326 ANNUAL OF SCIENTIFIC DISCOYERY. 







it receives no appreciable increase of weight, thus demonstrating that no 

 sulphuric acid is cither mechanically retained by it or chemically combined 

 widi it. It lias also been ascertained by analysis that no trace of sulphur 

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

 cal identity, constitutes an important distinction between it and the gun- 

 papers of Pclouzc and others. Unlike those substances, it is neither an elec- 

 tric, nor more combustible than unconverted paper of equal size and weight, 

 nor soluble in ether or potash. Unlike common paper, it is not disinte- 

 grated by water ; unlike common parchment, it is not decomposed by heat 

 find moisture. In this remarkable operation, the action of the sulphuric 

 acid may be classed among the phenomena ascribed to catalysis (or con- 

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

 with the woody fibre, with or without the elimination of oxygen and hy- 

 drogen, as water ; and that this compound is subsequently 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 be- 

 fore stated, the weight of the paper remains the same before and after its 

 conversion. 



Those who arc interested in chemical inquiry will recall many instances 

 of physical changes omirring in compound bodies, while these bodies re- 

 tain the same elements in the same relative weights. The red iodide of 

 mercury is readily converted, by heat, into its yellow modifications ; yet, 

 by the mere act of being rubbed, it is made to resume its former color. 

 Nothing is added to or taken from this substance in the course of these 

 changes. The inert and permanent crystals of cyanuric acid arc resolved 

 by heat into cyanic acid a volatile liquid characterized by its pungent 

 and penetrating odor, and so unstable that, soon alter its preparation, it 

 changes into a substance (cyamclide) which is solid, amorphous, and des- 

 titute 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 proportion. But the closest 

 analogy to the production of Parchment-paper, scientifically considered, is 

 perhaps afforded by what is called " the continuous process" in cthcrifi- 

 cation. It will be remembered 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 Wil- 

 liamson, 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 coining 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 result- 

 ing 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 sulphuric acid docs not form a permanent constituent 

 of the resulting substance, though it takes so important a share in its pro- 

 duction. The strength of this new substance, before alluded to, and its 

 indestructibility by water, indicate many uses to which it may be applied. 



