Am.  Tour.  Pharm. 
Oct.,  1918. 
Dissolving  Zinc  Chloride. 
717 
neutral  to  litmus ;  they  did  not  dissolve  zinc  chloride  completely 
until  boric  acid  or  ammonium  chloride  was  added.  An  experience 
some  time  past,  but  well  remembered,  leads  us  to  believe  that  speci- 
mens of  rose  water  may  be  encountered  which  will  give  clear  solu- 
tions. 
Mucilage  of  sassafras  pith  did  not  dissolve  the  zinc  chloride, 
until  boric  acid  or  ammonium  chloride  was  added ;  but  though  the 
zinc  oxychloride  went  into  solution  the  mucilage  was  rendered 
cloudy  by  its  contents. 
The  statement  that  zinc  chloride  forms  soluble  double  salts  with 
some  alkaloids  as  well  as  with  ammonium  chloride  was  tried  out 
with  some  of  those  used  in  eye-washes,  with  the  following  results : 
Equal  parts  of  morphine  hydrochloride  and  zinc  chloride  did  not 
yield  a  clear  solution,  until  ammonium  chloride  was  added.  Equal 
parts  of  pilocarpine  hydrochloride  and  zinc  chloride  did  dissolve 
clear.  Equal  parts  of  cocaine  hydrochloride  and  zinc  chloride  did 
not  dissolve  clear,  without  the  addition  of  ammonium  chloride ;  boric 
acid  likewise  carried  the  mixture  into  solution. 
Ammonium  chloride  produced  clear  solutions  when  zinc  chloride 
was  brought  together  with  morphine  sulphate  and  atropine  sulphate. 
Our  conclusions,  from  this  mass  of  experiments  and  data  may 
be  summed  up  in  short  as  follows  :  the  separation  of  zinc  oxychloride 
when  zinc  chloride  is  dissolved  in  water  is  always  accompanied  by 
liberation  of  free  hydrochloric  acid  which  remains  in  the  solution, 
at  the  same  time  a  loss  of  zinc  is  experienced.  Both  of  these  objec- 
tions may  be  overcome  in  solutions  up  to  approximately  twenty 
grains  to  the  ounce  by  the  use  of  boric  acid  weight  for  weight  of 
the  zinc  chloride  taken.  For  solutions  exceeding  this  strength,  or 
for  any  strength,  ammonium  chloride  in  quantity  of  not  less  than 
one-fifth  of  the  amount  of  zinc  chloride  used,  will  insure  complete 
and  permanent  solution.  Camphor  wTater  will  dissolve  only  a  few 
grains  of  zinc  chloride  per  ounce.  Carbonic  acid  water  may  be  em- 
ployed if  intended  for  immediate  use.  And  finally  the  comparative 
ease  with  which  a  minute  quantity  of  either  boric  acid  or  ammonium 
chloride  prevents  a  precipitate  as  against  the  larger  quantity  needed 
to  redissolve  oxychloride  once  formed  may  be  impressed  upon  our 
minds  by  the  wisdom  of  that  renowned  maxim:  "An  ounce  of  pre- 
vention is  worth  a  pound  of  cure." 
