[ 405 J 



XXXVI. Heat of Combination of Metals in the Formation of 

 Alloys. By Alexander Galt, I).Sc, F.R.S.E* 



IN a lecture delivered at the Royal Institution, London, 

 in 1 883, Lord Kelvin f refers to the want of knowledge 

 regarding the heat of combination of zinc and copper. Two 

 or three years ago few experiments and no measurements had 

 been made to determine the heat of combination of these or of 

 other pairs of solid metals. Not only in connexion with the 

 theory of contact electricity in particular, but generally in 

 respect to chemical affinities, it is important that we should 

 have some knowledge in regard to this question ; and at 

 Lord Kelvin's request I have since made an experimental 

 investigation on the heat of combination of pairs of solid 

 metals, particularly zinc and copper. 



The results obtained have been communicated from time to 

 time to the Royal Society of Edinburgh J and the British 

 Association for the Advancement of Science §. The British 

 Association in 1898 granted £20 in aid of the further prose- 

 cution of the work. 



The method of procedure was to dissolve a known weight 

 of an alloy of two metals, and also under similar conditions 

 the same weight of a mixture of the metals which are present 

 in the alloy, the proportions taken being the same as those 

 known to be in the alloy, and noting the initial and final 

 temperature in each case. The heat of combination of the 

 metals in the alloy may be estimated after noting the difference 

 between the heats of solution in the two cases. 



Messrs. Johnson, Matthey, & Co., of London, kindly made 

 for me and analysed twenty-two different alloys of practically 

 pure zinc and copper, whose composition varied from 5 to 

 90 per cent, of copper; and they also supplied separate 

 specimens of zinc and copper similar to those used in making 

 the alloys. To facilitate solution the metals and alloys were 

 first reduced to powder by filing with a fine file. The method 

 of experimenting finally adopted was carried out in detail as 

 follows : — One end of a short length of closed thin glass 

 tubing was sealed to the top of a very small glass globe (see 

 fig. 1) . Near the point of attachment there were, on opposite 



* Communicated by Lord Kelvin. 



f l Popular Lectures and Addresses,' vol. i.. " The Size of Atoms " 

 pp. 160-166. 



| Proc. Roy. Soc. Edinb. 1898, pp. 137-149 ; 1899, pp. 619-621. 

 § British Association Eeport 1898, pp, 787-788 ; 1899, pp. 246-249, 



