XV. 



On Tico Neiv Crystalline Compounds of Zinc and Antimony, and on the Cause of the 

 Variation of Composition observed in their Crystals. 



By JOSIAH p. COOKE, Jr., A.M., 



EBVUiG PROFESSOR OF CHB^IST&T IN BJiaVABD rNU'ERStir. 



{Communicated June 27, 1854.) 



The metallic alloys have not received that share of investigation which their im- 

 portance would seem to demand ; nevertheless, the researches which have been made 

 during the last twenty years are sufficient to refute the foiTuerly received opinion, that 

 they are all merely mechanical mixtures. In 1830, F. Eudberg,* while determining 

 the latent heat of the alloys of tin and lead, observed that, when the proportions of the 

 two metals corresponded to PbSns, the temperature of the melted alloy fell uniformly 

 to the point of fusion, 187° C, where it remained constant for some minutes, owing to 

 the escape of latent heat. If, however, the metals were mixed in other proportions 

 while the same fixed point was observed, he found that the thermometer also stood 

 still at a second and higher point, which approached nearer and nearer the point of 

 solidification of lead or tin, according as the alloy contained a greater excess of one or 

 the other of these two metals. From these facts he concluded that the alloy PbSn, 

 was a definite chemical compound, having but one point of solidification, and that the 

 other alloys were mixtures of this compound with one or the other metal, and that the 

 two stationary points of temperature corresponded, the lower to the point of solidifi- 

 cation of PbSus, the higher to that of tin or lead, according as one or the other was 

 present in excess. Similar phenomena were afterwards observed in several other alloys, 



• Poggendorf, Annalen, Vol. XVIII. p. 240. 

 VOL T. NEW SERIES. -46 



