26 
Ammonio-nitrate  of  Silver. 
f  Ajii.  Jour.  Pharm. 
I       Jan.,  1887. 
Heated  at  100°  C.  it  did  not  lose  weight. 
Heated  to  redness,  it  afforded  a  residue  of  metallic  silver  which  was 
weighed,  and  the  loss  of  weight  compared  with  that  which  would  have 
occurred  with  silver  oxide. 
(a)  1*249  grammes  gave  Ag  1141,  a  loss  of  20.60  where  Ag20=16. 
(6)  0-915  grammes  gave  Ag  0-836,  a  loss  of  20*01  where  Ag20=16. 
The  precipitate  heated  alone,  or  with  potassium  hydrate,  does  not 
evolve  ammonia. 
Dissolved  in  dilute  nitric  acid,  bubbles  of  gas  are  evolved. 
The  precipitate  is  therefore  silver  oxide,  apparently  mixed  with 
silver  carbonate,  formed  by  the  absorption  of  carbonic  acid  gas  during 
drying*. 
The  conclusions  which  may,  I  think,  be  drawn  from  the  foregoing 
experiments  are  as  follows  : — 
When  ammonia  is  added  to  a  solution  of  neutral  silver  nitrate  the 
first  addition  produces  a  precipitate  of  silver  oxide  (if  the  solution  be 
acid  no  precipitate  is  formed,  the  oxide  dissolving  in  the  simultaneously 
produced  ammonium  nitrate).  When  the  quantity  of  ammonia  added 
is  just  enough  to  form  ammonium  nitrate  the  reaction 
2Ag]ST03-f2NH4OH=2NH4]ST03-f  Ag20+H20, 
takes  place,  but  by  far  the  greater  part  of  the  silver  oxide  dissolves  in 
the  ammonium  nitrate  formed,  and  it  is  only  on  the  further  addition 
of  ammonia  and  silver-ammonium  nitrate  (Ag!N"03,2]SrHg)  is  pro- 
duced— 
Ag^T03+2XH4OH=:AgK03,2NH3+2H20, 
a  result  which  may  also  be  obtained  by  the  solution  of  silver  oxide  in 
a  mixture  of  ammonium  nitrate  with  ammonia, 
Ag20  +  21STH4,]ST03+2NH4OH=2AgN03,2NH3  -|-3H20 
This  body,  described  by  Mitscherlich,1  may  be  obtained  by  the  slow 
evaporation  of  its  solution.  It  forms  rhombic  crystals  permanent  in 
the  air,  and  easily  soluble  in  water.  Their  solution  reacts  strongly 
alkaline  towards  both  phenolphthalein  and  turmeric.  When  heated — 
as  may  be  done  with  perfect  safety — they  fuse,  and  leave  a  residue  of 
metallic  silver. 
It  is  this  compound  which  is  contained  in  the  ammonia-nitrate  of 
silver  solution  of  the  Pharmacopoeia,  and  of  our  laboratories,  and  I 
cannot  fitly  conclude  this  paper  without  pointing  out  that  it  is  a  very 
1  Gmelin,'  vol.  vi.,  p.  177. 
