54 Memoir upon the Conversion of ligneous Bodies into 



with weak sulphuric acid, furnished acetic acid and a precipitate 

 of sulphate of lime. 



I repeated the experiment with 16 grammes (247*1 gr.) of 

 the saW-dust ; but instead of pouting the sulphuric acid on the 

 whole of this quantity, I triturated it, in sm;ill portions, adding 

 the acid by little and little. In spite of these precautions, sul- 

 phurous acid was still disengaged ; but I obtained a very thick 

 tenacious mucilage, which I dissolved in a certain quantity of 

 water and filtered through a cloth ; tliere remained a blackish in- 

 soluble matter of the weight of five grammes (77 "2 gr.) sihiilar 

 nearly to that in the preceding experiment. The acid liquor 

 saturated with chalk, and then evaporated, yielded 10 grammes 

 (lo4'5 gr.) of a gummy substance of a reddish-brown colour. 

 As Messrs. Fourcroy and Vauqnelin say in their memoir, that ve- 

 getable substances are not decomposed by cold sulphuric acid, 

 I thought that this disengagement of sulphurous acid must at 

 least be very rare, and I therefore gave over experimenting with 

 the saw-diKt of elm. 



In order to arrive at greater certainty in the results, I tried to 

 prepare the ligneous matter : but finding it difficult to bring it to 

 a state of perfect purity, I found it more convenient to have re- 

 course to strips of linen cloth, which may be considered as pure 

 ligneous matter. 



Action of Sulphuric Acid on Liven Cloth which had been used. 



Twenty-five grammes (386* 1 gr.) of this cloth cut into small 

 pieces lost by heat one gramme (15*5 gr.) of water. I put this cloth 

 into a glass mortar, and moistened it with 34 grammes (525 gr.) 

 of sulphuric acid, taking care to agitate continually the mixture 

 with a strong rod of glass, in order that the acid might pene- 

 trate as uniformly as possible all the parts of the cloth ; and that 

 there should be a long enough interval between each addition of 

 acid, to allow the heat which it developed to be entirely dissi- 

 pated. Not the slightest portion of sulphurous acid was disen- 

 gaged. A quarter of an hour after the mixture had been made, 

 I pounded it with a glass pestle : all the tissue of the cloth dis- 

 appeared, and there remained a mucilaginous mass extremely 

 tenacious, heavy, homogeneous, and faintly coloured, which I al- 

 lowed to stand for twenty four hours. 1 mention these precau- 

 tions as proper to be followed, in order to obtain the purest pro- 

 ducts ; for, whatever the process adopted may be, no sulphurous 

 acid is disengaged, nor is there the least indication of matter of 

 a carbonous appearance. This mucilaginous mass dissolved en- 

 tirely in water, with the exception of an amylaceous matter which 

 weighed when dry 25 gram. (38*6), and which was nothing but 

 a part of the cloth which had not been sufficiently acted upon by 



the 



