THE 



AMERICAN JOURNALOFSCIENCE 



[FOURTH SERIES.] 



Art. I. — The Platinum- Rhodium. Thermoelement from 0° 

 to 1755° J by Robeet B. Sosman. 



Contents : 



1. Introduction and Plan. 



2. Scale of Temperatnres. 



3. Melting Point of Platinum. 



4. Interpolation. 



5. Eelation of Thermal E.M.F. to Composition. 



6. Summary. 



1. Introduction and Plan. 



In two recent papers from this laboratory,* there have been 

 published the results of a revision of tlie nitroo;en thermometer 

 scale from 400° to L100° and of an extension of the scale to 

 1550°. The plan of that research was essentially as follows : 

 it consisted, first, in selecting certain lixed thermometric points, 

 xisually melting points of metals, and in determining their 

 reproducibility ; second, in making a measurement of the true 

 temperature on the nitrogen scale at or close by one of these 

 iixed points ; third, in transferring this known temperature by 

 means of a thermoelement over to the fixed point in question. 

 This transference by the thermoelement was necessary because 

 the platinum-rhodium thermometer bulb could not be put 

 directly into melting or solidifying substances at high tempera- 

 tures. 



A portion of the second paperf was taken up with a 

 discussion of the standardization of the platinum-rhodium 



* Some New Measurements with the Gas Thermometer, A. L. Day and 

 J. K. Clement, this Journal (4), xxvi, 405-463, 1908 ; The Nitrogen Ther- 

 mometer from Zinc to Palladium, A. L. Day and E. B. Sosman, ibid. (4), 

 xxix, 93-161, 1910. 



fLoc. cit., pp. 131-128, 140, and 147-151. 



Am. Jour. Sci.— Fourth Series, Vol. XXX, No. 175.— July, 1910. 

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