By AR'I'HUR GEORGE PERKIN and W. POYPLEM'ELL 13Los.m. .IT is well known that naturd indigo contains, in aclditioii to indigotin and indirubin, certain impurities such as indigo-brown, indigo-gluten, mineral matter, and frequently traces of kaeiiipfei*ol. Indigo-brown and indigo-gluten have been hut little examined, for not only do they possess a somewhat uninviting nature, but their general reactions do not indicate any points of special interest. The present work has originated from a desire to improve the present methods of iiidigo analysis, a i d this it appeared could only be accomplished by the isolation and subsequent examination of the properties of tlicse i~npurities. As a result, .z new annlyticnl methotl Iins lieen tlevisetl, tcri~ctl the '' tetrasulphonnte " process, and a clesci*iption of this h:ts :d iwuly I)CWI given by one of us (J. ,Yoc. C'hent. Intl., 100G, 25, $35). r i i ~o i i i i t~s i o i i with iiitligo-brown, the snbject of this pqwr, it W:IS i~~i~~w t ;~~i to 'cletermine if any relationship existed between this substance :mcl indigotin itself, for should such be the cabe, an explitnetion could u 2
IN the pieceding investigation (this vol., p. 793), a n account has been given of the hydrolysis of indican by means of acids, and the present paper deals with the still more important question of the behaviour of the glucoside with its specific enzyme, indimulsin. With the exception of some preliminary experinierits by Gaunt, Thomas, and Bloxam
Being unable to obtain by purchase ammonium sulphite or ammonium thiopulphate in a state of piirityr, Mr. W. B. Giles kindly undertook their preparation. and was eminently successful. An account of tlie preparation and properties o t these salts will appear in another journal.
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