Compound of Gold and Tin. 



97 



the two liquids. Then, on immersing the first alloy, contain- 

 ing 10 per cent, of tin, a further rise of E.M.F. was obtained, 

 showing quite a marked difference between the gold and the 

 alloy. In other cases where a compound has been found in 

 the series, very little, if an}', rise of E.M.F. has taken place 

 until that compound has been passed. This seems to indicate 

 that in the case of these alloys the energy required to decom- 

 pose the compound is not so great as to reduce the E.M.F. of 

 the cell to that obtained with gold alone. 



Another peculiarity of a more objectionable kind was the 

 fluctuations in the readings taken on different days. These 

 were small and did not affect the relative positions of the 

 alloys one to another, all rising or falling together in E.M.F., 

 and was doubtless due to changes in the unstable solutions 

 used. The results obtained are given in the following Table: — 



Weight of Metals taken. 



Percentage of 

 Tin in Alloy. 



E.M.F. in volts. 



Gold— Gold 



ib-07 



23-1 



26-01 



28-5 



34-9 



35-9 



400 



50 



•667 



•923 



•932 



'923 



•941 



•932 



•950 



1-215 



1-279 



1-425 



Gold 1 -803 grms. Tin -202 grms. . . . 

 Gold 2-000 grms. Tin -602 grms.... 

 Gold 2-002 grms. Tin '704 grms.... 

 Gold 2 000 grms. Tin -800 grms.... 

 Gold 1-303 grms. Tin "700 grms.... 

 Gold 1-284 grms. Tin '722 grms.... 

 Gold 1-201 grms. Tin *801 grms.... 

 Gold 3-001 grms. Tin 3-001 grms.... 

 Gold— Tin 





On looking at this Table it will be noticed that the readings 

 remain nearly the same from the first alloy up to the one 

 which contains 35*9 per cent, of tin ; but in passing from that 

 to the alloy containing 40 per cent, of tin, a rapid rise in the 

 E.M.F. takes place. From this point up to pure tin the 

 E.M.F. only rises # 21 volt, the curve being approximately a 

 straight line. This shows that between these two alloys an 

 alloy exists containing the metals in the right proportion to 

 form a compound, and that on reaching the alloy of 40 per 

 cent, of tin the compound has been passed and free tin is 

 present. In order to push this point closer home I prepared 

 an alloy which is not given in the Table and which I made up 

 to contain 38*1 per cent, of tin. This alloy was assayed at 

 the Mint, with the following result : — 



Gold 61*7 per cent. 



Tin 38*3 „ by difference. 



lOO'O 

 FhiL May. S. 5. Vol. 33. No. 200. Jan. 1892. 



11 



