A class book of elementary chemistry / by W.W. Fisher.

  • Walter William Fisher
Date:
1897
Catalogue details

Licence: Public Domain Mark

Credit: A class book of elementary chemistry / by W.W. Fisher. Source: Wellcome Collection.

    248/304 (page 228)
    present is replaced by the radicle NH2. It is therefore called mercuric chlor-amide, and is formed according to the following equation:— Hg Cl, + 2 NH3 = Hg Cl, NH, + NH, Cl. The black substance produced when solution of ammonia is poured upon calomel is similar in character, and is mercurous chlor-amide, HggCl, NHg. Molecular Weight of Calomel. Much difference of opinion has existed as to the mole- cular formula of calomel; whether it should be written 235-5 = Hg Cl, or as 47i=Hg2 Clg. By numerous experi- ments it has been shown that the vapour-density is about 118, which corresponds to the molecule HgCl; but, on the other hand, it has been shown that calomel vapour amalgamates gold leaf and apparently dissociates by heating into mercuric chloride and mercury. If the dissociation were complete we should get:— Hg,Cl, = Hg + HgCl,. [2 vols.] ? 2 vols. 2 vols. The dissociation, however, is certainly limited in amount, and not complete as represented by the equation: and the vapour-density does not vary in such a way as to support the hypothesis of gradual dissociation. We may therefore suppose that the molecule of calomel vapour is really represented by Hg Cl, which may be more or less dissociated without change of density— 2HgCl = Hg + HgCl,. 2x2 vols. 2 vols. 2 vols. Experiments on the density of the vapour of a mixture of calomel and corrosive sublimate give for calomel a value about 118, and so support this view. In the case of such mixtures, too, no free mercury could be detected in the vapour when it came into contact with a gilt surface.