Manual of qualitative analysis / by Robert Galloway.

  • Galloway, Robert
Date:
1861
Catalogue details

Licence: Public Domain Mark

Credit: Manual of qualitative analysis / by Robert Galloway. Source: Wellcome Collection.

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    as fluids dissolve generally larger quantities of a substance the higher their temperature, the term saturated, as applied to simple solutions, is only relative, and refers invariably to a certain temperature.” From the tendency of heat to diminish the force of cohesion, it naturally results that the solubility of most bodies is increased by heat ; this, however, is not always the case; some bodies, as common salt, are equally soluble in water at all temperatures, whilst, in other cases, the solubility is greater at particular temperatures than either above or below them. The liquids employed as solvents in simple solutions are water, alcohol, ether, oils, &e. The most important solvent is water; the others are only resorted to when the substance to be dissolved is in- soluble in that liquid. 32. “ A chemical solution may be accelerated by eleva- tion of temperature; and this is, indeed, usually the case, since heat generally promotes the action of bodies upon each other. But the guantity of the dissolved body remains always the same in proportion to a given quantity of the solvent, whatever may be the difference in temperature— the combining proportions of substances being invariable, and altogether independent of the gradations of tempera- ture.” The liquids which produce chemical solutions are, in most cases, either acids or alkalies. 33. The process of solution is conducted either in evapo- rating dishes or test-tubes. The latter are generally em- ployed when the quantity of the solid operated upon is small. The more minutely any substance is powdered, the more its solution is facilitated. Solid substances are gene- rally reduced to powder in mortars. PRECIPITATION, 34. It is frequently necessary to remove a constituent—
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