92  Ammonium  Chloride  and  Lead  Iodide.  ,{Ax^Tehr'iSi'rm' 
phosphite,  and  more  freely  soluble  than  the  deliquescent  potassium 
carbonate. 
The  test  of  the  Pharmacopoeia  was  evidently  copied  from  "  Hager's 
Pharmaceutische  Praxis,"  vol.  2,  p.  741,  but  not  without  making  a 
mistake  in  its  rendition.  A  proper  version  from  Hager  follows:  u  If 
1  part  of  lead  iodide  be  triturated  in  a  porcelain  mortar  with  2  parts 
of  ammonium  chloride,  and  2  parts  of  water  are  added,  decoloration 
must  soon  follow ;  otherwise  the  salt  may  possibly  contain  lead 
chromate." 
If  2  grams  of  lead  iodide  be  triturated  in  a  mortar  with  4  grams  of 
ammonium  chloride,  transferred  to  a  test  tube,  and  4  grams  of  water 
are  added,  a  magma  of  a  white  or  whitish  color  entirely  free  from  any 
yellow  tint,  results,  but  not  a  solution,  as  stated  by  the  Pharmacopoeia. 
If  heat  be  now  applied  the  golden  yellow  color  of  lead  iodide  again 
makes  its  appearance  and  changes,  on  further  application  of  heat,  to  a 
pale  yellowr  or  yellowish  white  before  dissolving.  This  solution  is  of  a 
brownish  yellow  color  and  deposits  lemon-yellow  ramifying  crystals  ;  if 
allowed  to  cool  slowly,  these  are  soon  covered  by  pale  yellow  or  white 
silky,  fine,  acicular  crystals ;  but  if  rapidly  cooled  the  latter  crystals 
only  form. 
If  to  another  mixture  of  the  two  salts  in  the  same  proportion  with 
the  same  amount  of  water  as  above,  4  parts  more  of  water  are  added,  the 
golden  yellow  color  of  lead  iodide  makes  its  appearance  at  the  point  of 
contact.  On  heating  this  mixture  to  boiling  the  color  changes  to  a 
greenish  yellow,  and  before  dissolving  to  a  yellowish  white  as  in  the 
first  experiment.  On  cooling,  this  solution  deposits  lemon  colored 
crystals  as  in  the  other  solution,  which  are  soon  covered  by  the  white 
silky  crystals  as  in  the  other  solution.  In  both  cases  solution  is  not 
effected  in  the  cold  but  only  on  heating. 
If,  as  a  third  experiment,  a  small  quantity  of  lead  chronaate  is  added 
to  lead  iodide,  and  the  salt  is  then  triturated  with  2  parts  of  ammonium 
chloride  and  with  2  parts  of  water,  the  mixture  becomes  somewhat 
lighter  in  color.  Now,  on  heating,  this  mixture  only  partly  dissolves, 
leaving  a  brick-red  precipitate  with  a  brownish  yellow  solution.  On 
cooling,  crystals  of  a  white  color  are  formed  on  top  of  the  precipitate. 
Thinking  it  would  be  of  interest  to'  know  something  about  the 
reactions  which  take  place  in  the  foregoing  experiments,  I  looked 
through  the  literature  on  the  subject.    In  Gmelin's  Inorganic  Chemis- 
