OF ZINC AND ANTIMONY. 



347 



better adapted for measurement, but they contain an excess of antimony. In their 

 natural state the crystals of SbZna, like those of SbZug, have a silver-white color, and 

 a very bright metallic lustre. Their hardness = 3.5. Their specific gravity varies 

 with their composition ; that of crystals containing 33.6 per cent of zinc = 6.38-i. 

 They are frequently perfect, and their faces so plane and bright that the angles 

 can be measured to a minute. Fig. 3 represents an isolated crystal, which was 

 formed in an alloy containing 32.5 per cent of zinc. The angles given at the side of 

 the figure were all obtained by measurement, except that over Y, which measured six 

 minutes more than that required by the other two. 



on 1 = 122° 15' measnred the same on each side. 



1 on 1 over Z = 115° 30'. 



1 on 1 over Y = 95° 24' measured 95° 30'. 

 1 on 1 overX= 118° 24'. 



The isolated crystals of SbZu., like those of SbZug, are usually small ; but, like the 

 latter, they tend to combine together, with parallel axes, forming large, flat plates. 

 They also frequently unite by a plane parallel to the octohedral face 1, producing a 

 cellular structure which is especially characteristic of the thin plates which form in 

 the alloys between 33 and 43 per cent of zinc. From this it appears that the crystals 

 of SbZn, differ from those of SbZuj, not simply in their dimensions, but also in their 

 whole character and conformation. Indeed, the difierence in this respect could hardly 

 be greater, and will be found to have been of great assistance in the subsequent part of 

 the investigation. 



The composition of the crystals of SbZn^ varies with the composition of the alloy in 

 which they form. The three analyses given below, made by Mr. F. H. Storer, arc of 

 crystals from three different alloys. No. 1 is the analysis of ciystals from the alloy of 

 31.5 per cent of zinc ; No. 2, from the alloy of 29.5 per cent of zinc ; No. 3, from the 

 alloy of 27.5 per cent of zinc. 



