242 BERZELIUS ON THE ALLOTROPY 
very rarely in the mineral kingdom, but more frequently by art. 
Its crystalline form has not been accurately ascertained; but so 
far is certain, that it cannot be referred to the forms assumed by 
the diamond. The carbon in these two modifications is thus 
dimorphous. Graphite has a metallic lustre, is dark gray and 
transparent. The specific gravity of the diamond is 3:5, that of 
graphite barely amounts to 25. The specific heat of the dia- 
mond is 0°147, that of graphite from 0°197 to 0°20. ‘Two dif- 
ferent elements could scarcely differ more than these allotropic 
modifications of one and the same element; the diamond is a 
non-conductor of electricity ; graphite and coke are good con- 
ductors. 
The allotropic states of carbon are thus remarkably distinct 
in their different specific gravity and specific heat (which seem 
to depend on one another), in their crystalline form and their 
ready combustion with oxygen. 
I will here observe, that in like manner as we are acquainted 
with carbon in the condition Cz, and nevertheless find it impos- 
sible to transform into it carbon of either of the other two con- 
ditions, this may also be the case with regard to other elements, 
i. e. allotropic conditions of them may exist, into which we 
cannot bring them. 
We know not whether the allotropic conditions of the carbon 
in the majority of compounds, especially organic, into which it 
enters, and among which so many isomeric forms occur, in- 
fluence in any way the difference of their properties; when, 
however, we compare the chemical properties of carbonic acid 
with those of oxalic acid, we are led to suppose that they con- 
tribute to it. 
Silicium most resembles carbon as regards its first two allo- 
tropic states. 
Si. is produced when the silicium is obtained by reduction 
with potassium. It takes fire and burns vividly at a slightly 
elevated temperature; it detonates when thrown on nitre in a 
state of fusion; it evolves heat, and is volatilized with hydro- 
fluoric acid; combines with sulphur when gently heated with 
it, and the resulting compound is decomposed by water, sulphu- 
retted hydrogen being evolved and silicic acid formed, which last 
is soluble in water, and still more so in hydrochloric acid. 
Sig is formed when the preceding modification is exposed to 
a strong red heat; the silicium, however, requires a far less in- 
