1813.1 



from Bota7iy Bay, 



in alcohol. It is thrown down in yellow flocks by oxymoriatic 

 acid . it dyes cotton brown. In all these respatts the solid matter 

 of liquid gura agrees with it. 



Chei>iists ha^ ? m hitherto perceived that extractive and 

 tannin of .^I'g:; lli itand at the two extremes of a series of 

 substances vvhicii g' /iually pass into each other^ and that they 

 are so closely connected that ihey iniglit all be not improperly 

 arranged under one genus, and receive a common name. 

 < In Jee-l, till this is done the confusion, which at presents subsists 

 in thirs department of vegetable chemistry, cannot easily be 

 removed. 



When nitric acid is poured upon the solid matter of liquid 

 gum, it softens and dissolves it with the evolution of a little 

 nitrous gas. The solution has a very dark red colour; but on 

 being heated, that colour rapidly disappears, and the solution 

 becomes a very light yellow. When distilled it diffuses the 

 smell of prussic arid; by continuing the distillation to dryness in 

 a very moderate heat a solid matter is obtained, while if the 

 heat has been a minimum, yellow if a little higher, and brown 

 if the fire has been urged too far. This matter is soft and 

 spongy. Is has an intensely bitter taste, readily dissolves iu 

 water and alcohol, melts when heated, without undergoing any 

 other change. When the solution of this matter in water is 

 evaporated, small crystals are formed, which detonate when 

 heated. This matter is similar to what has been called the bitter 

 principle of V/elter. It is best procured by treating indigo with 

 nitric acid. Its properties have been detailed at full length by 

 Hatchett, Fourcroy, and Vauquelin. 



When the tanno-extractive of our gum is exposed to heat it 

 swells, blackens, and melts, and a considerable portion of gas is 

 evolved. The first portion of gas is attended with a dense white 

 vapour, and is absorbed by water so rapidly that I have little doubt 

 that it is ammonia, though I had too little of the gum to be able" 

 to verify this supposition by repetition of the experiment. After 

 this the gas obtained is carbonic acid, and carbureted hydrogen. 

 Water comes into the receiver, which is strongly impregnated 

 with a portion of tanno-extractive, not much altered. The 

 charcoal that remains burns to ashes as easily as tinder. The ash 

 that remains is very trifling. It consists, as far as I can judge, 

 of sulphate of lime and carbonate of lime; but other earths 

 might easily have escaped my detection, for the quantity of ashes 

 which I examined did not exceed the hundredth part of a grain. 



From the preceding detail it is obvious that the substance 

 which we have been examining is a combination of a variety of 

 tannin and water, and that it has no resemblance whatever to 

 gum. 



1 



