PARCHMENT-PAPER. 
425 
Rue  and  Dr.  Miiller  are  engaged  in  researches  on  this  subject, 
which  will  be  hereafter  published. 
Those  who  are  interested  in  chemical  inquiry  will  recall  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  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  are  resolved 
by  heat  into  cyanic  acid — a  volatile  liquid,  characterized  by  its 
pungent  and  penetrating  odor,  and  so  unstable  that,  soon  after 
its  preparation,  it  changes  into  a  substance  (cyamelide)  which  is 
solid,  amorphous,  and  destitute  of  all  acid  properties.  These 
substances,  as  well  as  fulminic  acid  (which,  however,  is  known  in 
combination  only),  contain  carbon,  nitrogen,  oxygen,  and  hydro- 
gen, 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 
etherification.  It  will  be  remembered  that,  in  this  process,  sul- 
phuric acid,  at  a  temperature  of  284°  Fah.,  converts  an  unlimited 
quantity  of  alcohol  into  ether  and  water.  In  the  first  stage  of 
this  process,  as  explained  by  Williamson,  it  would  appear  that 
the  sulphuric  acid  combines  with  the  elements  of  ether  to  form 
sulphovinic  acid ;  and  that,  in  the  further  progress  of  the  opera- 
tion, this  compound,  by  coming  into  contact  with  a  fresh  equiva- 
lent 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  sul- 
phuric acid  remains  in  the  retort,  ready  to  act  on  the  next  por- 
tion. Here,  as  in  the  case  of  the  Parchment-paper,  the  sulphuric 
acid  does  not  form  a  permanent  constituent  of  the  resulting  sub- 
stance, though  it  takes  so  important  a  share  in  its  production. 
The  strength  of  this  new  substance  before  alluded  to,  and  its 
indestructibility  by  water,  indicate  many  uses  to  which  it  may 
be  applied.  It  will  probably  replace  to  some  extent  vellum  in 
bookbinding  ;  it  will  furnish  material  for  legal  documents,  such 
as  policies  of  insurance,  scrip  certificates,  &c. ;  it  will  take  the 
place  of  ordinary  paper  in  school-books,  and  other  books  exposed 
