ABSORBING POWER AND FLUORESCENCE OF RESORUFIN. 



27 



R.C30rx>f(r. 



3. The effect of diluting a fluorescent solution is similar to that of 

 diminishing the distance through which the fluorescent light travels. 



METHOD OF OBSERVATION. 



The instrument used for this work was the spectrophotometer of Lummer 

 and Brodhun. 



The source of light was an acetylene flame 6" (Fig. 22) from which light 

 was diffusely reflected by a block of magnesium carbonate, n, mounted at an 

 angle at 45 with axis of the collimator A . For observations on transmission 

 a similar block of magnesium carbonate was placed in front of the slit D. 



The work was performed in a room with black walls, the acetylene flame 

 being the only source of light. Screens were adjusted so that no stray light 

 could strike any part of the instrument. 



The solution under consideration was placed in front of slit D, the width 

 of which was kept constant during a 

 single set of observations. The ocular 

 lenses of the telescope were removed, 

 the eye being focused upon the face 

 of the prism magnified by the objec- 

 tive of the telescope T. 



In making observations the width 

 of slit C was adjusted by means of a 

 micrometer screw until the central 

 band of light reflected from KL was 

 brought into the best possible coinci- 1 ytlT 



dence with that transmitted from D 

 through the upper and lower parts of 

 the cube. The results given represent 

 an average of from 5 to 10 settings, 

 the zero point of the screw attached to 

 C being carefully determined and care 

 being taken to avoid errors due to lost 

 motion. 



The hydrogen lines of a vacuum Fig 



tube, together with a few of the Fraun- 

 hofer lines, were used for calibration. 



22. Apparatus arranged for 

 measuring fluorescence. 



COMPOSITION OF RESORUFIN. 



Weselski's diazo-resorufin, 1 the fluorescent substance used in this investi- 

 gation, 2 has the formula 



I ' 



c o c 



: 1 p . 

 I '_ I 



Berichte der deutschen chetnischen Gesellschaft, 22, 3036. 



2 Acknowledgment should be made to Prof. W. R. Orndorff for his kindness in preparing the resorufin used 

 in this work. 



o=c 



(J OH 



