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The Edinburgh new Dispensatory : containing 1. The Elements of pharmaceutical Chemistry ; 2. The Materia Medica; or the natural, pharmaceutical and medical History, or the Substances employed in Medicine ; 3. The pharmaceutical Preparations and Compositions ; including Translations of the Edinburgh Pharmacopoeia published in 1805, of the Dublin Pharmacopoeia in 1807, and of the London Pharmacopoeia in 1815
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Sect. 2. Pharmaceutical Operations.

GX1X

a. At every temperature, as potassium and sodium.

b. At ordinary temperatures, as iron, zinc, manganese, &c.

c. At elevated temperatures, as antimony and tin; or

d. When acted upon at. the same time by an acid or analkali, as copper, lead, bismuth ; or, lastly,

e. They are incapable of decomposing it, as gold, silver,

mercury, platinum.

580. The oxygenizement of metals by water is promoted bythe action of air. Iron, for example, is more quickly rustedby being merely moistened with water, than when totally im-mersed in water.

581. But the acids ase the most powerful agents in oxy-genizing metals. They act, in two ways, either,

1. By enabling them to decompose water ;

2. By being decomposed themselves.

582. The metals are susceptible of different degrees of oxy-genizement, some of them even of acidification, and, in gene-ral, they are more oxygenized according to the rapidity of theprocess. When proceeding too slowly, it may be acceleratedby heat; when too violent, it must be checked by diminutionof temperature, as by plunging the vessel in which the opera-tion is performed into cold water.

583. When the degree of oxygenizement is not very great,the oxide formed generally enters into combination with theacid employed, and forms a metallic salt; but when carried toits highest degree, the oxide is often insoluble.

DISOXYGENIZEMENT OF METALLIC OXIDES AND ACIDS.

58-t. This process was formerly termed reduction, from itsrestoring the metals to their metallic splendour, and is per-formed by causing some body to act upon them, which has agreater affinity for oxygen than they have. The different me-tals themselves vary very much in the degree of this affinity,so that thay are reduced with very different degrees of facili-ty. Gold, silver, platinum, and mercury, are reduced by mere-ly exposing them to a sufficient degree of heat in close vessels.The oxygen at this temperature has a greater affinity for ca-loric than for the metals, and is therefore driven off in theform of very pure oxygen gas.

585. Some other metallic oxides which resist the simple ac-tion of heat, may be reduced by melting them in contact with

 
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