SANGER AND RIEGEL. — DETERMINATION OF ANTIMONY. 27 



these pieces lengthwise, giving a piece 2 mm. wide and 35 mm. long. 

 This is inserted in a tube of 2 mm. diameter, affixed to the usual depo- 

 sition tube by a rubber connector. A series of standards is then made 

 of any amounts of the smaller quantities of which it may be desirable 

 to get an approximate estimate. The upper part of the Plate shows 

 the bands obtained from amounts of antimony equivalent to 0.5, 0.8, 

 1.0, 2.0, 5.0, and 10.0 mmg. of antimonious oxide. 



The bands obtained from 0.5 and 0.8 mmg. are perfectly distinct, but 

 not always differentiated with clearness. From amounts below 0.5 

 mmg. we have not been able to obtain any indication on the 2 mm. 

 strip. It is safe, therefore, to set the practical limit of the delicacy of 

 the method at 1 mmg. (0.001 mg.) of antimonious oxide (0.0008 mg. 

 of antimony). The absolute delicacy, however, is very nearly half of 

 this amount, — 0.0005 mg. of antimonious oxide, which is equivalent 

 to 0.0004 mg., or one twenty-five-hundredth of a milligram of an- 

 timony. 



Sanger and Gibson 5 were able to detect and identify by the Berzelius- 

 Marsh method 0.005 mg. of antimonious oxide, but the deposit in the 

 tube from 0.001 mg. was faint. It will thus be seen that the "band " 

 method is much more delicate than the "mirror " method. It is also 

 more convenient and accurate, for the bands are subject to no irregu- 

 larity of formation comparable to the difficulty of obtaining a mirror of 

 metallic antimony entirely free from oxide. The mirror method, how- 

 ever, is still of value as a confirmation of the other and a check upon 

 its results. The two methods can be applied, if desired, to different 

 portions of the solution which has been prepared for analysis. 



The application of the method to the analysis of products containing 

 antimony is under consideration in this laboratory, but we have con- 

 tented ourselves for the present with showing that very small amounts 

 of antimony may be estimated by it in a solution properly prepared for 

 analysis. A study of its application should include the separation of 

 small amounts of arsenic or antimony from relatively large amounts 

 of the other, concerning which we have now no reliable information. 



Harvard University, Cambridge, Mass., 

 U. S. A., August, 1909. 



