1 78 MR. E. SCHUNCK OX THE 



State of the system. It is therefore a substance which is 

 formed sparingly indeed, but* in widely distant parts of the 

 organic world. The properties of indigo-blue, which are so 

 peculiar as almost to separate it from all other organic bodies, 

 and to constitute it one sui generis, naturally suggest the 

 inquiry, in what form it is contained in the plants and animals 

 from which it is derived. If it exists ready formed in the 

 indigo-bearing plants, how is it that though, when in a free 

 state, insoluble in water, acids, alkalies, alcohol, and most 

 simple menstrua, it should so easily be extracted from those 

 plants by a mere infusion with cold water? If it does not 

 pre-exist in the plant, in what state of combination is it 

 contained therein, and what is the>. nature of the process by 

 which it is eliminated ? The usual method of preparing 

 indigo from the indigoferse consists in steeping the plant, 

 especially the leaves, in water, drawing off the infusion, 

 allowing it to undergo fermentation, and then precipitating 

 by means of agitation with air and the addition of lime 

 water. Now it may be asked, is this process of fermentation, 

 which is often very te4ious and difficult to manage, essential 

 to the formation of indigo-blue, or is it merely an accidental 

 phenomenon attending its preparation ? If it is essential, at 

 what stage of the process is the formation of the colouring 

 matter to be considered as completed, and is it necessary, as 

 some persons assert, to continue it until actual putrefaction 

 has commenced, or not? These are points, which though 

 perhaps of little consequence to the dyer and consumer of 

 indigo, are of great interest in a chemical point of view, and 

 are of the greatest importance to the manufacturer of indigo. 

 To the latter it must surely be extremely desirable to know 

 the exact nature of the process on which his manufacture 

 depends, and to ascertain whether this process yields into his 

 hands the whole quantity of the product which the material 

 employed is capable of yielding, and also whether the manner 

 of conducting it is in perfect accordance with theoretical re- 



