Dr. Schunck on the Formation of Indigo-blue. 127 



the peculiar kind of sugar produced by the decomposition of in- 

 dicaUj and to which, as having a composition differing from that 

 of most other species of sugai', I propose to give the name of 



Indiglucine. 



In order to purify it, the brown syrup, after the crystals of 

 leucine had been separated by decantation, was dissolved in 

 water, and acetate of lead was added to the solution. A slight 

 precipitate was thereby produced, which was separated by filtra- 

 tion ; and on adding ammonia to the liquid, a bulky yellowish 

 precipitate fell, consisting chiefly of the lead compound of indi- 

 glucine. This was filtered off, completely washed with water, 

 and decomposed with sulphuretted hydrogen. The filtered 

 liquid was agitated with animal charcoal until it had quite lost 

 the yellowish tinge which it showed at first, and until a portion 

 of it, on being mixed with acetate of lead and ammonia, gave a 

 perfectly white precipitate. It was then filtered again, and eva- 

 porated either in the apparatus above described by means of a 

 current of air, or over sulphuric acid. The syrup left after eva- 

 poration was dissolved in alcohol, and the solution was mixed 

 with twice its volume of sether, when the indiglucine was preci- 

 pitated as a pale yellow syrup, having a sweetish taste. 



To the description formerly given of this substance I have 

 only a few particulars to add. Baryta-water gives no precipitate 

 in the watery solution, but on adding alcohol a slight flocculent 

 yellow precipitate is produced. The watery solution, after being 

 mixed with milk of lime and filtered, is found to have become 

 strongly alkaline, and on being boiled becomes quite thick in 

 consequence of the separation of a bulky yellow mass of flocks, 

 which on the liquid cooling is completely redissolved, forming a 

 clear yellow solution as before, an experiment which may be 

 repeated any number of times. The solution of the lime com- 

 pound, when mixed with an excess of alcohol, gives a bulky yel- 

 lowish precipitate, after which the liquid appears almost colour- 

 less. When treated with boiling nitric acid, indiglucine is de- 

 composed and yields oxalic acid. When a watery solution of 

 indiglucine is mixed with yeast and left to stand in a warm 

 place, no disengagement of gas is observed, nor is any sign of 

 fermentation taking place manifested. After some days, how- 

 ever, the solution begins to acquire a strongly acid taste and re- 

 action, showing that it has entered into a state of acetous fer- 

 mentation witliout having passed through the intermediate stage 

 of the alcoholic fermentation. 



The new analyses which I have made of the lead compound, 

 confirm the conclusion at which I arrived at an early period of 

 the investigation, viz. that when in combination with oxide of 



