Am.  Jour.  Pharm. 
December,  1908. 
|    Preparing  Pharmaceutic  Chemicals.  587 
When  the  reaction  is  thought  to  be  complete,  which  can  be  judged 
by  the  disappearance  of  silver  permanganate  crystals,  a  few  c.c.  of 
the  liquid  are  decolorized  by  heating  with  nitric  acid  and  for- 
maldehyde, divided  in  two  portions  and  tested  for  silver  or  chlorides, 
respectively,  with  sodium  chloride  or  silver  nitrate  test  solutions.  If 
the  right  amount  of  zinc  chloride  was  added,  the  decolorized  solu- 
tion will,  after  completion  of  the  reaction,  give  only  a  slight  test 
either  for  silver  or  chlorides.  If  the  former  is  present,  a  small 
amount  of  zinc  chloride  should  be  added  and  the  heating  continued 
until  the  solution  gives  just  a  slight  test  for  chlorides.  If  the  con- 
tents of  zinc  chloride  is  found  to  be  too  large,  some  silver  perman- 
ganate, or  if  none  of  the  same  is  at  hand,  some  silver  oxide,  should 
be  added  until  only  traces  of  chloride  are  found  in  the  zinc  perman- 
ganate solution,  which  then  is  filtered  from  the  silver  chloride  and 
evaporated  to  dryness  on  a  steam  bath.  The  yield  of  Zn  (Mn0.t)2 
6H20,  is  somewhat  more  than  the  potassium  permanganate  orig- 
inally taken. 
The  collected  silver  chloride  is  reduced  to  the  metallic  state  by 
means  of  zinc  in  a  hydrochloric  acid  solution.  The  amount  of  silver 
recovered  is  quantitative,  and  if  desired  the  original  amount  of 
silver  nitrate  can  be  restored  by  dissolving  the  metal  in  nitric  acid, 
evaporating  and  crystallizing.  The  cost  of  the  preparation  will 
therefore  not  much  exceed  that  of  potassium  permanganate. 
It  is  evident  that  by  decomposing  silver  permanganate  with 
barium,  calcium,  magnesium,  or  other  metallic-chlorides,  the  cor- 
responding permanganates  will  result.  Hence  the  barium  perman- 
ganate, after  having  been  prepared  from  the  silver  salt  can  be  used, 
if  so  desired,  for  manufacturing  other  permanganates. 
As  a  fact  of  curiosity  rather  than  a  matter  of  any  practical 
value  the  author  observed  the  interaction  between  manganese 
sulphate  and  barium  permanganate.  Theoretically  a  manganese 
permanganate  Mn(Mn04)2  should  be  formed.  Such  a  combination 
does  not,  at  least  under  ordinary  conditions,  exist,  the  result  of  the 
reaction  being  a  solution  of  permanganic  acid  with  a  precipitate  of 
barium  sulphate  and  manganese  dioxide  according  to  the  equation: 
3Ba(Mn04)2  +  3MnS04  =  3BaS04  +  5Mn02  +  2HMn04 
The  reaction  is  remarkable  in  the  respect,  that  an  acid  is  formed 
through  the  interaction  of  two  perfectly  neutral  salts. 
Experimental  Laboratory  of  The  Norwich  Pharmacal  Company, 
