192 



M. J. A. Groshans on the 



may be permitted to embody in the following pages the prin- 

 cipal observations that I have been able to make on this 

 subject ; and as in doing so I shall have frequently to refer 

 to glycerine, it is perhaps as well to make a few remarks on 

 its boiling-point. 



There is but little agreement to be found among the figures 

 given by various experimenters who have attempted to deter- 

 mine the boiling-point of this compound, C 3 H 8 3 . The older 

 experiments point to 9 as the value for x } the more recent 

 to 9*5. 



5x/9 = 275'l and sn/9'5 = 290'1*. 



In this connection I may add that Wurtz's butylic glycol, 

 C 4 H 10 O 2 , boils at ]83°-184°, that of Kekule at 201°-204° : 



^^5 = 182-9, *^9 = 196°-2. 

 In the following table I have adopted 9 as the value of x for 

 glycerine. 



Glycerine exhibits a peculiar property with regard to x — 

 it is this : — In glycerine, 3 H 5 (OH) 3 one, two, or three of 

 the hydrogens in hydroxyl groups may be replaced by ethyl, 

 C 2 H 5 , to form ethylines. The original glycerine and its three 

 derivatives form a species of homologous series the members 

 of which have the common difference C 2 H 4 , and yet the 

 increase of molecular weight is attended by a lowering of the 

 boiling-point, exactly the opposite of what is observed in the 

 case of other homologous series : this anomalous behaviour I 

 attribute to the " constancy of x" In fact glycerine and its 

 derivatives have all the same constant Tn/a, and consequently 

 the same value of x — i. e. 9. The theoretical value of Tn/a, 

 when # = 9, is 83*41, as will be seen from the table. Other 

 derivatives similar to the ethylic ones also possess the same 

 constants. 



Table XV. 



Name of substance. 



Formula. 



a. 



n. 



observed. 



Tn/a. 



Glycerine 



C 3 H 8 3 

 C 6 H 12 3 



C 7 H ]6 3 



O 12 H, O 3 



92 

 120 

 148 

 176 

 212 



14 

 20 

 26 

 32 

 35 



277 

 227 

 191 

 185 

 232 



83-69 

 83-33 

 81-51 

 83-28 

 83-37 



Monoethyline 



Dietbyline 



Trietbyline 



Triallyline 





* Mendelejetf gives 290° at 760 millim.— W. W. J. N. 



