Food : its adulterations, and the methods for their detecton / by Arthur Hill Hassall.

  • Arthur Hill Hassall
Date:
1876
Catalogue details

Licence: Public Domain Mark

Credit: Food : its adulterations, and the methods for their detecton / by Arthur Hill Hassall. Source: Wellcome Collection.

    41/973 page 25
    OK THE aiTALITY OF WATER. The quality of a water and its suitability or otherwise for domestic use depend first upon the nature and quantity of the several mineral constituents which enter into its composition, and secondly, on the on/anic ingredients, in solution, in suspmmon, or in the form ol living ^^it has been shown that aU the salts of lime and magnesia found i^n water render it hard, and therefore if they are present m considerable amount, the water is thereby rendered unsuitable for di-inlnng, cooking, and washing. , . , . ^ j_ • .^^ Other mineral constituents of water, which, if present m anything like considerable amount, are to be viewed with suspicion, are the chlorides, especially chloride of sodium, and the sulphates, particu- larly sulphate of lime. The reason of this is, that while there are but few natural sources of sidphates and of chloride of sodium, they are abundantly contained in the excreta, and make their way into om- drinking water either by percolation thi-ough the soil, or by beino- cast as sewage into om- rivers and streams, which are too often the soiu-ce of om- water supplies. Dr. Angus Smith, in his evidence before the Koval Commission on Water Supply in 1869, thus refers to the occm-rence of nitrates and chloride of sodium in waters. The niti-ates, he says, ' are what I have caUed Old Organic Matter. Where nitrates are caused by matter from animals, there is always a corre- sponding amount of common salt. Men take fi-om 200 to 300 grains at least of common salt eveiy day, and it is given out every day. This is the most unchangeable accompaniment of sewage. Whenever chlorine is largely in water, it is necessary to look for nitrates derived from sewage; and, as a rule, it is so constant that there is scarcely any exception. When we find much more than the average quantity in a we'll-water, nitrates are foimd also, and if the water in a distiict is pretty well known—that is to say, if the amoimt of chlorine in water Irom'any district is pretty weU known, and a specimen of that water should indicate rather more chlorides than usual—you may conclude vrith almost certainty that it is from sewage.' With regard to its organic constituents any considerable amoimt of albuminoid organic matter renders the water unfit for use, and the same may be said to a certain extent of the organic matter sus- pended in water, and especially of the living productions which impiu-e waters so frequently contain in such abundance. But it must be remembered that in this latter case this dead and living organic matter is capable of being removed to a large extent by an efficient process of filtration. Another circumstance to be taken into consideration in expressing an. opinion as to the quality of a water supply are the fluctuations in
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