Am.  Jour.  Pharm. \ 
February,  1906.  J 
Nascent  Silver  Iodide. 
67 
part  in  the  probable  activity  of  the  completed  mixture,  so  that  by 
varying  the  nature  of  the  resulting  precipitate  the  activity  of  the 
mixture  itself  may  be  regulated,  within  a  rather  wide  range,  without 
varying  the  amount  of  the  contained  active  ingredient. 
The  following  formula  for  a  mixture  containing  approximately 
3  per  cent,  of  silver  iodide  has  been  in  use  at  the  German  Hospital 
for  some  time,  and  may  be  considered  as  a  type-formula  that  may 
readily  be  varied  to  suit  the  needs  or  the  whim  of  the  prescriber  or 
the  ability  and  the  resources  of  the  dispenser. 
$    Silver  nitrate  2*2  gm. 
Potassium  iodide   2*2  " 
Distilled  water  50  c.c. 
Mucilage  of  Irish  moss,  N.  F.,  to  make  100 
To  be  mixed  according  to  directions. 
For  a  heavy,  coarse  precipitate  the  potassium  iodide  and  the 
silver  nitrate  are  dissolved  separately,  each  in  5  c.c.  of  distilled 
water.  The  two  solutions  are  subsequently  mixed  and  the  mixture, 
after  being  thoroughly  well  shaken,  is  diluted  with  the  requisite 
amount  of  distilled  water  and  mucilage  to  make  100  c.c. 
For  a  light  flocculent  precipitate  the  soluble  salts  are  separately 
dissolved,  each  in  50  c.c.  of  distilled  water.  The  solutions  are  then 
mixed,  and,  after  being  thoroughly  well  shaken,  the  resulting  mix- 
ture is  allowed  to  stand  for  a  sufficient  length  of  time  for  the  pre- 
cipitate to  subside,  so  as  to  allow  of  decanting  50  c.c.  of  the  super- 
natant liquid,  which  is  replaced  by  the  required  mucilage.  It  will 
be  noted  that  no  provisions  are  made  for  washing  the  precipitates. 
In  mixtures  up  to  and  including  the  equivalent  of  5  per  cent,  of 
silver  iodide  it  has  been  found  that  the  accompanying  potassium 
iodide  and  potassium  nitrate  do  no  material  harm  and  are,  if  any- 
thing, an  advantage  in  that  they  facilitate  osmosis.  When  mixtures 
of  a  higher  percentage  content  of  silver  iodide  are  to  be  used,  the 
accompanying  soluble  salts  may  prove  to  be  in  excess  and  should 
be  removed  by  decantation,  preferably  in  a  dark  room. 
The  peculiar  properties  of  silver  iodide,  to  disintegrate  when 
brought  in  contact  with  reducing  agents,  would  appear  to  suggest 
its  use  for  a  number  of  other  purposes,  either  in  mixtures  or  as  a 
dry  powder. 
Where  silver  iodide  is  to  be  used  locally  as  a  dusting  powder,  the 
precipitate  should  be  washed  with  distilled  water,  to  free  it  from  the 
