OF ZINC AND ANTIMONY. " 349 



In the alloys between 20 and 33 per cent of zinc, well-defined crystals, like those 

 described under SbZno, were formed, and finally there separated from the alloys be- 

 tween 33 and 42 per cent of zinc thin metallic plates, which evidently belonged to the 

 same crystalline form. In making the alloys from 43 to 95 per cent of zinc, the zinc 

 was melted first, and when in fusion the antimony added. As the melting point of 

 antimony is much above that of zinc, the fluid zinc acted on the solid antimony as a 

 solvent, dissolving the pure metal, but not the impurity, Avhich rose to the surface, 

 forming a scum. The scum seemed to take with it some of the antimony, and thus 

 caused a loss, which, together with the impurity, was found by experiment to be about 

 three per cent of the antimony used. This resulted in raising the percentage of zinc in 

 the alloy at most about eight tenths of one per cent. The alloys below 43 per cent of 

 zinc were made by melting the antimony first, and then adding the zinc. By this 

 method the loss of antimony was very greatly diminished, and, counting the impurity, 

 was found to be only about one per cent and a half of the antimony used. In prepar- 

 ing the alloys, this loss was always allowed for, and the crystallizations were all made 

 as nearly as possible under the same circumstances, so that any unsuspected cause of 

 error should affect all equally. The crystals formed in the alloys were all analyzed. 

 Several methods for separating zinc and antimony were tried, but the process which 

 finally recommended itself as the most accurate was the following. 



Method and Results of Analysis. 



From five decigrammes to one gramme of the crystals were dissolved in strong hy- 

 di'ochloric acid, to which had been added about one tenth of nitric acid, and the solu- 

 tion heated until the excess of the latter was expelled. It was then diluted largely 

 with water, which precipitated oxide of antimony ; sulphuretted hydrogen Avas passed 

 through the liquid for at least an hour, and the beaker left standing on the sand-bath 

 untU the odor of the gas had disappeared. The precipitate, which was now a mixture 

 of sulphur and of sulphide and a little oxide of antimony, was next collected on a tared 

 filter, and, having been dried at 100° C. and weighed, the amount of antimony which 

 it contained was determined by reducing a portion with hydrogen in the usual Avay. 

 The loss of antimony in the last step can be almost entirely avoided by making the exit- 

 tube of the bulb, used for reducing the mixed sulphide, very small, and keeping an 

 inch of it red hot during the process, and also by a little practice in regulating the 

 temperature of the bulb and the current of hydrogen so as to drive off all the free 

 sulphur before the sulphide begins to decompose. In order to show how great accu- 

 racy may be attained by this method, I will subjoin the results of two reductions of dif- 

 ferent portions from the same mass of mixed sulphides. 



