A manual of qualitative analysis / by Robert Galloway.

  • Galloway, Robert, 1822-1896.
Date:
1858
Catalogue details

Licence: Public Domain Mark

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

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    kind of solid, and the amount of any particular solid varying with the solvent. When the solution contains as great a quan- tity of the solid matter as it is capable of dissolving, it is said to be saturated. A solution is known to be saturated when fresh solid matter of the same sort, on being put into it, remains un- dissolved. “ But 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 inva- riably to a certain temperature.” From the tendency of heat to diminish the force of cohesion, it naturally results that the solu- bility 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, &c. The most important solvent is water; the others are only resorted to when the substance to be dissolved is insoluble in that liquid. 32. “A chemical solution may be accelerated by elevation of temperature; and this is, indeed, usually the case, since heat generally promotes the action of bodies upon each other. But the quantity 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 temperature.” The liquids which produce chemical solutions are, in most cases, either acids or alkalies. 33. The process of solution is conducted either in evaporating dishes or test-tubes. The latter are generally employed 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 generally reduced to powder in mortars.