H74 



with gold and platinum (see Comm. N". 119, III and Comm. N". 120, 

 IV of this series) that we should be able to get more than a systematic 

 survey of different cases of additive admixture-resistance (see Comm. 

 VII of this series § lOj. Very soon, however, the surprising results 

 with iiji and lead were obtained, which we mentioned in Comm. 

 VII § 1 and § 12. 



In the first place on Dec. 3"^ 1912 we investigated a wire of 

 pure tin, and perceived that this metal too, at helium temperatures 

 became super-conducting. 



The tin was of the specially pure kind supplied by KahlbaUxM. 

 It was melted in a vacuum and poured into a glass capillary U-tube. 

 The capillary tube had tin branches at either end, by which the 

 conducting wires and the measuring wires were attached. The 

 resistance at the ordinary temperature, 290° K., was 0.27 ii. 



We foinid that at the boiling point of helium a small ordinary 

 resistance l.S.lO-'^ii remained. At 3° K. this had disappeared 

 [^ 10-6 ^) and when the field of temperature between 4°.25 and 

 3° K. was gradually gone through, we found that the disappearance 

 took place suddenly at 3°. 78 K. 



In order to be better able to judge of the micro-residual resistance, 

 we tried to make a tin wire of greater resistance, in the same way 

 in which we had formerly succeeded in making a long thin lead 

 wire '). A steel core was covered with a substantial layer of pure 

 tin, and turned down on the lathe. Then with a razorshaped chisel 

 a thin spiral shaving was cut off'). This method, which seemed 

 preferable to drawing (comp. § 14a) by which the metal might 

 undergo a greater change, yields without difficulty wires of 0,01 mm^ 

 section. Several of these wires were then joined into one long wire 

 by melting them on to eachother, during w^hich it was necessary to 

 carefully avoid the possibility of oxide being introduced into the 

 surfaces to be united. The tin wires, one of which 1.75 m. long 

 had a resistance of 19.2 <2, and the other 1.5 m. long a resistance 

 of 6,7 52, w^ere wound upon glass cylinders, between a spiral of 

 silk thread which separated the windings of the tin thread from 

 each other. Leading wires of tin fastened to the up turned ends of 

 the w4re, were led downwards through the liquid and attached to 

 copper wires. With these resistances immersed in liquid helium the 



1) Kameelingh Onnes and Bengt Beckman. Comm N". 132c. Dec. 1912. 



2} A few of the tin wires first made did not become super-conducting; the inferior 

 method of working the metal had perhaps caused additive admixture resistance, or 

 more probably very insufficient continuity of material. 



