Class I. 61. Qleate of lime. When hot solutions of chloride of calcium and oleate of potash are mixed, oleate of lime precipitates. It is white and pulverulent when dry. It melts when exposed to a gentle heat.* 62. Phocenate of lime. It may be formed by neutralizing phocenic acid in solution in water by carbonate of lime. When the solution thus obtained is concentrated in vacuo over quicklime, phocenate of lime crystallizes in prisms. It is soluble in water, and possesses characters analogous to those of phocenate of barytes.† 63. Butyrate of lime. This salt may be prepared in the same way as butyrate of barytes. It crystallizes in very small prismatic needles, and is transparent. At 60°, 100 parts of water dissolve 17.58 parts of this salt. When this solution is heated, the salt crystallizes so abundantly, that the liquid becomes solid. But it again dissolves when cooled down to 60°. Two parts of butyrate of lime, and 3 of butyrate of barytes, dissolved in water, and left to spontaneous evaporation, deposite octahedrons, consisting of the two salts in combination. 64. Caproate of lime. This salt crystallizes in brilliant plates, many of which are squares.§ 65. Cholesterate of lime. This salt is very little soluble in water. 66. Pinate of lime. It may be formed when a calcareous salt is dropped into a solution of pinate of potash. It falls in the state of a yellowish white powder. It has no resemblance to a resin, and does not become coherent when exposed to the heat of boiling water. It is slightly soluble in alcohol, very soluble in ether, and in oil of turpentine and olive oil. Its constituents, according to Unverdorben, are 67. Silvate of lime. It may be prepared by a process similar to that which yields the preceding salt. It dissolves in about 5000 times its weight of water. It is slightly soluble in alcohol of the specific gravity of 0.883; but it dissolves in 6 times its weight of absolute alcohol, and it is still more soluble when the alcohol is boiling hot. As the solution cools, * Chevreul, sur les corps gras, p. 93. $ Ibid. † Ibid. p. 109. Poggendorf's Annalen, vii. 314. the salt is deposited in white flocks, which before the micro- Sect. VII. scope appear crystalline. These flocks dissolve in ether. When the ether solutions is mixed with absolute alcohol, and left to spontaneous evaporation, the silvate is deposited in colourless grains, which appear under the microscope as small spherical masses attached to each other." 68. Carbazotate of lime. Obtained by the same process as carbazotate of barytes. Crystals flat, four-sided prisms, very soluble in water. They detonate like carbazotate of potash.+ 69. Urate of lime. A white powder, scarcely distinguishable in appearance from uric acid. 70. Pyrurate of lime. This salt crystallizes in mamillary masses, it is soluble in water, and has a bitter and slightly acrid taste. When gently heated it melts, and on cooling assumes the appearance of yellow wax. When calcined in a platinum crucible, it leaves 8.6 per cent. of pure lime. 71. Aspartate of lime. This salt forms a gummy mass. Its taste is similar to that of aspartate of soda. When boiled with carbonate of lime it becomes sensibly alkaline.§ 72. Hydro-carbo-sulphate of lime. This salt is obtained by mixing a solution of chloride of calcium in alcohol, with a solution of hydro-carbo-sulphate of potash, chloride of potassium is precipitated, and hydro-carbo-sulphate of lime remains pretty pure, dissolved in the alcohol. || The properties of this salt have not been investigated. 73. Sulphovinate of lime. This salt may be obtained by saturating the residue after the preparation of ether with carbonate of lime, filtering the solution, and setting it aside to spontaneous crystallization. The crystals are long four-sided tables, not altered by exposure to the air. The taste is sweetish. The salt dissolves readily in water and in alcohol. When placed in vacuo over sulphuric acid, the crystals lose their water of crystallization and become opaque. When heated to redness they take fire and burn with flame, leaving sulphate of lime behind. When distilled in a retort it loses its water of crystallization, then becomes black, giving out an empyreumatic ether, with a white heavy oil which sinks in water. At the Class I. Characters. same time a quantity of sulphurous acid gas is extricated. There remains in the retort sulphate of lime mixed with charcoal.* 74. Sulphonaphthalate of lime. A white salt with a bitter taste, soluble in alcohol, and when the solution is evaporated imperfect crystals are deposited. It burns with flame.+ 75. Sinapate of lime is very soluble in water, and shoots into mamillary masses.‡ SECTION VIII.-SALTS OF MAGNESIA. The salts of magnesia can scarcely be said to have been known till Dr. Black published his celebrated experiments on magnesia alba, and quicklime, in the year 1755. They were afterwards examined more in detail by Bergman, and different salts of magnesia have been since described by different chemists. 1. A very great proportion of them is soluble in water, and capable of crystallizing. 2. When any of the fixed alkalies or of their carbonates is dropped into a salt of magnesia a white flocky precipitate falls. 3. No precipitate appears when sulphate of soda is dropped into a salt of magnesia. 4. If phosphate of soda be dropped into a salt of magnesia, no precipitate appears; but if any ammonia be added, a white precipitate falls, which is a double salt composed of phosphoric acid, ammonia, and magnesia. This precipitation furnishes the best method yet known for separating magnesia from other bodies, and determining its quantity. It was first pointed out by Dr. Wollaston. 5. Prussiate of potash occasions no precipitate in a salt of magnesia, unless the acid happen to have a metal for its basis. 6. Magnesia has a greater tendency than any of the bases whose salts have been already described to enter into double compounds. The base with which it is most given to unite is ammonia. 7. When a salt of magnesia is tinged with a little nitrate of cobalt, and fused before the blow-pipe with a strong blast, it assumes a fine flesh colour, the tint of which is very feeble, and not easily distinguished till the assay is perfectly cold. This fact was discovered by Assessor Gahn, and was used by him with success to discover the presence of magnesia in mineral * Vogel, Gilbert's Annalen, lxiii. 90. Faraday, Annals of Philosophy (2d series), xii. 210. bodies. It answers also with several of the salts of magnesia; but when the acid is combustible or volatile, and leaves pure magnesia, we are not able to accomplish the fusion by the blowpipe, in such cases we must add borax or biphosphate of soda. 1. Sulphate of magnesia. This salt is held in solution in the springs at Epsom in England, and was procured from them by evaporation more than a century ago. Hence the term Epsom salt, by which it was long distinguished. It was called also sal catharticus amarus from its taste and properties, and Seydler salt, because it exists in the Seydler spring at Seydschutch a village in Bohemia. Some account of it was given by Grew in 1675; and in 1723, Mr. Brown published a description of the process employed in extracting it from the springs, and in purifying it. In Italy it is manufactured from schistose minerals, containing sulphur and magnesia. By roasting these minerals, and then moistening them and exposing them to the air, the salt effloresces on their surface. By solution in water, with the addition of a little lime to precipitate any metallic substance that may be in solution, and repeated crystallizations, the salt is obtained in a state of purity.+ It exists in considerable quantity in sea-water; and the uncrystallized residuum in the salt pans, after all the common salt has crystallized, consists partly of this salt dissolved in water. This residuum is usually called bittern, and sometimes in Scotland spirit of salt. Sulphate of magnesia crystallizes in rightsbiboso prisms, the bases of which to the eye appear squares; but from the measurements of Mr. Brooke, it appears that the angles deviate an Bl M on M' M on h M on e a on a The crystals refract double. Phil. Trans. xxxii. 348. † Ann. de Chim. xlviii. 80. Іва в дом 11 ..90° 30' 134 45 129 00 120 nearly. See also Gehlen's Jour. iii. 549. An ac count of the manufactory has been published by Dr. Holland in Phil. Trans. 1816, p. 294. Annals of Philosophy (2d series), vi. 40. This salt has an intensely bitter taste. Its specific gravity § 1·66.* At the temperature of 55° 100 water dissolves 90-01 of the crystals at 60° it is soluble in its own weight of water, and in less than two-thirds of its weight of boiling water.† The volume of water is increased ths by adding the salt.‡ When exposed to the air it effloresces, and is reduced to powder. When exposed to heat it undergoes the watery fusion; and by increasing the temperature its water is evaporated, but it cannot be decomposed by means of heat. Before the blowripe it melts with difficulty into an opaque vitreous globule.§ Its constituents are It appears from the observations of M. Planche, that when dry sulphate of magnesia in powder is mixed with dry bicarbonate of soda, the two powders gradually act upon each other, and a double decomposition takes place.|| 2. Sulphite of magnesia. This salt has only been examined by Foureroy and Vauquelin. It is prepared, like the others, by saturating carbonate of magnesia with sulphurous acid; a viclent effervescence takes place, and the liquid becomes warm. The sulphite as it forms remains at the bottom in the form of a white powder: but if an excess of acid be added, it dissolves, and may be obtained in crystals by subsequent exposure to the air. Its crystals are white and transparent and in the form of depressed tetrahedrons. Its specific gravity is 1·3802.¶ Its taste is mild and earthy at first, and afterwards sulphureous. It becomes opaque when exposed to the air; but is very slowly converted into a sulphate. At the temperature of 60° it is soluble in 20 parts of water. Boiling water dissolves a greater proportion of it; but the solution crystallizes on cooling. When its solution in water is exposed to the air, this salt is very soon converted into a sulphate. By exposure to heat, it softens, swells up, and becomes ductile like gum, and loses 0·45 parts of its weight. In a strong heat the acid is disengaged, and * Hassenfratz, Ann. Chim. xxviii. 12. # Bergman, Opuse. i. 377. + Bergman, Opusc. i. 377. $ Ibid. Annals of Philosophy (2d series), xii. 403. Hassenfratz, Ann, de Chim. xxviii. 12. |