Chemistry / by George Wilson.

  • George Wilson
Date:
1859
Catalogue details

Licence: Public Domain Mark

Credit: Chemistry / by George Wilson. Source: Wellcome Collection.

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    neither black nor yellow, nor of any intermediate tint, but ns colourless as water. Multitudes of other examples might be given, but these may suffice so far as change of colour is concerned. 43. The other properties of the chemical elements, however, are quite as much altered when they combine as their tints are. Thus the heavy metal antimony, which we. are accus- tomed to see as a massive solid, forms an invisible gas when it combines with hydrogen. The greenish-yellow gas chlo- rine, on the other hand, when it unites with quicksilver, forms white crystals of corrosive sublimate. Solid sulphur and charcoal change into a very volatile liquid. Phosphorus, which resembles wax in appearance, and oxygen, a colourless, invisible gas, form phosphoric acid, a body exceedingly like snow. Nitrogen and oxygen have no taste; neither has a mixture of them. One of their compounds, laughing gas, is pleasantly sweet to the palate; another, nitric acid, intensely sour. Charcoal, hydrogen, and oxygen, are all tasteless; gum is one combination of them, arrow-root another, sugar a third. 44. Chlorine gas has a suffocating odour; common salt, of which it forms more than one-half by weight, is odourless. Charcoal and hydrogen, on the other hand, have no odour; nevertheless, a large number of our choicest perfumes, such as attar of roses, oil of bergamot, and oil of citron, consist solely of those two elements. In like manner the scentless nitrogen and hydrogen are the only constituents of one of the most odorous of all substances, spirits of hartshorn, or ammonia. 45. Again, the deadly poison prussic acid is made up of carbon, hydrogen, and nitrogen, which, taken singly or mixed, are not injurious to animal life. Oxalic acid, another poison, consists of charcoal, hydrogen, and oxygen. The same elements constitute spirits of wine and sulphuric ether. 46. The preceding examples of change in specific gravity, colour, form, taste, odour, and relation to living animals, will serve, in the meanwhile, to prove how totally dissimilar in properties a chemical compound is, from a mere mechanical mixture of its elements. 47. Every chemical compound exhibits this character of newness of properties. No substance, indeed, is entitled to be called a chemical compound in which the properties are only the sum or the mean of those of its ingredients. The charac- teristic difference between the products of mechanical attrac- tion and chemical affinity may be illustrated thus: the least complex kind of combination being selected to be commented on. If we call the one element of the mechanical mixture A,
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