THE ARTIFICIAL PRODUCTION OF 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 CO 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 no 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. 3G'56 
Iron oxide and alumina. 44 "09 
Lime. 10’4 5 
Magnesia. 5‘57 
Summary 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 
