Food and its adulterations : comprising the reports of the Analytical sanitary commission of "The Lancet" for the years 1851 to 1854 inclusive, revised and extended being records of the results of some thousands of original microscopical and chemical analyses of the solids and fluids consumed by all classes of the public ... / by Arthur Hill Hassall.
- Arthur Hill Hassall
- Date:
- 1855
Licence: Public Domain Mark
Credit: Food and its adulterations : comprising the reports of the Analytical sanitary commission of "The Lancet" for the years 1851 to 1854 inclusive, revised and extended being records of the results of some thousands of original microscopical and chemical analyses of the solids and fluids consumed by all classes of the public ... / by Arthur Hill Hassall. Source: Wellcome Collection.
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![can employ such processes as I have described, properly ; or even if they could, that they would do so regularly. It is evidently the duty of those who have to supply a large population with water, to procure the pleasantest, softest, and purest water which is obtainable at any reasonable expense. On the Effects of Boilmrj on Water.—The effects of boiling on water are very numerous ; the chief, however, are the expulsion of the oxygen con- tained in it, as well as of the excess of carbonic acid, which holds the earthy salts in solution ; this causes the precipitation of the salts of lime, and the con- sequent softening of the water: for these effects to be produced fully, it is necessary that the boiling should be long continued. Professor Clark gives the following evidence on the effects of boiling on water: — Connected with this water, I may mention that all water holding carbonate of li me is softened by prolonged boiling. There is a misapprehension, however, in regard to the effect of boiling; a short boiling has very little effect indeed in softening water: when you subject water to even a sharp boiling, under the most favourable circumstances, I find two hours and three quarters, or three hours, necessary for decomposing all the bicarbonate of lime, precautions being taken to prevent any evaporation of water in the form of steam. By boiling, this water was reduced to 3-j2jj.°. In the case of the New River water the hard- ness was 13^°, the alkalinity was 12//; this purified by lime-water, in the proportion of 3 to 40, was reduced to 3,^° of hardness; by prolonged boiling it was reduced to 3^° of hardness. I got another specimen of New River water, 11^^°, which, by using the proportion of 1 of lime-water to 14^° of the water, was reduced to the hardness of 2^°. At University College a large boiler of water, being kept heated for two hours and a half, showed 8-^2-° of hardness. [There is a very remarkable fact that I have observed on the comparative result of the process of prolonged boiling, and of the process of softening by means of lime-water. Both processes result in nearly the same degree of hardness, but the lime process gives a result much less alkaline than the boiling process, although the contrary might have been expected.] Other effects of boiling on water are, to dissipate the greater part of any noxious gas which may be contained in it, as well as to destroy the vitality of the living animal and vegetable productions which may happen to be present. It is to the precipitation of the earthy carbonates that the incrustation which takes place in kettles, boilers, and pipes which convey hot water, is due. In the case of steam-boilers, this accumulation often results in fatal accidents. On the Addition of Acids to Water. — In a previous part of this Report, it has been shown that the kind of living productions contained in impure water are dependent, not only upon the quality and quantity of dead organic matter present, but upon the reaction of the water, whether it be alkaline or acid. Thus it was evidenced, that if water contain much animal matter in a fluid condition, and exhibit an alkaline reaction, the living productions present in it will consist principally of infusoria. Also, that if the same water be rendered acid, then little or no development of infusoi-ia will take place, but fungi principally form in it. It was stated, further, that while alkaline waters, containing much fluid animal matter, smell offensively, and betray evidence of progressing decompo- sition, acid waters, on the contrary, evolve little or no odour, the process of putrefaction in them being much retarded. From these facts it has occurred to us that a practical application of much importance might be deduced. Thames water, within some miles of the metropolis, holds in solution a large quantity of fluid animal matter; it swarms with infusoria, exhibits an alkaline reaction, and when kept for any length of time it emits an offensive smell, indicative of decomposition. Now, if to this, or any other water resembling it, we add a small quantity of acid, these changes will be arrested, the animalcules will be killed, and the water will soon cease to smell disagreeably.](https://iiif.wellcomecollection.org/image/b20385419_0132.jp2/full/800%2C/0/default.jpg)
