354 
Journal of Agricultural Research 
Vol. XXVI, No. 8 
of the dyestuff contained in any two solutions, provided each dyestuff is 
known to belong to the same class and to be dissolved in the same solvent. 
Change of solvent may occasion a change in the location of the point of 
maximum absorption, or even alter completely the appearance of the 
absorption curve; while turbidity of the solution will occasion a uniform 
absorption throughout the length of the spectrum without altering, 
however, the location of the point of maximum absorption or chancing' 
the general aspect of the curve. 
Referring to figure i, it will be observed that some degree of uniform 
absorption has occurred in case of solution b. With due allowance for 
the slight turbidity of the solution 6, the curves obtained from solutions 
a and b are seen to be practically identical, being similar in contour and 
exhibiting maximum absorption for the same wave length of light. In¬ 
asmuch as each color is known to be a phloroglucid of a carbonyl com¬ 
pound, and to be dissolved in the same solvent, identity of composition 
is clearly established, proving that the phloroglucid obtained from mix¬ 
tures of acrolein and hydrogen peroxid is identical with that obtained 
from epihydrin aldehyde diethylacetal. 
In case of solution c, the turbidity was so great in proportion to the 
intensity of color that each reading was subject to a comparatively large 
experimental error. While the location of the point of maximum ab- 
