716 
Dissolving  Zinc  Chloride. 
Am.  Jour.  Pharm. 
Oct.,  1918. 
be  considered  to  abide  the  solvent  effect  of  ammonium  chloride  on 
zinc  oxychloride — an  effect  again  attributable  to  acidity  of  medium. 
Representing  the  action  by  the  equation : 
Zn(OH)Cl  +  NH4Cl  —  ZnCl2  +  H20  +  NH3,  ' 
ammonia  gas  might  at  first  be  expected  to  be  in  evidence.  But  when 
it  is  recalled  that  free  hydrochloric  acid  is  present  or  producible  in 
a  quantity  definitely  proportionate  to  the  oxychloride  to  be  dealt 
with,  it  is  readily  understood  that  no  ammonia  should  be  evolved, 
nor  was  any,  as  proven  by  test. 
Sodium  and  potassium  chlorides  have  no  solvent  effect  upon  zinc 
chloride,  but  ammonium  chloride  gives  a  clear  solution  of  zinc 
chloride  in  normal  salt  solution,  and  so  does  boric  acid. 
A  sample  of  zinc  ammonium  chloride,  was  prepared  by  adding 
to  a  solution  of  zinc  chloride  of  known  strength  the  calculated 
amount  of  ammonium  chloride  to  supply  an  equal  number  of  mole- 
cules of  the  two  salts.  Crystallization  of  this  solution  yielded  a 
product  which  was  recrystallized  to  obtain  the  sample  shown  at  this 
time.    The  identity  of  the  product  was  established  by  tests. 
Zinc  ammonium  chloride  forms  colorless,  transparent  crystals, 
without  odor  and  having  an  intensely  caustic  taste.  It  is  readily  and 
completely  soluble  in  water ;  the  aqueous  solution  is  acid  to  litmus ; 
the  solution  remains  permanently  clear.  This  salt  is  not  an  article 
of  commerce  in  channels  through  which  the  pharmacist  trades, 
nor  is  its  use  suggested,  for  the  acquisition  of  it  needlessly  .increases 
one's  stock,  especially  since  boric  acid  and  ammonia  chloride  must 
always  be  at  hand. 
Since  medicated  waters  are  frequently  used  in  solutions  for 
treating  conditions  wherein  zinc  chloride  is  likely  to  be  employed, 
some  experiments  were  made  to  observe  the  behavior  of  these 
liquids  toward  zinc  chloride.  Peppermint  water  was  found  to  act 
as  does  distilled  water ;  but  with  boric  acid  or  ammonium  chloride 
yields  clear  solutions.  Camphor  water  was  found  to  possess  acidity 
sufficient  to  dissolve  zinc  chloride  up  to  ten  grains  per  ounce.  Be- 
yond that  strength  camphor  water  takes  on  a  satiny  opalescence  due 
to  the  separation  of  microscopic  crystals  of  camphor.  The  addi- 
tion of  ammonium  chloride  increases  this  opalescence.  But  with  or 
without  ammonium  chloride  these  camphor  crystals  reenter  solution 
within  a  few  days,  or  immediately  upon  the  addition  of  a  few  drops 
of  alcohol.    The  samples  of  rose  water  at  our  command  were 
