Influence of Atomic Weight. 



373 



termined the boiling-points of a large number of compounds, 

 concludes that the differences of boiling-point between conse- 

 cutive members of homologous series are by no means exactly 

 equal, but exhibit considerable variation, even as much as 3°. 



The following are a few further examples of regularity in 

 the boiliug-points of organic compounds which have recently 

 been pointed out. 



In silicon compounds the substitution of (C 2 H 5 ) for CI 

 raises the boiling-point, as does also an increase in the num- 

 ber of oxygen atoms (Ladenburg, Ann 

 p. 300):— 



Boiling- 

 point. 



SiCl 4 



. 58 



SiCl 3 (C 2 H 5 ). 



. 10Q 



SiCl (C,H 5 V 



. 129 



SiCl(C 2 H 5 ) 3 . 



. 144 



Si(C a H 5 ) 4 . 



. 152 



SiClgCCH^O . 

 SiCl o (C" 2 H 5 ) 0. 

 SiCl(C 2 H 6 ) 3 . 



Boiling- 

 point. 



Boiling- 

 point. 



o 



104 



? 



147 

 153 



Ch. Pharm. clxiv. 



Boiling- 

 point. 



SiCl 2 (C H 5 )A 

 SiCl(C. 2 H 8 ) 3 2 

 Si(0 2 H 6 ) 4 O 2 



Boiling- 

 point. 



137 

 151 



156 



SiCl(C H 5 ) 3 3 

 Si(C 2 H 5 ) 4 3 



156 

 159 



Si(C 2 H 5 ) 4 4 ... 166 



Here the differences between every two consecutive mem- 

 bers of each series diminish as we pass down each vertical 

 column, i. e. as the number of chlorine atoms replaced by 

 C 2 H 5 increases ; and these same differe aces also diminish in 

 each horizontal line from left to right, L e. as the number of 

 atoms increases. The differences between each two conse- 

 cutive members of a horizontal series increase from left to 

 right, i. e. with the number of atoms. 



Mendeljeff has called attention to the fact that Si com- 

 pounds boil lower than the corresponding C compounds. 



The iodides of the alcohol-radicals always boil 53° higher 

 than the corresponding amides (Linnemann, Ann. Ch. Pharm. 

 clxii. p. 12), thus : — 





Etbyl. 



Propyl. 



Butyl. 



Isobutyl. 



Tertiary 

 butyl/ 



Amyl. 



I- 







72 

 18-7 



O 



1022 

 49-0 



1299 

 765 







120-6 







98-5 



148-0 

 95 



NH 2 = ... 



67-5 



460 

 52-5 



Difference 



533 



53-2 



534 



53-1 



53-0 



Salomon (Journ. f. Chem. [2] vi. p. 433) has shown that 

 Phil Mag. S. 5. Vol. 8. No. 50. Nov. 1879. 2 C 



