Licence: Public Domain Mark
Credit: Qualitative chemical analysis / by C. Remigius Fresenius. Source: Wellcome Collection.
Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.
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![their temperature, the term saturated, as applied to simple solutions, is only relative, and refers invariably to a certain temperature. _ It may be laid down as a general rule that elevation of temperature facihtates and accelerates simple solution, . ^ A chemical solution contains the dissolved substance m a ait- ferent state and with different properties from what it had before ; it is no longer free, but intimately combined with the solvent which has also- lost its original properties ; a new substance has thus been produced, and the solution therefore has now the properties of this new substance. Chemical dissolution* also maybe accelerated by elevation of temperature;; this indeed is usually the case, since heat generally promotes the action of substances on one another, but the amount of substance dissolved always remains the same in proportion to the solvent, whatever may be the difference of temperature—the combining proportions of sub- stances being invariably and altogether independent of the temperature. The reason of this is, that in a chemical solution the solvent and the substance on which it acts have invariably opposite properties, which they strive mutually to neutralize; when this tendency of mutual neutralization is satisfied, dissolution ceases. The solutionis m this case also said to be saturated or, rather, neutralized, and the point which denotes it to be so is termed the point of saturation or neutraHzation. The substances which produce chemical solutions are, m most cases, either acids or alkahes. With few exceptions, they must first be reduced to the liquid form by means of a simple solvent When the opposite properties of acid and base are mutually neutralized, and the new compound is formed, the actual transition to the hqmd state wiU ensue only if the new compound has the property of forming a simple solution with the liquid present; for example, if solution of acetic acid in water is brought into contact with oxide of lead, there ensues,_first, a chemical combination of the acid with the oxide, and then a simple solution of the newly-formed acetate of lead in the water present. In chemical laboratories, solutions are usually made by digestmg or heating the substance to be dissolved along with the liquid in a beaker, flask, test-tube, or dish. In preparing chemical solutions, the best way generally is to mix the substance to be dissolved m the first p ace with water (or with whatever other indifferent liquid may happen to be used), Ind then gradually to add the chemical agent. In this way a large Scess of the latter is avoided, the action is not too violent, and dissolu- tion takes place readily and completely. It sometimes happens m chemi- S coXatioBs that^the product formed does not dissolve if an excess of the chemical solvent is present; in this case the particles of the new salt first formed, being soluble in the menstruum present, surround the pttS stTunked on, thereby weakening or altogether preventing further action. Thus, for instance, witherite (carbonate of baryta) dlsolves readi y if water is poured on to the pulverized mineral and hyTSorL ac^^^ added gLdually;. but on the -ntivary it d^^^^^^^^^^^ with difficulty and imperfectly if it is projected into a concent^^^^^^^ solution of hydrochloric acid in water; since chloride o barium although it dissolves readily in water, does not do so m hydrochloric acid. * The word solution is commonly used to -g-fy ^^J^ *^«,!,trit U^^^^^ tSe [Editok].](https://iiif.wellcomecollection.org/image/b21966953_0028.jp2/full/800%2C/0/default.jpg)
