Chemistry and Physics. 279 
of the sulphuric acid is purely molecular, the ultimate chemical composi- 
i —cellulose—remaining unchanged. [As already stated 
by Poumarede and Figuier doc. cit. and by J. Barlow, Proc. of the Royal 
' acid in this instance is comparable with that which a longer action of this 
ti tance 
_ Well known to be isomeric with cellulose. Indeed, the vegetable parch- 
_ ment may be regarded as a middle term between dextrine and cellulose, 
_ The samples of parchment-paper examined by Hofmann [and by Bar- 
) contained no trace of free sulphuric acid ; small portions of sulphate 
ine and of sulphate of ammonia being the only soluble impurities 
t. 
There is no apparent reason why the parchment-paper should not en- 
ure for an indefinite length of time. It is evident that if its destruction 
ie dependent in any way upon the chemicals used in preparing it, de- 
osition would set in at once. Nothing of the kind occurs, however. 
ecimens of the factitious parchment which have been in Hofmann’s 
assion during four years being undistinguishable from those recently 
a experiments made in order to ascertain the strength of parch- 
paper, as compared with that of true parchment and of unsized pa- 
it appeared that while strips of unsized paper broke when subjected 
_ aweight of 15 or 16 pounds, similar strips of vegetable parchment 
‘ipported 74 Ibs., and those of ordinary parchment 75 lbs., before break- 
tig: The cohesive force of unsized paper is thus increased five-fold by 
a treatment with sulphuric acid. It was also proved by experiment that 
am weights of the two substances parchment-paper exhibited about 
Was nearly constant, that of strips of animal parchment, even when 
hand 4 single piece, was extremely variable, owing to the differences 
oe to which it is liable. ; 
el ment-paper although not quite so strong as ordinary parchment, 
: shale more capable than the latter of withstanding the action of 
 belet ; agents, and especially of resisting the action of water; it may 
cS in this liquid for days, or even boiled in it, without undergoing any 
¢hange, other than the increase of volume already alluded to, its original 
vl ned indeed all its properties being regained on drying. As is 
“vith; Wn, animal parchment is soon converted into glue when boiled 
oval Water, 
oo the parchment- r contains no nitrogen, it is much less liable 
7 ig putrefy when exposed to moisture, and will 
e 
ray be substituted for that ordinari ly employed for legal documents, 
; Sut from its cheapness it will probably soon be used for ledgers and 
‘ane records—possibly for bank-notes—instead of the more 
“Paper j ® paper now employed. [It will take the place of ane 
—ttleo 'n school books, and other books exposed to constant wear.” “it 
<a to be of value for photographie purposes, and for artistic 
Consequence of the manner in which it bears both oil and water- 
