Aberrations from the ideal gas laws in systems of one and two components

The principal object of the research described in this paper was a measure­ment of the deviations from Dalton’s Law in gaseous mixtures. Such measure­ments have been made at low pressures by Maass and Morrison* and Sivertz in this laboratory and at high pressures by Masson and Dolley. They worked, however, only at room temperature. It was desired to investigate systems containing water vapour as one component, and this entailed using higher temperatures. An apparatus was devised in which density measurements could be carried out with an accuracy of at least 0·1 per cent, at temperatures up to 200° C. and pressures up to 1 atmosphere, either on a two-component mixture or on a single substance, whether liquid at room temperature or not. The two-component systems studied were water-carbon dioxide and water- ammonia. As a preliminary to their investigation, it was necessary to determine the density values for the individual components over the desired temperature range. This was done with particular care for water vapour, not only to form a basis for the later measurements, but in the hope of throwing light on the question of the molecular complexity of water in the vapour state, a question which has been the subject of several recent papers.* In the case of carbon dioxide the density measurements were carried out over the whole range from 200° C. to —70° C., those at the lower temperatures being made with an older apparatus of somewhat different design. These are considered to be accurate to 0·05 per cent., and they have been used to test a new equation of state which the authors have developed.