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

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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    ties. It is also bad for wasliin<?. ' Each degree of hardness- indicates the destruction and waste of 12 lbs. of the best hard soap by 100,000 lbs. of water.' (Frankland.) The carbonate of lime in water decomposes about ten times its weight of soap in washing—more exactly, 8'8 of white curd soap, and 10-7 of common yeUow soap ; and other salts of lime act injuriously upon soap in proportion to the lime they contain, the soluble soap, stearate and olente of soda, being converted into an insoluble and useless compound, stearate and oleate of lime: the water, then, is deprived of lime, or softened, at the expense of the soap. The lime in 100 gallons of Thames or New River water thus occasions the destruc- tion of about 34 ounces of soap before any portion of it becomes available as a detergent. The Chemical Commission of 1851 treated fuUy of this subject, especially as connected with the Metropolitan water supply, and their evidence was to the following effect:— ' The softer the water the better it is adapted for washing with soap, the earthy salts present causing a definite and calculable loss of soap, which may be taken as amoimting, in every gallon of water used in washing, to 10 grains of soap to each degree of hardness of the water. Thus, with one gallon of Thames water of 14 degTees of hard- ness before boiling, the loss of soap would be 140 grains, and at 5 degrees of hardness, after boiling, the loss of soap would be 50 grains; or with 100 gallons of water, the loss in the fij'st case would be 32 oimces, and in the second about l\h ounces.' Taking the whole quantity of soap used in the washing of linen, first to soften the water, and afterwards to cleanse the linen, the Commissioners estimate the loss at 42 per cent, when the water is employed cold, and 14 per cent, with woollens; or where the same water is softened by boiling, at 20 per cent, for linen, and 5 per cent, for woollens. Now there is a great fallacy or source of error pervading the cal- culations as to the loss of soap, arising from the use of the boiled water. Much of the water thus used has not been softened to anything like five degrees of hardness; and hence the destruction of soap is much greater than that stated in the calculations above given. Now, the hardness of the London waters has led to the extensive employment of soda. This precipitates all salts of lime, and so softens the water, and therefore effects a great saving of soap ; but the soda costs something, and it exei-ts a highly injurious effect on the fibre of the linen or cotton, as also on the colours of certain prints. _ Further, the Commissioners state, ' It is found proper to avoid boiling any portion of the Thames water that is used m tiie wash-tub, or even heating the water above a cez-tain point; for the carbonate of lime precipitates on the linen, carrj-ing down the colouring matter of the water with it, producing stains which there is the greatest difficulty in afterwards removing from the linen. The colour of the water is thus, indeed, fixed upon the cloth by the precipitated lime