Experiments on Indigo. 271 



By way of examining in a more unexceptionable manner, 

 the gas given out during fermentation, the operation was con- 

 ducted on a small scale, by steeping some of the leaves in a 

 glass cylindric vessel furnished with stopcocks and tubes to 

 convey the gas, which should be emitted, into a glass receiver. 



After twenty-four hours, (for the process of fermentation does 

 not proceed so rapidly as in a large vat,) the quantity of air 

 given out by twelve sicca weight (= 2160 grs.) of leaves, was 

 26.1 cubic inches: the disengagement still went on, but very 

 slowly. 



The gas was analyzed at two different periods : towards the 

 middle of the disengagement it was found to be composed of 



Carbonic Acid . . . 27.5 

 Oxygen . » .5.8 



Azote . . . 66.7 



100 

 And at the conclusion it contained — 



Carbonic Acid . .40.5 

 Oxygen ... .4.5 

 Azote ... . 55.0 



100 

 Probably the atmospherical air of the apparatus, as well 

 as that contained in the water, and that which remained 

 entangled among the leaves, may account in some measure for 

 the presence of the oxygen and azote in the first analysis ; but 

 the large proportion of azote, especially in the second experi- 

 ment, so much surpasses what might be expected from this 

 source alone, that it seems necessary to attribute it, in part, at 

 least, to an emission from the leaves during the fermentation ; 

 or probably the leaves, still retaining atmospheric air on their 

 absorbent surfaces, convert the oxygen thereof into carbonic 

 acid, and allow the azote to escape. After the disengagement 

 has ceased, it will be seen by the next experiment that the pro- 

 portion of azote decreases very much. Some of the fermented 

 liquid of a large vat was well boiled, and the gas collected over 

 water : on analysis, it proved to be composed of — 



Carbonic Acid . . . 78. 



Oxygen . 2.3 



Azote . . .19.7 



100 



