CONTRIBUTIONS FROM THE CHEMICAL LABORATORY OF 



HARVARD COLLEGE. 



THE DETERMINATION OF SMALL AMOUNTS OP ANTI- 

 MONY BY THE BERZELIUS-MARSH PROCESS. 



Br Chakles Robert Sanger and James Andrew Gibson. 



Presented January 9, 1907. Received March II, 1907. 



The Berzelius-Mar.sh method has been successfully applied to the 

 quantitative determination of arsenic. On the one hand, the process 

 which depends upon the weighing of the " mirror," first suggested by 

 Berzelius himself,^ has been carefully worked out by Gautier,^ Chitten- 

 den and Donaldson,^ and several others, and is applicable to cases in 

 which the amount of arsenic is too small for precipitation as sulphide 

 or in which the separation of the latter would be inconvenient. On 

 the other hand, for cases in which the mirror of arsenic is too small for 

 weighing, or in the rapid estimation of very small amounts, methods 

 similar to that which was first described by one of us ^ have found 

 wide application. 



The extension of the gravimetric Berzelius-Marsh method to the de- 

 termination of antimony is impossible for the reason that, under ordi- 

 nary circumstances, a large part of the antimony is deposited on the zinc 

 in the reduction flask and does not leave the solution as the hydride. 

 In attempting to apply the method of Sanger * to the determination of 

 small amounts of antimony, we were met not only by this difficulty, 

 but also by the well-known irregularity in the deposition of the anti- 

 mony in the heated tube, the temperature at which the antimony 

 hydride is decomposed being so low that much of the deposit is formed 



^ Berzelius, Jahresbericlit, 17, 191 (1837). The decomposition of the arsenic 

 hydride by heating the tube was also suggested by Liebig, Ann., 23, 217 (1837), 

 but the idea of weighing tlie arsenic seems to have originated witli Berzelius. 



2 Bull. Soc. Chim. (2) 24, 2")0 (1876). 



3 Am. Chem. Journ., 2, 2:^>5 (1881) ; Chem. News., 43, 21 (1881). 



* Tlicse Proceedings, 26, 24 (1891); Amer. Chem. Journ., 13, 431 (1891). 

 Abstracted in Jour. Chem. Soc, 62, 882 (1892) ; Jour. Soc. Chem. Ind., 11, 370 

 (1892) ; Chem. Centralbl., 63, 335 (1892) ; Ber., 25, 47, r, (1892) ; Zeitschr. Anal. 

 Chem., 38, 137 and 377 (1899). 



