Another change might involve the in terpolating thermometer to be used in defining the scale. The present scale specifies the platinum/10% rhodium vs. platinum thermocouple thermometer as the defining instrument between 630° C and 1064° C, although its limited accuracy results in calibration uncertainties of 0.2° C or more in that range. Research on construction of the platinum resistance thermometer in several laboratories in dicates that improved models may yield uncertainties as low as 0.04° C over some or all of the 630° C to 1064° C range. Success might result in elimination of the thermocouple thermometer as a defining instrument. No single interpolating thermometer has been found to be clearly superior to all others below 13.8° K, but several possible devices are currently under study. A further alteration might result in a change in the number and nature of the defining fixed points of the scale—for example, use of superconductivity, as in the EPT-76 scale. Researchers in several laboratories have suggested the elimina tion of boiling point temperatures as de fining fixed points because of the com plications resulting from the necessary pressure measurement and because of the danger of contamination of such devices. Scientists are studying the use of a variety of sealed triple point and freezing point devices. No pressure measurements are needed, contamination problems are greatly reduced, and the devices are readily transportable. Other changes might be made in the equations used in the scale interpolation procedure, as well as in the methods of providing primary calibrations. Whatever the eventual changes, the Consultative Committee has come up with a tentative timetable for a new IPTS, depending on the progress of temperature research. The timetable sets 1980 for adoption of the principles for a new scale—deletion of the thermocouple thermometer as a standard interpolating instrument, for example; 1982 for agree ment on a skeleton scale, with numerical values still to be settled; 1984 for essential agreement on the final form of a new scale; and 1986 for presentation of the new IPTS to the International Committee on Weights & Measures. At its meeting, the Consultative Com mittee also made four recommendations that encourage research work in specific, "critical" areas of thermometry. The committee recommended that: • Research be directed toward devel opment of platinum resistance ther mometers that are satisfactory for use at all temperatures up to the junction tem perature between contact and radiation pyrometry. • A more accurate value be sought for the gas constant. • A simplified method for realization of the IPTS-68 be sought. • Thermodynamic temperatures be tween 14° Κ and 1064° C be studied, and especially between 14° and 90° Κ and between 400° and 700° C. ο 22
C&EN August 7, 1978
Ozonolysis yields malonic anhydrides Ozonolysis of ketene dimers produces malonic anhydrides, according to Dr. Charles L. Perrin and Thomas Arrhenius of the University of California, San Diego, in La Jolla [J. Am. Chem. Soc, 100,5249 (1978)]. This finding marks the end of a dec ades-long quest in many laboratories to make these highly strained, reactive, monomeric, cyclic anhydrides. It also may furnish a useful synthesis of such unsymmetrical derivatives as monoesters and monoamides. Ozonolysis of diketene in methylene chloride at - 7 8 ° C produced malonic anhydride, which could be converted to malonanilic acid in 72% overall yield and to ethyl hydrogen malonate in 77% overall yield. The infrared spectrum of malonic anhydride showed a strong doublet at 1830 and 1820 cm" 1 , the UCSD chemists report. They ascribe a 4.12-ppm singlet in the proton magnetic resonance (PMR) spectrum to methylene protons, a 45.4ppm peak in the 13C magnetic resonance (CMR) spectrum to the methylene car bon, and a 160.3-ppm CMR peak to the carbonyl carbons. Ozonolysis of 3-hydroxy-2,2,4-tri-
.0 V
CH3 H3C
cr Malonic anhydride
J
