PARCHMENT. 
553 
performed  by  Messrs.  Depouilly  Brothers,  is  based  upon  tbe 
fact  that  phthalic  acid  mingled  with  a  surplus  of  lime,  and  at  a 
temperature  of  625°  to  660°  F,  is  converted  into  benzoate  of 
lime.  It  must  be  performed  in  vacuum.  This  reaction  may  be 
expressed  by  the  following  equation  :  naphthalate  of  lime  =  G^^, 
IP,  O^H-2CaO,  and  hydrate  of  lime  =  CaO,  HO,  yield,  when 
heated  to  the  above  temperature,  benzoate  of  lime  —  C^^  H^,  0^ 
+  CaO,  and  carbonate  of  lime  =  2(CaO,  00^)  Decomposition 
of  water  and  formation  of  carbonic  acid  then  takes  place.  To 
successfully  accomplish  this  operation,  however,  requires  con- 
siderable skill  and  practice. 
Benzoic  acid  is  separated  from  benzoate  of  lime  by  hydrochlo- 
ric acid,  and  with  respect  to  the  benzol,  it  can  be  obtained  by 
subjecting  benzoate  of  lime  to  distillation  with  lime.  This 
operation  is  nearly  always  successful.  The  following  formulae 
give  the  successive  steps  in  these  operations : 
NaphthalinzzrrC^'^  W. 
Phthalic  acid==:C^^  0*^. 
Benzoic  acid^rC^^  0\ 
Benzol=:C^2  jjg^ 
The  latter  may  serve  for  the  production  of  nitro-benzol,  C^^, 
also  aniline,  the  formula  of  which  is  C^',  H^,  N.— 
Jou7\  Applied  Chemistry^  Sept.,  1869. 
PARCHMENT. 
The  ancient  process  employed  for  producing  parchment  was 
nearly  analogous  to  that  now  actually  in  use.  Goat  and  sheep- 
skins are  preferred  for  making  parchment  ;  white  calf,  lamb,  and 
still-born  kid-skins  are  reserved  for  vellum.  The  art  of  the 
parchment  maker  consists  in  making  these  skins  very  thin  and 
almost  transparent,  they  yet  being  perfectly  firm  and  strong  for 
use.  After  the  hides  have  been  depilated,  unfleshed,  and  partly 
ungreased,  they  are  immersed  into  a  solution  of  alum  and  sea 
salt ;  they  are  then  very  quickly  dried  and  stretched  out  on 
wooden  frames,  by  means  of  screws,  and  drawn  so  tightly  that 
no  wrinkle  or  fold  remains.  When  the  skin  is  very  dry  the 
workman,  with  a  sharp  iron,  takes  off  all  the  flesh  which  may 
