3987. To Obtain Hydrated Baryta

3987.    To Obtain Hydrated Baryta. It may be precipitated from a solution of either nitrate or chloride of barium, by adding to it a solution of pure potassa or soda, collecting and drying the precipitate.

It is obtained in crystals, by boiling a strong solution of sulphuret or barium with successive portions of black oxide (protoxide) of copper, until it ceases to give a black precipitate with a salt of lead. The liquid, after filtration, yields crystals of hydrate of baryta on cooling.

3988. Test for Baryta

3988.    Test for Baryta. Its solutions give an immediate clear white precipitate with dilute sulphuric acid, which is insoluble in both acids and alkalies.

3989. Strontia

3989.    Strontia. An alkaline earth, the oxide of a metal called strontium. It greatly resembles baryta. Hydrate of strontia is freely soluble in boiling water, and the saturated solution deposits crystals on cooling. The solution exhibits an alkaline reaction, and, like baryta, is precipitated white by sulphuric acid and the alkaline sulphates and carbonates. It is distinguished from baryta by its inferior solubility and by its soluble salts giving a red tinge to flame, while the salts of baryta impart a yellow tinge. The salts of strontia may all be prepared by dissolving the native carbonate in the respective acids. Tho nitrate is the only one met with in commerce, and is employed to form colored fireworks.

3990. Magnesia

3990.    Magnesia, An alkaline earth, the oxide of the metal magnesium, in the form of a very light, white, odorless and tasteless powder, almost insoluble in cold and boiling water. It slowly absorbs carbonic acid from the atmosphere. "With the acids it forms salts, most of which may be made by tho direct solution of the earth, or its hydrate of carbonate. It dissolves in hydrochloric acid without effervescence. Neither bicarbonate of potassa nor chloride of barium throws down anything from the solution. It turns turmeric paper brown when moistened.

3991. To Obtain Magnesia

3991.    To Obtain Magnesia. Expose carbonate of magnesia in a crucible to a full red heat for 2 hours, or till the powder suspended in water does not effervesce on tho addition of muriatic acid. On the large scale, covered crucibles, made of porous earthenware, are employed as the containing vessels, and tho heat is applied by placing them in a sort of furnace or oven heated with coke.

3992. Test for Magnesia

3992.    Test for Magnesia. Magnesia is precipitated as a bulky white hydrate, by pure alkalies; and as a bulky white carbonate, by the carbonates of potassa and soda. Both the above precipitates dissolve in nitric and muriatic acid, forming salts which are very deliquescent, and soluble in alcohol.

Solutions of magnesian salts are not precipitated by the alkaline sulphates or sulphuric acid, nor, when very dilute, by oxalate of ammonia. By these tests it may be distinguished and separated from lime. These tests distinguish it from the other earths, and its insolubility in alkaline solutions marks its difference from alumina.

3993. Lime

3993.    Lime. A highly acrid, alkaline and caustic earth, less insoluble in cold than in hot water. It is the oxide of calcium. When heated to a high degree, it becomes intensely luminous, and is well known in use as the calcium light.

3994. To Obtain Lime

3994.   To Obtain Lime. Lime, or quicklime, is obtained by exposing limestone, or chalk, which arc carbonates of lime, to a red heat. Shell-lime is got in the same manner from the shells of the oyster and other shellfish. "When sprinkled with water, heat is generated, and the lime, combining with the water, crumbles down into a powder, which is hydrate of lime, or slacked lime.

3995. Tests for Lime

3995. Tests for Lime. The alkaline carbonates, phosphates, oxalates, and sulphates, occasion white precipitates in solutions of lime. The precipitates occasioned by the first three tests are soluble in dilute nitric or muriatic acid; that by the last is insoluble in those menstrua, but soluble in solution of salt, and not reprecipitated by dilute sulphuric acid.

Oxalate of ammonia or potassa is the most delicate test of lime. If the substance under examination be a solid, dissolve it in muriatic acid, filter, evaporate to dryness, redissolve in water, and test as above. All the soluble 6alts of lime tinge the flame of alcohol of an orange color, but this may be confounded with the color produced by the salts of strontia.