748 
4). 10:1637 „eu 5 AD MANIERE AROAONEE" 
D)R0:16 030,0 > DA OL Euer 
6) 10187507 1, NOBIAI er U 
corresponding to: 
1) 74600, e UT 
2) 1432, , 1:65, 
2) MALTE N E, 174 , 
n 
4) 7482, „ ua: 
5) 7492, „ 737, ; 
6) 7489, , 145, , 
Middle 1470, © USB, Is 
These results agree well with those of former observers. Etti 
found 74:64°/, © and 7:66°/, H aud Zwick 74715°/, C and 7:81°/, H. 
The formula C,, H,, O, proposed for the first time by Etti requi- 
res: 74:66°/, C and 7-550/, H and seems to be in view of the above 
results well established. 
Optical properties of bixin. 
The speetrum of bixin in highly interesting. A comparison of 
the reproduetion of our photographs (Plate XIX) representing the 
the absorption spectrum of bixin dissolved in ehloroform or aleohol 
and obtained by using quarz lenses and Iceland prism with the 
spectra of lipochroms reproduced by ©. A. Schunck 1) will show 
that these spectra are of the same type. In the bixin spectrum 
however we have not only the three bands characteristie for lipo- 
chroms but still two more situated in the ultraviolet in the region 
of the solar lines N and O. 
The extraordinary colouring power of bixin is elearly demon- 
strated by the first 6 stripes on the photograph (plate XIX). The 
photographs were started with a solution of bixin in chloroform, 
containing in 1 eem 00001 g, thiekness of layer 19 mm. This 
solution did not let through any light, similarly the next solution, 
containing 0‘00005 g per centimeter, was not penetrated by light. 
The third solution, with the concentration of 0:000025 g per cem 
shows already a broad dark band and two very faint already 
mentioned bands in the extreme ultraviolet end of the speetrum. 
These bands were not noticed by former observers. The fourth 
1) Proc. Roy. Soc 63, 389 (1898), 65, (1899). 
