An analysis of the Carinthian molybdate of lead ... : To which are added some experiments and observations on the decomposition of the sulphate of ammoniac / [Charles Hatchett].

  • Hatchett, Charles, 1765?-1847
Date:
[1796]
Catalogue details

Licence: Public Domain Mark

Credit: An analysis of the Carinthian molybdate of lead ... : To which are added some experiments and observations on the decomposition of the sulphate of ammoniac / [Charles Hatchett]. Source: Wellcome Collection.

    55/58 (page 53)
    degree is the yellow acid, or that which is supersaturated with oxygen. The affinity between molybdcena and oxygen is but weak, at least in respect to that portion which is required to consti¬ tute molybdic acid; for it has been proved, in the course of these experiments, that considerable changes are produced by a very small difference in the proportions of the acids or al¬ kalies, and even by the degrees of heat. Scheele and-Mr. Islmann have observed, that all of the metals, excepting gold and platina, are able in the humid way to deprive the molybdic acid of oxygen, so as to cause it to become blue; but here their effects appear to cease. M. Pelletier found that a solution of molybdic acid was turned blue when hydrogenous gas was passed through it. Mr. Klaproth has also remarked that light, under certain circumstances, changed the colour of molybdic acid to blue. And the effects of light appear in some measure to be connected with the following experiment. I made a solution of the molybdic acid, by digesting sul¬ phuric acid on molybdate of lead, and diluted it with an equal quantity of water. The solution was filtrated, and I then added a solution of hepar sulphuris until the brownish- red precipitate which was produced began to fall much paler. After this the liquor was filtrated, and was of a pale beer colour. I placed it accidentally in an open glass jar, on a shelf near a window, on which the sun shone during a great part of the day, and was surprised to observe that in about two days it began to assume a greenish tinge, which gradually became deeper; on the third clay it was of a full green, on the fourth it had a tinge of blue, on the fifth the colour was greenish-