Ail.  Jour.  Pharm.  ) 
April  1,  1871.  J 
Iodoform. 
167 
HO).  Five  atoms  of  oxygen  of  the  carbonate  of  potassa  join  2  (CgH^ 
HO),  forming  2  (HCHO2)  +  3  (H^O)  +  2  (CH).  2  (HCHO^)  com- 
bines with  K20==2  (KCHO2,  H2O)  while  10  K  +  10  1=10  (KI),  and 
6  I  and  the  2  (CH)  of  the  alcohol  form  2  (CHI3),  carbonic  acid 
escaping. 
According  to  this,  the  gain  of  iodoform  would  be  38  per  cent. ;  but 
the  reaction  never  takes  place  so  completely,  and  we  must  remember 
that  all  these  changes  take  place  at  once,  and  that  iodoform  is  very 
volatile  (must  never  be  made  in  an  open  vessel)  the  alcohol  evaporates, 
and  must  be  used  in  larger  quantities  ;  the  excess  of  carb.  of  potass, 
does  not  retard,  but  seems  to  increase  the  reaction. 
By  using  six  ounces  of  iodine,  only  one  ounce  of  iodoform  is  col- 
lected, or  about  17  per  cent.  It  would  therefore  be  very  expensive  if 
we  could  not  make  use  of  the  filtrate  for  making  iodide  of  potassium. 
This  liquid  contains,  besides  traces  of  iodoform,  the  balance  of  the 
iodine  as  iodate  of  potassa  and  iodide  of  potassium,  and  also  formate 
and  carbonate  of  potassa. 
Evaporate  this  solution  to  dryness,  and  triturate  with  one-eighth  of 
its  weight  of  charcoal,  and  then  heat  to  redness  for  a  short  time  in  an 
iron  crucible,  then  digest  in  alcohol  and  filter;  the  residue  is  carbonate 
■of  potass.,  while  the  filtered  solution  contains  the  iodide  of  potassium  ; 
the  alcoholic  solution  is  evaporated,  and  allowed  to  crystallize.  By 
this  means  no  iodine  is  lost,  and  teriodide  of  formyl  ought  to  be  not 
more  expensive  than  iodine. 
Iodoform  appears  in  the  shape  of  yellow,  shining,  six-sided  scales, 
with  a  spicy  odor  (like  saifron  or  iodine  and  chloroform) ;  is  volatile 
at  ordinary  temperature.  Almost  insoluble  in  water  (one  part  in 
13,000),  but  more  so  in  alcohol  (one  part  in  80).  If  it  be  used  in  a 
mixture,  must  avoid  alcoholic  solution  of  potassa,  which  decomposes 
it,  forming  formate  of  potassa  and  iodide  of  potassium  :  CHI3  -f-  2 
(K,0)=KCH02  +  3  KI. 
Besides  the  well-known  effects  of  iodine  and  its  preparations,  iodo- 
form has  the  advantage  of  the  former  preparation  of  being  stronger 
and  more  uniform  in  its  action  on  the  system;  that  is,  does  not  cor- 
rode, nor  act  as  a  local  irritant,  and  that,  therefore,  it  may  be  given 
uninterruptedly.  It  is  anodyne,  and,  consequently,  often  useful  in 
neuralgia  ;  produces,  also,  a  local  and  partial  anaesthesia  of  the  colon. 
It  has  less  anaesthetic  powers  than  chloroform,  although  recommended 
by  Eugenio  Franchino  (Gaz.  Sarda.,  28,  1858)  as  a  general  anses- 
