In 1964 the authors published preliminary results of their work on establishing the practical temperature scale in the temperature range from 4.2 K to 20 K [I].

we considered the important problem of the degree of smoothness of the second differences d2T required for precision heat cnpacity measurements. An evaluation of this requirement showed that the irregularities in the values of these second differences must be less than 0.0001 "K. In a table, however, due to the rounding of the function values, irregularities up to 2 in the last decimal place of the table can occur in the second differences. Consequently, the values of T, AT and A2T are given in the table to 5 decimal places. After resolving these questions, connected with the construction of the table, the approximating €unction was tabulated with the stated spacing of d W, the values of T thus determined were rounded off to the fifth digit after the decimal point and the first and second differences AT and A2T were calculated with the same number of digits. Thus an average smoothed table for the function of T versus W was established for the range 12 to 95 "K. The table derived covering the range from 12 to 95 OK coincides quite well with the experimental results obtained from the international comparison of 4 national scales, and is sufficiently smooth (irregularities in AZT do not exceed l.lO-*).

Experimentally obtained data [3] of thermometers made of 10 different grades of platinum were compared with the calculated data:

The resistivity characteristic of platinum thermometers of different origins (1.39178≤W100°C ≤1.39251) was studied in the range of 10.8–273.16°K and it was established that Nernst's reduction formula holds in the range of 273-50°K with an error of 0.01° and does not hold at temperatures lower than 50°.