THE ARTIFICIAL PRODUCTION OP DIAMOND. 85 



It occurred to us to try the effect of great mechanical pressure accompanied by heat 

 upon small particles and powders, the interstices being exhausted to a high vacuum. 



Several experiments were made in the press under a mass pressure of 3000 atmo- 

 spheres. 



A layer of cast-iron turnings resting on a layer of carborundum grit, the exhaustion 

 being effected through a hole in the side of the mould covered by a perforated steel 

 plate within the layer of grit, heat was applied as usual by a central carbon rod. 



Analysis yielded some thin crystal plates from the grit which had lain in the line 

 between the cast iron and the suction outlet at the grid, and also from the layer of 

 grit which had lain against the cast-iron turnings which had become heated but not 

 melted by the central carbon rod. 



To ascertain the cause of the occurrence of these plates, experiments were made 

 without bulk pressure on the concentrated action of the gases given off" from cast-iron 

 turnings heated up to a good red, and drawn by a high-vacuum pump through 

 carborundum grit placed in a silica tube heated by a gas burner at the centre of its 

 length to dull red. These yielded similar crystal plates. 



Control experiments showed that no similar plates existed in the untreated grit. 



It was also found that the cast-iron turnings would not produce this effect on a 

 second heating unless they had been subjected to GO at atmospheric pressure for 

 some hours. Carbon monoxide, sulphur dioxide, cyanogen, hydrogen, nitrogen, 

 oxygen, nitric acid gas, chlorine, ammonia, ammonium oxalate vapour, ammonium 

 chloride, acetylene, coal gas, produced 110 plates. 



These plates resemble diamond very closely in appearance and form of crystalli- 

 zation, they do not polarize, and some have triangular markings ; they will not, 

 however, burn in oxygen at 900 C., and are completely destroyed by chlorine 

 purified from oxygen and water vapour at 1100 C. ; their specific gravity is about 

 3'2, they are therefore not diamond. 



Note, Recent experiments have shown that carbon monoxide passed over molten 

 iron sulphide and then over carborundum grit below red heat at atmospheric pressure 

 also produces these plates, and that if coal gas is substituted for carbon monoxide no 

 plates are formed. Also that only a few of the grains produce plates. 



The composition of the grains is 



Carborundum 36 '5G 



Iron oxide and alumina 44 '09 



Lime 10'45 



Magnesia 5' 57 



t 



Summai-y of Experiments and Conclusions. 



The experiments have shown that all the hydrocarbons, chlorides of carbon, and 

 oxides of carbon tested, deposit amorphous carbon or graphite on a carbon rod 



N 2 



