132 



ANNUAL, REPORT SMITHSONIAN INSTITUTION, 19 31 



remarkable possibilities of an old grating ruled for the Smithsonian 

 by Rowland for infra-red work shorter than 6/i. Two echelette 

 gratings have been ruled for the division by the Johns Hopkins 

 University and have been given preliminary tests in the near infra- 

 red. While these tests have so far been discouraging, they may 

 still prove satisfactory in the deeper infra-red beyond Qfx, for which 

 they were more particularly designed. 



The near infra-red work has been continued in cooperation with 

 the Fixed Nitrogen Research Laboratory. Investigations of the 



4000 A 



Fkjuub 4. 



5000 

 Wnve length 

 -Comparison of spectra using single and double monochromntors 



single monochronintor. 



double monochvomator. 



zooo 



halogen derivatives of benzene have been extended; the near infra- 

 red spectrum of HCN has been investigated in both liquid and vapor, 

 the results being presented at the Pacific coast meetings of the Physi- 

 cal Society during the summer. Investigations of HCl in vapor and 

 dissolved in carbon tetrachloride have been carried out with a view 

 to determining the rotational freedom existing in such solutions. 

 This work has been carried out by Doctor Brackett, in association 

 with Urner Liddel and Dr. Oliver Wulf, of the Fixed Nitrogen 

 Research Laboratory. 



