178 MAGNESIUM 



obtaining magnesium on the large scale for commercial purposes. The process pur- 

 sued by Sonstadt is that of Deville and Caron, somewhat modified. Magnesium may, 

 however, be obtained in much larger quantity, by heating a mixture of 600 grains 

 of chloride of magnesium, 100 grains of fused chloride of sodium, and 100 grains of 

 pulverised fluoride of calcium, -with 100 grains of sodium, to bright redness, in a 

 covered earthen crucible. The magnesium is thereby obtained in globules, which 

 are afterwards heated nearly to whiteness in a boat of compact charcoal placed within 

 an inclined tube of the same material, through which a stream of dry hydrogen is 

 passed. The magnesium then volatilises and condenses in the upper part of the tube. 

 Lastly, it is re-melted with a flux composed of chloride of magnesium, chloride of 

 sodium, and fluoride of calcium, and is thus obtained in large globules. It still, how- 

 ever, usually retains portions of carbon, silicium, and nitrogen, from which it may be 

 purified by careful distillation in a current of hydrogen. 



Magnesium is an easily inflammable metal ; a wire of considerable thickness can be 

 ignited in the flame of a candle, and the light evolved by the combustion is of great 

 intensity. It has been ascertained that a wire of 0-297 millimeter diameter will 

 give as much light as 74 stearine candles of five to the pound. The powerfully 

 actinic character of the light has been demonstrated by Mr. Brothers, of Manchester, 

 and Mr. Sydney Smith, both of whom have produced good pictures by its use. 



The metal is neither ductile nor very malleable. It cannot be drawn, but, by 

 employing a method devised by Dr. Matthiessen, it can be forced in a softened state 

 through a small opening in an iron cylinder, and thus strands of wire of consider- 

 able length can be formed. The wire has been found to burn more steadily when 

 three or four strands are twisted into a rope ; and a simple clockwork arrangement 

 will deliver such a rope to a spirit- or oil-lamp, in the flame of which it may bo 

 burned. 



Alloys of Magnesium. Dr. T. L. Phipson has paid some attention to these. In 

 a communication to the Chemical Society, he says : 



1 1 have examined only a few alloys of magnesium. Unlike zinc, magnesium will 

 not unite with mercury at the ordinary temperature of the air. With tin 85 parts, 

 and magnesium 15 parts, I formed a very curious alloy of a beautiful lavender colour, 

 very hard and brittle, easily pulverised, and decomposing water with considerable 

 rapidity at ordinary temperatures. If the air has access during the formation of this 

 alloy the mixture takes fire ; and if the crucible be then suddenly withdrawn from 

 the lamp the flame disappears, but a vivid phosphorescence ensues, and the xinfused 

 mass remains highly luminous for a considerable time. A white powdery mass, 

 containing stannic acid and magnesia, is the result. (With platinum, according to 

 M. Sonstadt, magnesium forms a fusible alloy ; so that platinum crucibles can be 

 easily perforated by heating magnesium in them.) Sodium and potassium unite with 

 magnesium and form very malleable alloys, which decompose water at the ordinary 

 temperature. It is probable that an alloy of copper and magnesinm, which I have 

 not yet obtained, would differ from brass, not only in lightness, but by decomposing 

 water at the usual temperature with more or less rapidity.' 



Photochemical Power of the Magnesium flame. To Professors Bunsen and Eoscoe 

 we are especially indebted for an examination of this question. Their experiments 

 showed that a burning-surface of magnesium-wire which, seen from a point at the 

 sea's level, has an apparent magnitude equal to that of the sun, effects on that point 

 the same chemical action as tho sun would do when shining from a cloudless sky at 

 a height of 9 58' above the horizon. On comparing the chemical with the visible 

 brightness of these two sources of light, it was found that the brightness of the sun's 

 disc, as measured by the eye when tho sun's zenith distance was 67 22', is 524-7 

 times as great as that of the burning magnesium-wire ; whilst, at the same zenith 

 distance, the chemical brightness of the sun is only 36 - 6 times as great. Hence the 

 value of this light as a source of tho chemically-active rays for photographic purposes 

 becomes apparent. 



Professors Bunsen and Eoscoe say in their memoir : ' The steady and equable light 

 evolved by magnesium-wire burning in the air, and the immense chemical action 

 thus produced, render this source of light valuable as a simpler means of obtaining a 

 given amount of illumination expressed in our terms of measurement of light. 

 The combustion of magnesium constitutes so definite and simple a source of light 

 for the purpose of photochemical measurement that the wide distribution of this 

 metal becomes desirable. The application of this metal as a source of light may 

 even become of technical importance. A burning magnesium-wire of the thickness 

 of 0-297 millimeter evolves, according to a measurement we have made, as much 

 light as seventy-four stearine candles, of which five go to a pound. If this light 

 lasted one minute, 0'987 meter of wire, weighing 0-1204 grain, would be burnt. Jr 

 order to produce a light equal to seventy-four candles burning for ten hours 



