Abstract
IN connection with the discussion on the “Nature of Solution,” in Section B, at the Birmingham meeting of the British Association, the following paper was read by Spencer Umfreville Pickering, Professor of Chemistry at Bedford College:—
Article PDF
References
Abstract of a Paper read at the Birmingham meeting, 1886, of the British Association, by Lord Rayleigh.
Continued from p. 22. From theChemical News.
See especially Berthelot, Ann. Chim. Phys. (5), 4, 445 to 537.
Dr. Nicol, (phil. Mag. 1885, i. 453, and ii. 295) quotes experiments with sodium sulphate in oppoisition to this View. He shows that the dehydrated salt may dissolve in water under certain circumstances without any signs of previous hydration. When it does so, however, it forms a supersaturated solution, Which is certainly very different form a normal solution, being, according to Dr. Nicol's determination of the solubility, due to the extension at lover temperatures of conditions which exist naturally only above 33°; but when it dissolves to form a normal solution it is with evident signs of hydration. whatever this may prove as to the supersaturated solution, it certainly does not prove that the normal solution contains the anhydrous salt,—rather the opposite.
Thus the "true" heat of dissolution of MgSO47H2O is +7000 cal., and even this number is probably 1000 to 3000 cal. too low, as it contains no allowance for the heat of fusion of the MgSO4 molecule. (SeeChew. Soc. Trans. 1886, 279.)
For a general summary and discussion of the results from the point of view of these physicists, see De Coppet, Ann. Chim. Phys. (4), 23, 366; 25, 502; and 26, 98.
In a Paper read before this Section last year (Report, p. 989), I argued that our formulae adequately represented the molecules of solids and liquids with which chemical reactions deal, although I fully recognised the existence of far more complex aggregates; my opinions have so far altered that at present I consider these aggregates to be recognisable in many operations which must be termed chemical, although in the great bulk of ordinary reactions the simpler or ultimate molecules need al.me be considered.
A power or "affinity" so strong that it will sometimes induce a salt to separate out in a crystalline form and with a proportion of water foreign to its nature, as well as from a solution too weak to yield it of its own accord (Aston and Pickering, " Multiple Sulphates," Chem. Soc. Trans., 1886).
J. M. Thomson, on the "Double Sulphates of Nickel and Cobalt" (Brit. Assoc. Rep. 1877, 209).
A study of the thermal results attending the dilution of salt-solutions, established by Thomsen ("Thermo-chem.," iii., especially plate iv., and also the curves given by formic and acetic acids and by potassium and sodium hydrates), impresses very forcibly the co-existence of these two actions, although Thomsen himself does not seem to have noticed it.
Rights and permissions
About this article
Cite this article
On the Nature of Solution 2 . Nature 35, 64–67 (1886). https://doi.org/10.1038/035064b0
Issue Date:
DOI: https://doi.org/10.1038/035064b0