16 
ANTIDOTE  AT  ONCE  FOR  PRUSSIC  ACID,  ETC. 
mix  in  now  a  cream  formed  of  ninety  grains  of  calcined  mag- 
nesia, rubbed  up  with  water  in  a  mortar,  stir  till,  after  gelatiniz- 
ing, the  mixture  again  gets  thin ;  empty  the  mixture  into  a 
calico  or  muslin  cloth,  and  press  out  the  liquid  ;  remove  the  mass 
from  the  cloth  into  a  clean  mortar,  and  rub  it  up  with  a  little 
water  into  a  smooth  cream ;  in  this  state,  it  can  destroy 
upwards  of  twenty  grains  of  tartar  emetic.  It  may  also  be 
used  as  an  antidote  for  arsenious  acid,  of  which  it  absorbs 
about  ten  grains. — Lond.  Pharm.  Joum.,  Oct.  1,  1865. 
SUPPLEMENT  TO  PAPER  ON  AN  ANTIDOTE  AT  ONCE  FOR 
PRUSSIC  ACID,  ANTIMONY,  AND  ARSENIC. 
By  Messrs.  T.  and  H.  Smith. 
In  addition  to  and  completion  of  our  late  remarks,  in  this 
Journal,  on  Sol.  Ferri  Perchloridi  as  an  antidotal  agent  in 
poisoning  by  either  prussic  acid,  antimony,  or  arsenic,  it  oc- 
curred to  us,  while  our  manuscript  was  'in  the  compositors' 
hands,  that  the  question  may  be  asked — what  effect  would  the 
not  unlikely  occurrence  of  free  acid  in  the  stomach  have  on 
the  action  of  the  prussic  acid  antidote  when  its  use  may  be 
indicated  ?  If  the  amount  of  acid  could  be  known,  the  an- 
swer would  be  easy,  viz. :  the  corresponding  quantity  of  an 
alkali  given  in  advance  would  prevent  any  interference  with 
the  desired  action ;  but  a  quantity  of  alkali  so  great  would  be 
required  to  meet  the  most  extreme  case  that  the  remedy  might 
itself  have  an  injurious  action,  or  might  form  a  soluble  yellow 
prussiate  which,  although  not  poisonous,  would  be  a  less  desir- 
able product  than  the  insoluble  and  inert  Prussian  blue.  It 
therefore  suggested  itself  to  our  minds  that  caustic  magnesia 
might  be  a  more  desirable  agent  in  such  a  case.  A  single 
trial  showed  that  every  difficulty  is  removed  by  the  use  of 
that  substance,  and  that  it  does  not  interfere  with  the  action  of 
the  antidote. 
Ninety  grains  of  calcined  magnesia  were  made  into  a  smooth 
cream  with  a  little  water ;  two  drachms  of  muriatic  acid  were 
then  added,  and  the  acid  was  instantly  neutralized,  yet  leaving 
a  large  excess  of  magnesia.    100  minims  of  medicinal  prussic 
