226 Thermoelectric Diagram for some Pure Metals. 



washed with water, dried, digested with pure, hot hydro- 

 chloric acid, washed with boiling water, and dried at 100° C. 

 The chloride was then reduced with pure sodium carbonate 

 and wood charcoal, the ingot being treated as before. It was 

 hammered into a rod with a polished steel hammer, on a 

 similar anvil, and drawn through steel and agate draw-plates 

 and annealed. 



Antimony. — This was also prepared by Mr. Wilkinson, 

 being reduced by him from pure antimony oxide, and con- 

 sidered by him to be " very pure/' I melted it and cast it 

 into a long rod in an iron mould, and broke off the ends and 

 soldered them on at right angles so as to dip into the oil 

 baths, and also soldered copper wires on to the ends to form 

 the junction. (This was the only case in which I used solder ; 

 in all others I merely twisted the wires together.) 



Gold. — This was an exceedingly pure specimen supplied by 

 the Melbourne branch of the Royal Mint. The percentage 

 of gold being 99" 994 according to the most delicate tests that 

 could be made at the Mint. The Mint has also supplied the 

 Physical Laboratory with a specimen of purity 99 '9 98, but I 

 was content to use the inferior of the two. The wire was 

 drawn through three holes of the draw-plate after the last 

 annealing, and may therefore be considered hard- drawn. 



Zinc. — The zinc I used was supplied in rods by Messrs. 

 Baird and Tatlock as pure redistilled zinc for making Clark 

 cells. I could not draw it, and fused several rods end to 

 end and bent it into the required shape. 



Thallium.— -This was given me by Mr. Wilkinson, who 

 obtained it from Schuchardt as pure. Professor Masson 

 analyzed it for me and found it contained 97*9 per cent of 

 thallium, 1*5 per cent, lead, and traces of arsenic and copper. 



Cadmium was also Schuchardt's pure, given me by Mr. 

 Wilkinson. It was in form of a thick rod, which I hammered 

 into a finer one and drew it through steel draw-plates. 



Tin. — From same source and treated in same way as 

 cadmium. 



Copper. — " Pure Swedish Copper," as sold in the city for 

 gold-refining processes. I used it in the hard-drawn state. 



Aluminium. — Commercial Neuchatel aluminium. 



