 

 ment from the Corporation of Brown University for a copy 

 of the Memoirs of the Academy, Vol. VIII. Part I. 



Dr. John Dean, of Boston, was elected a Fellow, in Class II. 

 Section 2. 



*■ Die Silber-Probirmethode, voa G. J. Mulder, (Leipzig, 1859,) S. 165. 



VOL. V. 47 



