ENDOTHIA PIGMENTS 
349 
petroleum ether. Pigment B was soluble in water. It is obvious 
then that these pigments are lacking in many of the properties of 
lipochrome and there is little reason at present for assuming that they 
belong in this rather indefinite group. 
There is some evidence to support the conclusion of Anderson that 
the pigment in E. parasitica is aurine. According to Rota's^^ system 
for the classification of coloring matters these two pigments might 
be classed as aurin. 
Aurin is the trade name^ applied to a red pigment obtained by 
heating phenol and oxalic acid with sulphuric acid. According to 
Dale and Schorlemmer,^^ it was applied to this preparation as pre- 
pared by Kolbe and Schmitt.^^ Dale and Schorlemmer found this 
preparation to be a mixture of compounds and succeeded in separating 
out what they considered pure aurin. The name aurin is retained: 
by Schultz and Julius^^ and by Allen^^ for para-rosolic acid which' 
according to Allen has a formula C19H14O3. This dye, however, is 
insoluble in benzol and carbon-bisulphide and by boiling with sodium 
hydroxide and zinc dust it is decorolorized. This is not true of the 
pigment from E. parasitica. Moreover, a comparison of pigments 
A and C in both alkaline and acid solutions with solutions of com- 
mercial aurin shows that they are not the same color. 
Other points of difference might be mentioned. It is, however, 
apparent that while aurin and the pigments from E. parasitica have 
some properties in common the conclusion that they are the same is 
unwarranted. Whether any of the three pigments considered in 
this paper are similar in structure to aurin is a problem which needs 
further investigation. It lies within the scope of this paper to take 
up the chemical and physical properties of these pigments only in so 
far as is necessary for separating and distinguishing them from each 
other. Their chemistry is under investigation and will be considered 
in a later paper. 
^1 Wiley, H. W., et al. Official Methods of Analysis of the Association of 
Official Agricultural Chemists. U. S. Dept. Agr. Bur. Chem. Bull. 107. 1910. 
12 Dale, R. S., und Schorlemmer, C. Ueber das Aurin. Ber. Deutsch. Chem. 
Ges. 4: 574-576. 1 87 1. 
12 Kolbe, H., u. Schmitt, C. Rother Farbstoff aus dem Kreosot. Annalen der 
Chemie und Pharmacie. 119: 169-172. 1861. 
14 Schultz, G., u. Julius, P. Tabellarische Ubersicht der Kiinstlichen Organ- 
ischen Farbstoffe. Dritte Aufllage. 124, 1897. 
15 Allen, Alfred, H. Commerical Organic Analyses, ed. 3. 3:310-311, 1902. 
