boiling a precipitate forms having the composition Mg(BO2)2, 2Mg(OH)2.7H2O. This compound has had some use as an antiseptic.

Magnesium Carbonate, MgCO,.—This is the normal magnesium carbonate, and is found abundantly in nature as magnesite. It is somtimes found in rhombohedral crystals, which are isomorphous with those of calcite. In pharmacy and medicine we are concerned chiefly with the artificially prepared or basic magnesium carbonate (MgCO3)4, Mg(OH)2.5H,O, Magnesii Carbonas, U. S. P. This compound became known as a valuable medicinal agent about the beginning of the eighteenth century, under the name of magnesia alba.

Preparation.-10 parts of magnesium sulphate and 12 parts of sodium carbonate are each dissolved separately in 80 parts of distilled water, the solutions are mixed in the cold, and the mixture boiled for 15 minutes. The precipitate is collected on a muslin filter and washed with hot water until the washings cease to give a reaction with barium chloride for sulphuric acid. The heavy carbonate of magnesia, magnesia carbonas ponderosa of the British Pharmacopoeia, is prepared by dissolving each of the above salts in 20 parts of water, mixing, and evaporating the resulting mixture to dryness. The dry residue is then washed thoroughly with hot water until all sodium sulphate is removed. The product is a dense powder. The reaction which takes place in these processes is as follows:

The method of Pattinson consists in igniting dolomite, a magnesium and calcium carbonate, and treating the product with solution of carbon dioxide under a pressure of 5 to 6 atmospheres. The magnesium carbonate goes into solution much easier than the calcium carbonate. The clear solution is separated from the precipitate of the latter, and on heating deposits a precipitate of the official carbonate, with evolution of some carbon dioxide, which may be used again.

Properties. The official magnesium carbonate comes in commerce in loose, white, easily-pulverized masses, which are readily reduced to a fine, white, amorphous powder, without odor, having an earthy taste, and permanent in the air. It dissolves in 2500 parts of cold water, and in 9000 parts of hot water, and

imparts to the water an alkaline reaction; alcohol exerts no solvent action upon it. Dilute acids dissolve it with active effervescence, and without leaving any residue.

Solution of ammonium salts have considerable solvent action on magnesium carbonate, and in the presence of ammonium chloride no precipitation of the carbonate will occur.

On the application of heat, water is first given off, and at 170° (Mendelejeff) the decomposition of the carbonate is complete, magnesium oxide remaining. This is considerably lower than the temperature of dissociation given by other authorities, and would consequently require more time than that usually given for the preparation of magnesium oxide.

When the official magnesium carbonate is shaken with water until a uniform mixture results, and carbon dioxide is passed in, there results a clear solution of acid magnesium carbonate, MgH,(CO), which has not been separated in the solid state. This solution on exposure to the air, and warming to 50°, deposits crystals of the neutral carbonate with 3 molecules of water, MgCO3.3H2O, or at a winter temperature MgCO,.5H2O separates. Under ordinary atmospheric pressure 1 part of magnesium carbonate requires 761 parts of carbonic acid water to dissolve it, under 3 atmospheres of pressure the solubility is 1 to 134, and at 6 atmospheres it is 1 to 76 of the carbonic acid

water.

The Liquor Magnesii Carbonatis of the British Pharmacopoeia is such a solution, and contains about 2 per cent. of the official carbonate. It is clear, and free from bitter taste.

Uses.-Magnesium carbonate is used in medicine as an antacid, and in the presence of acids becomes cathartic in its action.

Magnesium Silicates.-A number of these compounds occur widely distributed in the mineral kingdom. Talc has the composition 3MgSiOHSiO,, serpentine 3MgO, 2SiO.2H2O, etc.

Symbol, Be.

BERYLLIUM (Glucinum, G1).

Atomic Weight, 9.03.

Valence, II.

Historical. The mineral beryl was formerly supposed to be a compound of silica with calcium or aluminum, but Vauquelin, in 1798, showed the base to be different from both of these, and the name glucina was given to this new earth. Wöhler, in 1828, first obtained the metal, by fusing the chloride with potassium.

Occurrence.-Beryllium occurs in nature in a few rare minerals. Beryl is a silicate of beryllium and aluminum, 3BeSiO, Al(SiO), which

occurs in beautiful hexagonal crystals of a green color; the transparent, green-colored varieties are known as emerald, and those of a bluishgreen tint are termed aquamarine. Phenacite is a beryllium silicate of the composition BegSiO4, and chrysoberyl is a beryllium and aluminum oxide, BeO, Al2O3.

Preparation. Metallic beryllium is prepared by passing the vapor of beryllium chloride, along with hydrogen, over heated sodium. A violent reaction occurs, and the chloride is reduced to the metallic state and is obtained in the form of powder. It is afterwards caused to cohere by fusing in a crucible under a layer of sodium chloride. Any of the modern processes for the preparation of aluminum may be successfully applied to the preparation of beryllium.

Properties.-Beryllium is a silver-white, lustrous metal; malleable, and having the specific gravity 1.64. It remains unchanged in the air at ordinary temperatures, but when heated it becomes coated with a thin film of oxide which prevents further change. If the metal be in a finelypowdered state it will inflame when heated in the air. It does not act upon water, even when the latter is boiled with it. Dilute acids, like hydrochloric and sulphuric, dissolve it, as do also the hydrates of sodium and potassium, but nitric acid, even when hot and concentrated, acts on it very slowly.

Beryllium Chloride, BeCl2, is obtained in the anhydrous condition by passing chlorine over a heated mixture of beryllium oxide and charcoal. It is easily fusible and volatile, and may be obtained with 4 molecules of water of crystallization from aqueous solution. The chloride may also be obtained by dissolving the oxide in hydrochloric acid. In many of its characters it resembles magnesium chloride.

Beryllium Bromide, BeBr2, Iodide, Belg, and Fluoride, BeF2, are known, and may be prepared like the chloride.

Beryllium Oxide, BeO, yields with acids salts having a sweet taste. The solutions of these salts give precipitates of the hydrate, Be(OH)2, on the addition of sodium or potassium hydrate; this hydrate is distinguished from that of magnesium by being soluble in excess of the reagent, and from the hydrate of aluminum by its solubility in excess of alkali carbonate.

Beryllium Sulphate, BeSO4.4H2O, separates from hot, concentrated solutions, while from acid solution BeSO4.7H2O crystallizes; it is isomorphous with magnesium sulphate.

Beryllium Nitrate, Be(NO3)2.3H2O, is an extremely deliquescent salt, easily soluble in alcohol.

Beryllium Phosphate, BeHPO4.3H2O, is obtained by precipitating a soluble salt of beryllium with sodium phosphate.

Beryllium Carbonate, BeCO3.4H2O, separates in crystals of this composition, when a solution of the basic carbonate in carbon dioxide is concentrated over sulphuric acid with exclusion of oxygen.