354 Mr. Gervaise Le Bas on the 



first pair. This is also the case in the second pair, but sulphur 

 also changes — in the opposite direction. The evidence is 

 not conclusive. In an}- case the difference is small. 



Closely associated with this subject is the question o£ 

 Unsaturation. 



The double bond ( = ) and triple bond ( = ) so-called, have 

 very little effect on volume at the B.P., as is shown by the 

 similar values obtained for C and H by a comparison of the 

 Paraffins with the Olefins and Acetylenes and the values 

 derived from a consideration o£ the n Paraffins alone. Thus 

 the groups : 



-CH 2 -OH 2 -, -CH=CH-, -0 = 0- 



possess volumes in accordance with their composition. 

 It follows that the volumes of 



C — j C = 5 — C = are the same viz. : 14.8. 



C has never any other value. 



Nitrogen K Free value 15*8. 



Trivalent nitrogen possesses the volume 15*6 as is shown 

 by the compounds 



N s . s ft, N - CI N = C — C = N 

 X C1 



iV-CN is 30-4. Since is 14'8, =N is 15-6. 



Pentavalent N has still the same value. 



N — N ^ V ■, 63.95 (64 approx.) 



' ^ 



= 8-3, and N is thus (64-0-33-2) x 4 = 15-4. 

 The group N0 2 is also found in 



C,H 3 ,N0 2 , C 3 H u -0 -NO* 



and its volumes in these compounds differ little from its 

 volume in the free state. 



In the Amines (Primary): — W" 8. 



(Secondary & Tertiary) :— N'" 10-11-5. 



