Conservation by sanitation ; air and water supply, disposal of waste, including a laboratory guide for sanitary engineers.

  • Richards, Ellen H. (Ellen Henrietta), 1842-1911.
Date:
1911
Catalogue details

Licence: Public Domain Mark

Credit: Conservation by sanitation ; air and water supply, disposal of waste, including a laboratory guide for sanitary engineers. Source: Wellcome Collection.

Provider: This material has been provided by the Harvey Cushing/John Hay Whitney Medical Library at Yale University, through the Medical Heritage Library. The original may be consulted at the Harvey Cushing/John Hay Whitney Medical Library at Yale University.

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    over sulphuric acid for several hours and weigh. The increase in weight gives the total solids, or residue on evaporation. If from a ground water, save the residue for the determination of the iron. In the case of surface waters the residue should be ignited and the loss on ignition noted. Heat the dish in a radiator, Loss on which consists of another platinum dish enough Ignition. larger to allow an air space of about half an inch between the two dishes, the inner dish being supported by a triangle of platinum wire. Over the inner dish is suspended a disk of platinum foil to radiate back the heat into the dish. The larger platinum dish is heated to bright redness by a triple gas burner. Heat the dish in the radiator until the residue is white or nearly so. Note any blackening or charring of the residue and any peculiar burnt odor which may be given off. After the dish has cooled, slightly moisten the residue with a few drops of distilled water to secure weighing under the same conditions. Heat the residue in the oven for half an hour; cool in a desiccator and weigh. This gives the weight of fixed solids, the difference being the loss on ignition. Surface waters carrying much mud or other suspended matter are often filtered. The differ- ence gives the suspended matter removed by passing through filter paper. For the use of the Gooch crucible see Exercise X, p. 267. Before the introduction of modern methods of water analysis the determination of loss on ignition was the only method for the estimation of organic matter in water. In order, how- ever, that the determination shall possess any real value, it is necessary to regulate carefully the heat during the ignition, so as to destroy the organic matter without decomposing calcium carbonate or volatilizing the alkali chlorides. This is what the use of the radiator is intended to acccomplish, and in the case of surface waters with low mineral content and considerable organic matter the method gives generally satisfactory results. But in the case of ground waters having little or no organic matter and high mineral content the loss is