472 Transactions. — Chemistry and Physics. 



mum, though not so sudden, among the data for the acid 

 chlorides, and to the characteristic minimum, which occurs in 

 the next number of this series for the fatty acids. 



Table XII. 



Boiling-point. Differences. 

 Nitromethane ... 101° ,q r 



Nitroethane ... ... 114'5 ir if . 



Nitropropane ... 131 nn.K 



Nitrobutane... ... 151'5 , R „ 



Nitropentane ...(150-160)? a ~ W 



Nitrohexane... ... 176 ^ ' ,q 



Nitroheptane ... 195 



The numbers in brackets are rendered doubtful owing to 

 the result obtained for the boiling-point of nitropentane. The 

 higher limit is taken as the more probable, but this cannot 

 affect the general conclusions. This series is exactly similar 

 to the nitriles. The changes occur in the same positions, and 

 are perhaps a little more marked, indicating a greater mole- 

 cular complexity of the gaseous molecules.* 

 ?<!> The hydrocarbons, their halogen derivatives, the alcohols, 

 amines, and ethers, exhibit no such behaviour. But in none of 

 these series has any considerable association been noticed. 

 In all the instances where the wavy character occurs there is 

 either a carboxyl group > C = in the molecule or a nitrogen 

 atom. In the cases of the acids and ketones the molecular 

 complexes are possibly of the types 



OH E' 



I I 



E- C • E ■ C • 



II II 

 E • C • E- C • 



I I 



OH E' 



For monobasic acids a greater complexity has never been 

 observed either in vapour-density determinations or in ben- 



* A measure of the association at the boiling-point may be obtained 



from Teouton's law, -— - = a constant, where W is the latent heat of 



vaporisation. For substances known to be normal in the liquid and 

 gaseous states the value of the constant is in the neighbourhood of 21. 

 For the esters and ketones a regular value of about 21 is obtained, but 

 the acids and nitriles give exceedingly low values, indicating that the 

 vapour at their boiling-points is strongly associated. The nitriles give 

 fairly constant values, but still a little too low. Thus we find the order 

 of complexity is nitroparafhn, fatty acid, nitrile, ketone, ester — the same 

 order as indicated from the data for the boiling-points. The alcohols, on 

 the other hand, give a high value, indicating association of the lighter 

 molecules. 



