Notes on analytical chemistry : for students in medicine / by Albert J. Bernays.
- Albert Bernays
- Date:
- 1886
Licence: Public Domain Mark
Credit: Notes on analytical chemistry : for students in medicine / by Albert J. Bernays. Source: Wellcome Collection.
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![• Sulphates. 250 c.c. of the water are acidulated strongly by nCI, heated to boiling, pptd. by BaCL, boiled till the pr. settles clear, and the BaSO^ collected, washed, ignited, weighed, and calcnlated as SO., [BaSO, = '238; SO3 = 80]. Nitrites are an indication that a water is insufiSciently aerated or oxitlized. Boil 100 c.c. rapidly down to 5 c.c ; make a mixture of KI solution, a little starch paste, and HCl; no reaction should ap})ear: on adding the concentrated water, if nitrite be present blue iodide of starch will bo produced. The quantitative determination of the mineral constituents is not often required for a drinking water. A complete analysis of cour.'^e requires a larger quantity of water, say two gallons. Characteristics of sewage. Absence of dissolved oxygen, high chlorides, phosphates, potassium salts, and free and albuminoid ammonia. Nitrates in recent sewage are almost absent, but after dilution, and oxidation of nitrogenous compounds, the nitrates become high. Microscopic examination, odor, color, and a careful examination of the source, are required before deciding. If the water alters much in composition from time to time, surface contamination is probable. ULTIMATE ORGANIC ANALYSIS Is rarely of use except for finding the formula of a pure com- pound. To estimate the carbon and hydrogen. About 0-2 grm. of dried substance is taken. A perfectly clean hard-glass tube, about thirty inches long, closed at one end (tube-retort), is filled as follows. Granulated cui)ric oxide is ignited in a crucible, and allowed to cool. While still warm, one inch of the tube is filled with it, then the substance, mixed rapidly with more of the warm cupric oxide, is added. The mixture should now occupy three inches of the tube-retort. Add cupric oxide (hot from the crucible) up to 27 inches, put in a plug of ignited asbestos, and attach by a perforated cork the absorption apparatus. This consists, firstly, of a previously weighed U-tube containing HpSO.,, and, secondly, of a Liebig's potasli bulb containing KOH in solution. When the tube-retort is heated to redness in a combustion-furnace, the carbon and hydrogen are oxydizcd by the cupric oxide to carbon dioxide and water. The former is al)Sorbcd by the potash, and the latter by the sulphuric acid, and the gain in weight gives by calculation the amount of carbon and hydrogen. For some substances, fused and pounded lead chromate is used instead of cupric oxide. To estimate the nitrogen, the substance is burnt as above, a plug of metallic copper being sulistituted for the asbestos, so as 'to reduce any oxides of nitrogen. The tube is previously exhausted](https://iiif.wellcomecollection.org/image/b21499056_0111.jp2/full/800%2C/0/default.jpg)
