1852.] OF THE ROYAL INSTITUTION. 203 
melts to a transparent yellow fluid; at about 160° C. it changes in 
appearance, becoming red, and between 220° and 250° C., it becomes 
deep red and viscid. Heated beyond this point it again becomes 
liquid, and just before it boils appears as a deep black fluid. These 
changes in the sulphur have been connected with certain thermic 
phenomena, which leave no doubt but that they are truly transitions 
from one allotropic form to another. During cooling, sulphur 
passes through the same changes, but in an inverse order; and it 
has been observed that the sulphur does not cool by regular 
gradation, but that at certain points its temperature is stationary, or 
falls much slower than at other points; this can only be explained 
by assuming a developement of heat from the sulphur itself, which 
compensates for that which it loses; and this developement of heat 
takes place just about the points of transition from one state to 
another. By cooling suddenly the viscid sulphur, it may be re- 
tained for a long time in the form of a transparent elastic substance, 
which ultimately solidifies to a sulphur differing in many respects 
from the ordinary modification of the body, especially in being in 
great measure insoluble in bisulphide of carbon.— An experiment 
was shewn of the reconversion of this peculiar sulphur into the 
viscid form; this can be effected without melting the body by a 
proper regulation of the temperature. 
It had been long known that Phosphorus exposed to sun-light 
assumed a red colour. Berzelius suspected this to be an allotropic 
modification of the element; and the experiments of Schrétter, who 
produced the same body by the action of heat, have established this 
view and enable us to procure this phosphorus in large quantities. 
In its chemical properties, as well as in appearance, this red phos- 
phorus is entirely different from the ordinary modification. 
The change thus produced by heat can also be effected by chemical 
agency. By the action of iodine ordinary phosphorus can be con- 
verted in large quantities into the allotropic modification. This 
can be done by projecting iodine into phosphorus melted under 
strong hydrochloric acid, or into phosphorus simply melted in a 
tube, and subsequently heating the substance. The iodine is em- 
ployed in very small quantities. It first dissolves in the liquid phos- 
phorus ; at a certain point as the temperature is raised a violent 
evolution of heat takes place, which causes a kind of explosion in 
the substance, and the mass of the phosphorus passes at this moment 
into the other condition. A small quantity of iodine will in this 
manner convert (if sufficient time be allowed) an absolutely unlimited 
quantity of phosphorus.* 
On a former occasion certain experiments were shown as evidence 
that the formation of oxygen, and indeed of other elements, was a 
* The theory of this action and the detailed experiments are given in a 
Paper on the action of Iodine upon Phosphorus, read by the Author before the 
Chemical Society on the 21st of June. 
