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Physics. - "Somt remarks on the expansion of platinum at low 

 temperatures". Hv Prof. II. Kamerlingh Onnks and J. Clay. 

 Supplement N°. 17 to the Communications from t lie Physical 

 Laboratory at Leiden. 



(Communicated in the meeting of September 28, 1907 ). 



The communication from the "Physikalisch-technische Reiehsanstalt" 

 by K. Scheel in the meeting of Jan. 11, 1907 of the "Deutsche 

 physikalische Gesellschaft" led us to make a remark already 

 in the Meeting of June 29, 1907 (These Proc. Sept. 1907 p. 200). 

 In Communication N°. 95^ (These Proc. Sept. '06 p. 199) we had 

 given a quadratic formula for the expansion of platinum beloiv 0°, 

 from which followed that, as was remarked in the Introduction of 

 that Communication, a formula of the third degree is required if we 

 wish to represent the expansion of platinum from — 180° to -f- 100 J 

 by one polynomial with increasing powers of t, and if we have to 

 deal with observations which if repeated a sufficient number of 

 times, allow us to reach an accuracy (comp. § 1 of Comm. N°. 85, 

 June '03, These Proc. April '05) of '/joo U1 the expansion. We found 

 this confirmed by the measurements of Scheel, who arrived at the 

 same result by determining a quadratic formula for the expansion 

 of platinum above 0°, and by measuring the length at — 190°. 



We now consider the striking difference of the expansion at low 

 temperatures according to the formula given by us, and that according 

 to Scheel's formula, viz.: 43 f* for the expansion of a bar of 1 meter 

 between — 183° and -(-16°, (cf. Scheel loc. cit. p. 19, note 1), a 

 difference much greater than could be accounted for by the inaccuracy 

 of the observations. 



For an explanation of this discrepancy we call attention to the 

 difference of the observations of Dec. 16 1904 and Febr. 3, 1905 

 in Table II of Comm. N\ 95 6 , which give as length of the platinum 

 bar provided with the two glass extremities, at 16 01 ) before it had 

 ever been reduced to low temperature, 1027.460 m.m., and a long 

 time after it had been reduced to low temperature for the last lime, 

 1027.457 m.m., mean 1027.458 m.m., with that of Dec.19, 21 and 

 23 in the same table which yield the mean value 1027.441 mm. 

 (from 1027.441, 1027.442 and 1027.440) for the length at 16°, 

 which was observed on return to the ordinary temperature a day after 



!) In Table II of this communication under L\6° for the ordinary temperatures 

 the length of the bar at 16° reduced on the measuring rod at 16' has been 

 given and not the length at b as in the tables of Comm. N u . 85. 



