XI. On evaporation and dissociation.―Part V. A study of the thermal properties of methyl-alcohol

Abstract

In previous memoirs we have given the results of investigations of the thermal properties of ethyl-alcohol, acetic acid, and ethyl oxide (ether). The subject of the present paper is the vapour-pressures, vapour-densities, and expansion of methylalcohol; and from these results the heats of vaporisation have been deduced. The range of temperature is from —16° to the critical temperature 240°; and the range of pressure from 11 millims. to 60,000 millims. Preparation of pure methyl-alcohol. ―A finely crystallised sample of methyl oxalate was distilled with ammonia; the distillate was rectified, and when partially freed from water was distilled with quicklime. The distillate was again distilled from barium oxide, and then allowed to stand for some weeks over anhydrous copper sulphate; but the boiling-point was found to be by no means constant. It was then distilled six times over small quantities of sodium; and the rise of temperature during the last distillation was less than 0.1°. The boiling-point was 64.85° at 761.9 millims. A series of determinations of vapour-pressure at low temperatures was then made, and it was decided, before employing the alcohol for determinations of vapour-density, to re-distil it. It boiled at 64.95°, under the same pressure, 761.9 millims. Preliminary experiments were then carried out, with a view to determining the critical temperature and pressure; but the volume-tube burst, and the experiments were delayed until a new volume-tube had been calibrated. As the boiling-point of the alcohol was not absolutely constant, it was repeatedly fractionated, and the greater part was obtained, boiling at 64.7°, under 760 millims. pressure. The rise of temperature did not exceed 0.05° during the complete distillation.