Chemistry, inorganic and organic : with experiments and a comparison of equivalent and molecular formulæ / by Charles Loudon Bloxam.
- Charles Bloxam
- Date:
- 1867
Licence: Public Domain Mark
Credit: Chemistry, inorganic and organic : with experiments and a comparison of equivalent and molecular formulæ / by Charles Loudon Bloxam. Source: Wellcome Collection.
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![well waters as to the nature of the substances which they contain, though, in the case of river waters more jjarticularly, the quantity of tliese sub- stances is materially influenced by the conditions of rapid motion and exposure to air under which such Avaters are placed. Household experience has established a chissification of the waters from natural sources into soft and hard waters—a division which depends chiefly upon the manner in wliich they act upon soap. If a piece of soap be gently rubbed in soft water (rain water, for example) it speedily fivrnishes a froth or latlier, and its cleansing powers can be readily brought into action ; but if a hard water (spring water) be substituted for rain water, the soap must be rubbed for a much longer time before a lather can be produced, or its effect in cleansing rendered evident; a number of white curdy flakes also make then- appearance in the hard water, which were not seen when soft water was used. Tlie explana- tion of tliis difference is a purely chemical one. Soap is formed by the combination of a fatty acid Avith an alkali; it is manufactured by boiHng oil or fat with potash or soda, the former for soft, the latter for hard soaps. In the preparation of ordinary hard soap, the soda takes from the oil or fat two acids, stearic and oleic acids, which exist in abundance in most varieties of fat, and unites with them to form soap, wliich in chemical language would be spoken of as a mixture of stearate and oleate of soda. If soap be rubbed in soft water until a Kttle of it has dissolved, and some Epsom salts (sulphate of magnesia) be dissolved in water, and poured into the soap water, curdy flakes will be produced, as when soap is rubbed in hard water, and the soap water will lose its property of frothing when stirred; the sulphate of magnesia has decomposed the soap, the soda contained in the latter has combined with tire sulphuric acid existing in the sulphate of magnesia, to form a sidphate of soda which remains dissolved in the watei-, while the magnesia, uniting mth the stearic and oleic acids, produces the insoluble ciuxiy flakes which consist of stearate and oleate of magnesia. Similar to the effect of the sulphate of magnesia is that of hard watei-s ; their hardness is attributable to the presence of the different salts of lime and magnesia, all of which decompose the soap in the manner exem- plified above ; the peciiliar properties of the soap in forming a lather and dissolving grease can, therefore, be manifested only when a sufficient quantity has been employed to decompose the whole of the salts of lime and magnesia contained in the quantity of water operated on, and thus a considerable amount of soap must be rendered useless when hard water is employed. On exarauiing the interior of a kettle in which s]3ring, well, or river water has been boiled, it will be found to be coated more or less thicldy with a fur or incrustation, generally of a brown colour, and the harder the water, the more speedily will this incrustation be deposited. A chemical examination shoAvs this deposit to consist cliiefly of carbonate of lime, in the form of minute crystals, wliich may be discovered by the microscope; it usually contains, in addition, some carbonate of magnesia, sulphate of lime, and small quantities of sesquioxide of iron (rust), and vegetable matter, the last two substances imparting its brown colour. In order to explain the formation of this deposit, it is necessary to be- come acquainted with the particular condition in which the carbonate of Inne exists in natural waters. Carbonate of lime is hardly dissolved to](https://iiif.wellcomecollection.org/image/b21496602_0068.jp2/full/800%2C/0/default.jpg)
