of the combinations of phosphorus . 337 
by distillation. In experiments made in the laboratory of 
the Royal Institution, in which it has been twice carefully 
distilled at a low heat, it has still contained minute quantities 
of phosphorus. 
It has been supposed that dry phosphoric acid is fixed at a 
white heat ; but I find that this is not the case : it rapidly 
rises in vapour at this temperature, and evaporates even at 
the point of fusion of flint glass : and the hydrate of phos- 
phoric acid is susceptible of being volatilized at a much lower 
temperature. 
In converting the solid sublimate composed of phosphorus 
and chlorine into the liquid compound, when the phosphorus 
is first fused in contact with the sublimate, a yellow crystal- 
line mass is formed, which, when acted on by a higher 
degree of heat, affords the liquid chloride, which rises from it 
in vapour, and leaves phosphorus behind. It is possible that 
this yellow solid is a compound of phosphorus and chlorine, 
containing half as much chlorine as the liquid. Should this be 
proved to be the case bv future experiments, it will give 
weight to the idea, tha the hypophosphorous acid is a binary 
compound of oxygen and phosphorus. 
