Hygiene / by J. Lane Notter and R. H. Firth.

  • James Lane-Notter
Date:
1894
Catalogue details

Licence: Public Domain Mark

Credit: Hygiene / by J. Lane Notter and R. H. Firth. Source: Wellcome Collection.

Provider: This material has been provided by London School of Hygiene & Tropical Medicine Library & Archives Service. The original may be consulted at London School of Hygiene & Tropical Medicine Library & Archives Service.

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    Ammonia is detected by Nessler’s solution; if present in water, a yellow colour or yellow-brown precipitate is formed. If in small quantity the colour should be observed through a column of water 4 or 5 inches in depth, the glass being placed on a white ground. Iron.—Ferrocyanide of potassium (yellow prussiate) gives a blue colour with ferric salts, and ferricyanide (red prussiate) with • ferrous salts. The water should be rendered acid with dilute hydrochloric acid, free from iron. A comparative test should be made with distilled water. Hydrogen Sulphide, with a salt of lead, gives a black colour. Oxidizable Organic Matter.—The water should be neutral or feebly acid; boil for 20 minutes, adding about 1 c.c. of a solution of chloride of gold (1 grm. to 1 litre). Colour varies from rose- pink through violet to olive or a dark violet to a dark precipitate, according to the amount of oxidizable matters present. If there • is no nitrous acid in the water, the reaction may be considered due to organic matter; or add a strong solution of nitrate of silver and expose to diffused light; if organic matters be present, the darkening of the solution will take place rapidly. Lead or Copper.—Place some water (100 c.c.) in a white dish, and stir with a rod dipped in ammonium sulphide ; wait till colour is produced, then add a drop or two of hydrochloric acid. If the colour disappears, it is due to iron; if not, to lead or copper. The following test is best applied to water concentrated to one-fiftieth part of its original volume :— 1 Magnesia.—Add oxalate of ammonium to precipitate the lime, then after filtration a few drops of phosphate of sodium, of chloride of ammonium and of liquor ammonise. A crystalline precipitate of triple phosphate appears within twenty-four hours. The Quantitative Analysis of Water. The chief points which require determination in an ordinary . quantitative analysis are the total solids, the chlorides, the hard- ness and the organic matter as represented by what are called the free and albuminoid ammonia. If additional evidence as to the quality of the water is required, to these may be added the determination of the amount of oxygen absorbed, and the amount of nitrogen existing as nitrites and nitrates. The main principle of a quantitative, or volumetric analysis, is the submission of the substance to be estimated to certain characteristic reactions, employing for such reactions, solutions of known strength ; and from the volume of solution necessary
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