Am7uiyj9ooarnJ'}    Production  of  Arsenic  from  Phosphorus.  343 
ON  THE  REPORTED  PRODUCTION  OF  ARSENIC  FROM 
PHOSPHORUS   AND   THE  COMPOUND   NATURE  OF 
THE  FORMER. 
Note;  by  Sami,.  P.  Sadt^er,  Ph.D. 
The  announcement  by  Prof.  F.  Fittica,  of  Marburg,  the  well- 
known  editor  of  the  Jahresbericht,  that  he  had  succeeded  in  chang- 
ing both  the  clear  and  the  amorphous  varieties  of  phosphorus  into 
arsenic  by  following  certain  lines  of  treatment  comes  with  some- 
thing of  a  surprise  to  chemists. 
Already  near  the  beginning  of  this  century  the  observation  was 
made  that,  under  the  influence  of  ammonia,  phosphorus,  whether 
on  exposure  to  light  or  when  in  the  molten  condition,  passed 
into  a  so-called  black  modification,  and  in  1892  Fluckiger  showed 
that  this  was  arsenic  and  nothing  else.  However,  it  was  assumed 
that  the  arsenic  had  existed  in  the  phosphorus  as  an  impurity,  and 
had  merely  separated  out  under  this  treatment. 
The  author  soon  found,  on  repeating  the  earlier  experiments,  that 
atmospheric  oxidation  was  an  essential  part  of  the  process  yielding 
the  result  noted,  and  he  then  began  the  treatment  of  the  phos- 
phorus with  ammonia  in  the  presence  of  stronger  oxidizing  agents 
like  hydrogen  dioxide  and  with  nitric  acid  alone  and  in  conjunction 
with  barium  dioxide.  Amorphous  phosphorus  was  found  to  give 
better  results  than  the  clear  variety. 
The  method  finally  chosen  by  which  he  succeeded  in  obtaining 
the  maximum  yield  (8-10  per  cent.)  was  the  following:  2  grammes 
of  amorphous  phosphorus,  free  from  arsenic,  were  heated  on  the  sand 
bath  with  12  9  grammes  of  finely  powdered  ammonium  nitrate  after 
being  carefully  mixed  in  a  rather  wide  tube  connected  with  a  con- 
denser, and  the  temperature  gradually  raised  to  1800  C.  When  the 
reaction  begins  care  must  be  taken  to  moderate  the  heat,  which, 
however,  rises  to  about  2000.  After  allowing  to  cool,  the  contents 
of  the  tube,  a  fused  grayish  mass,  are  dissolved  out,  and,  after  filter- 
ing, hydrogen  sulphide  added.  The  yellow  precipitate  is  dis- 
solved in  ammonium  carbonate  and  the  arsenic  sulphide  precipitated 
from  the  solution  on  addition  of  hydrochloric  acid.  Its  identity  is 
established  by  its  conversion  into  arsenious  acid  and  by  Marsh's 
test. 
The  author  gives  a  provisional  formula  for  arsenic,  PN20,  accord- 
ing  to  which  it  is  a  nitrogen  monoxide  compound  of  phosphorus. 
Further  communications  are  promised. 
