434 Mr. R. S. Willows on the Variation of the 



Cailletet and Bouty * : and the numerous papers of Callendar 

 and Griffiths f on the change in resistance of platinum wires 

 over wide intervals of temperature. 



The experiments described in the above-mentioned papers 

 do not deal with the particular case of amalgams. C. L. 

 "Weber (toe. cit.) has studied the s] ecific resistance and the 

 temperature-coefficients of amalgams of a few metals. 



§ 1. Method. 



The amalgams were formed synthetically by adding known 

 weights of the different metals employed to a quantity of 

 mercury whose weight was also known ; the temperature was 

 gradually raised until the whole mass was fluid, (hen when it, 

 had cooled the weight was again found to guard against an 

 error in the calculated composition through the driving off of 

 mercury. No correction was found necessary on this account. 



The mercury used had been first well washed, treated with 

 acid, and distilled. 



The amalgams tested were those having for their second 

 metal zinc, tin, cadmium, and magnesium. 



The zinc used was obtained from the sticks of that metal 

 sold as " redistilled," used in setting up Clark's cells. The 

 other metals were not specially purified before using, but 

 they were obtained as " pure " from various dealers. 



The amalgams so formed were then introduced into flat 

 spirals of quill-tubing. The diameter of a spiral was about 

 5 inches, and it contained about four feet of glass tubing. 

 So formed it did not occupy much space in the heating-bath, 

 and hence it could easily be bi ought to a uniform tempera- 

 ture throughout, but its shape made it more difficult to fill 

 so as to obtain a perfectly air-free, regular thread of the sub- 

 stance to be experimented on. 



Various methods were employed to secure this last con- 

 dition. On to the ends of the flat spiral vertical wider tubes 

 were fused, the open ends being somewhat narrower than the 

 rest of the tube. One of these tubes was connected to a 

 water-pump. The amalgam was melted in a beaker, the 

 spiral inverted, and the other wide limb after heating placed 

 with its mouth well below the surface. The air was now 

 gradually withdrawn by the pump, the fluid was gently 

 stirred and allowed to fill the tube. This method is objection- 

 able for two reasons : — (1) Unless a large amount of amalgam 



* Journal de Physique (1885), p. 297. 



t Callendar, Phil. Trans. 1887, p. 161 ; Phil. Mag. July 1891, p. 104 ; 

 Phil. Mag. February 1892, p. 220 ; Griffiths, Phil. Trans. 1891, p. 43 ; 

 Phil. Mag. Dec. 1892, p. 516. 



