182 SCIENCE PROGRESS. 



copper chloride or sulphate. This is Laurie's compound, and 

 they draw attention to the fact that many observers have 

 pointed out this alloy as possessing remarkable properties. 

 The alloy Cu 3 Sn has the greatest density of all copper-tin 

 alloys, it does not liquate, and it is the best conductor of 

 heat and electricity. It is difficult to deny its right to be 

 regarded as a chemical compound. 



Mylius and Fromm have made many experiments in 

 addition to the above, and indeed have opened up a new 

 field of research in which much fruit will no doubt be 

 gathered. 



Purely chemical methods have been employed very suc- 

 cessfully by Deville and Debray in their study of the definite 

 compounds formed by zinc or tin with some of the metals of 

 the platinum group. 1 They found that palladium, platinum, 

 rhodium, iridium, and ruthenium, if dissolved in a large ex- 

 cess of zinc, produce alloys that, treated with dilute hydro- 

 chloric acid, do not yield up the whole of the zinc. A con- 

 siderable proportion remains apparently in combination with 

 the noble metal. In the case of rhodium, iridium, and 

 ruthenium there is a very large evolution of heat during 

 their solution in zinc. The residual alloys after treatment 

 with hydrochloric acid leave residues possessing a remark- 

 able property. These residues, well washed and dried at 

 100° C, were heated in vacuo to 300° C, when there was a 

 change of state accompanied by a large evolution of heat. 

 We see here indications of chemical action even when 

 alloys of definite composition have not been found. 



Debray 2 has also studied the alloys produced by dis- 

 solving the above metals in an excess of tin, and in this 

 process, as before, a large evolution of heat was observed. 

 The ingot was afterwards slowly acted on by dilute hydro- 

 chloric acid. In the case of the platinum-tin, as the solution 

 proceeded, brilliant plates were observed to stand out from 

 the surface of the mass. These could be easily detached and 

 analysed, and were found to have very exactly the formula 

 PtSn 4 . By a similar method crystals of the bodies RhSn, 



1 Comptes Rendus, p. 1557, 1882. 

 - Ibid.) p. 1470, 1887. 



