METALU'KiiY. 



467 



-oomlueting process being all effected in the 

 nonconductor outside of it. The neutral tempera- 

 ture of two thermo-couples that is. the mean tem- 

 perature of the two junctions when they are at dif- 

 ferent temperatures at the instant when the current 

 in the circuit is at zero and the temperatures "f 

 inversion of electro-motive force have been fixed by 

 the author for an extensn metals at low 



temperatures between ('. and 200 : and in the 

 thermo-electric lines of several metals sudden al- 

 terations in direction have been found indicating 

 molecular changes at certain low temperatures, 

 aid upon the value of the knowledge 

 gained about the electrical resistance of metals at 

 low temperatures as a means of testing the purity 

 of a metal rivaling the spectroscope in deli 



The special rules under the factory ac; 



issued to all brass manufacturers by an Eng- 

 lish departmental committee on the conditions of 

 labor certify the processes in the mixing and cast- 

 ing of bra<s. gun metal, bell metal, white metal, 

 delta metal, phosphor bronze, and manilla mixture. 

 to be dangerous or injurious to health: order the 

 the provision of adequate means for facilitating as 

 far as possible the emission or escape from the shop 

 of any noxious fumes or dust arising from them, 

 and for preventing their entrance into any other 

 shop ; direct the cleaning of the shops every nine 

 months and the provision of suitable washing facili- 

 ties for the workmen : forbid the employment of 

 young women and girls in the mixing rooms or in 

 any other rooms that are not wholly separated from 

 them : and prohibit the eating or cooking of food 

 in such shops within a period of at least ten min- 

 utes after the completion of the last pouring of 

 metal in'the room. The committee say in their re- 

 port that they were fully satisfied that the symp- 

 toms commonly described as brass-founder's ague 

 were caused by the inhalation of the fumes of defla- 

 grated zinc or by eating food contaminated with 

 the fumes. 



Until recently no definite compounds of carbon 

 with metals had been certainly determined except 

 the acetylides of some of the metals of the alkalies 

 and alkaline earths, which were known only in an 

 amorphous and impure state. The application of 

 the electric furnace by M. Moissan. enabling him to 

 work at extremely high temperatures, has led the 

 way to the formation of definite metallic carbides 

 of great stability and having properties of great in- 

 terest : and experiments in the preparation and in- 

 vestigation of them have been systematically car- 

 ried on by M. Moj^an. Such metals as gold, bis- 

 muth, lead, and tin have not been found to form 

 carbides at any temperatures yet reached, or to dis- 

 solve any carbon. The metals of the platinum 

 group dissolve carbon readily, but deposit it all on 

 cooling in the form of graphite, without themselves 

 being changed. Copper, silver, and iron take up 

 carbon in small quantities, but sufficient to cause 

 considerable changes in their physical properties. 

 Xo ilcfinite crystalline compound has been obtained 

 with iron. A considerable number of carbides are 

 decomposed under the influence of water : thus car- 

 bide of potassium gives out acetylene : carbide of 

 aluminum gives the pure metal : the carbides of 

 cerium, lanthanum, and yttrium decompose into a 

 mixture of carbides: carbide of uranium separates 

 from three fourths of its carbon, which escapes in 

 liquid carbides. Among the carbides not decompos- 

 able by water are those of molybdenum and tungsten, 

 which are stable. Chromium is the only example 

 of a metal giving two carbides at different tempera- 

 tures of the electric furnace. 



The experiments of M. Moissan in producing dia- 

 monds by the action of the pressure of solidifying 

 cast iron suggested to M. Rossel that the conditions 



under which very hard steels ar p now made should 

 also result in their formation. He examined a large 

 number of the steels, and found that his theor- 

 borne out by the fact. The diamonds are nbt. ; : 

 by dissolving the metal and then submittin. 

 residue to the influence of concentrated nitric acid, 

 fused potassium chlorate, hydrofluoric acid, and 

 sulphuric acid. The diamonds are almost micro- 

 scopic, but are true diamonds. 



Recognizing the possibility of finding new ma- 

 terials for construction affording desirable quali- 

 ties, in themselves or in combination, among the 

 rare metals. Prof. R. H. Thurston has given much 

 study to the properties of magnesium. Pure, it re- 

 sembles the other white metals in color, is soft and 

 weak, oxidizes more readily than nickel and alumi- 

 num, and in the form of a ribbon or powder burns 

 readily, steadily and brilliantly. Its light is very 

 rich in the actinic rays, and is so bright as to be 

 visible at the distance of 30 miles or more a' 

 Chlorine and hydrochloric acid attack it rapidly, 

 sulphuric acid but slowly. It is very light, weigh- 

 ing only about two thirds as much as aluminum, 

 and between one fourth and one fifth as much as 

 steel. It seems more likely to prove serviceable in 

 alloys than pure. It combines readily with many 

 of the other metals, and forms alloys which are usu- 

 ally too hard and brittle to be useful in the arts. It 

 is sufficiently malleable and rolls into ribbons and 

 sheets. It has not that combination of strength 

 and ductility requisite for successful wire drawing. 

 Its flame has a temperature of 2.444" F.. but the 

 light is similar to that of an ordinary flame at three 

 times this temperature. Its radiant light energy is 

 higher than that of any other known flame, and 

 constitutes three fourths its total energy of com- 

 bustion and four times that of illuminating gas. 

 Its tenacity is low. but exceeds that of pure alumi- 

 num. The author has not been able to obtain an 

 alloy of magnesium and copper. Brass will take up 

 a minute proportion of this metal, but with no sen- 

 sible useful result. The presence of the lighter 

 metal produced neither accession of strength nor 

 increased tenacity, but in every instance the alloy 

 was unsound and weaker than the brass itself. Iron 

 refuses to alloy with magnesium in any sensible 

 amount, and the magnesium seems to have no value 

 either as flux or as a strengthening element. Mag- 

 nesium and aluminum alloy with increase of strength 

 up to 10 per cent, magnesium, when the alloy be- 

 comes brittle and valueless for constructive pur- 

 poses. The addition of magnesium to cast alumi- 

 num increases its tenacity by a percentage which 

 exceeds five times that of the percent, of admix- 

 ture. The best of these alloys are ductile. The 

 author estimates that magnesium is capable of sus- 

 taining from 30,000 to 40.000 lineal feet of its own 

 substance or the equivalent of steel of from 100,000 

 to 150,000 pounds tenacity. Were it practicable to- 

 construct .engines, their weights would be reduced 

 about 50 per cent., but the advantage would still be 

 on the side of steel if the ultimate tenacity of abso- 

 lutely pure steel in the form of fine wire or watch 

 spring could be used. Magnesium has thus no 

 promise of competition with steel in general con- 

 struction. 



The ancient Egyptian copper mines of the Sina- 

 itic peninsula, which were extensively worked in 

 their day. have been examined by M. de Morgan, 

 who has shown M. Berthelot specimens of the min- 

 eral, the fluxes used in the working, and the residual 

 scoriae. The mineral consists of hydrosilicates 

 mingled with carbonates, phosphates (or turquoises), 

 and sandstones, impregnated with salts of copper, 

 and is very poor in ore. which occurs in nodules or 

 veins. The copper (the metal) was reduced tinder 

 the action of charcoal, with a ferruginous sandstone 



