fi)20] on Researches at High Pressures and Temperatures 5 



temperatures on carbon, compounds of carbon and some other 

 substances. 



The apparatus consisted of an 80-ton press under which suitable 

 containers were placed, and a turbo-generator of 24 kilowatts output 

 at 80 volts provided the current. It had been discovered by 

 Cheesborough that the carbon filaments for incandescent lamps 

 became very hard and resilient when heated in a hydrocarbon 

 atmosphere of about \ H g absolute pressure, and I was anxious to try 

 what would be the result if a rod of carbon were electrically heated 

 when submerged in a liquid hydrocarbon under high pressure. 

 Benzine, paraffin, treacle, chloride and bisulphide of carbon were 

 tested under a pressure of 2200 atmospheres, or about 15 tons per sq. 

 inch. The results were not successful in producing a hard coating 

 to the rod, or of increasing materially its density and hardness, except 

 in the case of tetrachloride of carbon, which slightly consolidated 

 and hardened it ; on the contrary, the carbon deposited from the 

 liquids always appeared as soft amorphous carbon like soot. These 

 experiments were extended by substituting instead of the liquids 

 mentioned, silica, alumina and other substances, and increasing the 

 pressure to 30 tons per square inch. When the current density was 

 sufficiently increased the rod was converted to soft graphite. Moissan, 

 in 1903, expressed the view that iron in a pasty condition was the 

 matrix of the diamond, and that great pressure was the determining 

 factor, which compelled a minute fraction of the carbon present to 

 appear as diamond. He further speaks of the probability of carbon 

 being liquefied when under a pressure sufficient to prevent its volatili- 

 sation, and that from the liquid state it may pass into the crystalline 

 form on cooling. Crookes, in his lecture delivered before the British 

 Association at Kimberley in 1905, emphasized the same view as to 

 the probability of the crystallization of carbon directly from the 

 molten state on cooling. 



Though my original experiments in 1888 were not favourable to 

 these views, it seemed however desirable to carry the investigations 

 up to the greatest possible pressures attainable. Experiments were 

 consequently resumed in 1907 with a new equipment, which con- 

 sisted of a 2000 ton hydraulic press and a storage battery of 

 360 kilowatts output. The battery can be coupled for 2, 1, 8, 16, 

 48 volt as required, and the mains and the main switch can carry 

 currents up to 80,000 amperes to the hydraulic press, which is placed 

 by itself in a small strong house, partly below ground, with walls of 

 2 feet thickness reinforced with steel bars ; the door is of 3 inches 

 thick, the roof is of light galvanised iron. The container under 

 the press is further enclosed by 2 inch thick telescoping steel rings, 

 raised into position by steel ropes and counterweights. These 

 precautions, as experience showed, were necessary, as several violent 

 explosions occurred which cracked the steel rings and blew off the 

 roof. A charo-e of iron and carbon when confined and raised to 



