Resistance of certain Amalgams with Temperature. 443 



If the bath is raised to 100°, and then alternately cooled and 

 heated between 50° and 90°, we get E, fig. 3. (It is slightly 

 displaced for clearness.) The first cooling makes the resist- 

 ance assume the value shown by the upper part, afterwards 

 it goes backwards and forwards along the lower part. This 

 seems to show that the change, whatever it may be, that 

 occurs in the amalgam when the resistance falls is not wholly 

 completed at one heating unless sufficient time be allowed. 



Between 100° and 30° the lower parts of the curves (figs. 3 

 and 6) are straight lines ; calculating the percentage de- 

 crease in resistance for a fall in temperature of 1° (a say), 

 we get the following : — 



Table II. 



Percent, of Zinc. 



as. 



16'5 



•1876 



23-9 



•1850 



283 



•1814 



33-3 



•1844 



401 



•1807 



Hence it appears that a decreases as more zinc is added, 

 although for pure zinc its value is five times that for pure 

 mercury. 



Fig. 7. — Resistance of an Amalgam containing 19'3 per cent. Tin. 



Temperature 



125 135 14-5 



§ 3. Tin Amalgams. 



Three amalgams only of tin were taken, containing 9*6, 

 19*3, and 29"9 per cent, of tin. Fig. 7 shows the curve 

 obtained for the middle of this series. 



