M. Hittorf on Phosphorus. 313 



The vaporization of red phosphorus is exceedingly slow as 

 compared with that of a liquid body. 



An exhausted glass tube containing red phosphorus was screwed 

 up in an iron one, the interstices being filled with magnesia pressed 

 down. The tube was then heated in the flame of five Bunsen's 

 burners, the temperature of which was gradually raised. In the 

 cases in which the tubes held out, besides the drops of colourless 

 phosphorus, the red phosphorus was found to be merely sintered 

 together, and not melted. In this respect, as comparative expe- 

 riments showed, the deportment of phosphorus quite resembles 

 that of arsenic : arsenic heated in a closed tube volatilized and 

 formed beautiful crystals without melting. 



Colourless phosphorus, when heated in an hermetically sealed 

 vessel (an iron tube can be used), is changed into red phosphorus 

 by being heated for a short time to a temperature of 300° C. 



An attempt was made to determine directly the heat which 

 becomes free when colourless changes into red phosphorus, by 

 placing a thermometer in some phosphorus contained in a flask 

 which was heated in an air-bath. When the temperature of the 

 bath was 295°, the thermometer in the phosphorus marked 

 282° ; at this point the temperature of the latter began rapidly 

 to rise and soon attained 370° C. ; the cork in which the thermo- 

 meter was placed was not tight at this temperature, and phospho- 

 rus-vapours escaped and caused the experiment to be stopped. 



Schrotter found the tension of colourless phosphorus to be 

 760 millims. at 290° ; comparing this with that of red, which 

 at 358° is only 31 millims., and considering that above 300° 

 liquid colourless phosphorus cannot exist, it would appear pos- 

 sible to drive phosphorus from a position of lower temperature 

 to one of higher. An exhausted tube containing ordinary phos- 

 phorus was exposed at one end to the temperature 255°, and at 

 the other to that of 358° C; the hotter part remained, however, 

 quite empty; no red phosphorus was deposited there. It follows 

 from this that colourless phosphorus-vapour can retain a higher ten- 

 sion and density than that which is formed from red phosphorus. 

 A number of special experiments show that when colourless phos- 

 phorus was used instead of red, far higher densities and ten- 

 sions were obtained for the same temperatures. 



Colourless phosphorus in the exhausted tubes, when the tem- 

 perature is raised, has probably passed partially into the vaporous 

 state. The part which has remained liquid passes into the state of 

 red phosphorus, and, by its disengagement of heat, materially in- 

 creases the temperature of the surrounding medium, and thus 

 gives a higher density and tension to the vapour. Experiment 

 showed that the tension and density which the vapours at first 

 obtain are not stable and continually diminish, while red phos- 



