Water Analysis : a practical treatise on the examination of potable water / by J. Alfred Wanklyn.

Date:
1874
Catalogue details

Licence: Public Domain Mark

Credit: Water Analysis : a practical treatise on the examination of potable water / by J. Alfred Wanklyn. 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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    from the number of c. c. of soap test used. This one is sub- tracted because the 70 c. c. of distilled water would themselves neutralise about 1 c. c. of soap. If after this addition, more than another 17 c. c. of soap test are required, another 70 c. c. of distilled water must be added, and another “1” subtracted from the number of c. c. of soap test, and so on, if a further addition is required. This dilution is required because it is not easy to observe the exact point of lathering when there is much curded soap present in relation to the volume of water. If the result be desired in milligrammes of CajOCOs in a litre of water, take 100 c. c. of the water, and each c. c. of standard soap will be equal to 10 milligrammes of Ca^OCOj per litre. As in the former case, we must here dilute when a certain amount of soap test has been used, but in this case, as there is more water operated upon, we may use more soap test before diluting, in the proportion— 70 ; 100 : ; 17 : a; = 24’3. Therefore, when we have added about 24'3 of soap test with- out producing a lather, we must dilute with 100 c. c. of distilled water. But if 70 c. c. of distilled water requires 1 c. c. of soap test to form a lather, 100 c. c. will require T43 c. c. We must, therefore, deduct 1'4 from the number of c. c. of soap test for every time we are compelled to dilute. A very neat way of taking hardness is as follows:—Take a known volume of unstandardised soap-solution and dilute it with 70 c. c. of pure water, and then note the number of c. c. of standard CaCl solution (1 c. c. = 1 milligramme CajOCOj) required to slo]) lathering. (The number of c. c. of CaCl solution must approximate to 16.) The number of c. c. of CaCl solution -f 1 = the number of milligrammes of