^°March  1^85™* }       Apjmvatus  fov  CoYitinuous  Percolatwn.  149 
suffocating  odor,  and  its  vapor  when  inhaled  in  large  quantity  pro- 
duces a  cramp,  which  for  a  few  seconds  takes  away  the  power  of 
resj)iration  (Liebig).  The  question  suggests  itself,  may  not  the  peculiar 
suffocating  sensation  often  experienced  during  ether  inhalation  be 
caused  by  the  presence  of  this  compound  ? 
The  test  I  have  described  may  be  applied  in  two  ways ;  two  or  three 
drachms  of  the  ether  are  poured  into  a  test  tube,  and  about  a  drachm 
of  a  freshly  prepared  solution  of  iodide  of  potassium  in  water  added, 
the  tube  corked,  and  the  contents  well  agitated.  If  the  ether  be  pure, 
on  looking  down  the  tube,  while  standing  on  a  white  surface,  no  yellow 
coloration  of  the  aqueous  stratum  will  be  apparent.  The  other  plan 
of  applying  the  test  is  to  add  a  few  drops  of  starch  mucilage  to  the 
ether  and  iodide  of  potassium  solution  and  then  to  agitate  ;  if  iodine 
be  liberated,  it  is  recognized  by  the  blueing  of  the  starch. — Phar. 
Jour,  and  Trans.,  Jan.  3,  1885,  p.  521. 
APPARATUS  FOR  CONTINUOUS  PERCOLATION  WITH 
BOILING  FLUIDS. 
By  W.  Watson  Will. 
In  the  issue  of  the  "Pharmaceutical  Journal'^  of  October  11th, 
there  is  a  description  of  an  apparatus  for  continuous  percolation,  by 
Dr.  Thresh,  which  is  evidently  an  improvement  upon  the  apparatus 
originally  used  by  Tollens  for  the  same  purpose,  the  difli^erence  between 
the  two  apparatus  consisting  in  the  arrangement  of  the  percolating 
tube ;  otherwise  in  principle  they  are  the  same. 
In  examining  Dr.  Thresh's  apparatus  I  came  to  the  conclusion  that 
unless  such  an  apparatus  were  employed  in  the  hands  of  a  skillful 
operator  there  is  a  considerable  liability  that  the  fine  tube,  with  curved 
apex,  would  be  broken  in  packing  the  substance  for  exhaustion  ;  also 
that  to  make  a  punted  and  perforated  tube  such  as  he  describes  re- 
quires a  considerable  amount  of  skill.  Otherwise  it  has  the  advantage 
over  Tollen's  apparatus,  that  through  the  centre  of  the  substance  there 
would  pass  a  constant  current  of  the  vapor  of  the  solvent  by  means  of 
the  fine  tube,  by  which  means  the  substance  under  examination  is 
quickly  heated  throughout  the  mass. 
I  have  used  for  some  considerable  time  an  apparatus  much  similar, 
but  simpler  in  its  construction,  for  the  estimation  of  cinchona  barks, 
scammony,  etc.    It  consists  of  the  following  parts : 
