VALENCY 85 



In other cases, such as chloral, C 2 C1 3 OH, more than one 

 possibility exists ; these may be conveniently arranged by 

 separating the multivalent from the univalent elements, 

 thus : 



(C 2 0)C1 3 H, 



and then calculating the number of bonds by which the 

 skeleton of multivalent atoms is held together. Since each 

 bond involves the use of two valencies, 



Total number of valencies in C 2 O .... 10 

 Deduct for combination with C1 3 H ... 4 



Remainder 6 = 3 bonds. 



Hence the possibilities for C 2 O are 



(j) C = C O (2) C-C = O (3) C-C 



O 



to which the chlorine and hydrogen atoms are to be added, 

 giving 



= C O Cl (i 6)j}>C = C-0 Cl 

 Cl H 



= C O H 



Cl 



CK Cl\ 



(2 a)Cl-"C C = (2 6)C1SC C=O 



- 



H/ I Cl/ | 



Cl H 



O 



The choice between these six possible formulae must be 

 made on other grounds. 



Simple as the method is, and valuable in cases such as 

 the above, in which the valency of the elements combined 

 is hardly open to doubt, it must be remarked that it is 

 restricted in application, owing to uncertainty in the 



