Physics. — "Further experiments ujith Uqaid helium. S. -On the 

 electric resistance of pure metals, etc. XII. Measitrements 

 concerning the electric re-si-sla)ice of indium in the tempera- 

 ture field of li(/uid helium". (Conim. N*. 167^ from llie 

 Physical Laboratory at Leiden). By W. Tuyn and Prof. H. 

 Kameklingh Onnes. 



(Communicated at Ihe meeting of June 30, 1923). 



^ I. Purpose of the investigation. Method of construction of the 

 resistances. For the fnrtlier detection of snpi-a-conducling n)elals it 

 seems desirable to investigate tlie beliaviour of those elements whicii 

 take a place near already known snpra-condnclors in the periodic 

 sjstem. Indium — above tliallinm and by the side of tin — seemed 

 a suitable metal. 



Tiie chemically pnre indium (4 grammes) was supplied by E. de 

 Haën, G. m. b. H. '). From wire extruded from this to a thickness of 

 0.1. m.m. we constructed the resistances hi — 1922 — /, IF„=4,704- 

 /_>,/« — 1922— //, jr. = 3,708, ii and In-lQ22—lfl, Tr.=3,799! 

 £1 ; the resistances were, however, not enclosed in helium gas. 

 A fourth re.sistance, Jn—1922 A, T'F, = 4,609, 42 was obtained 

 by winding another- piece of Ihe same wire also bililarly on a glass 

 tube; silk thread served here for in.sulatiou '). The values !!'„ were 

 determined on December 22'"^ 1922 in the way as described in 

 Comm. N". 160«. 



^ 2. Measurements in li(/uid helium. The four resistances were 

 placed in Ihe ci-yoslal pi-ovided with a stirring apparatus, re|iresented 

 in Comm. N°. 124c, fig. 4. The measurements look place by com- 

 pensation of the potential at the extremities of a known and an 

 unknown resistance connected in series, by the aid of a compensation 



') The high amount of I -rr^ ol u/l (lie lesistances constructed 



V'>„/7=4°,2K. 



from this made us doubt the purity of tlie indium supplied. On inquiry tlie firm 



told us in a letter dated March 22"'' 1923 "that they had sent chemically pure 



indium metal, free from impurities". 



') Old indium wires are difficult to fuse together to obtain the four required 



extremities; treatment with HCI removes this difficulty. 



