386 EffiS! of Sht^huiUjictd en FigctabU Matter. 



time proper in Tome refpcc(s to cxphin and ameliorate their daily procefles, particularly 

 thofe which relate to fevcral pharmaceutical operations. 



When a dry vegct.ible fublUnce, fuch as wood, llraw, or gum, is plunged in the concen- 

 trated fulphuric acid, this matter becomes coloured and foft, appears to diflblve in the acid, 

 and forms with it a magma or kind of brown or black imperfc£lly fluid matter, well kni'wn 

 to every chemill as the producl of their experiments. If, after die mutual aiTlion of thefc 

 bodies is exhaufted, the mixture be diluted with a fulhcient quantity of water, two pheno- 

 mena equally intcrefting are obferved. The one is the precipitation of a black powder, 

 poflining all the characters of carbone nearly pure ; the other is the flight degree of heat 

 which the mixture produces with the water. It is far beneath the temperature which an 

 equal qua.Ttity of the fulphuric acid, originally employed, would have exhibited with a like 

 quantity of water. 



The vegetable matter is certainly much altered, and has undergone a great decompofition 

 in this experiment; Cnce the carbone which entered into its compofition is feparated, nearly 

 f ure, from the other principles with which it was combined. It is well proved at prefent, 

 that vegetable fubllances are compofed of carbone, hydrogene, and oxygene united in 

 various proportions, and remaining in a conftant equilibrium of compofition, fo long as new 

 attraftions do not come to deftroy it. In the prefent cafe the equilibrium is manifcftly broken, 

 becaufe the carbone is feparated from the two other principles. It was at firfl imagined, 

 and in this manner it is that Citizen BtrthoUct has particularly determined the caufe of this 

 phenomenon in feveral of his works; namely, that the hydrogene of the vegetable fubftance 

 united with the oxygene of the fulphuric acid, and, by thus forming water and fulphureous 

 acid, the carbonic principle was feparated and thrown down. We have ourfcives adopted 

 and admitted the fame explanation, until repeated experiments fliewed us that this 

 opinion is erroneous. In faift, in the cafe here mentioned, and obferved for a great 

 number of times with the utmoft; attention and care, we have not perceived that an atojn 

 of fulphureous acid was produced, but that the fulphuric acid remains entire without aiiy 

 alteration or change in the proportion of its coiiftituent parts. Since, therefore, this acid is 

 not decompofcd in the cold by vegetable matters, it is neceflary tc conclude, that the changes 

 produced in thofe bodies are the confequence of a re-a£\ion between their proper principles; 

 a rc-a£tion of which the fulphuric acid is only the occafional or fubfidiary caufe. 



But in order to determine by what energy this acid produces fuch an alteration in ve- 

 getable matters; it is requifite to examine with accuracy what the alteration may confift in; 

 and this examination, to which we have a great number of times directed our attention, 

 has fhewn the error adopted with regard to the pretended decompofition of the acid, and 

 the true caufe of the changes thus produced in organic bodies. When the carbonic pre- 

 cipitate of the experiment above defcribcd is feparated, it is found that the fulphuric acid 

 which floats above it, is Angularly weakened, and cont.ins the acid of vinegar, which may 

 be feparated by diftillation. Here therefore we fee the vegetable matter converted into 

 acetous acid and carbone. If the quantity of this lad, together with that of the vinegar, be 

 compared with the quantity of vegetable matter employed, a conGderable lofs is perceived 

 in the mafs of thefe produfls, compared with that of the fubftance which aflbrded them. 

 Nothing can have been loft in the experiment, becaufe no elallic fluid is difengaged ; and 

 as the fulphitric acid has loft much of its denfity, and becomes much lefs heated with 



water. 



