SANGER AND RIEGEL. — DETERMINATION OF ANTIMONY. 25 



small quantities of hydrogen sulphide will be completely retained by 

 the lead acetate disk. There is little danger from phosphine, for phos- 

 phites and hypophosphites would be oxidized in any treatment of the 

 substance to be analyzed which would convert the antimony to the 

 oxide. Traces of phosphine would be readily recognized in presence of 

 antimony 4 , but are likely to interfere with its estimation. It is obvi- 

 ous that there must be a very thorough separation from arsenic. 



The Evolution of Stibine in the Reduction Bottle. Sanger and Gib- 

 son 5 have shown that amounts of antimony under one milligram are 

 practically all converted to hydride in the presence of zinc and hydro- 

 chloric acid, hence a retention of antimony by precipitation upon the 

 zinc is not to be considered in the estimation of the small amounts pro- 

 vided for by this method. 



Special Precautions. In order to be certain of uniformity in length 

 and density of bands from the same concentration of solution, the fol- 

 lowing points must be observed : 



1. The reduction bottles must be of equal capacity, and other parts 

 of the apparatus of equal dimensions. 



2. The amount of zinc must always be the same, similarly sensitized, 

 and the granulation must be uniform. 



3. The volume and concentration of the acid must be definite. 



4. The moisture conditions in the deposition tube must be carefully 

 regulated, as explained above. 



In the " Analytical Notes " of the article by Sanger and Black 1 , 

 many suggestions will be found which will contribute to a clearer un- 

 derstanding of this method as well, but which are not included here 

 for the sake of brevity. 



Analytical Data. 



The method, as far as it concerns the determination of antimony in 

 a solution properly prepared for reduction, was tested by the analysis 

 of solutions containing varying amounts of antimony, which were un- 

 known to the analyst. See Table, p. 26. 



We do not claim for the method a greater accuracy than within ten 

 per cent. 



The Delicacy of the Method. 



Amounts of antimony as small as five micromilligrams are readily 

 recognized by use of the 4 mm. strip. Less than this quantity may be 



4 See Table II, Sanger and Black 1 . 



5 These Proceedings, 42, 719 (1907) ; Jour. Soc. Chem. Ind., 26, 585 (1907) ; 

 Zeitschr. f. anorg. Chem., 55, 205 (1907). 



