A new process for purifying the waters supplied to the Metropolis by the existing Water Companies: rendering each water much softer, preventing a fur on boiling, separating vegetating and colouring matter, destroying numerous water-insects, and withdrawing from solution large quantities of solid matter, not separable by mere filtration / [Thomas Clark].

  • Clark, Thomas, 1801-1867
Date:
1841
Catalogue details

Licence: Public Domain Mark

Credit: A new process for purifying the waters supplied to the Metropolis by the existing Water Companies: rendering each water much softer, preventing a fur on boiling, separating vegetating and colouring matter, destroying numerous water-insects, and withdrawing from solution large quantities of solid matter, not separable by mere filtration / [Thomas Clark]. Source: Wellcome Collection.

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    chemists call carbonate of lime, becomes what they call bi¬ carbonate of lime, when it is dissolved in water by carbonic acid. Any lime-water may be mixed with another, and any so¬ lution of bicarbonate of lime with another, without any change being produced : the clearness of the mixed solutions would be undisturbed. Not so, however, if lime-water be mixed with a solution of bicarbonate of lime : very soon a haziness appears ; this deepens into a whiteness, and the mixture soon acquires the appearance of a well-mixed white¬ wash. When the white matter ceases to be produced, it subsides, and in process of time leaves the water above per¬ fectly clear. The subsided matter is nothing but chalk. What occurs in this operation will be understood, if we suppose that one pound of chalk, after being burned to nine ounces of caustic lime, is dissolved, so as to form forty gallons of lime-water; that another pound is dissolved by seven ounces of extra-carbonic acid, so as to form 500 gallons of a solution of bicarbonate of lime; and that the two solutions are mixed, making up together 540 gallons. The nine ounces of caustic lime from the one pound of chalk unites with the seven extra ounces of carbonic acid that hold the other pound of chalk in solution. These nine ounces of caustic lime and seven ounces of carbonic acidNform sixteen ounces, , that is, one pound of chalk, which, being insoluble in water, becomes visible, at the same time that the other pound of chalk, being deprived of the extra seven ounces of carbonic acid that kept it in solution, reappears. Both pounds of chalk will be found at the bottom after subsidence. The 540 gallons of water will remain above, clear and colourless, without holding in solution any sensible quantity either of caustic lime or of bicarbonate of lime. This will give a sufficient idea of the theory of the patented process. The rules, the precautions, and the details neces-