ON  THE  PURIFICATION  OF  SAL-AMMONIAC. 
141 
about  the  same  blue  coloration  with  prussiate  of  potash,  and  red 
with  sulphocyanide  of  potassium.  The  yellow  substance  in  the 
colored  bands  I  am  disposed  to  regard  as  some  organic  matter. 
The  iron  is  evidently  all  present  in  the  form  of  protochloride,  which 
has  sublimed  together  with  the  vapor  of  the  sal-ammoniac  in  the 
process  of  manufacture.  In  fact,  judging  a  priori  from  the  well 
known  reducing  properties  of  sal-ammoniac,  when  aided  by  heat, 
the  presence  of  sesquichloride  of  iron,  which,  from  its  yellow 
color,  and  easy  volatility  previous  to  examination,  would  naturally 
be  supposed  present  in  the  yellow  portions,  seems  improbable.  The 
reaction  between  sal-ammoniac  and  sesquichloride  of  iron,  when 
heated  together,  would  probably  be  something  like  the  following: 
3  Fe2  CP  +  NIP  CI  —  6  Fe  CI  +  4  H  CI  +  N. 
The  sesquichloride  of  iron  being  thus  converted  into  protochlo- 
ride. 
Gmelin*  who  does  not  notice  the  presence  of  iron,  states  that 
commercial  sal-ammoniac  may  be  purified  both  by  resublimation 
and  recrystallization.  To  test  this,  two  experiments  were  made. 
First,  a  quantity  of  crude  sal-ammoniac  was  slowly  and  carefully 
sublimed  in  a  glass  tube.  An  aqueous  solution  of  the  sublimate 
which,  it  is  worthy  of  observation,  had  a  slightly  brown  color, 
and  an  empyreumatic  smell,  when  tested  with  prussiate  of  potash 
and  sulphide  of  ammonium,  still  gave  most  unmistakeable  indica- 
tions of  the  presence  of  protochloride  of  iron.  Next,  some  of  the 
crude  sal-ammoniac  was  crystallized  from  water — the  crystals 
rinsed  with  distilled  water  and  dried  by  strong  pressure  between 
folds  of  filtering  paper.  A  solution  of  these  crystals  still  gave  a 
coloration,  though  faint,  with  sulphide  of  ammonium.  By  two  or 
more  recrystallizations  every  trace  of  iron  might,  in  all  probabil- 
ity, be  separated,  but  at  the  expense  of  a  large  loss  of  material. 
While  an  instructor  in  the  Chemical  School,  connected  with 
Yale  College,  at  New  Haven,  I  became  acquainted  with  a  method 
of  separating  the  iron  from  ferriferous  sal-ammoniac,  devised,  I  be- 
lieve, by  Mr.  Wra.  H.  Brewer,  a  former  student  in  that  institution, 
and  in  common  use  in  the  analytical  department  for  the  prepara- 
tion of  pure  sal-ammoniac  solution,  for  use  in  analysis,  which 
leaves  nothing  whatever  to  be  desired  in  point  of  economy,  per- 
fection and  facility  of  execution  ;  and  as  Mr.  Brewer  has  never,  to 
my  knowledge,  published  his  process,  I  have  concluded,  in  view 
*Handbuch  der  Chemie,  i.,  887. 
