The principles of inorganic chemistry / by Wilhelm Ostwald ; tr.with the author's sanction by Alexander Findlay.

Date:
1902
Catalogue details

Licence: In copyright

Credit: The principles of inorganic chemistry / by Wilhelm Ostwald ; tr.with the author's sanction by Alexander Findlay. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

    692/826 (page 660)
    Mercurous Chloride, IlgCl, is a white salt, soluble with extieme difficulty in water, and has long been employed in medicine under the name calomel. By reason of its small solubility it passes only slowly into the system, and therefore exhibits correspondingly mild actions. Its application in medicine depends on this. , Calomel is obtained on bringing together a soluble mercurous salt with chloridion; thus mercurous salts are precipitated not only by solutions of normal chlorides, but also just as completely by hydro- chloric acid. This behaviour could be foreseen, for the solubility of difficultly soluble salts in acids depends, indeed, on the fact that their anions can form undissociated compounds with the hydrion of the «j acid added, so that the concentration of the anion is diminished, and the solubility product thereby not attained. In the present case this cannot happen, because the anion of calomel, viz. chloridion, is « that of one of the strongest acids, and is therefore not converted to any considerable extent into the undissociated condition even by the addition of hydrion. For this reason the solubility product of a calomel solution also remains essentially unchanged on the addition of i a strong acid, and no more passes into solution.. On treating calomel with a concentrated solution of sodium c onde* or hydrochloric acid, however, a quite appreciable amount of it passes I into solution; at the same time some mercury is deposited. Ihis- reaction will be explained in the case of the iodine compound, in which j it is much more distinct. ,,i Mercurous sulphate also is converted into calomel on being treated- with a solution oT sodium chloride or hydrochloric acid because the, latter is far more difficultly soluble Asa rule, however it is from the sulphate by subliming it with common salt, whore^ .the calomel is obtained in semi-transparent crystalline masses with *j diamond lustre (on account of its high index of refraction). , mce. ordinarily, more or less mercuric chloride is mixed with it, calomel, which is7to be used for medicinal purposes, must be previously ca^; fully extracted with water in order to remove the very poisonous, - soluble mercuric chloride. , .. therefore* * Calomel readily volatilises, and its vapour density was theieiore. earlv determLd This yields the molar weight 235, corresponding c i . if i Ti .pi q;ru,P mercury was regarded as being* to the simple formula HgU. bince mercury => sneciallv Sed'^umptk^ according* to which the different demente po«»- according to the formulation ClHg - HgCl. nl.w therefore arose as to whether the vapour of calomel is uniform or has decomposed° into mercuric chloride and mercury. accorimg < equation Hg2Cl2 = HgCl2 + Hg An nneqmvocal decision P supported by numerical data, has not yet been eftecte .