Historical introduction to chemistry / by T.M. Lowry.

  • Martin Lowry
Date:
1915
Catalogue details

Licence: In copyright

Credit: Historical introduction to chemistry / by T.M. Lowry. Source: Wellcome Collection.

    42/608 page 22
    sulphate of potash identical with that prepared from oil of vitriol and “ tartar” or potash. These actions were studied carefully by John Mayow, a London Physician (1645-1697), who pointed out in 1674 that “ although [acids] and [alkalis] pass into a neutral sub¬ stance when they meet, yet they do not, as is generally supposed, entirely destroy each other,” since when the conditions are suitable both the acid and the alkali may be recovered from the salt. Thus:— “ If oil of vitriol is poured upon nitre, which consists of an [alkali] and of a volatile [acid] (as was shown above), the fixed salt \i.e., the base] of the nitre will soon leave its own acid and will enter into union with the acid of the vitriol, which is more concordant with it ... . That the case is so, is clear, for if nitre mixed with oil of vitriol be distilled, the spirit, or [acid] of the nitre will pass under a mild heat into the receiving vessel, while yet in other circumstances that spirit will not be carried up except by a very vehement fire .... It is a corroboration of this view that the mass left in the retort after a distillation of this kind, closely resembles vitriolated tartar, and can be properly substituted for it.” (“ Of the combination of contrary salts,” Medico-physical Works, A.C.R. XVII. 161 —162.) As oil of vitriol was found to liberate nitric acid from any nitrate and muriatic acid from any muriate, it was regarded as stronger than either of these acids, whilst vinegar was found by similar tests to be weaker than the three mineral acids. It is recognised now that this rough and ready method is not the best test of the strength of an acid, as it depends too largely on the readiness with which the various acids can be driven off in the form of vapour. But observations such as these were of great importance because they showed clearly that all salts possessed a dual structure; they thus prepared the way for the system of classifying salts which is described in the preceding paragraphs.
    digitised image 1
    digitised image 2
    digitised image 3