Chemical analysis, qualitative and quantitative / by Henry M. Noad ; with numerous additions by Campbell Morfit.

  • Henry Minchin Noad
Date:
1849
Catalogue details

Licence: Public Domain Mark

Credit: Chemical analysis, qualitative and quantitative / by Henry M. Noad ; with numerous additions by Campbell Morfit. Source: Wellcome Collection.

Provider: This material has been provided by the National Library of Medicine (U.S.), through the Medical Heritage Library. The original may be consulted at the National Library of Medicine (U.S.)

    177/592
    Note.—Had hydrochloric acid caused a precipitate, it may have consisted of chloride of silver, chloride of lead, or proto- chloride of mercury, either or all. It may also have been occasioned by benzoic acid, uric acid, arsenious acid, antimo- nic acid, and basic salts of antimony and bismuth. In either of these latter cases, however, the precipitate vanishes on the addition of a large excess of hydrochloric acid and boiling: this is not the case if the precipitate contains silver or mercu- ry; which metals, if present, must be completely precipitated by adding excess of hydrochloric acid to the solution; and the precipitate, after having been washed and dried, must be tested for mercury, silver, and lead, as described at page 161. The benzoic acid, uric acid, &c. remain in solution, provided a sufficient quantity of hydrochloric acid has been added, and are detected in subsequent stages of the analysis. B. A small portion of the solution, when agitated with solution of sulphuretted hydrogen, becomes black. A stream of the gas is, therefore, passed through about three-fourths of the whole solution until it smells strongly of it: a copious black precipitate is formed: present, some metal or metals of the fifth or sixth group, or of both. Note.—Had the precipitate occasioned by sulphuretted hydrogen been of a milky white color, it would have been sul- phur, and would have indicated peroxide of iron. Examination of the precipitate.—It is separated by filtra- tion from the solution, and well washed; it is then digested with sulphuret of potassium, the original fluid having indicated copper by testing with a clean knife blade ; it is not completely dissolved. ]sT0TE>—Sulphuret of potassium is employed instead of hy- drosulphuret of ammonia, because bisulphuret of copper is not altogether insoluble in the latter reagent. B. 1. Examination of the portion soluble in Sulphuret of Potassium.—It is separated by filtration from the insoluble portion, diluted with distilled water, and boiled with acetic acid in excess, a precipitate is formed, which has a brownish black color; it certainly, therefore, contains gold or platinum, or both; and it may also contain all the other members of the sixth group. B. 1, a. Special testing for Gold.—To a portion of the 12
    digitised image 1
    digitised image 2
    digitised image 3