Preparation of Amorphous Carbon

Amorphous carbon may be formed in a variety of ways, but its preparation in a state of purity is difficult. It is liberated in the following reactions:

1. Decomposition of carbonaceous matter at high temperature (sugar, vegetable and animal charcoal, coke).
2. Deposition from dissociated hydrocarbon vapours (lampblack, soot, gas-carbon).
3. Explosive decomposition of endothermic compounds, e.g. acetylene.
4. Deposition in electrolysis:
   
   
   1. at anode in electrolysis of silver acetylide;
   2. at kathode in electrolysis of concentrated sulphuric acid with carbon electrodes;
   3. at kathode in electrolysis of fused BaCO₃ + BaCl₂ at 600° C.
5. Reduction of CO and CO₂ by metals: e.g. CO₂ by magnesium, calcium and the alkali metals, and CO by iron at high temperature.
6. Decomposition of CO:
   
   
   1. by heat at 1690° C. into CO₂ and free carbon;
   2. by radium emanation into O₂, CO₂, and carbon.

Sugar-charcoal and lampblack yield the purest forms of amorphous carbon, because they need contain no mineral impurity.