[ 53 J 



VII. Memoir upon the Conversion of ligneous Bodies into Gwm, 

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

 and on the Conversion of the saine ligneous Substance into 

 Ulmin ly Potash. By M. Henry Buaconnot*. 



[Read at the Royal Academical Society of Sciences of Nancy the 4th of 

 November 1819.] 



X HE ancient chemists contented themselves with repeating, that 

 the action of sulphuric acid concentrated on vegetable substances 

 does no more than carbonize them. Among the moderns, M. 

 BerthoHet was of opinion that the hydrogen of the vegetable sub- 

 stance united itself to the oxygen of the sulphuric acid, and that, 

 in thus forming of it water and sulphurous acid, the carbonous 

 principle was separated and precipitated. Messrs. Fourcroy and 

 Vauquelin endeavoured afterwards to throw some light on this 

 phaenomenon. They imagined that it did not disengage itself 

 from the sulphurous acid ; and they devised an ingenious theory 

 to this effect, but which seems to me to rest on very slender 

 grounds. 



In examining the remarkable changes which organic com- 

 pounds experience from the action of sulphuric acid, I have been 

 led to results very different from those obtained by these illus- 

 trious chemists ; and I flatter myself that the important facts 

 which I have to present will contribute to cast a new light on 

 many phaenomena of vegetation, and may be usefully applied to 

 the arts. 



Action of Sulphuric Acid on Elm Saw-dust. 



Twenty grammes (30S-9 gr.) of elm saw-dust well dried, were 

 moistened with cold sulphuric acid of commerce of the spe- 

 cific gravity 1*827, and the mixture stirred with a glass tube. 

 It became very hot; and, according to the theory of M.Berthollet, 

 the sulphurous acid gas disengaged itself with impetuosity ; the 

 ashes became black, and appeared to be in the state of charcoal; 

 but it was only in appearance. I poured on the whole a quan- 

 tity of water. I then separated the black powder, which, on being 

 dried and thrown into the fire, burned with flame. It did not 

 sensibly colour cold water; but it communicated to boiling water, 

 and to alkaline solutions it gave a deep brown colour. It was 

 nearly in the same state which the saw dust would have been by 

 exposure for some years to air and humidity. The acid liquor, 

 which was almost as colourless as water after having been satu- 

 rated with carbonate of lime, yielded, on evaporation, a yellowish 

 gummy matter, with a solution of which the subacetate of lead 

 formed an abundant white magma. This gummy matter, treated 



• Translated from the Annala de Chimie, xii. 



D 3 with 



