1890 - 91 .] Prof. C. G. Knott on Cobalt and Bismuth. 
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Bismuth had to be one of them, as it alone was known to lie below 
cobalt. The other metal fixed upon was palladium, a substance 
convenient in every way. Its diagram line is straight up to high 
temperatures ; and its character does not perceptibly change even 
after severe heatings. Unfortunately, however, the use of bismuth 
limited the investigation to moderate temperatures only. 
The bismuth was broken up into small pieces, which were packed 
tightly into the bore of a siphon-shaped glass tube. Gentle heating 
in a Bunsen flame sufficed to melt the metal, which ran together and 
solidified on cooling into a fairly uniform rod. The junction wires 
were fused into the ends of the bismuth rod. 
As finally set up, the apparatus consisted of a triple cobalt 
palladium bismuth junction dipping in oil. This formed the “hot 
junction.” Besistance boxes were included in the palladium and 
bismuth branches. Because of the magnitude of the thermoelectric 
forces between these three metals and copper, great precaution was 
necessary in keeping the various cold j unctions at the same tem- 
perature. The palladium branch always contained 100 ohms resist- 
ance j and the bismuth branch never contained less than 200. For 
each of the seven selected ratios of resistance, a careful series of 
thermoelectric observations was made. A delicate high-resistance 
galvanometer was used ; and the temperatures were measured by a 
mercurial thermometer. The electromotive forces between the 
cobalt and each intermediate “ equivalent metal ” were in this way 
measured directly. From these the thermoelectric powers at chosen 
temperatures could be calculated. But one of these equivalent metals 
was palladium itself, obtained by making the resistance of the 
bismuth branch infinite. Thus, by a simple process of subtraction, 
we obtained the thermoelectric powers between palladium and all 
the others. These quantities, calculated for 0° and 100° C., are 
given in the following table. The symbols Bi, Co, Pd stand for the 
metals bismuth, cobalt, and palladium respectively. The various 
equivalent metals are represented by the symbol Pd Bi w , where the 
number n represents the ratio of the resistances in the bismuth and 
palladium branches. Thus Pd Bi 2 means that, since the palladium 
branch always contained 100 ohms, the bismuth branch contained 
in this case 200 ohms. The electromotive forces, from which these 
values were calculated, were measured in microvolts. 
