402 Mr Gustav Mann on the 



bands in the blue, and afterwards through a thicker layer, 

 to bring out the bands in the red and orange : — 



Band 1. X 676 [centre = X 666] — X 656. 



„ 2. X 656 -X 643. 



„ 3. centre = X 613. 



„ 4. centre = X 492. 



„ 5. centre = X 458. 



Spectrum 10 represents an extract with a petroleum 

 ether, which has the peculiarity that it does not dissolve out 

 any material producing absorption in the red end of the 

 spectrum. The extract was quite free from any green tinge, as 

 occurring in extracts made with benzol and xylol. The wave- 

 lengths of the bands in fig. 10 are these : — 



Band 1. X 488 [centre = X 479] — X 469. 

 „ 2. X 456 [centre = X 441] - X 431. 



The least absorption between these two bands is at X 461. 



To extract a pure yellow colouring-matter which will give 

 no absorption band in the red end of the spectrum, even if 

 liighly concentrated, it is best to triturate fresh Spirogyra till 

 the petroleum ether shows a faint yellowish tinge, which it 

 will do after ten minutes. Of this pale yellow extract 100— 

 150 c.cm. are allowed to evaporate spontaneously in an 

 evaporating chamber till the extract is of a deep golden 

 colour ; great care must be taken not to have a flame near 

 the chamber, for the vapours are very apt to ignite and 

 cause an explosion ; also, when examining the extract, a 

 tightly-fitting cork should be inserted in the test-tube, or 

 there may be a risk of the vapours extending to the Argand- 

 burner, and causing mischief. 



To recapitulate shortly, T consider the absorption-spectrum 

 of chlorophyll in Spirogyra to be as follows : — 



1. A band X 678 - X 662 ,_ ^^ 



2. „ X 654 -X 638 ^ " ^^^^^^ 



3. 

 4. 

 5. 

 6. 



} = 



centre = X 604 = „ II. 



centre = X 575 = „ III. 



centre about = X 484 = Kraus' V. 

 centre about = X 450 = „ VI. 



