PROCEEDINGS OF SECTION B. 103 



by a more or less rapid fall. The order of the salts from the point 

 of view of effect on solubility was illustrated by curves, and shown to 

 be very similar to the order given by curves showing the deviation of 

 freezing point lowering from that calculated from the simple theory 

 of solutions, plotted against concentration. The question was then 

 discussed of whether these relations could be understood in terms of a 

 simple hydrate theory, the supposition being that water forming 

 hydrates was not any longer available for the role of solvent. An 

 alternative supposition, suggested by Arrhenius, is that the salt 

 molecules and ions are capable of exerting an effect on the phthalic acid 

 molecules of a kind which is not chemical, and for want of a better 

 term may be called physicai. If this alternative idea be true it shoulp 

 be possible to connect solubility in a salt solution with the concen- 

 trations of ions and molecules respectively in that solution. Figures 

 were quoted showing the application of the equation — 



S=S„{I + kaa + k' {I-a)a] 

 where S is the solubility experimentally found, S„ is a value obtained 

 from the curves by extrapolation to zero salt concentration of the later 

 part of each curve, and may be taken to represent what the solubility 

 in pure water would be if only those conditions ruled in accordance 

 -with which the later part of the curve is traced, a is the degree of 

 dissociation of the salt at concentration a. 



The agreement between calculated and found solubilities, using 

 certain figures for the constants k and ¥, was shown in those cases 

 where the equation could be applied, to be within the limits of experi- 

 mental error in all but the most concentrated solutions. A comparison 

 of the ionic and molecular constants k and k' respectively shows that 

 these may be positive or negative, and if there be a definite meaning 

 attachable to the above equation, they represent quantitatively the 

 so-called neutral salt action for ions and molecules respectively on the 

 solubility of ortho-phthalic acid. 



8.— LAEVA-PHELLANDRENE. 

 By Royston Barry Dreiv, M.Sc. 

 (Abstract.) 

 Phellandrene is a colourless liquid with peculiar odour, occurring 

 in many essential oils, e.g., in fennel oil, and in the laeva form in euca- 

 lyptus oil. 



Several continental scientists have isolated it and described its 

 properties. Their results differ because attempts to remove impurities 

 often alter the substance itself. 



The paper describes the separation of phellandrene from eucalyptus 

 oil, and gives an account of experiments with it, and puts on record the 

 physical constants. 



