874 Wisconsin Academy of Sciences, Arts, and Letters. 
should have dyeing properties. Both of these compounds are 
dyestuffs, the former not agreeing with the rule as laid down 
by Liebermann. 
‘ ‘ In those compounds in which the OH groups are not connected 
to neighboring carbons atoms as is the case in the dihydroxanthra- 
quinones, 1, 3, 1, 4; 1, 5, etc., the separation of the OH groups 
from one another decreases the tendency to form metallic de¬ 
rivatives with trivalent metals and therefore these compounds 
have no dyeing properties. 
“On the basis of the same reasoning, the least strain of all 
would result and, therefore, an aluminum, iron or chromium 
derivative would be most readily formed in those cases in which 
there are three OH groups connected to neighboring carbon 
atoms. This is substantiated by the fact that anthragallol, 1, 
2, 3, trihydroxanthraquinone. 
has more intense dyeing properties than alizarin, 1, 2, dihydroxy 
derivative. ’ ’ 
Of greater interest to the biochemist, however, than the re¬ 
lation of number and position of hydroxy groups to the color 
and dyeing properties of the compound is the coexistence of a 
number of these closely related compounds in the same or closely 
related plants and the possibility of the formation of one from 
another, or of all of them from simpler products of plant meta¬ 
bolism. From the root of Oldenlandia umbellata there have 
been isolated monohydroxy -2- anthraquinone; alizarin, dihy¬ 
droxy -1, 2-anthraquinone and its monomethyl ether; hystazarin, 
dihydroxy -2, 3- anthraquinone and its monomethyl ether; anth¬ 
ragallol, -1, 2, 3- trihydroxy anthraquinone and three of its 
dimethyl ethers (A. B. C.). From Rubia tinctorium there have 
been isolated alizarin, dihydroxy -1, 2- anthraquinone; xanth- 
opurpurin dihydroxy -1, 3- anthraquinone; purpurin, trihydroxy 
