358 ON TWO NEW CRYSTALLINE COMPOUNDS 



1. 2. 



Weight of antimony, 18.8642 12.5433 



" water displaced at 4° C, 2.8250 1.8785 



Specific gravity of antimony at 15"" compared with water at 4°, . 6.677 



"Weight of zinc, ........ 



" " water displaced at 4' C, 



Specific gravity of zinc at 12^4 C. compared with water at 4", . 7.153 7.153 



In the table on the opposite page, the results of the specific gravity determinations are 

 given in the column headed " Sp. Gr. of Crystals by Experiment." Each number is the 

 mean of at least two, and generally of three experiments, agreeing within a few thou- 

 sandths. The column headed " Mean Sp. Gr. of Zinc and Antimony," is the calculated 

 specific gravity of the same crystals, on the supposition that the two metals had under- 

 gone no expansion on imiting. The last column gives the differences of these two num- 

 bers, and therefore shows the amount of expansion. On examining the table it will be 

 found, — 1st. That the union of antimony and zinc is accompanied with expansion; 2d. 

 That the specific gravity of the ciystals varies slightly with the composition; 3d. That 

 the two minimum specific gravities correspond precisely to the composition of SbZuj 

 and SbZu3, so that the specific gravity increases, and the expansion diminishes, as you de- 

 part on either side from these two centres ; 4th. That the specific gravity of SbZuj is 

 smaller than that of SbZna. We find, then, that the specific gravity determinations 

 confirm, in general, the results of the analyses, pointing out the same two centres of 

 crystallization. 



Crystalline Form. 



It has already been stated, that only two crystalline forms can be obtained from the 

 alloys of zinc and antimony, — that of SbZug and that of SbZna. A large number of 

 crystals of SbZug from difi"erent alloys, and therefore containing different proportions of 

 zinc, were carefully measured for the purpose of ascertaining whether the angle was at 

 all affected by the variation of composition. Fortunately, four different crystallizations 

 afforded excellent crystals, the angles of which could be measured to a minute. The 

 crystals contained, respectively, 43.15, 44.14, 46.90, and 55.00 per cent of zinc, and 

 on all these, by repeated measurements, the angles were found to be identical with those 

 given under Figs. 1 and 2. Crystals from many of the other alloys were also meas- 

 ured, but on account of the imperfections of their surfaces the angles could not be 



