88 DR. EDWARD SCHUNCK ON SOME 



of some use in facilitating the classification of facts. At 

 all events, the circumstance of indigo-blue yielding, by the 

 combined action of alcohol, acetic acid, and alkalies, bodies 

 so closely resembling the products obtained along with 

 indigo-blue in the decomposition of indican seems to aflPord 

 a striking confirmation of the view which I have taken 

 regarding the composition of these products. 



There is another point of view from which these bodies 

 may be considered. They may be represented as substitu- 

 tion products of indigo-blue, one or more of the atoms of 

 hydrogen in the latter being replaced by one or more or- 

 ganic radicals. For instance, the body C may be looked 

 upon as the hydrate of a compound, in which one atom of 

 the hydrogen of indigo-blue is replaced by phenyl (C,j, Hy), 



since 



C,,H,,NO, = C,3H,(C,,H,)NO,+2HO. 



In order to obtain some confirmation for this hypothesis 

 I took some of the body J), of which 1 had a considerable 

 quantity, and which only differs from C by containing 

 more water, and subjected it to the action of hydriodic 

 acid and phosphorus in a sealed tube. By the action of 

 the nascent hydrogen I expected that indigo-blue might 

 possibly be regenerated, but the experiment led only to a 

 negative result ; for though the tube was heated in the 

 water -bath for several days, the substance, on its being 

 opened, was found to be almost unchanged, a small part 

 only having 'been converted into a resinous matter easily 

 soluble in alcohol. A similar negative result was obtained 

 when an amalgam of sodium was employed as a source of 

 hydrogen. After these failures I felt but little encourage- 

 ment in making farther experiments in this direction ; and 

 this part of the subject must, therefore, be left in its pre- 

 sent state of obscurity. 



6. The occasional disappearance of the indigo-blue in 

 the woad-vat, in consequence of mismanagement, now 



