CARBON AND THE HYDROCARBONS 353 



carbon in molten cast iron, and allowing the solution with an 

 excess of carbon, to cool under the powerful pressure exerted by 

 rapidly cooling the metal. 17 bis K. Chroustchoff attained the same end 

 by means of silver, which dissolves carbon to the extent of 6 p.c. 



volts) not only do all metals melt, but even lime and magnesia (when placed in the space 

 between the carbon electrodes, i.e. in the voltaic arc) become soft and crystallise on 

 cooling. At 8,000 lime becomes very fluid, metallic calcium partially separates 

 out and a carbon compound, which remains liquid for a long time. At this tem- 

 perature oxide of uranium is reduced to the suboxide and metal, zirconia and rock 

 crystal fuse and partially volatilisej as also does alumina; platinum, gold, and even 

 carbon distinctly volatilise ; the majority of the metals form carbides. At such a tem- 

 perature also cast iron and carbon give graphite, while according to Rousseau, between 

 2,000 and 8,000 the diamond passes into graphite and conversely graphite into the 

 diamond, so that this is a kind of reversible reaction. 



IT bis Moissan first investigated the solution of carbon in molten metals (and the 

 formation of the carbides) such as magnesium, aluminium, iron, manganese, chromium, 

 uranium, silver, platinum, and silicon. At the same time Friedel, owing to the discovery 

 of the diamond in meteoric iron, admitted that the formation of the diamond is depen- 

 dent upon the influence of iron and sulphur. With this object, that is to obtain the 

 diamond, Friedel caused sulphur to react upon samples of cast iron rich in carbon, in a 

 closed vessel at a maximum temperature of 500, and after dissolving the sulphide of iron 

 formed, he obtained a small quantity of a black powder which scratched corundum, i.e. 

 diamond. Moissan's experiments (1893) were more successful, probably owing to his- 

 having employed the electrical furnace. If iron be saturated with carbon at a tem- 

 perature between 1,100 and 8,000, then at 1,100-1,200 a mixture of amorphous- 

 carbon and graphite is formed, while at 3,000 graphite alone is obtained in very' 

 beautiful crystals. Thus under these conditions the diamond is not formed, and it can; 

 only be obtained if the high temperature be aided by powerful pressures. For this" 

 purpose Moissan took advantage of the pressure produced in the passage of a mass of 

 molten cast iron from a liquid into a solid state. He first melted 150-200 grams of iron 

 in the electrical furnace, and quickly introduced a cylinder of carbon into the molten 

 iron. He then removed .the crucible with the molten iron from the furnace and plunged 

 it into a reservoir containing water. After treating with boiling hydrochloric acid, three 

 varieties of carbon were obtained : (1) a small amount of graphite (if the cooling be 

 rapid) ; (2) carbon of a chestnut colour in very fine twisted threads, showing that it had 

 been subjected to a very high pressure '(a similar variety was met with in various 

 samples of the Canon Diabolo), and lastly (8) an inconsiderable quantity of an 

 exceeding dense mass which was freed from the admixture of the lighter modifications 

 by treatment with aqua regia, sulphuric and hydrofluoric acids, and from which Moissan, 

 by means of liquid bromoform (sp. gr. 2 - 900), succeeded in separating some small pieces, 

 having a greater density than bromoform, which scratched the ruby and had the 

 properties of the diamond. Some of these pieces were black, others were transparent 

 and refracted light strongly. The dark grey tint of the former resembled that of the 

 black diamonds (carbonado). Their density was between 8 and 3'5. The transparent 

 specimens had a greasy appearance and seemed to be, as it were, surrounded by an 

 envelope of carbon. At 1,050 they did not burn entirely in a current of air, so that the 

 imperfectly burnt particles, and a peculiar form of grains of a light ochre colour, 

 which retained their crystalline form, could be examined under the microscope. Similar 

 grains also remain after the imperfect combustion of the ordinary diamond. Moissan 

 obtained the same results by rapidly cooling in a stream of coal gas a piece of cast iron, 

 saturated with carbon obtained from sugar and first heated to 2,000 In this instance 

 he obtained small crystals of diamonds. K. Chroustchoff showed that at its boiling 

 point silver dissolves 6 p.c. of carbon. This silver was rapidly cooled, so that a crust 



