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X. On the Existence of a Compound of Gold and Tin. 

 By A. P. Laueje, M.A* 



MATTHIESSElST, in his classical researches on alloys, 

 divides the metals into three classes — namely, those 

 which when melted together seem to be merely mixed ; 

 secondly, those in which a complete change of properties 

 takes place on the addition of a very small quantity of another 

 metal ; and, lastly, those between which something of the 

 nature of chemical combination seems to take place. 



He finds, on determining the electric conductivity of alio}- s 

 belonging to these different classes, that in the case of the 

 first group the curve of conductivity is a straight line, that in 

 the case of the second, and by far the largest group, the 

 curve of conductivity resembles a (J ; but that in the case of 

 the third group the conductivity abruptly rises at some point 

 and then falls again, such discontinuities, according to 

 Matthiessen, indicating the existence of compounds formed 

 between the two metals. 



It is, I think, open to question whether many of the alloys 

 placed by Matthiessen in the second group should not be 

 removed to the third group, as in some instances, owing to 

 the difficulties of the research, he has not made a sufficient 

 number of observations to prove the absence of a rapid rise 

 and fall in the course of the conductivity-curve. 



This view is confirmed by the experiments made by Prof. 

 Roberts-Austen on the copper-tin alloys. On examining the 

 conductivity of these alloys by means of the induction-balance, 

 he found that such a discontinuity existed lying between two 

 observations of Matthiessen's, and which he consequently had 

 never suspected — thus removing these metals into the class 

 which combine with each other. 



Nobody, as far as I am aware, has attempted the task of 

 redetermining the electric conductivity of the alloys as a 

 whole ; and it is therefore, I think, of some interest to search 

 for these compounds by a new method, and thus throw fresh 

 light on the results obtained by a determination of the physical 

 properties of the alloys. 



The method I have adopted has been already described in 

 former papers. 



Briefly it is based on the fact that if in, let us say, a 

 DanielPs cell the zinc plate is replaced by a copper plate, so 

 as to reduce the E.M.F. practically to zero, and if then a 

 very minute portion of zinc be attached to this copper plate, 



* Communicated by the Author, 



