OF ZINC AND ANTIMONY. 339 



Quite recently Levol * has examined the alloys of copper and silver, of copper and 

 gold, and of lead and silver, in regard to their chemical constitution, starting on the 

 supposition that these metals are capable of forming definite chemical compounds with 

 each other, and that the ordinary alloys employed in coinage and in the arts are mix- 

 tures of such compounds and an excess of metal, and moreover considering as proved, 

 that, when such melted alloys cool slowly, these compounds tend to separate from the 

 metal, producing inequality of composition in the cast lingot, so that homogeneity in 

 such cases is an indication of definite composition. In the alloys of copper and silver, 

 AggCu^ was the only one of which the lingots carefully cast in spherical or cubical 

 moulds were found, by analysis of portions taken from the interior and exterior of the 

 mass, to have a uniform composition throughout. The alloys either of copper or 

 silver with gold were all found to give homogeneous lingots, and the reverse was the 

 case with the alloys of lead and silver, except PbAgioo- If the hypotheses from which 

 this investigation starts are assumed to be correct, the conclusions to be drawn from 

 the results are, — 1st, that the only definite compound of copper and silver is AgjCu^ ; 

 2d, that either gold is not capable of forming a definite compound with silver or with 

 copper, or else that their compounds, being isomorphous with each other and with the 

 metals, are capable of mixing uniformly in any proportions ; 3d, that lead and silver do 

 not form with each other any definite compounds. 



Karstenf found that dilute sulphuric acid or a solution of sulphate of copper is 

 not decomposed by alloys of zinc and copper when the zinc equals or exceeds the pro- 

 portion corresponding to ZnCu ; also that nitric acid or a solution of nitrate of silver 

 is not decomposed by alloys of copper and silver when the amount of silver exceeds 

 or equals that of CuAg. If, however, the zinc in the first, and the copper in the last, 

 were in excess, he observed that decomposition took place, and continued until these 

 metals were completely removed from their respective alloys, and pure copper or silver 

 left. He opposes the opinion that these alloys are mixtures of a definite compound 

 with an excess of one or the other metal, arguing that, if this were the case, the acids 

 would dissolve only the excess of metal, and leave the compounds ZuCu and CuAg. 



The above are the most important investigations, bearing directly on the chemical 

 nature of metallic alloys, which have fallen under the notice of the author, and they 

 concur to support the opinion that, in many cases at least, the metals tend to unite in 

 definite proportions. The alloys of zinc and antimony, which form the subject of this 



* Annales de Chimie et de Physique, Vol. XXXVI. p. 193, and Vol. XXXIX. p. 163; 

 t Poggendorf, AnnaJen, Vol. XL VI. p. 160. 



