NOTES
451
The Thermal Conductivity of Aqueous Solutions of Alkali Hydroxides
perature difference between the mercury and the cooling liquid was measured with thermocouples placed in ceramic bicapillaries (1.O mm in diameter). Filippov used the formula & / U z = a (b/X), where & is the measured thermal electromotive force and U is the voltage across the heating wire. Constants a and b were determined experimentally by using two different liquids of lrnowii A. According to our measurements an error in X of up to several per cent is produced by heat losses dependent upon the axial heat flow from the heated space. These heat losses were excluded by using the cooler (A) by means of which any temperature difference between the mercury and the oil layer was eliminated. If, as in the present experiment, the value of U is kept constant (with a maximum deviation of 0.05%), then the above-mentioned Filippov’s formula gives the relation a = X(& - P). From this our X’s were calculated. Constants a and P were determined by using toluene, mercury, water, aniline, and ethyl alcohol whose X’s are well known to within =kl%.’o-16 The calculation of a and p was based upon the method of least squares. The thermocouple circuit consisted of four copperconstantan thermocouples connected in series, and the thermal emf, 8, produced was measured with a potentiometer, the error being = k l pV. The cooling liquid was supplied by Hoppler’s ultrathermostats (=kO.Ol” error). The maximum radial temperature difference in the layer of liquid specimen was about 2 ” ) so that the convection condition Pr.Gr
