118 Memoir upon the Conversion of ligneous Bodies into 



Iccted the multiplied and apparently incontrovertible indications 

 and proofs of both theories, which, like all other theories of na- 

 ture, must, when impartially examined, centre in the great crea- 

 tive, omnipotent Power— the formator, protector, and governor 

 of all. Yours truly, 



Jan. 31, 1820. GaVIN InGLIS. 



XVI. Memoir upon the Conversion of ligneous Bodies into Gum, 

 Sugar, and a particular Acid, hy means of Sulphuric Acid ; 

 and on the Conversion of the same ligneous Substance into 

 Ulmine by Potash. By M. Henri Braconnot. 



[Concluded from p. 56.] 



Exanwiation of the artificial Gum produced by the Action of 

 Sulphuric Acid on Linen. 



We have seen that this gum, obtained by saturating sulphuric 

 acid with chalk, contains in combination, lime which may in 

 fact be separated by oxalic acid. This gum may be also purified 

 by adding to a solution of it some of the sub-acetate of lead : 

 this produces a very abundant white precipitate, which being de- 

 composed by an excess of sulphuric acid, the liquid is evaporated 

 .to a sufficient degree, the sulphate of lead is separated, and the 

 gum precipitated by alcohol. I prefer however in place of chalk 

 to saturate the sulphuric acid with the oxide of lead heated : 

 there results from it a liquid of a sugary, smart taste, owing to 

 the lead held in solution : the latter is separated by passing 

 through a current of hydrosulphuric gas ; and the filtered liquor 

 being evaporated, the artificial gum is obtained as pure as possi- 

 ble. Barytes may also be used in place of the oxide of lead ; but 

 as this gum retains barytes in combination, it is necessary to se- 

 parate it by sulphuric acid. 



This gummy matter, such as I have obtained, resembles gum 

 arable. It is transparent, of a slight yellow colour, inodorous, 

 insipid, though it reddened the tincture of turnsole, and seemed 

 to act in the manner of acids. Its fracture is vitreous. It ad- 

 hered strongly to the vessels in which it was dried, always when 

 it was prepared with care, and formed on them a very shining 

 kind of varnish. It forms a mucilage less tenacious than that of 

 gum arable: its cohesive properties are also inferior: but this 

 does not prevent its being of use in many of the arts. Exposed to 

 the fire, it consumed, giving out a penetrating odour of snlphurous 

 acid, owing to the decomposition of the sulphuric acid which it 

 contains in a particular state of combination, such as the usual 



reagents 



