4G4 



MAGNESIUM. 



Presbyterian Church, to which he belonged. 

 Possessing a vigorous and thoroughly cultured 

 mind, and a well-balanced judgment, he suc- 

 ceeded in all he attempted. His expositions of 

 Scripture, and his religious addresses and ser- 

 mons, were exceedingly rich and instructive, 

 and held the attention of all his hearers, while 

 his influence over his students was unbounded. 

 He had published several works, mostly on 

 theological topics, and numerous occasional 

 sermons, addresses, and controversial pam- 

 phlets. 



MAGNESIUM. This metal has not yet como 

 into general favor with photographers. Its 

 cost, though greatly reduced, since the suc- 

 cess of Sonstadt's method, and the practical 

 difficulties in the way of its use, such as its 

 want of steady and equable combustion and the 

 production and dilfusion of clouds of oxide, are 

 objections which remain in force. It has been 

 used in Europe in taking photographs of grot- 

 toes, caves, and other dark interiors, and pro- 

 'duces fair pictures. As a general substitute for 

 the actinic power of sunlight, it would seem to 

 have found a successful rival in the new electric 

 light of Mr. Wilde's apparatus. (See ELECTRICI- 

 TY.) Experiments have been made with mag- 

 nesium in England for purposes of signalling, 

 but the British Government has not given it 

 the sanction of its approval. Several valuable 

 uses have been discovered for this beautiful new 

 metal during the year, and it must still be re- 

 garded as the most important addition which 

 has been made for many years to the stock of 

 serviceable elements. 



Mr. W. N. Hartley (Chem. Neics, No. 350) 

 states that no hydrogen is evolved by the metal 

 in solutions of phosphate of ammonia, the ni- 

 trates and sulphides of the alkalies and alkaline 

 earths, permanganate of potash and peroxide 

 of hydrogen. To the nitrates the ammonia salt 

 is an exception ; the evolution of gas being as 

 brisk as from other salts. Most metals are pre- 

 cipitated by magnesium from their solutions, 

 but he did not succeed in precipitating iron ; 

 the magnesium becomes blackened probably 

 from a deterioration of metallic iron, but this 

 disappears as the magnesium dissolves. He 

 could not get satisfactory results with cobalt. 

 Magnesium may be amalgamated like zinc, by 

 shaking it in a bottle containing mercury cov- 

 ered with a layer of dilute sulphuric acid; 

 when so treated it possesses the power of 

 decomposing water violently. This amalga- 

 mated magnesium may be used instead of sodi- 

 um-amalgam to act on an organic substance 

 with nascent hydrogen. In testing for nitric 

 acid by boiling cadmium with the solution, and 

 after addition of acid testing with iodide of 

 potassium and starch-paste, magnesium may be 

 used with advantage. If a small battery be 

 made of a piece of magnesium ribbon and pla- 

 tinum foil and this be placed in water very 

 faintly acidulated, without the joining of the 

 platinum and magnesium being immersed, the 

 presence of nitric acid may be shown by its 



conversion into nitrous acid, and the conse- 

 quent coloration of paper dipped in the acidified 

 liquid. Should the trace of nitric acid be very 

 small, the action must go on slowly for several 

 hours, in which case the liquid should be neu- 

 tral when acting on the magnesium. 



The alloys of magnesium, so far as known, 

 are of no practical value. They are generally 

 prepared by bringing magnesium wire into con- 

 tact with the primary metals fused under a layer 

 of salt, fluor-spar, or a mixture of the latter 

 with cryolite. The alloys are invariably very 

 brittle, and easily tarnished. The zinc alloy is 

 the only one that is permanent; whilst, on the 

 other hand, the alloys with lead and bismuth 

 are quickly affected by the air. At a red heat 

 the metal decomposes even carbonic acid ; and 

 when mixed with fine sand and strongly ignited 

 a metallic silicide is formed, which disengages a 

 spontaneously inflammable hydrogen compound 

 by the action of water or dilute acids. 



The electro-chemical properties of magne- 

 sium have been applied to a very useful pur- 

 pose by M. Roussin. Hitherto in the toxico- 

 logical examinations for metals, zinc has been 

 exclusively used ; but this metal, as met with 

 in commerce, is always impure, and magnesium 

 is now proposed as a substitute. Pure magne- 

 sium has the double advantage of rapidly and 

 completely precipitating the poisonous metals 

 without the danger of introducing any other 

 poisonous substance. Arsenic and antimony 

 are not precipitated, but they will be found in 

 the gas disengaged and in the liquid remaining. 

 The organic matter is first destroyed by the 

 usual methods, the acid liquor concentrated, 

 and then ribbons or bars of magnesium (now 

 made expressly for the purpose) are introduced 

 as long as any deposit is formed. The opera- 

 tion for arsenic and antimony may be conducted 

 in a Marsh's apparatus. 



Among the metals which M. Roussin has 

 precipitated in the metallic state, by means of 

 magnesium, from slightly acidulated solutions 

 of their salts, are gold, silver, platinum, bis- 

 muth, tin, mercury, copper, lead, cadmium, 

 thallium, iron, zinc, cobalt, and nickel. The 

 precipitated metals, when washed, dried, and 

 compressed, exhibit a high degree of brilliancy. 

 The precipitated iron, cobalt, and nickel are 

 highly magnetic. Magnesium does not precipi- 

 tate aluminium at all, and chromium and man- 

 ganese only in the form of oxides. The author 

 states that a small plate of magnesium, -^ of a 

 grain in weight, placed beside a copper plate in 

 a small tube of glass filled with acidulated cop- 

 per, produced in less than ten minutes an elec- 

 tro-magnetic appearance, and illuminated a 

 Geisler's tube ten centimetres long. 



MM. Deville and Caron have found that 

 magnesium will burn brilliantly in an atmos- 

 phere of steam. They passed steam through a 

 tube containing magnesium, heated by the 

 flame of a spirit-lamp. The metal burnt viv- 

 idly, liberating hydrogen. They tried the same 

 experiment with zinc, and succeeded in making 



