THE CHEMICAL HISTORY OF THE TERPENES 59 



vation of Baeyer that the nitrosochlorides are generally bimole- 

 cular — that is, the molecule consists of (C^HieNOCl);,. 1 The 

 production of an intense blue colour during the process of 

 combination and before the compound begins to be deposited 

 in the crystalline form is a sign that the compound first formed 

 is a nitroso compound and has not assumed the constitution of 

 an oxime. If the white crystalline nitrosochloride is dissolved in 

 chloroform or benzene, a faint reproduction of the same colour 

 is observable. These facts, together with its behaviour with 

 aromatic bases, already referred to, afford proof that the NO 

 group is present as such and that the hydrogen attached to 

 the same carbon atom in pinene has not left the carbon to 

 produce : N . OH. It is interesting to observe that when the 

 chlorine atom is displaced by CN, by NH 2 or by N 3 , the link 

 between the two molecules of nitroso compound is unloosed 

 and the compounds formed are z//;/molecular, while the nitroso 

 compound becomes an oxime. 



The union between the two constituent molecules in the 

 ^/^nitrosochloride appears to be due to the oxygen, 



C 10 H 16 C1 . N : O : O : N . C 10 H l6 Cl, 



which, as in so many other cases now recognised, exerts four 

 units of valency. That the union is not effected by the nitrogen 

 or the chlorine is indicated by the fact that when these two 

 elements are retained and the oxygen displaced the compound 

 is again zm/molecular, as in the base represented by the 

 following formula 2 : 



CH 



Cl.CMe 



The bisnitrosochloride is optically inactive and is probably 

 racemic in character and if the two semi-molecules could be 

 separated they would probably be found to exhibit respectively 

 dextro and laevo rotatory power. It has been found that a 

 greatly increased yield of the nitrosochloride is obtained when, 



1 Berichte [1895], 28, 639 and 652. 



2 Tilden and Stokes, Trans. Chew. Soc. [1905], 836. 



