SANGER AND GIBSON. — DETERMINATION OF ANTIMONY. 725 



it as a means of determining the temperatures by observation of the 

 electromotive forces produced. 



The study, as far as it concerned the separation of arsenic and anti- 

 mony, is not completed, hence the results are reserved for another 

 publication. Sufficient data were obtained to show that there was a 

 possibility of separating arsenic and antimony by the difTovence in 

 decomposition points of their diluted hydrides, and the investigation 

 will be continued in this laboratory. Concerning the arsenic hydride, 

 it will be sufficient to say that an amount of diluted hydride corre- 

 sponding to 0.04 mg. of arsenious oxide is completely decomposed at 

 340° if the length of capillary heated is 3.5 cm. ; at 410° if the length 

 is 2 cm. ; and at about 450° if the length is 1 cm. Conversely, no 

 arsenic is deposited from this amount at 330° with a heating length of 



I cm. ; none at about 300° if the length is 2 cm. ; and none at about 

 250° if the length is 3.5 cm. 



We were unable to get as definite results on the decomposition of 

 antimony hydride, since the difficulty in deposition of the antimony 

 mirror on the glass tubing used, which was afterwards solved as ex- 

 plained later, prevented the results from being uniform. We think, 

 however, that we are safe in saying that amounts of hydride from 0.1 

 mg. antimonious oxide and under are entirely decomposed at a tem- 

 perature of 300° and a heating length of 2 cm. 



Having shown that practically all the antimony may be evolved as 

 hydride from the small amounts to be used in our work, and that the 

 hydride, diluted with hydrogen, can be entirely decomposed by heat- 

 ing the capillary through which the gases pass at a temperature which 

 is easily controlled, we then proceeded to develop a method for estimat- 

 ing minimal amounts of antimony. 



The Apparatus. 



The apparatus ^^ is essentially the same as that proposed by Sanger 

 for the estimation of small amounts of arsenic. Slight modifications 

 of this have been introduced by subsequent workers, many of whom 

 have overlooked the original article. As shown in the figure, the parts 

 comprise a constant hydrogen generator, two reduction flasks, and two 

 heating tubes, so that duplicate determinations may be carried out at 



^'^ This apparatus, wliic^li is shown in Figure 2, is essentially the same as that 

 described, but not illustrated, in the paper of Sanger (1891) above referred to. 

 An apparatus of practically the same principle is shown on page 220 of Volume 



II of tlie Final Eeport of the Koyal Commission on Arsenical Poisoning (Appen- 

 dix 22, Report to the Commission 1)3' McGowan and Finlow on the methods em- 

 ployi'd in testing for arsenic) ; London, Eyre and Spottiswoode, 1903. 



