412 Hev, J. Barlow, on Woody Fibre. [April 3, 



either mechanically retained by it, or chemically combined with it. 

 It has also been ascertained by analysis, that no trace of sulphur 

 exists in the Parchment-paper. The fact of this paper retaining its 

 chemical identity, constitutes an important distinction between it 

 and the gun-papers of Pelouze and others. Unlike those substances, 

 it is neither an electric, nor more combustible than unconverted 

 paper of equal size and weight, nor soluble in ether or potash. 

 Unlike common paper, it is not disintegrated by water; unlike 

 common parchment, it is not decomposed by heat and moisture. 

 In this remarkable operation, the action of the sulphuric acid may 

 be classed among the phenomena ascribed to catalysis (or contact 

 action). It is, however, conceivable that this acid does, at first, 

 combine with the woody fibre, with or without the elimination of 

 oxygen and hydrogen, as water ; and that this compound is subse- 

 quently decomposed by the action of water, in mass, during the 

 washing process, the sulphuric acid being again replaced by an 

 equivalent of water ; for, as has been before stated, the weight of 

 the paper remains the same before and after its conversion. Mr. 

 Warren De la Rue and Dr. Miiller are engaged in researches on 

 this subject, which will be hereafter published. 



Those who are interested in chemical, inquiry, will recal many 

 instances of physical changes occurring in compound bodies, while 

 these bodies retain the same elements in the same relative weights. 

 The red iodide of mercury is readily converted, by heat, into its 

 yellow modification ; yet, by the mere act of being rubbed, it is 

 made to resume its former colour. Nothing is added to or taken 

 from this substance in the course of these changes. The inert and 

 permanent crystals of cyanuric acid are resolved by heat into cyanic 

 acid — a volatile liquid, characterised by its pungent and penetrating 

 odour, and so unstable that, soon after its preparation, it changes 

 into a substance (cyam elide) which is solid, amorphous, and de- 

 stitute of all acid properties. These substances, as well as fulminic 

 acid, (which, however, is known in combination only,) contain 

 carbon, nitrogen, oxygen, and hydrogen, in the same relative pro- 

 portion. But the closest analogy to the production of Parchment- 

 paper, scientifically considered, is perhaps, afforded by what is 

 called " the continuous process " in etherification. It will be re- 

 membered that, in this process, sulphuric acid, at a temperature of 

 284° Fahr. converts an unlimited quantity of alcohol into ether and 

 water. In the first stage of this process, as explained by William- 

 son, it would appear that the sulphuric acid combines with the ele- 

 ments of ether to form sulphovinic acid ; and that, in the further 

 progress of the operation, this compound, by coming into contact 

 with a fresh equivalent of alcohol, is, in its turn, decomposed, and 

 resolved into ether and sulphuric acid. The ether distils over 

 together with the water resulting from the decomposition of the 

 alcohol : the sulphuric acid remains in the retort, ready to act on the 

 next portion. Here, as in the case of the Parchment-paper, the 



