Water supply : considered mainly from a chemical and sanitary standpoint / by Wm. Ripley Nichols.

  • Nichols, Wm. Ripley (William Ripley), 1847-1886.
Date:
1883
Catalogue details

Licence: Public Domain Mark

Credit: Water supply : considered mainly from a chemical and sanitary standpoint / by Wm. Ripley Nichols. Source: Wellcome Collection.

    28/252 (page 14)
    obtain satisfactory indications with the eye, and complete separa- tion of suspended particles is often impossible. The solution of a difficultly soluble colorless liquid may sometimes be watched by coloring the liquid with some substance which does not inter- fere with the action. Thus, if amylic alcohol be colored with a little iodine, the process of solution may be followed more readily than would otherwise be possible. As in the case of solids and gases, we have the same grada- tion from cases of marked chemical action, accompanied by dis- play of heat and decrease of bulk, to cases where we seem to be dealing with a simple mechanical mixture. Distinction between Solution and Suspension. There is a great deal of confusion, even among well-educated people, as to the proper use of the terms in solution and in suspen- sion, and in the same connection it may be said that a great deal of confusion exists with reference to the distinction between clear and colorless, terms which are by no means synonymous. The accurate use of the terms can probably best be made plain by illustrations. If, to take an example already made use of, we put some common salt into a quantity of water, after a time the salt disappears, the ultimate particles being distributed through the water so that they are no longer distinguishable by the eye, even aided by the most powerful microscope; the salt cannot be removed by simple filtration ; and, although the solution is some- what less mobile than water, it is still transparent. This, as we have seen, is a case of solution. Suppose that, instead of the salt, we take a quantity of sulphate of copper (blue vitriol). The phenomena will be similar, but the blue color of the compound shows itself in the solution. The more concentrated the solu- tion, the more will its transparency be diminished on account of the depth of color; it is easy, however, by taking a thin layer of the solution to satisfy one's self of the transparency of the liquid and of the absence of suspended particles. Such a liquid, although colored, is clear. Suppose, now, we take some clay, shake it with water, and then allow it to settle. The grosser particles will subside to the bottom of the vessel, but the finer particles will remain in sus- pension. Very finely divided clay will refuse to settle for weeks,