Am.  Jour.  Phatm.  \ 
Oct.,  1918.  i 
Dissolving  Zinc  Chloride. 
709 
Indeed  we  find  that  this  problem  had  been  referred  to  a  commis- 
sion of  apothecaries  and  physicians  in  Belgium,  because  physicians 
were  objecting  to  the  use  of  the  acid.  This  body  discountenanced 
the  use  of  the  acid,  and  recommended  the  use  of  a  turbid  solution  or 
the  clear  liquid  therefrom,  either  of  which,  as  has  been  pointed  out, 
will  contain  the  same  amount  of  free  hydrochloric  acid,  produced 
but  not  added.  Referring  to  the  report  of  this  commission,  Dr.  Paul 
Wiskirchen,  in  the  Pharm.  Zeitung,  1899,  page  268,  states  that  he 
finds  "the  addition  of  acid  is  unnecessary.  He  finds  that  if  it  is 
attempted  to  dissolve  pure  zinc  chloride  in  cold  water,  or  if  cold 
water  is  added  to  a  clear  solution  of  zinc  chloride,  turbidity  is  in- 
variably produced,  but  if  the  solution  is  effected  with  hot  water,  or 
if  the  dilution  is  made  with  hot  water,  clear  solutions  result,  and  so 
remain  permanently."  This  quotation  is  from  the  proceedings  of 
the  American  Pharmaceutical  Association,  1900,  page  717,  for  which 
it  was  abstracted  from  the  Pharm.  Centralhalle  of  August  17,  1899, 
page  508.  In  the  same  Proceedings  for  1907,  page  850,  we  find  an- 
other abstract,  which  we  quote  in  its  entirety. 
"  Zinc  chloride — Simple  Method  to  Effect  a  Clear  Solution. 
Franz  Wippern  directs  attention  to  the  fact  that  while  pure  zinc 
chloride  usually  produces  a  turbid  solution  when  it  is  dissolved  in 
cold  water,  it  dissolves  perfectly  clear  in  hot  water  and  the  solution 
remains  clear  on  cooling.  Pharm.  Zeitung,  Li,  No.  73,  1906,  807." 
Wondering  whether  we  had  shut  our  minds  to  such  a  simple  and  effi- 
cient agent  as  hot  water,  we  hastened  to  try  the  suggestion,  but  only 
to  be  utterly  disappointed,  for  we  found  no  appreciable  difference 
in  either  the  immediate  or  prolonged  effect  of  hot  or  cold  water,  in 
dissolving  the  salt,  or  diluting  concentrated  solutions.  If  there  is 
any  perceptible  difference  in  the  effect  of  hot  water  from  that  of 
cold  water,  it  is  merely  in  making  the  sediment  more  dense  and  to 
settle  somewhat  faster,  perhaps  to  be  overlooked  more  easily.  Not 
satisfied  to  record  a  refutation  of  these  statements  without  sufficient 
proof,  we  made  dozens  of  tests  under  varying  conditions  and  quan- 
tities, but  all  to  no  avail.  The  statements  are  erroneous.  It  was 
now  decided  to  look  into  the  properties  of  zinc  chloride  itself  as  the 
most  rational  starting  point  of  our  quest. 
One  of  the  characters  of  zinc  chloride  which  should  be  borne  in 
mind  throughout  the  consideration  of  this  subiect  is  that  property 
of  its  solutions  to  turn  litmus  from  blue  to  red,  or,  as  usually  de- 
scribed, its  acid  reaction.    As  is  well  known  this  property  is  common 
