H. Van Dijk

The vapour pressure of liquid nitrogen

Abstract The vapour pressure-temperature relation of liquid nitrogen has been measured from the boiling point to the triple point. Temperatures have been measured with platinum resistance thermometers. According to our experimental results the boiling point and the triple point temperatures of nitrogen are 77.343°K and 63.141°K on the average reduced scale, the triple point pressure is 93.91 mm Hg, 0°C. The vapour pressure of liquid nitrogen has been computed also from a thermodynamic vapour pressure-temperature relation for every degree from the triple point to the boiling point.

On the temperature scale in the liquid 4He region

On the Kamerlingh Onnes conference on low temperature physics at Leiden in June, 1958, a new temperature scale for the liquid 4He region was presented jointly by J. R. Clement and J. K. Logan and the authors. It was recommended for use instead of the two scales, T55E and TL55, which have been used since 1955. Apart from information obtained with gas thermometers, with interpolation thermometers and from information on thermodynamic quantities of helium used for the former scales, new results of magnetic measurements are available. The way in which the results have been used for the scale is briefly discussed.

The vapour pressure of liquid oxygen

Abstract From a thermodynamic equation the temperature dependence of the pressure of the saturated vapour of liquid oxygen was calculated using available experimental information. Simultaneous measurements of the vapour pressure of liquid oxygen and of the resistance of a number of platinum thermometers were carried out in two different apparatuses. The platinum thermometers were previously calibrated on the gas thermometer scales of NBS, PSU, PRMI and NPL respectively. Temperatures derived from the pressure measurements using the thermodynamic p - T relation were compared with temperatures derived from the platinum thermometer readings. The temperatures are nearly equal. Fig. 5 shows that their difference can be represented by a smooth curve. The triple point of oxygen was also measured. We found for the vapour pressre at the triple point 1.097 5 mm Hg at 0°C and standard gravity and for the vapour pressure 54.350°K. A formula for the p - T relation of oxygen is proposed and a table has been calculated.

Thermodynamic temperature scale (TL55) in the liquid helium region

Synopsis An outline is given of the way in which an accurate temperature scale for the liquid helium region, the TL55-scale, has been obtained at Leiden. Section 1 Introduction. 2 Thermodynamic pT-relation, 3 Calculation of the principal terms from experimental data, 4 Calculation of the correction terms from experimental data, 5 Provisional Leiden 1955-scale, 6 Extension of the scale up to 5.2°K, 7 Consistent set of values for the boiling points of O2, H2 and He, 8 The heat of vaporization of 4He, 9 Accuracy and comparison with other results, 10 Numerical calculation of TL55, a table containing an abstract of the complete table of p as a function of T, and a table containing the basic data for the calculation of the complete table.

The temperatures at the transition points in solid oxygen

Abstract The temperatures at the transition points in solid oxygen have been measured with platinum thermometers in a calorimetric apparatus suitable for thermometer calibrations at low temperatures. As “best values” for the transition temperatures on the International Practical Temperature Scale of 1968 are found (by taking into account our results and results of Hoge and of Orlova): 23.866 K and 43.805 K. For the transition near 24 K there was no evidence of a latent heat.

On the use of the vapour pressure- temperature relation in thermometry

Abstract A thermodynamic relation for the pressure of the saturated vapour of condensed gases is deduced from thermodynamic principles, and its application in precision thermometry is discussed.

Results obtained from measurements on platinum resistance thermometers at the thermometry section of the Kamerlingh Onnes laboratorium, Leiden

Abstract Measurements on platinum resistance thermometers at temperatures between 1.5 and 4.3°K, between 9 and 20.3°K and between 54 and 90°K enabled us to deduce the temperature dependence of the reduced resistance, ω = R / R 0° C , of many platinum resistance thermometers for the whole temperature region from 1.5 to 90.2°K. The deviation curves, ω x -ω LN vs. T , for the whole temperature region differ considerably in shape. ω LN represents the reduced resistance of the standard resistance thermometer with which the other resistance thermometers have been compared. The difference in shape reduces the accuracy of interpolation specially between 4.2 and 10°K and makes calibration at more than a few temperatures necessary if high precision is required. The results obtained for ω at temperatures between 1.5 and 4.2°K can be represented within experimental accuracy ( Δω = 1 × 10 -7 ) by the formula ω = ω 0 + AT 2 + BT 5 The constants ω 0 , A and B differ considerably for thermometers made from platinum of different origin and purity. Values for the ideal reduced resistance were deduced from the results and compared with data obtained formerly.

Phosphorbronze resistance thermometers for temperatures below 1°K, and carbon and ink thermometers for use in high magnetic fields between 1 and 4°K

Summary The resistance of a few phosphorbronze thermometers was measured as a function of the Curie temperature of gadolinium sulphate in liquid helium down to 0.25°K, and showed a nearly exactly linear dependence on that temperature between 1.5 and 0.25°K. Several carbon and ink resistances were measured between 1 and 4°K in different magnetic fields. Those made from a kind of glass-ink appeared to be the most suitable for measurements in magnetic fields, because they change regularly and considerably with temperature and are very slightly affected even by strong magnetic fields.

Specific heat of Gd2(SO4)3.8H2O between 1.0 and 4.0°K

Summary New accurate measurements of the specific heat of Gd2(SO4)3.8H2O in zero magnetic field between 1.0 and 3.0°K are presented, and used to obtain information on the electronic part of the specific heat. The experimental results combined with theoretical considerations provide good evidence, that in a predominantly cubic field the eightfold degenerate basic state of the Gd+++-ion is split up into two doubly degenerate levels and one quadruply degenerate level between them, while the quadruple level lies nearer to the lower doublet and the ratio of the spacings is 3 : 5 δ/k amounts to 1.35 ± 0.01°K.

Measurements of specific heats of iron ammonium alum in high magnetic fields and at liquid helium temperatures

Abstract The authors developed the technique for measuring specific heats in constant strong magnetic fields. Measurements were made in magnetic fields at liquid helium temperatures and in field zero also at temperatures obtained by demagnetization. The specific heats of the specimen of iron ammonium alum showed an anomalous maximum at about 3.6°K. This behaviour can not be yet explained. Values of CHC0 were compared with a Brillouin function on the basis of six equidistant magnetic energy levels. Within a certain region the values nearly agree with theory. Outside that region they reveal, however, considerable deviations.