514 THE RARER METALS AND THEIR ALLOYS. 



therefore, on the ground that the subject might appear to be without 

 the limits of the title of his lecture, to point to one other result which 

 has been achieved by M. Moissan. Here is a fragment of pig iron 

 highly carburized ; melt it in the electric arc in the presence of car- 

 bon and cool the molten metal suddenly, preferably by plunging it 

 into molten lead. Cast iron expands on solidification, and the little 

 mass will become solid at its surface and will contract; but when, in 

 turn, the still fluid mass in the interior cools it expands against the 

 solid crust, and consequently solidifies under great pressure. Dissolve 

 such a mass of carburized iron in nitric acid to which chlorate of potash 

 is added; treat the residue with caustic potash, submit it to the pro- 

 longed attack of hydrofluoric acid, then to boiling sulphuric acid, and 

 finally fuse it with potash to remove any traces of carbide of silicon, 

 and you have carbon left, but in the form of diamonds. 



If you will not expect to see too much I will show you some diamonds 

 I have prepared by strictly following the directions of M. Moissan. As 

 he points out, these diamonds, being produced under stress, are not 

 entirely without action on polarized light, and they have sometimes the 

 singular property of flyiug to pieces like Rupert's drops when they are 

 mounted as preparations for the microscope. [The images of many 

 small specimens were projected on the screen from the microscope, and 

 fig. 4, E, PL XXVI, shows a sketch of one of these. The largest dia- 

 mond yet produced by M. Moissan is 0.5 millimeter in diameter.] 



A (fig. 4, PI. XXVI) represents the rounded, jutted surface of a 

 diamond, and B a crystal of diamond from the series prepared by M. 

 Moissan, drawings of which illustrate his paper. 1 The rest of the speci- 

 mens, C to F, were obtained by myself by the aid of his method as 

 above described. C represents a dendritic growth apparently com- 

 posed of hexagonal plates of graphite, while D is a specimen of much 

 interest, as it appears to be a hollow sphere of graphitic carbon, par- 

 tially crushed in. Such examples are very numerous, and their surfaces 

 are covered with minute round graphitic pits and prominences of great 

 brilliancy. Specimen E (which, as already stated, was one of a series 

 shown to the audience) is a broken crystal, probably a tetrahedron, and 

 is the best crystallized specimen of diamond I have as yet succeeded ia 

 preparing. Minute diamonds, similar to A, may be readily produced, 

 and brilliant fragments, with the lamellar structure shown in F, are 

 also often met with. 



The close association of the rarer metals and carbon and their inti- 

 mate relations with carbon, when they are hidden with it in iron, 

 enabled me to refer to the production of the diamond, and afford a 

 basis for the few observations I would offer in conclusion. These relate 

 to the singular attitude toward metallurgical research maintained by 

 those who are in a position to promote the advancement of science in 

 this country. Statements respecting the change of shining graphite 



^omptes Rendus, Vol. CXVIII, 1894, pago 324. 



