Catechism of Modern Elementary Chemistry; Or, Solutions of the Questions Set at the London University Matriculation Examinations 1844-82 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1882 Excerpt: ...readily with another element. For this reason hydric nitrate (HN03) is said to be an oxidising agent. Now chlorine, as it does not contain any oxygen, cannot be said to be an oxidising agent in the same sense as the abovementioned body is; but chlorine may be called such indirectly, because by its action upon metallic oxides it drives out the oxygen, which oxygen, being in the nascent state, may then easily combine with some other body. Thus if chlorine be made to act upon vegetable colouring matter to which a few drops of water have been added, it decomposes the water into hydrogen to form hydric chloride, setting the oxygen free. At the moment of its liberation the oxygen combines with the vegetable colouring matter, forming componnds destitute of colour. We have another example of the indirect oxidising action of chlorine when chlorine is made to decompose water in the presence of hydric sulphite. A similar reaction oxidiseB arsenious (As203) and phosphorous trioxides (P203), changing them into arsenic (As205) and phosphoric pentoxides (P205) respectively. When chlorine decomposes water in the presence of ferrous sulphate (FeS04), the liberated oxygen changes the ferrous sulphate into ferric sulphate, Fe2(S04)3. That such is the case may be easily proved. The ferrous salts are distinguished by their light green colour, and by their solutions giving a white precipitate with caustic alkalies (such as KH0) and a light blue precipitate with potassic ferrocyanide (KCy), which rapidly becomes dark. Ferric salts, on the other hand, are of a yellow colour, and their solutions yield a deep reddish brown precipitate with the caustic alkalies, and a deep blue precipitate with potassic ferrocyanide. That water is necessary for these reactions is thus shown: --If you ..