Qualitative analysis / by William Briggs and R.W. Stewart.

  • William Briggs
Date:
1913
Catalogue details

Licence: Public Domain Mark

Credit: Qualitative analysis / by William Briggs and R.W. Stewart. Source: Wellcome Collection.

    155/180 (page 139)
    iodides, and sulphates, mentioned above ; the fluorides of the alkaline earth metals, and most other fluorides. (AgF is soluble.) Note.—Of the salts insoluble in water, the following are usually soluble in dilute sulphuric acid :—carbonates (with decomposition), phosphates, arsenates, chromates, and (with decomposition) sulphites. M. Heat the substance to dull redness in a test-tube. Salts, when heated, in some cases melt or volatilize, and frequently give off acid vapours, which may be detected by the white fumes formed when a glass rod, moistened with ammonia, is held within the tube. Any water which con¬ denses on the upper part of the tube will in such cases also show a distinct acid reaction. This occurs especially in the case of nitrates, sulphates, and many fluorides and chlorides. Note.—(a) Salts which give off carbon dioxide :—Carbonates, except those of the alkali metals ; all bicarbonates. (b) Salts which give off S02:—Sulphites and some sulphates. (c) Salts which give off oxygen onlyChlorates, KN03, NaN03. (d) Salts which give off brown vapours (N204, etc.):— Nitrates, (except KN03, NaN03.) (e) Salts which readily melt:—Those of the alkali metals, and many salts with water of crystallization, (f) Salts which give sublimates:—Salts of NH4, As, Sb, Hg. (;g) Salts which undergo no apparent change :—Silicates, phosphates, arsenates, and chromates ; sulphates of the alkali metals and alkaline earth metals and of lead. N. Warm gently with concentrated sulphuric acid. From salts the volatile acids are expelled with, or with¬ out, decomposition; e.y., nitric acid, carbon dioxide, sul¬ phur dioxide (from sulphites), chloric acid (which breaks up into C102, oxygen, and moisture), and the haloid acids HF, HOI, HBr, HI, the two latter undergoing partial decomposition, so that free Br or I may be found amongst the vapours. Note.—S02 may be given off (arising from the decomposition of the sulphuric acid itself) in presence of certain elements, e.g., C, S, Cu, Hg, etc. (vide preparation of S02); Si02 and Sn02 may separate from silicates and stannates.