MAGNESIUM. 



519 



excess of barium exactly by carbonate of soda 

 or of potassa. Where this mother-liquor cannot 

 be obtained, and the chloride must be artificially 

 produced, the sulphate of magnesia (Epsom 

 salts) serves as a better crude material than the 

 so-called magnesia of commerce. The sulphate, 

 it appears, is decomposed by carbonate of soda, 

 and the carbonate of magnesia obtained is sub- 

 mitted to repeated washings with hot water, 

 alternated with drying by means of great press- 

 ure or by aid of a centrifugal machine. This 

 artificially prepared carbonate of magnesia gives 

 the best results; but the native carbonate, found 

 in many parts of the world, which never con- 

 tains sulphates and frequently so little of a cer- 

 tain undetermined prejudicial ingredient ( JT) 

 often arising during the operation with the com- 

 mercial carbonate, or of other impurities, that it 

 serves even without preliminary purification as 

 a good primary material. By saturating chlor- 

 hydric acid with this native carbonate, the chlo- 

 ride of magnesium is readily prepared. 



To extract, in the next place, the metallic 

 magnesium, equivalent quantities, in solutions, 

 of the chloride or magnesium obtained in any 

 of the ways now indicated and of the chloride 

 of potassium or sodium (M. Sonstadt, in the out- 

 set, at least, recommending the former, though 

 the latter appears now to be employed in prac- 

 tice), are mixed, and the mixture evaporated to 

 dryness, and fused at a* red heat to expel the last 

 remains of water ; the fused mass is turned into 

 shallow sheet-iron pans to cool, and after solidi- 

 fication is broken up into small pieces, and till 

 wanted kept excluded from the air ; finally, there 

 is added to the fused chlorides [47.5 parts by 

 weight of MgCl, with 74.5 of KC1, or 58.5 of 

 NaCl] also an equivalent [23 parts] of metallic 

 sodium, this being simply placed in one mass in 

 the bottom of the iron crucible employed, and 

 over it the other material ; and an iron cover 

 being carefully luted on, the crucible is heated for 

 a length of time depending on its size, in a con- 

 venient furnace. The reaction begins at a dull 

 red heat or below, and is speedily completed by 

 the heat developed by the change within the 

 material, when, to avoid loss of magnesium in 

 vapor, the crucible must be quickly removed : 

 the sodium has withdrawn the chlorine from 

 its union with magnesium, leaving the metal 

 free within the mass. Crucibles into which 

 silica enters, owing to the fact that at the temper- 

 atures required in the process magnesium com- 

 bines with the silicium, cannot be employed ; 

 nor can those of platinum, with which the met- 

 al forms an alloy. The contents of the cruci- 

 bles, having been allowed to cool, are then re- 

 moved in a block: on breaking this up, the 

 crude magnesium is found in masses of various 

 shape and size down to small grains. These 

 are separated by simply mechanical means from 

 the saline matrix, then washed with water, and 

 dried gently at below 100 0. Technologiste, 

 Nov., 1864; vol. xxvi. 



The fact that, melting at a bright-red heat, 

 magnesium then speedily volatilizes, is availed 



of for refining the crude metal, obtained in the 

 manner now described. The magnesium is dis- 

 tilled in a crucible, a tube within which extends 

 from near the lid down through the bottom into 

 an iron box beneath the bars of the furnace, 

 and which is kept cool. The crucible being 

 filled to the mouth of the tube with the crude 

 metal, and the lid carefully luted down, atmos- 

 pheric air is expelled by injection of hydrogen. 

 As the crucible becomes heated, magnesium 

 rises in vapor and free from impurities,"and de- 

 scends through the upright tube into the box 

 below, where, at the end of the operation, it is 

 found as a conical pile of drippings. It can 

 then be melted, and cast into ingots or other 

 desired form. A second distillation, however, 

 may be required. Artisan, July 12, 1865; 

 Technologiste, vol. xxv., p. 181. 



The preparation of magnesium, by Son- 

 stadt's process, is already being carried on 

 by Messrs. Mellon & Co., at Salford, in the 

 suburbs of Manchester, England. It is stated 

 that the metal is being produced in consider- 

 able quantities, and that the price of the or- 

 dinary magnesium wire, some months previ- 

 ously as high as six cents the foot, is already 

 reduced to at most but two cents. The 

 preparation of the metal, and by the process 

 named, has also been commenced recently 

 by the "American Magnesium Company," of 

 Boston. Statements met with are to the effect 

 that at the former of the two manufactories 

 named, the crude material used is the native car- 

 bonate of magnesia ; while that adopted at the 

 latter is the dolomite, or magnesian limestone, 

 in which magnesium is present to the amount 

 of thirteen or fourteen per cent. Faraday has 

 stated that every ton of sea-water contains 

 over two pounds of magnesium, in the form of 

 chloride, so that the entire ocean must contain 

 160,000 cubic miles of magnesium, a quantity 

 which would form a cubic block fifty-four miles 

 on a side. As, in the process of manufacture 

 above described, when through care no waste 

 of sodium is allowed, every twenty-three pounds 

 of that metal converted into chloride can re- 

 lease only twelve pounds of magnesinm, it fol- 

 lows that the cheapening to be desired in the 

 cost of this metal, as well as in that of alumin- 

 ium and cadmium obtained through a like 

 reaction, must, in an important degree, wait 

 for and depend on a prior reduction in the cost 

 of sodium. 



Properties of Magnesium. These are already 

 so well understood that they need not here be 

 stated in full. The metal, when yet untarnished, 

 is of a bluish-white color, resembling silver, than 

 which, however, it is said to be even more beau- 

 tiful. While the specific gravity of aluminium is 

 2.56, that of magnesium is only 1.75 ; so that 

 whilst the former has one-fourth, the latter has 

 but one-sixth the density of silver (10.50) ; and an 

 ounce of magnesium has accordingly six times 

 the bulk of an ounce of silver. Exposed for 

 some time to the atmosphere, the metal becomes 

 covered with a thin coating of oxide, taking on 



