308 
Preparation  of  Arsphenamine. 
Am.  Tour.  Pharm. 
May,  1 9 19. 
amount  of  colored  impurities  is  small  and  negligible.  In  fact  Ehr- 
lich,17  G.  T.  Morgan18  and  we  in  this  laboratory  have  found  that  a 
very  light-colored  arsphenamine  is  sometimes  very  toxic  compared 
to  a  darker  preparation.  Since  it  is  possible  also  to  alter  the  color 
of  the  solid  form  by  changing  its  physical  state,  comparison  of  the 
color  of  different  arsphenamines  should  be  based  on  the  color  of  the 
substance  in  standard  solutions. 
To  sum  up :  The  color  of  the  solid  arsphenamine  seems  to  be  due 
to  a  small  amount  of  highly  colored  impurities  in  an  otherwise 
colorless  substance. 
Our  experience  with  the  methyl  alcohol  and  ether  method  has 
brought  to  our  attention  four  possible  objections  against  the  use  of 
these  substances :  These  solvents  are  highly  inflammable ;  they  are 
expensive  even  in  peace  times ;  they  are  difficult  to  make  pure,  and 
finally  methyl  alcohol,  ether  and  other  solvents  are  easily  oxidized 
to  easily  reducible  substances.  As  a  concomitant  with  arsphena- 
mine, a  substance  easily  oxidized  to  very  toxic  and  therefore  danger- 
ous products,  methyl  alcohol  and  similar  substances,  are  a  priori 
not  safe  to  use  or  have  present. 
The  advantages  of  the  hydrochloric  acid  method  are : 
(a)  The  medium  of  precipitation,  both  the  water  and  the  hydro- 
chloric acid  can  be  absorbed  by  common  and  inexpensive  absorbents ; 
they  are  not  easily  oxidized  or  reduced. 
(b)  It  is  an  inexpensive  method  as  the  excess  hydrochloric  acid 
can  be  recovered  ready  for  use  by  simple  distillation. 
(c)  It  requires  no  inflammable  material. 
(d)  The  reagents  used  are  pharmacologically  suitable  and  raise 
no  question  as  to  toxicity,  such  as  does  the  use  of  methyl  alcohol 
and  ether. 
(e)  The  product,  being  less  hygroscopic,  is  less  liable  to  oxida- 
tion and  other  chemical  change,  when  exposed  to  the  air,  and  is 
therefore  more  stable. 
(/)  The  method,  as  some  preliminary  experiments  show,  can  be 
used  for  reprecipitation,  and  from  a  chemical  standpoint  seems 
better  calculated  to  eliminate  impurities. 
The  same  method  is  used  to  obtain  sodium  chloride  of  the  highest 
purity  for  atomic  weight  work. 
17  hoc.  cit. 
18  Longmans,  "  Organic  Compounds  of  Arsenic  and  Antimony,"  1918, 
p.  156. 
