New Modification of Phosphorus. 365 



(Proc. Roy. Soc. xlix. p. 11), so the mechanical depression is 

 robbed of its basis. The physical and chemical lowerings are 

 arrived at from a thorough confusion of heat with tempera- 

 ture. " A definite hydrate, such as H 2 S0 4 , 13H 2 0, can only 

 give up its water by decomposing into the next lower hydrate, 

 H 2 S0 4 , 9H 2 in the instance taken : the heat absorbed in 

 this change is given by the heat of dissolution curve (863 cal.), 

 and will lower the temperature of a mixture with a heat- 

 capacity of 223-5 cal. by 3°-ft ,; (Proc. Chem. Soc. 1889, 

 p. 151). This 3°*5 is the " chemical lowering." Now while 

 it may be true that the absorption of 863 cal. "will lower the 

 temperature of a mixture with a heat-capacity of 223*5 cal. 

 by 3°'5/' it is difficult to see what this has to do with the 

 freezing-point of sulphuric-acid solutions. The freezing-point 

 of an aqueous solution is the temperature at which it is in 

 equilibrium with ice ; and no matter what amount of heat 

 may be developed on the congelation, this temperature will 

 remain unaffected. Heat, whether from an external or an 

 internal source, cannot affect the temperature of equilibrium 

 between the solid and the liquid : it can only change in the 

 one case the relative proportions of the substances, and in the 

 other the latent heat of fusion. Calculations on such a 

 theoretical foundation need scarcely be further considered. 



Whatever of future development may await the hydrate 

 theory, it cannot to-day be looked upon as a serious rival to 

 the hypotheses of osmotic pressure and electrolytic dissociation, 

 the list of whose achievements is constantly increasing. 



University of Edinburgh, 

 Ausrust 1891. 



XLY1. On a New Modification of Phosphorus. 

 By H. M. Vernon, Scholar ofMtrtok College, Oxford*. 



HAVING occasion to melt some ordinary yellow phos- 

 phorus, it was noticed that in some cases the phosphorus 

 melted suddenly, and had no definitely marked melting-point, 

 while in other cases it exhibited a definite melting-point, ;is 

 most other bodies do when passing from the solid to the liquid 

 state. Further examination confirmed this, and showed that 

 these were two different crystalline varieties of phosphorus, 

 which differed in other properties as well. 



In order to examine the manner in which the phosphorus 

 passed from the solid to the liquid state, quantities of about 

 twenty-five grams were placed in a bulb-tube or broad test- 



* Communicated by the Author. 



