soMK s('(;(;estions uKciAinnNc. solttions.* 



15 V I'lol'. William Kamhay, \\ ]l. S. 



The brilliant presidential address of Prof. Orme ]V[asson at the Chem- 

 ical Seetum of the Anstrahisian Association for the Advancement of 

 Science marks a distinct advance in onr ideas of solntiou. The analogy 

 between the behavior of a, lie] aid and its vapor in presence of eacdi 

 other and of a pair of solvents capable of mutual solution is so striking" 

 as to carry conviction. The resemblance of the liipiid-vapor curve, 

 with its apex at the critical i)oint, to the solubility curve, with its apex 

 at the critical solution point, appears to me to prove beyond cavil that 

 the two phenomena are essentially of the same nature. 



There are two other phenomena, which, it ai)])ears to me, are made 

 clear by the ideas of Prof. Masson. The first of these has reference to 

 supersaturated solutions. The curves (i)ublished in N'atKre, February 

 iL', p. 348) showing the analogy l>etween liquid-gas and solution curves, 

 are isobaiic curves, or, more correctly, they re[)resent the terminations 

 of isobaric curves in the region of nuxtures, where, on the one hand, a 

 liqui<l exists in i)resence of its vapoi-, and on the other, one solvent in 

 the presence of another (for both solvents play the part of dissolved 

 substances, as well as of sohents). M. Alexeeff's data are not sulh- 

 cient to permit 'of the construction of a curve re]U'esentiug a similar 

 region ma])ped out l)y the termination of isothermal lines. l>ut it is 

 obvious that it would be ]K>ssible to determine osmotic pressun^s of 

 various mixtures by the i'r«'ezing-i)oint m(;thod, and so to constru(*t 

 isothermal curves for snch mixtures of solvents. And there can be no 

 reasonable doubt that, as the isobaric curves of li(|ind-gas an<l of sol- 

 vent-solvent display so close an analogy, the; isotherimd curvets would 

 also closely resend)le each other. 



(J ranting then that this is the case, w(^ may c(mstruct an imaginary 

 isotliermal curve on the model of the curve for alcohol ])u])lished in the 

 ritil. Trans, by Dr. Sydney Young and myself. Now, in one series of 

 papers on the liquid-gas relations, we showed that with constant volume 

 l)ressure is a linear function of temperature; and we were thus able to 

 calculate approximately the pressures and \ olunies for any isotlieriuitl 



*Kea»l l>efor*^ the; Koynl Sofiety «'ii I'lmisd;! y, >!;ir< li .">. isiil. Iioin \(tliiir, \\i\\\ 

 23, 1891; vol. xi.in, \»\>. 589, 590.) 



299 



