95 



May 21. 



SIR Wm. R. HAMILTON, LL.D., President, in the Chair. 



Mr. Robert Mallet read a paper " On the Physical Pro- 

 perties and Electro-Chemical and other Relations of the Al- 

 loys of Copper with Tin and Zinc." 



These experiments are collateral to the researches on the 

 action of air and water on iron, upon which the author has 

 been engaged at the desire of the British Association. In 

 the progress of these inquiries, it became necessary to deter- 

 mine the action of solvents on iron in presence of various 

 definite alloys of copper and tin and of copper and zinc. 

 Hence it was requisite to form many such alloys in rigidly 

 assigned proportions as to their constituents, a matter known 

 to experimenters to be one of difficulty, especially in the case 

 of so oxidable and volatile a metal as zinc. The difficulties 

 were overcome by a peculiar arrangement of apparatus, per- 

 mitting the metals to be fused and combined in close vessels. 

 The results were verified by assay. Having these alloys 

 which belong to the classes of brass or gun metal, of which 

 most of our instruments of precision are made, and their con- 

 stitution being atomic and certain, it seemed useful to de- 

 termine some of their properties for practical purposes. The 

 results are given in the two annexed tables. 



The author has also determined the numerical conditions 

 governing the i-ate of solution, or amount of loss sustained 

 in a given time by equal surfaces of iron in solvent menstrua, 

 when in presence of all these alloys, and of the alloys them- 

 selves. Tables of these were presented : the results do not 

 seem to coincide with the law of volta equivalents, which is 

 explained by showing galvanometrically that the c — and 

 I -\- metals of the alloy are often not acted on equally by a 

 solvent ; thus, that an alloy of Zn^ + Cu^ may assume a cop- 

 per surface after a certain time of reaction. This circumstance, 



