CHEMISTRY. 327 



CHEMISTRY. 



VEGK TABLE PAKCHMENT. 



The ipvestigation of the action of acids ou vegetable fibre has led to some very 

 interesting discoveries, which promised at first to be of great technical importance, 

 and although with some of them the expectations at first entertained have not been 

 completely fulfilled, the most recent one seems likely to form the basis of an 

 extensive branch of manufacture. It is well known that the action of strong 

 nitric acid is to convert vegetable fibre into the so-called gun-cotton, a body which 

 it was once supposed might replace gunpowder, but which is now used almost 

 solely in the manufacture of collodion for photographic and surgical purposes. 

 The long continued action of dilute acid converts vegetable fibre into grape sugar, 

 which it was once supposed might be used as a substitute for cane sugar ; although 

 this has not been found to be the case, large quantities of it are manufactured for 

 other purposes. It is also well known that the action of strong sulphuric acid on fibre, 

 as in the form of paper, is to char or blacken it ; but it is a discovery of only 

 recent origin, that the action of sulphuric acid (diluted with a certain amount of 

 water and properly cooled) on unsized paper is to convert it into a substance per- 

 fectly resembling animal parchment, and possessing many of its valuable proper- 

 ties. We have now before us a " Report on Vegetable Parchment, by Professor 

 George Wilson of Edinburgh," printed on the parchment itself. 



The altered paper resembles parchment, liaving more or less of a mottled 

 appearance, which, to a certain extent, interferes with the distinctness of fine 

 print ; it is quite free from acid, has no gelatinous or amylaceous substance on its 

 surface, is immensely strong, requiring great force to tear it, can be manufactured 

 much cheaper than parchment, and perhaps even than sized paper, jsossesses ap- 

 parently great durability, is not altered by boiling water as is the case with 

 animal parchment, is scarcely acted on by any chemical re-agent, and being con- 

 verted into the hard substance only on the surface, an attempt at erasure would" 

 expose the unaltered blotting paper below, which would at once reveal any 

 attempt to write ou the new surface. Prof. Wilson also states that it is free from 

 the greasy surface which parchment often presents, to which we cannot quite 

 agree, as the specimen before us is in some parts almost as difficult to write on as 

 animal parchment. 



The objections to this substance appear to be its liability to tear into two sheets 

 owing to the existence of unaltered paper in the middle, its liability to decrepitate 

 when strongly heated, and its power of resisting chemical re-agents which might 

 be capable of entirely removing the marks of ink. The first defect, it is stated, 

 may be remedied by using exceedingly thin paper, so that the whole mass of it 

 may be changed ; in that case, however, it seems probable that its property of ex- 

 hibiting writing over an erasure would be destroyed. 



Although not applicable to bank notes, it certainly is well adapted for all docu- 

 ments required to be durable, and which are not liable to erasure, alteration, or 

 forgery. 



