448 
On  American  Isinglass. 
(  Am.  Jour.  Pharm. 
\  September,  1894. 
while,  and  is  then  taken  out  and  pressed  between  two  iron  rollers, 
by  which  it  is  elongated  to  the  extent  of  half  a  yard  or  more. 
In  order  to  prepare  this  isinglass  for  the  purpose  here  indicated, 
it  is  packed  moderately  firmly  into  a  conical  glass  percolator,  having 
its  lower  orifice  corked,  covered  with  distilled  water  and  allowed  to 
stand  about  twelve  hours.  Then  the  cork  is  removed  and  the  water 
allowed  to  drain.  The  cork  is  then  replaced,  more  water  poured  on 
to  cover  the  isinglass,  and  the  operation  repeated  about  four  times 
or  more  until  the  water  that  drains  away  is  not  affected  on  the  addi- 
tion of  a  solution  of  tannic  acid.  During  the  warm  weather,  or  if 
the  isinglass  should  acquire  odor  indicating  putrefactive  decomposi- 
tion, the  addition  of  about  10  per  cent,  of  alcohol  to  the  water  will 
be  necessary.  The  isinglass  is  then  transferred  to  a  muslin  strainer, 
and  strongly  expressed  in  order  to  remove  as  much  of  the  water  as 
possible.  The  moist  mass  is  then  to  be  returned  to  the  percolator 
covered  with  stronger  alcohol,  allowed  to  stand  twelve  hours,  trans- 
ferred to  the  strainer  and  again  expressed.  The  cake  of  isinglass  is 
finally  spread  out  by  picking  it  apart,  and  laid  on  glass  or  porcelain 
plates,  and  allowed  to  dry  in  a  current  of  air. 
It  will  be  seen  that  the  mode  of  preparing  this  isinglass  for  de- 
tannating  solutions  is  an  exceedingly  simple  process,  standing 
strongly  in  contrast  with  the  preparation  of  hide  powder  as  directed 
by  Professor  von  Schroeder.  The  main  difficulty  in  reducing  the 
purified  and  dried  hide  to  the  state  of  fine  powder  seems  to  be  its 
toughness.  Fresh  depilated  hide  is  to  be  kneaded  repeatedly  daily 
in  running  water  for  eight  to  ten  days,  or  until  the  water  fails  to 
remove  anything  soluble  in  it.  The  hide  having  now  become 
nearly  white,  is  then  to  be  cut  up  into  squares  of  three  to  four 
millimetres,  these  dried  on  a  water-bath  at  ioo°  C,  and  finally 
ground  to  a  fine  powder  in  a  suitable  mill.  During  the  grinding,  the 
hide  will  have  to  be  kept  drying  at  intervals  on  the  water-bath,  so 
as  to  enable  it  to  be  wholly  ground  up. 
Where  time  is  an  object  it  will  be  seen  that  American  isinglass 
should  be  greatly  preferred,  inasmuch  as  its  preparation  stands  in 
the  ratio  of  three  days  to  twelve  days  for  the  hide  powder.  Also 
in  the  application  of  the  former  for  detannating  purposes  its  supe- 
riority is  manifest.  Professor  von  Schroeder  directs  3  grams  of 
the  hide  powder  to  be  used  for  50  cubic  centimetres  of  a  decoction 
of  oak  bark,  having  a  strength  of  2  grams  in. a  litre.    He  covers 
