= me oe Recto: "Notes ON SCIENTIFIC RESEARCH. : 101 
Whether the two different Guistandine types of vaporisation curves can be combined 
into a single one—the hexane curve —in view of the condition that in general, only 
relatively few substances follow the waterine, is discussed by the author, and declared 
to be possible. 
In order to render easy the use of the Duhring law, the author further gives an 
- exactly calculated table of the hexane vapour-pressure curve. 
_A final chapter is devoted to the (imaginary) zero point of vaporisation, which | 
can be obtained from Dihring’s formula for each substance, if it is assumed that that 
of water lies in the neighbourhood of — 273° C. The calculation of these new con- 
stants stands or falls with the certainty of this assumption; their true value is a matter 
of considerable uncertainty and even their theoretical and practical utility appears limited; 
thus whether, for example, the vapour pressure of glycerin at 27.9° C. is exactly zero 
or merely immeasurably small, has no practical bearing, and important theoretical 
inferences, perhaps about the molecular constitution of matter in connection with the 
latest ideas of Rutherford, Bohr, Sommerfeld, §c. does not come into the question. 
C. Neuberg*) reports on “hydrotropic’ phenomena. By “hydrotrophy“ the author 
means the property possessed by numerous salts of considerably increasing the solu- - 
bility of substances difficultly soluble, or insoluble, in water. In this sense the following 
substances for. example. are hydrotropic: —salts of benzoic acid, of benzene-sulphonic 
acid, of naphthoic acids and their derivatives, of thiophene-carboxylic acid, of pyro- 
_ mucic acid, of phenylacetic and similar aliphatic-aromatic acids, and of the acids of 
the hydroaromatic series. Hydrotrophy is manifested by the foregoing substances 
towards water-insoluble substances of many differing types, as hydrocarbons, alcohols, 
_ aldehydes, ketones, esters, nitro- compounds, bases, alkaloids, proteins, dye-stuffs, 
starches, and fats. ? 
In general hydrotropic sHbstances are of the nature of salts. The kind of cation 
has no essential importance, since the potassium, sodium, and lithium salts (of the 
" same acid) show equal capacities; the solubility in water of the salt is important, 
since in general the hydrotropic.action is greater, the greater the concentration of the | 
solution employed. It has not been possible to adduce any general law in regard to 
the nature of the anion; one must look for explanation in the first place to the 
formation of soluble double, and complex compounds; and it has in fact been possible 
in certain cases to isolate crystalline compounds from the aqueous solution. 
_ These phenomena have considerable physiological importance and are of practical 
interest, for example, for bringing difficultly soluble medicines into suitable aqueous 
solution, for the suppression of the coagutability of albuminous substances. 
In chemical analysis too, experiments are proposed, to show hydrotropic phenomena 
‘as valuable aids; since though as yet only benzoates, salicylates, and. isovalerianates 
have been investigated, these salts have the property of bringing into solution, or 
hindering the precipitation of, magnesium carbonate, calcium carbonate, and magnesium 
phosphate. ~ i | 
Certain of these hydrotropic effects have been fans known. von Wistinghausen*) 
describes an experiment in which oil diffused through a bile-soaked animal membrane 
into an aqueous bile solution. Otto’), and recently Wieland and Sorge*) have given 
further information as to the dissolving power of the bile-acid salts. Further, a patent 
*) Sitzungsberichte der Preuss. Akademie d. Wiss. Berlin 1916, p. 1034. — 7%) Diss. Inaug. Dorpat, 1851. 
— % Berl. Berichte 27 (1894), 2131. — +4) Zeitschr. f. physiol. Chem. 97 (1916), 1 
