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
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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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    other. When the whole was cold, which in winter was in about three days, the fluid was drawn off, the crystalized salt was de- tached from the slips of lead, and the rock of salt fixed to the bottom was separ- ated by a chisel and mallet. The salt being; washed in the same cistern, to free it from impurities, was then returned to the boil- er, dissolved in clear water, and evaporat- ed till a strong pellicle formed. Letting it cool till the hand could be dipped into it, it was kept at this temperature as long- as pellicles would form over the whole sur- face, and fall to the bottom. When no more pellicles appeared without blowing on the surface, the fire was put out, and the solution returned into the cistern to crystallize. If the solution be suffered to cool pretty low, very little sulphate of potash will be found mixed with the soda; but the rocky masses met with in the mar- ket generally contain a pretty large quan- tity. In the process above described, the produce of the mixed salt from 100 lbs. of sulphate of soda was in general from 136 to 139 lbs. Besides its use in seasoning our food, and preserving meat both for domestic consumption and during the longest voy- ages, and in furnishing us with the muri- atic acid and soda, salt forms a glaze for coarse pottery, by being thrown into the oven where it is baked ; it improves the Avhiteness and clearness of glass ; it gives greater hardness to soap ; in melting me- tals it preserves their surface from calci- nation, by defending them from the air, and is employed with advantage in some assays ; it is used as a mordant, and for im- proving certain colours, and enters more or less into many other processes of the arts. The muriate of strontian has not long been known. Dr. Hope first distinguished it from muriate of barytes. It crystallizes in very slender hexagonal prisms, has a cool pungent taste, without the austerity of the muriate of barytes, or the bitterness of the muriate of lime ; is soluble in 0.75 of water at 60°, and to almost any amount in boiling water; is likewise soluble in alcohol, and gives a blood-red colour to its flame. It has never been found in nature, but may be prepared in the same way as the muriate of barytes. The muriate of lime has been known by the names of marine selenite, calcareous marine salt, muria, and fixed sal ammoniac. It crystallizes in hexaedral prisms, termi- nated by acute pyramids; but if the solu- tion be greatly concentrated, and exposed to a low temperature, it is condensed in confused bundles of needly crystals. Its taste is acrid, bitter, and very disagreea- ble. It is soluble in half its weight of cold Yol. i. [9] water, and by heat in its own water of crystallization. It is one of the most de- liquescent salts known; and when deli- quesced has been called oil of lime. It exists in nature, but neither very abun- dantly nor very pure. It is formed in chemical laboratories, in the decomposi- tion of muriate of ammonia; and Romberg found, that, if it were urged by a violent heat, till it condensed, on cooling, into a vitreous mass, it emitted a phosphoric light upon being struck by any hard body, in which state it was called Romberg's phos- phorus. Hitherto it has been little used except for frigorific mixtures; and with snow it produces a very great degree of cold. Fourcroy, indeed, says he has found it of great utility in obstructions of the lym- phatics, and in scrofulous affections. The muriate of ammonia has long been known by the name of sal ammonia, or am- nionic. It is found native in the neigh- bourhood of volcanoes, where it is sub- limed sometimes nearly pure, and in dif- ferent parts of Asia and Africa. A great deal is carried annually to Russia and Si- beria from Bucharian Tartary; and we formerly imported large quantities from Egypt, but now manufacture it at home. See Ammonia. This salt is usually in the form of cakes, with a convex surface on one side, and concave on the other, from being sub- limed into large globular vessels ; but by solution it may be obtained in regular quadrangular crystals. It is remarkable for possessing a certain degree of ductili- ty, so that it is not easily pulverable. It is soluble in 3^ parts of water at 60°, and in little more than its own weight of boil- ing water. Its taste is cool, acrid, and bit- terish. Its specific gravity is 1.42. It attracts moisture from the air but very slightly. Muriate of ammonia has been more em- ployed in medicine than it is at present. It is sometimes useful as an auxiliary to the bark in intermittents; in gargles it is beneficial, and externally it is a good dis- cutient. In dyeing it improves or height- ens different colours. In tinning and sol- dering it is employed to preserve the sur- face of the metals from oxidation. In as- saying it discovers iron, and separates it from some of its combinations. The muriate of magnesia is extremely deliquescent, soluble in an equal weight of water, and difficultly crystallizable. It dis- solves also in five parts of alcohol. It is decomposable by heat, which expels its acid. Its taste is intensely bitter. With ammonia this muriate forms a tri- ple salt, crystallizable in little polyedrons, which separate quickly from the water, but arc not ven regularly formed. Its