ABSORPTION AND EMISSION CENTERS. 11 



nitrosobenzene, ON C 6 H 5 , which is green. Wallach, 1 and recently J. Schmidt, 2 

 have investigated the following compounds, which are of a deep blue color: 



CH CH C(CH 3 ), CH 3 CH C(CH 3 ) 2 



NO O NO NO O N0 2 



Alkylenenitrosite. Alkylenenitrosate. 



According to Wolff, 3 the following nitroso compounds, the first of which 

 is green and the second blue, have the structures: 



ON C C CH, ON C C CH, 



\ 



N 



N 



CH 3 C N C 6 H 5 CH 3 C NH 



l-phenyl-3.5-dimethyl-4- 3-5-dimethyl-4- 



nitrosopyrazol. nitrosopyrazol. 



The carrier of the color in these cases is the C N = group. Many of 

 the aliphatic nitroso compounds show polymerization and are then often col- 

 orless. The polymerization of R N = to (RNO) 2 is probably accompanied 

 by a rearrangement as follows: 



/\ 



R N< >N R. 



This would explain why the polymer is colorless. 



An application of the theory of isodynamic isomerism has been made by 

 K. Schaefer 4 to the absorption of the N0 3 group. An exhaustive study has 

 been made of the absorption of alkyl and metallic nitrates. In every nitrate 

 investigated, the characteristic ultra-violet absorption was detected, and in 

 general Beer's law was found to hold. It would be interesting to know whether 

 the presence of other salts, acids, or solvents would change the N0 3 absorption. 

 Schaefer finds for pure neutral solutions of inorganic salts that the absorption 

 is independent of the metal. The absorption band appears to be independ- 

 ent of the ionization, since in the case of potassium nitrate the absorption 

 is the same for the solid as for the concentrated and dilute aqueous solutions. 

 The absorption is suggested to be due to the following oscillation: 



Nf <= N< | 

 v x 



The character of the absorption is similar for metallic and many organic 

 salts. Methyl, ethyl, amyl, and allyl nitrates, however, show only general 

 absorption. There was no evidence here of selective absorption, either in 

 the liquid, vapor, or dissolved condition of the salts. 



1 Lieb. Ann., 241, 288 (1887); 322, 305 (1902). 



2 Ber. d. chem. Ges., 35, 2323, 3721 (1902); 36, 1768 (1903). 



3 Lieb. Ann.. 325, 192 (1902). 



*Zeit. wiss. Phot., 8, 212-234 and 257-287 (1910). 



