BASIC RADICALS. CLASS II. METALS OF ALKALINE EARTHS. Barium. Strontium. Calcium. Magnesium. THE alkaline earths are four in number: Barytes, Strontian, Lime, and Magnesia: the three first are distinguished by yielding no precipitate with ammonia, and falling when soda or potash is added, while magnesia does not fall with ammonia if salts of NH, be present. BARIUM. Ba. 8.5. This metal is obtained by exposing the hydrate of barytes (BaO HO) to the action of a galvanic battery, in contact with mercury. An amalgam of barium and mercury forms, from which the latter distils off when heated, leaving the pure barium behind. (Davy.) Protoxide of barium, barytes, heavy earth, terra ponderosa. BaO 9.5. This oxide occurs abundantly in nature, associated with lead ore, in union with sulphuric acid, as sulphate of barytes or heavy spar. To render this very insoluble substance soluble in water, it is to be heated with an equal bulk of finely pounded charcoal in a clay crucible, covered over with sand, and exposed for some hours to a strong red heat. By the charcoal, all the oxygen is removed from the mineral, and sulphuret of barium remains (BaO SO, and 2C becoming BaS and 2CO2), which is quite soluble in water. If the solution be now precipitated by carbonate of NH,, the carbonate of barytes dissolved in NO, and crystallized, BaO NO, remains; by ignition, the nitric acid is driven off, and barytes (BaO) remains. A grayish white solid; taste, caustic; a violent poison; tinges vegetable blues green; fuses before the blowpipe into globules; attracts water in the air, and slakes like limé; 100 parts of cold water dissolve 5 parts of barytes; boiling water more than half its weight. Peroxide of barium — BaO, 10·5, is obtained by passing oxygen over barytes in a porcelain tube. Gray powder, not decomposed at a red heat, but by boiling water, and acids. Chloride of barium - Ba Cl. 2HO 15.25, may be obtained by boiling a solution of the sulphuret (procured by the process already described) with hydrochloric acid, until all the sulphuretted hydrogen passes off; on evaporation it crystallizes in white rhombic prisms, or plates. Taste, bitter; poisonous. It is an important re-agent for detecting and estimating sulphuric acid quantitatively. Nitrate of barytes.- BaO NO, 15-25, 8-hedrons, obtained by neutralising the carbonate of barytes with nitric acid, and crystallising. 12 parts of water at 60°, and 3 or 4 of boiling water, dissolve 1 part of the salt; insoluble in alcohol. It is a useful re-agent, as in the distillation of nitric acid, for the separation of sulphuric acid. It affords the green fire of fire-works and theatres. This is made by mixing in a mortar 100 parts of nitrate of barytes, previously well dried, with 9 sulphur, 7 chlorate of potash, 2 of charcoal, and 4 sulphuret of antimony, all well dried. If a small heap of this is formed upon an iron plate, and heated by a lamp placed below, and touched immediately with a hot wire, a beautiful green combustion will take place after some time. Test. The salts of barium are distinguished by the green colour they afford to the flame of the blowpipe. The experiment may be made by holding the salt in a pair of forceps, or in the loop of a platinum wire, or by dipping a platinum wire in a strong solution of the salt: they are also distinguished by their affording an immediate precipitate to a solution of sulphate of lime, lime giving none; and strontian only after the lapse of some time; oxalic acid gives no precipitate in dilute solutions. STRONTIUM. Sr. 5.5. Strontium is obtained from strontian (SrO) in the same way as barium from barytes, as already described. The name is derived from the village of Strontian, in Argyleshire, where the substance was first discovered. Strontium is white, solid, and heavy, decomposing water, and absorbing oxygen from the air. —(Davy). Strontian, protoxide of Strontium, Strontites, Strontia, SrO 6·5, may be obtained from the sulphate of strontian or celestine, by the same process as described for barytes. The oxygen is removed from the mineral by means of charcoal, and the resulting sulphuret dissolved in water and neutralised by nitric acid or carbonate of soda, or ammonia. The nitrate or carbonate when strongly heated leaves caustic strontian (SrO), a grayish white mass with an acrid and alkaline taste, not poisonous, soluble in 50 times its weight of cold water (60°) and in twice its weight of hot water (2120). The solution, when evaporated, deposits square plates containing 68 per cent. of water. like lime, and forms a hydrate (SrO HO). vegetable blues green; insoluble in alcohol. Strontian slakes The solution turns Peroxide of Stron tian, SrO, 75, is obtained in bright scales when a solution of strontian is' mixed with deutoxide of hydrogen. Chloride of Strontium, Sr Cl 9 HO, 6-sided prisms, obtained by dissolving the carbonate in hydrochloric acid and crystallizing; a deliquescent salt, soluble in water and alcohol. The solution in alcohol, when set on fire, burns with a beautiful crimson flame, characteristic of the salts of Strontium. Nitrate of Strontian, SrO NO, 13-25, anhydrous octahedrons or oblique prisms, with 30 per cent, water, insoluble in alcohol. This salt is used in the preparation of the red fire of fire-works-100 parts of dry nitrate of strontian are carefully mixed with 12 parts of chlorate of potash, 30 sulphur, 10 sulphuret of antimony, and 5 charcoal, all carefully dried, and rubbed with great caution in a mortar to prevent friction, otherwise an explosion may occur. The powder is heaped up on a thin iron plate and heated from below by means of a lamp, and then touched with a hot wire. Tests. Salts of Strontian are recognised by their giving, with a solution of sulphate of lime, a precipitate only after some time. Oxalic acid affords no precipitate; while lime yields one at once. The salts of Strontian when heated in the blowpipe flame impart a crimson colour to it, as do their solutions. Their solution in alcohol burns with a fine crimson flame. CALCIUM. Ca 2.5. A white metal, similar to barium and strontium, and obtained by the same process. — (Davy). Protoxide of Calcium, Lime, quicklime, caustic lime, burned lime, CaO 3.5, is obtained by burning carbonate of lime, limestone, or chalk in a limekiln, along with coal. The intense heat produced expels the carbonic acid (CaO CO, becoming CaO and CO, set free). This experiment may be imitated by heating a splinter of marble or limestone before the blowpipe. Lime is white and easily pulverised. · Specific gravity 3.16. Hot taste and burning, destroying animal substances; tinges vegetable blues green, and gradually turns them yellow. Very refractory, and has never been fused except by the oxyhydrogen blowpipe. It glows or phosphoresces when exposed to a full red-heat. When pure it does not effervesce with dilute acids, and its solution does not precipitate prussiate of potash or caustic ammonia. Hydrate of lime. · - Slaked lime, CaO HO 4.625. When a few drops of water are poured upon a piece of quicklime they are immediately absorbed. If a larger amount is added heat is evolved, while vapour, and sometimes light, appear. The heat is so considerable that vessels loaded with lime have been set on fire, and an apparatus, consisting of a kind of cabinet of tin drawers, has been constructed, where, by placing slaking lime in a lower drawer and meat in that immediately over it, sufficient heat is evolved to cook a beef steak or mutton chop. This method of producing heat is said to have been practised by Mr. Green in his celebrated balloon voyage from London to Wiesbaden in one night. This operation is very familiar under the term of slaking lime, and may be seen every day where mortar is preparing. The evolution of heat depends on the fact that in all chemical combinations heat is given out. In the present example, the water unites with the lime, and, becoming solid, loses the heat which was necessary to retain it in a fluid form. During slaking the vapour given off renders vegetable blues green, and has a smell owing to a portion of the lime being carried with the vapour. Pure lime (CaO) is incapable of absorbing carbonic acid; but when it is slaked (CaO HO) it readily takes up carbonic acid, which replaces the water (CaO HO and CO, becoming CaO CO, and HO). Hydrate of lime dissolves sparingly in water-forming lime water — 1 part of lime dissolving in 778 parts of water at 60° - in 972 water at 130°, and in 1270 water at 212°. Lime-water is best prepared by throwing a quantity of pounded lime into a stoppered bottle filled nearly full of water, and allowing it to stand for some days, with frequent agitation. The clear liquor is then poured off or filtered away from the air. In contact with the atmosphere a pellicle of carbonate of lime soon forms on the surface from the absorption of carbonic acid from the air. It must therefore be preserved in well stoppered bottles. On the addition of water containing carbonic acid to lime water there is a precipitate of carbonate of lime, which disappears on the addition of a larger quantity of carbonic acid (CaO CO2 and CO2 becoming CaO 2CO,, a soluble bicarbonate), in which state carbonate of lime exists in well and river waters. Limewater is useful for the detection of carbonic acid, and for the diarrhoea of infants, to whom it may be given mixed with their milk. Lime is employed as a mortar to cement stones together, in consequence of its tendency to unite with water, carbonic acid, and sand or silica, and to set or harden during the combination. It is made best by mixing 1 part unslaked lime, 1 slaked lime, 1 fine and 1 coarse sand. Lime is also used as a manure for land, in consequence of its action in decomposing vegetable substances, and from its effect on alumina or clay. Thus when pipeclay and milk or cream of lime (hydrate of lime made of the consistence of cream by the addition of water) are mixed the whole becomes thick on agitation, and when left in contact for some months the mixture assumes the appearance of a jelly; on the addition of an acid, the clay is broken up by the union of some of its constituents with lime, and any alkalies present are set free. One essential use in applying lime to land BLEACHING POWDER. 121 appears therefore to be to liberate the alkalies in union with silica in the soil. Marl or carbonate of lime, when dissolved in water by an additional atom of carbonic acid, exercises the same effect on soil. Peroxide of Lime. — CaO, 4·5. — White brilliant scales obtained by dropping lime-water into peroxide of hydrogen. Chloride of Calcium, Ca Cl 7, exists in sea and mineral waters. It crystallizes in 6-sided prisms with 6 atoms of water. As usually prepared for use, it is made by saturating chalk or marble (CaO CO2) with hydrochloric acid, evaporating the solution to dryness, and heating up to 350°, to remove the crystalline water. Taste bitter and sharp-deliquescent. The crystallized salt, when mixed with snow, produces intense cold. The dry salt is employed to dry gases when transmitted through tubes, fig. 45. Bleaching Powder, Tennant's Bleaching Powder, Hypochlorite of Lime, Chloride of Lime. Berthollet first introduced chlorine as a bleaching agent. It was used afterwards in solution under the name of Eau de Javelle, when water was impregnated with it. In January 1797, Charles Tennant, of Darnley, near Glasgow, obtained a patent for impregnating lime and water with chlorine, and, in April 1799, a patent was taken out in his name for impregnating dry lime with chlorine. The process for producing bleaching-powder consists, at present, of three stages. 1. The formation of the hydrate of lime; 2. The evolution of chlorine; and, 3. The absorption of the gas by the lime. 1. In this country the lime usually employed is the Irish limestone, which is beautifully white and pure constituting the chalk of Ireland. It is burned in lime-kilns, and then slaked with water. 2. The chlorine is disengaged from large stone stills by the action of hydrochloric acid upon black oxide of manganese, assisted by a steam heat, or by any of the methods already recommended for the production of chlorine. The retort is a stone box, double, so as to admit steam round it. The materials are introduced into the still by an aperture on the top, and the acid by another opening, supplied with a funnel. The chlorine is conducted by a lead tube, and enters at the top of the lime chambers. 3. These chambers consist of apartments of sandstone, cemented with a mixture of pitch, rosin, and gypsum, supplied with doors, which are rendered air-tight during the extrication of the gas, being built close up. The hydrate of lime is strewed over the floor of the chamber to the depth of three or four inches; the chlorine is allowed to remain in contact with it for four days. Some makers of bleaching-powder strew the powder upon shelves, in order to present a greater surface to the action of the chlorine. Good bleaching-powder should be perfectly white, and attract moisture but slowly in the air; it should be soluble in twenty parts of water, without leaving much |