[ 45 ] 
II. On the Properties of Matter in the Gaseous and Liquid States under various 
Conditions of Temperature and Pressure.* 
By the late Thomas Andrews, M.D., LL.D., F.R.S. 
Communicated by Professor Stokes, D.C.L., P.R.S. 
Received February 7,—Read March 18, 1886. 
According to Dalton, the particles of one gas possess no repulsive or attractive 
power with regard to the particles of another gas ; and accordingly, if m measures of a 
gas A be mixed with n measures of another gas B, each will occupy m-\-n measures of 
TCL 7l> 
space. The density of A in such a mixture will be , and of B,-, the pressure 
1 J m + n m-\-n 1 
upon any one particle of such a gaseous mixture arising solely from particles of its 
own kind. “ It is scarcely necessary,' - ’ Dalton remarks, “ to insist upon the applica¬ 
tion of this hypothesis to the solution of all our difficulties respecting the constitution 
of mixed gases where no chemical union ensues. The moment we admit it every 
difficulty vanishes. The atmosphere, or, to speak more properly, the compound of 
atmospheres, may exist together in the most intimate mixture without any regard to 
their specific gravities, and without any pressure upon one another. Oxygen gas, 
azotic gas, hydrogenous gas, carbonic acid gas, aqueous vapour, and probably several 
other elastic fluids, may exist in company under any pressure, and at any temperature, 
without any regard to their specific gravities, and without any pressure upon one 
another, while each of them, however paradoxical it may appear, occupies the whole 
space allotted to them all.”+ 
In conformity with this law, Gay Lussac found that the vapours of alcohol and 
water mix like two gases which have no action upon one another. The density of the 
* The manuscript of this memoir was found among the author’s papers, and was sent to me by 
Professor Tait, who thought that, as the former papers on the same subject were published in the 
‘ Philosophical Transactions,’ the manuscript ought to be submitted to the Royal Society. It has every 
appearance of being complete, though probably intended to be, in part at least, fair-copied before presen¬ 
tation. It was without title, but the title has been supplied from an earlier di’aft. This title shows that 
the paper must have been written a great many years ago, while Dr. Andrews was still connected with 
Queen’s College, Belfast. For many years before his death the state of Dr. Andrews’ health prevented 
him from continuing his scientific labours, even to the extent of preparing for publication an account of 
the results at which he had arrived in an investigation which was doubtless carried on with that con¬ 
scientious accuracy which characterised all his work.—G. G. S. 
t ‘ Manchester, Phil. Soc. Mem.,’ vol. 5, 1802, p. 543. 
MDCCCLXXXVII.-A. 
2. 5.87 
