A dictionary of chemistry, on the basis of Mr. Nicholson's: in which the principles of the science are investigated anew, and its applications to the phenomena of nature, medicine, mineralogy, agriculture, and manufactures, detailed (Volume 1).
- Andrew Ure
- Date:
- 1821
Licence: Public Domain Mark
Credit: A dictionary of chemistry, on the basis of Mr. Nicholson's: in which the principles of the science are investigated anew, and its applications to the phenomena of nature, medicine, mineralogy, agriculture, and manufactures, detailed (Volume 1). Source: Wellcome Collection.
Provider: This material has been provided by the National Library of Medicine (U.S.), through the Medical Heritage Library. The original may be consulted at the National Library of Medicine (U.S.)
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![grate will be found under the article Am- monia. To obtain carbonate of magnesia satu- rated with acid, a solution of sulphate of magnesia may be mixed cold with a solu- tion of carbonate of potash ; and at the ex- piration of a few hours, as the superfluous carbonic acid that held it in solution flies off, the carbonate of magnesia will crys- tallize in very regular transparent prisms of six equal sides. It maybe equally ob- tained by dissolving magnesia in water im- pregnated with carbonic acid, and expos- ing die solution to the open air. Dr. Thomson says, the most regular crystals will be obtained by mixing together 125 parts of sulphate of magncsiaand 1 >6 parts of carbonate of soda, both dissolved in water, filtering the solution, and then set- ting it aside for two or three da\ s. These crystals soon lose their transparen- cy, and become covered with a white pow- der. Exposed to the fire in a crucible, they decrepitate slightly, lose their water and acid, fall to powder, and are reduced to one-fourth of the original weight. When the common carbonate is calcined in the great, it appears as if boiling, from the ex- trication of carbonic acid; a small portion ascends like a vapour, and is deposited in a white powder on the cold bodies with which it comes into contact; and in a dark place, towards the end of the operation, it shines with a bluish phosphoric light. It thus loses half its weight, and the magne- sia is left quite pure. As the magnesia of the shops is some- times adulterated with chalk, this may be detected by the addition of a little sulphu- ric acid diluted with 8 or 10 times its weight of water, as this will form with the magnesia a very soluble salt, while the sulphate of lime w,ll remain undissolved. Calcined magnesia should dissolve in this dilute acid without any effervescence. The crystallized carbonate dissolves in forty-eight times its weight of cold water; the common carbonate requires at least ten times as much, and first forms a paste with a small quantity of the fluid. Guyton Morveau has lately found the carbonate of magnesia native, near Castel- la-Monte, in a stone considered there as a clay very rich in alumina. It is amorphous, as white as ceruse, and as compact as the hardest chalk ; does not sensibly adhere to the tongue ; and has no argillaceous smell. Its specific gravity, when all the bubbles of air it contains have escaped, is 2.612. In the fire it lost 0.585 of its weight, and became sufficiently hard to scratch Bohemian glass slightly. On analysis it was found to contain magnesia 26.3, silex 14.2, carbonic acid 46, water 12, iron an inap- preciable quantity. The carbonate of ammonia, once vulgarly Vojd. r. [5] known by the name of volatile sal amm? niac, and abroad by that of English volatile salt, because it was first prepared in this country, was commonly called mild volatile alkali, before its true nature was known. When very pure it is in a crystalline form, but seldom very regular. Its crystals are so small, that it is difficult to deter- mine their figure. Bergmann describes them as acute octal drons, the four angles of which are truncated. Komi de Lisle had compressed tetra-dral prisms, terminated by a diedral summit. Bergmann obtained his by saturating warm water with the salt, stopping the bottle closely, and ex- posing it to great cold. The crystals com- monly produced by sublimation are little bundles of needles, or very slender prisms, so arranged as to represent herboriza- tions, fern leaves, or feathers. The taste and smell of this salt are the same with those of pure ammonia, but much weaker. It turns the colour of violets green, and that of turmeric brown. It is soluble in rather more than twice its weight of cold water, and in its own weight of hot water; but a boiling heat volatilizes it. When pure, and thoroughly saturated, it is not perceptibly alterable in the air; but when it has an excess of ammonia, it softens and grows moist. It cannot be doubted, how- ever, that it is soluble in air; for if left in an open vessel, it gradually diminishes in weight, and its peculiar smell is diffused to a certain distance. Heat readily sub- limes, but does not decompose it. It has been prepared by the destructive distillation of animal substances, and some others, in large iron pots, with a fire in- creased by degrees to a strong red heat, the aqueous liquor that first comes over being removed, that the salt might not be dissolved in it. Thus we had the salt of hartshorn, salt of soot, essential salt of vi- pers, &c. If the salt were dissolved in the water, it was called spirit of the substance from which it was obtained. Thus, how- ever, it was much contaminated by a fetid animal oil, from which it required to be subsequently purified, and is much better fabricated by mixing one part of muriate of ammonia and two of carbonate of lime, both as dry as possible, and subliming in an earthen retort. Sir H. Davy has shown that its compo- nent parts vary, according to the manner of preparing it. The lower the tempera- ture at which it is formed, the greater the proportion of acid and water. Thus, if formed at the temperature of 300°, it con- tains more than fifty per cent of alkali; if at 60°, not more than twenty per cent. * There are three or four definite com- pounds of carbonic acid and ammonia. The 1st is the solid sub-carbonate of the shops, it consists of 55 carbonic acid, 30](https://iiif.wellcomecollection.org/image/b21160909_0057.jp2/full/800%2C/0/default.jpg)
