File:On Vapour-Pressure and Osmotic Pressure of Strong Solutions (1908) (14758839376).jpg

Identifier: philtrans08812111 (find matches)
Title: On Vapour-Pressure and Osmotic Pressure of Strong Solutions
Year: 1908 (1900s)
Authors: Callendar, H.
Subjects: Proceedings of the Royal Society of London Philosophical Transactions of the Royal Society
Publisher: Royal Society of London

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may be to someextent merely different aspects of the same phenomenon. As an illustration of the deviation of the experimental results from theusually accepted theory, the observations of Lord Berkeley and Mr. Hartleyon the osmotic pressures of strong solutions of cane-sugar and dextrose atO C. are plotted in the accompanying diagram, fig. 5. In their papers theresults are tabulated and plotted in terms of concentration C in grammes 1908.) Osmotic Pressure of Strong Solutions, 479 of sugar per Hire of solution, which has generally been adopted in dealingwith osmotic pressure in consequence of Vant Hoffs theory. It is moreconvenient, however, in dealing with osmotic pressures or depressions of thefreezing-point in strong solutions, to plot the results in terms of concentra-tion 0 expressed in grammes of solute per gramme of solvent, because fornormal solutions such as cane-sugar the curves are more nearly straight,and the deviation of the observations from the theoretical curves can be
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1 2. 3 4 5 6 7 8 Fig. 5.— Osmotic Pressures of Solutions of Cane-sugar and Dextrose. more readily estimated. In dealing with densities or specific volumes it isgenerally better to employ the percentage concentration 100 C (grammesof solute per 100 grammes of solution) in terms of which they are usuallytabulated. The relation between the three modes of expressing the concen-tration is 0^7=: G = 0^7(1 +CO- In comparing solutions of different substances it is necessary to plot theresults in terms of the ratio of the number of molecules qi of the dissolvedsubstance to the number of molecules N of ifie solvent in the solution, 480 Prof. H. L. Callendar. On Vapour-pressure and (Mar. 10, because the relations involved are of a molecular nature. We havenjN = mGJM, where m and M are the molecular weights of solvent andsolute respectively. In plotting the observations in fig. 5, N is taken asequal to 100, and the values of the osmotic pressure are plotted against thenumber n of molecules of s

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