520 
Mer  cur  ammonium  Chlorides. 
Am.  Jour.  Pharm. 
Oct.,  1889. 
8  vols,  of  the  ammonia  solution,  and  this  treatment  repeated  after  a 
second  24  hours,  the  final  product  consists  entirely  of  Millon's  com- 
pound, whereas  the  original  precipitate  contained  only  25  per  cent,  of 
it.  If  the  solutions  are  mixed  in  equal  proportions,  allowed  to  remain 
24  hours,  the  liquid  decanted  off,  4  vols,  of  water  added  to  the  precip- 
itate, and  this  treatment  repeated  twice  at  intervals  of  48  hours,  the 
product  has  the  composition  OTI2HgCl,3NH2'HgOHgCl.  Direct 
experiments  with  equal  volumes  of  the  solutions,  and  using  equal 
volumes  of  water  for  washing,  showed  that  the  decomposing  action  of 
the  water  diminishes  as  the  concentration  of  the  ammonia  increases. 
Ammonium  chloride  acts  in  exactly  the  opposite  way  to  water.  The 
addition  of  1  vol.  of  the  mercuric  chloride  solution  to  5  vols,  of  the 
ammonia  solution  gives  a  precipitate  which  consists  almost  entirely 
of  Millon's  compound;  but  if  after  24  hours  the  liquid  is  decanted  off 
and  the  precipitate  is  treated  with  2  vols,  of  a  solution  of  ammonium 
chloride  of  similar  strength,  and  allowed  to  remain  for  two  days  with 
occasional  agitation  the  precipitate  is  completely  converted  into  the 
compound  NH2HgCl.  The  proportion  of  ammonium  chloride  required 
to  produce  this  result  is  smaller  the  smaller  the  quantity  of  dilute 
ammonia  used  in  the  precipitation.  The  addition  of  ammonium 
chloride  without  previously  decanting  the  liquid  from  the  precipitate 
has  very  little  effect  upon  the  latter. 
If  potassium  hydroxide  is  present,  so  that  some  mercuric  oxide  is 
formed,  the  product  contains  dimercurammonium  chloride,  NHg2Cl. 
The  solutions  employed  contained,  as  a  rule,  one-eighth  of  a  gram- 
molecule  per  liter.  When  mercuric  chloride  is  mixed  with  an  equal  vol- 
ume of  potash  solution  and  then  with  the  same  volume  of  ammonium 
clhoride  solution,  and  the  precipitate,  which  becomes  quite  white,  is 
washed  and  dried  at  100°,  it  has  the  composition  NHg2Cl,2NH2HgCl,- 
NH2HgOHgCL  If  the  mercuric  chloride  and  ammonium  chloride 
are  first  mixed  and  the  potash  added  afterwards,  the  precipitate  remains 
yellowish,  and  whether  filtered  off  after  a  few  minutes  or  after  several 
hours,  has  the  composition  NHg2Cl,NH2HgCl,NH2Hg  ■  O  ■  HgCl.  The 
smaller  the  excess  of  ammonium  chloride  the  greater  the  proportion 
of  NHg2Cl.  If  equal  volumes  of  mercuric  chloride  and  potash  solu- 
tion are  mixed  and  heated  to  boiling  for  some  minutes,  then  mixed 
with  an  equal  volume  of  ammonium  chloride  and  again  boiled  for  a 
short  time,  the  precipitate  has  the  composition  NHg^ljNHgHg-O* 
HgCl,  a  result  due  to  the  conversion  of  mercurammonium  chloride, 
