400 Mr Gustav Mann on the 



By pouring the alcoholic extract into test-tubes of different 

 diameters we get the same effect as if we were working with 

 extracts of different strengths. A moderately strong solution 

 is to the naked eye dark green by transmitted light, and shows 

 the well-known fluorescence, of a colour like fresh blood-clot. 

 It has the following absorption-spectrum (spectrum 2, Plate 

 11.):— 



1. Band I. of Kraus, X 678 -X 628. 



2. „ II. „ its centre = X 604. 



3. „ III. „ its centre = X 575. 



4. General absorption commencing at X 518, very dark 



at X 504. 



It will be seen that there is no absorption in the green part 

 of the spectrum corresponding to Kraus' band IV., and a 

 solution which will show the three first bands as plainly as 

 shown in spectrum 2, Plate II., will not show the slightest 

 trace of a band in the green. 



Spectra 3, 4, 5, 6, and 7 (Plate 11.) are of special import- 

 ance for the understanding of the band in the gi^een. I shall, 

 however, state only shortly at present wliat these figures 

 represent, and shall discuss the band fully afterwards. 



Spectrum 3 shows the absorption-spectrum of a very con- 

 centrated alcoholic extract from fresh material after standing 

 for forty-eight hours. The layer used was so thick as to 

 appear to the naked eye on transmitted light of a dark red 

 colour : — - 



1. Absorption from X 690 — X 555. 



2. „ „ X 543 [centre = X 535] -X 527. 



3. „ commencing at X 515. 



Spectrum 4, the alcoholic extract, the spectrum of which 

 is shown in spectrum 3, was evaporated on a water-bath, the 

 black-green residue dissolved in as much benzol as to have 

 the same bulk as used in spectrum 3. The exposure to 

 the oxygen of the air probably caused the change in Kraus' 

 band IV. 



1. Absorption from X 690 — X 550. 



2. Band from X 544 [centre = X 535] - X 525. 



3. Absorption commencing at X 515. 



