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Physics. — "On the change of the resistance of the metals at very 

 low temperatures and the influence exerted on it by small 

 amounts of admixtures' I. By Prof. H. Kamerlingh Onnes 

 and J. Clay. Communication N°. 99 c from the Physical 

 Laboratory at Leiden. 



(Communicated in the meeting of June 29, 1907). 



$ 1. Introduction. In Comm. N°. 99 6 we called attention to the 

 very large differences in the change of the galvanic resistance with 

 the temperature, which different platinum wires show when we 

 descend to the low temperatures which are to be reached with liquid 

 hydrogen. Such differences were still more pronounced for different 

 gold wires which we investigated. With this metal (see Comm. N". 95 rf 

 These Proc. Sept. 1906) we had taken in hand the investigation of 

 the influence of small amounts of admixture announced in Comm. 

 N°. 77, because the influence of admixing silver would probably be 

 important and the percentage of silver could be determined very 

 accurately, the possibility of drawing out wires of the different kinds 

 of gold and its high melting point moreover rendering this metal 

 preferable to the for the rest very suitable mercury. 



Besides, the inquiry into the influence of small amounts of admixture 

 on the change of the resistance of gold with the temperature proved 

 at once useful as we thought that the gold resistance thermometer 

 would be preferable to the platinum resistance thermometer. Dr. C. 

 Hoitsema, who already obliged us before (see Comm. X". 95^ by putting 

 pure gold at our disposal, has had the kindness of supplying us 

 again with different samples of gold of high purity, further of pre- 

 paring for us different alloys with accurately known small percen- 

 tages of admixture, and of determining the impurity which was 

 finally left in the wires after they had been melted down. For all 

 this valuable help and for the information which Mr. Hoitsema was 

 enabled to give us by his wide experience we express our hearty thanks. 



The investigation of the different gold wires with very small 

 amounts of admixture may of course also be considered as the 

 calibration of different gold resistance thermometers. (Comp. Comm. 

 X°. 99^ § 1). We prefer, however, to consider it as a part of our more 

 general investigation (Comm. N°. 77) on the change of the resistance 

 with the temperature for pure metals, and on the influence which 

 small amounts of admixture exert on it. 



As to the change of the specific resistance for the pure metals reduced 

 to the most normal state, attention is drawn to the temperature of the 



14 



Proceedings Royal Acad. Amsterdam. Vol. X. 



