Topics in..
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Chemical lnsfrumenfation Edited by GALEN W. EWING, Seton Hall University,
So. Orange, N. J. 07079
These articles, most of which are to be contributed by guest outhms, are intended to serve the readers of this J o m ~ by u calling attention to new developments i n the themy, design,m wailability of chemical laboratory instmmentalion, or by presenting useful insights and explanations of topics that are of practical importance to those who use, or leach the use of, modern inslmmentation and instmmatal techniques.
XXXIII.
Recent Developments in
Calorimetry (Continued) Part Two.
Some Associated Measurements
RANDOLPH C. WILHOIT, Thermodynamics Research Center, Department of Chemistry, Texas ABM University, College Station, Texas
77843 THERMOMETRY The edolarimetrist is likely to spend mwe of his time in measuring and cant~.olling temperature than in m y other single activity. Progress in calorimetry is dependent on the availahllity of suitable thermometers of sufficient sensitivitv and stability in the temperature ran& of ilrterest. The demands of cslorimetry have, in turn, given impetus to the development of better thermometers. Ideally, temperature should he measwed on the t.hermadynamic scale, which is defined through the use of the secmd Ina. of 1,hermadynamicsand is indepei~det~t of the properties of any particular substanre. However, the dil.ert ure of thc themwdynsmic scale is too diffirolt f w prwiical measurements. The International l'rl~cticalTemperature Srele (IPTS) was filxt, defined by the Seventh General Cut&i.euce on Weights and Meaanres i l l ln2i and has been revised slightly sevetd timer since. I t is based on six fixed points raugiug from the boiling point of ox*gell tu the freesing point of gold. Interpulalion hetween these point,s is made b>- a platinum resistance t,hemwmetel. fwm - 18°C to 630.5'C, and by s plxtin~tm, plntinum-rhodium thermononple ftwn 030..5 to 1063°C. Higher tempemlures are measured with an optird pywmeter. Thp IPTS is not defined helow -1X"'C, rind several scales, which direr slighbl)f n m esoh other, are now in use. According tu the best current estimate.;, the IPTS differs from the thermodynamiv temppralwe by about 0.04" at 200'K, is idenli
