109 



whicli tlie (|iiaiiüty Tlnp is plotted as funotioii of 7^ (tlie line nli). 

 We see froin this that the different points jfield an almost straiglit 

 line, whose shape is exceedingly little conoave with respect to the 

 temperature axis. This had accordingly proved that the preceding 

 determinations had been vitiated by the spontaneous heating of the 

 white phosphorus in conversion. 



If in the same diagram we now give Tlnp as function of 7' also 

 for the liquid violet phosphorus, we get the already discussed straight 

 line rd. 



The consideration of tiiese two lines ali and cd brings us at once 

 to the conviction that tiiey belong together, i.e. that they are two 

 parts of one and the same curve, the intermediate part of which 

 cannot be realized here. 



It follows then from this that the second part cd cannot be 

 perfectly straight in reality, no more than the first part ah, and 

 that there must be a rational formula to be found, which represents 

 both portions with sufficient accuracy. 



To find this formula the following course is taken. 



The line ah which represents Tlnp as function of 7' for the liquid 

 white phosphorus, is only very slightly curved. If we now assume 

 for a moment that this line is straight, then as was already shown 

 before, the constant C' can be found by the aid of two points, 

 on the application of the relations: 



'J\lnp,^-\^CT, (1) 



and 



TM\ = -\^r01\ (2) 



If this value of C is substituted in one of the above equations, 

 then follows from this the value for Q, which indicates the molecular 

 heat of evaporation. 



If this is done, we find (^=: 12.17 kg. cal., 9.96 kg. cal. being 

 found for the moi. heat of evaporation of the liquid \iolet phosphorus. 

 The latter result was obtained in the same way as hei-e the Q for 

 the liquid white phosphorus was calculated viz. on the assumption 

 that Q is no temperature function. 



Now this is, evidently, indeed not the case, for Tlnp plotted as 

 function of T is no perfectly straight line. 



We can now accept by appioximation that 12.17 kg. cal. is the 

 mean value of the heat of evaporation of the liquid white phosphorus 

 in the temperature interv.^l from 160° to 360", and that this heat 



