New temperature scale, accurate to better than plus or minus 0.001 Kelvin over low temperature region, is based on National Bureau of Standards 1955 platinum resistance thermometer scale and utilizes precise susceptibility measurements on two paramagnetic salts

Cetas, T. C.

Swenson, C. A.

English

NASA Technical Reports Server

1972
	 B72-10146 
AEC-NASA TECH BRIEF 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Low Temperature Scale For a 1- To 20- Degree Kelvin Region 
A new and more accurate temperature scale has 
been developed for use in the region of one to twenty 
Kelvin. It is based on the National Bureau of Standards 
1955 platinum resistance thermometer scale and is be-
lieved to be accurate to better than ±0.001 Kelvin over 
the low temperature region. 
The new scale is based on precise susceptibility 
measurements on two paramagnetic salts, chromic meth-
yl-ammonium alum and manganous ammonium sulfate. 
Temperatures below 18 K were obtained by calibrating 
the paramagnetic salt thermometer from 20 to 30 K 
against the NBS 1955 platinum resistance thermometer 
and then extrapolating this calibration into the liquid 
helium region. The procedure, which is completely in-
dependent of the systematic errors which enter into 
gas thermometer or acoustic measurements, has a pre-
cision which varies from 0.001 K above approximately 
5 K to 0.0005 K at lower temperatures. 
These data confirm that while the accepted tem-
perature scales in the liquid helium region are internally 
consistent below 3.5 K, they are not consistent with the 
platinum resistance thermometer scales. If the NBS 
scale is correct, for instance, the accepted boiling point 
for He4 is too low by 0.007 K and all of the vapor 
pressure temperatures below 3.5 K are too low by 0.18 
per cent. 
Many experiments are referenced to an NBS scale 
between 2 and 20 K which is based on acoustic ther-
mometry. This acoustic scale lies systematically 0.03 per 
cent higher than the paramagnetic scale at all tempera-
tures from 2 to 19 K. If the two scales are "normalized" 
by this amount, the maximum deviation of any of the
19 acoustic calibration points from the new scale is 
0.005 K. 
Reference: 
Cetas, T. C. and Swenson, C. A.: Deviation of T58 from 
Thermodynamic Temperatures, Phys. Rev. Letters 25, 
337 (1970). 
Note:
Requests for further information may be directed 
to:
W. E. Dreeszen 
Manager, Information and Security 
Ames Laboratory 
Ames, Iowa 50010 
Reference: B72-10146 
Patent status: 
Inquiries concerning rights for commercial use of 
this information may be made to: 
Mr. G. H. Lee, Chief 
Chicago Patent Group 
U. S. Atomic Energy Commission 
Chicago Operations Office 
9800 South Cass Avenue 
Argonne, Illinois 60439 
Source: T. C. Cetas and C. A. Swenson 
Ames Laboratory
under contract to
Atomic Energy Commission 
(AEC-10007) 
Category 03 
This document was prepared under the sponsorship of the National 	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States 	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States 	 will be free from privately owned rights.
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Low temperature scale for a 1 to 20 degree Kelvin region

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