ates out in transparent forms minutely microscopic, it is true all the same veritable diamonds, with crystalline form and appearance, colour, hardness, and action on light, the same as the natural gem.
Now commences the tedious part of the process. The metallic ingot is attacked with hot nitro-hydrochloric acid until no more iron is dissolved. The bulky residue consists chiefly of graphite, together with translucent chestnut-coloured flakes of carbon, black opaque carbon of a density of from 3-0 to 3-5 and hard as diamonds black diamonds or carbonado, in fact and a small portion of transparent, colourless diamonds showing crystalline structure. Besides these there may be carbide of silicon and corundum, arising from impurities in the materials employed.
The residue is first heated for some hours with strong sulphuric acid at the boilingpoint, with the cautious addition of powdered nitre. It is then well washed and for 118
