Water and its purification : a handbook for the use of local authorities, sanitary officers, and others interested in water supply / by Samuel Rideal.

Date:
1902
Catalogue details

Licence: In copyright

Credit: Water and its purification : a handbook for the use of local authorities, sanitary officers, and others interested in water supply / by Samuel Rideal. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    volume of the water alternately before a bright light, as a window, and a dark surface, such as cloth. Contrary to general opinion, most suspended particles in moderate quantity do not affect the flavour of the water, as can be proved by tasting in the dark a water which is “thick” and one that is perfectly clear. But, besides being unsightly, they afford evidence that the water has not been efficiently filtered, and it is mainly for this reason that a turbid water is condemned. Finely divided mineral matter in sus- pension is believed by some to be a cause of intestinal irritation and diarrhoea. Clarification can in most cases be effected by dissolving in it a small quantity of alum, from one to six grains per gallon, afterwards adding the equivalent amount of carbonate of soda (see p. 158) and allowing the gelatinous precipitate of hydrate of alumina, which carries down with it the suspended matter, to subside. Such a process must be carried out with caro, as its success depends on the character of the water, and if more than the requisite quantity of either reagent be used, the liquid will be rendered unfit for drinking. The water should always he poured off directly the deposition is com- plete, as the bacteria and other organisms commence to multiply very rapidly when in such close contact with their food, and will then re-enter the water, making its condition worse than before. It is obvious that there are two kinds of insoluble or suspended matters, inorganic or mineral and organic,