244 BERZELIUS ON THE ALLOTROPY 
luded to, satisfactorily prove that sulphur is capable of assuming 
three allotropic states. Scheerer and Marchand have shown 
that S« and Sg possess peculiar crystalline forms with different 
specific heat and gravity. Frankenheim demonstrated that Sy 
possesses a still lower specific heat than either of the others, and 
proved that the abnormal specific gravity of the vapour of sul- 
phur arises from its having been evolved from S,. We know, 
however, that the vapour of sulphur in sulphurous acid and sul- 
phuretted hydrogen, which probably contain S.z, possesses its 
normal specific gravity. 
It is not altogether improbable that these different allotropic 
conditions of the sulphur exist in the various classes of its acids. 
Phosphorus, also, in all probability, has three allotropic states, 
two of which may be traced in the different compounds of phos- 
phorus, by a method which I think I have shown in my treatise 
on the combinations of phosphorus with sulphur*. The possi- 
bility, in this case, of tracing its relations accurately, laid the 
foundation for extending the same views to other elementary 
bodies. 
Selenium resembles sulphur ; it exists in a soft uncrystalline 
state, when it may be drawn into threads, representing Sy. In 
its steel-gray crystalline and its beautiful red state, in which it 
is precipitated from its gaseous form upon cold bodies, or in the 
moist way by sulphurous acid, phosphorous acid, zinc, &c., it 
may represent, the former S., and the latter Sg; but we have 
hitherto been unable to detect any combination of selenium 
which appears to belong to either allotropic conditionaore than 
the other. 
We are acquainted with two allotropic conditions of arsenic. 
One, Asa, is produced when arsenic existing in the gaseous state 
with another gas which is heated, condenses upon the cool part 
of the subliming apparatus. It is of a dark gray colour, crystal- 
lizes, and becomes oxidized by exposure to the air, especially at 
a temperature of about 104° F., when it then crumbles to a black 
suboxide. The other form, Asg, is formed when arsenic is 
strongly heated or sublimed in a vessel, in which that part on 
which the sublimate is deposited is retained at about the tem- 
perature at which arsenic assumes the state of vapour. It is then 
deposited from an atmosphere of arsenic vapour. It is nearly 
* Kongl. Vet. Akad. Handl., f. 1842, p. 87. Poggendorff’s Annalen, vol. 
lix. pp. 76, 463 and 539. 
