AMseJptURi,i87A3RM'}  Toxicological  Detection  of  Phosphorus.  417 
before  being  burnt,  is  freed  from  every  trace  of  sulphuretted  hydro- 
gen by  being  passed  through  tubes  filled  with  pumice  steeped  in  pot- 
assa-lye.  It  should  be  burnt  at  a  platinum  orifice,  for  the  yellow  col- 
oration of  soda  in  the  glass  would  otherwise  mask  the  reaction.  The 
hydrogen  must  not  be  mixed  with  arseniuretted  or  antimoniuretted 
hydrogen.  The  presence  of  alcohol,  ether,  and  other  organic  matters 
is  fatal  to  the  reaction.  The  green  color  is  more  distinct  by  daylight 
than  in  a  darkened  room.  Blondlot  has  remarked  that  the  phosphu- 
retted  hydrogen  disengaged  gives  a  black  precipitate,  phosphide  of 
silver,  in  solutions  of  nitrate  of  silver.  The  phosphide,  placed  in  a 
suitable  apparatus  with  zinc  and  hydrochloric  acid,  gives  off  a  gas 
which  burns  with  a  green  flame.  In  this  manner  he  removes  the  or- 
ganic matters  which  interfere  with  Dussard's  procedure.  The  follow- 
ing is  his  method  :  The  suspected  matters  are  converted  into  a  homo- 
geneous paste,  and  introduced  into  a  roomy  hydrogen  apparatus  with 
zinc  and  sulphuric  acid.  The  gas  is  passed  through  a  solution  of  ni- 
trate of  silver.  The  precipitate  is  filtered  off,  when  it  no  longer  in- 
creases in  bulk,  washed  and  introduced  into  a  small  apparatus,  and 
treated  as  above.  This  process  occasions  the  loss  of  a  part  of  the 
phosphorus.  Fresenius  and  Neubauer  have  proved  that  merely  two- 
thirds  of  the  phosphorus  are  thrown  down  as  phosphide  of  silver. 
These  two  chemists  combine  the  two  procedures  of  Mitscherlich- 
Scheerer  and  of  Dussard-Blondlot.  They  first  employ  the  method  of 
Mitscherlich,  or  that  of  Scheerer,  according  as  there  appears  to  be 
more  or  less  of  the  poison  present.  In  some  cases  not  merely  dis- 
tinct luminous  vapors  are  seen,  but  granules  of  phosphorus  are  iso- 
lated. As  soon  as  these  characteristics  cease  to  appear,  nitrate  of 
silver  is  added  to  the  condensed  liquid,  and  the  distillation  is  contin- 
ued. The  well-washed  precipitate  is  introduced  into  the  hydrogen 
apparatus.  The  purity  of  the  zinc  and  sulphuric  acid  employed  should 
be  determined  by  a  previous  experiment.  Fresenius  and  Neubauer 
have  analyzed  a  liquid  (putrid  blood  and  water),  containing  1  milligrm. 
of  phosphorus  in  200,000.  The  first  400  c.c.  of  hydrogen  presented 
the  most  characteristic  reactions.  The  coloration  was  more  feeble 
with  the  400  next,  and  very  faint  but  still  perceptible  with  the  400 
last.  Christoffe  and  Beilstein  recommend  the  examination  of  the 
flame  with  the  spectroscope.  The  residue  of  the  distillation  may  con- 
tain phosphorous  acid  formed  by  the  oxidation  of  the  phosphorus.  It 
may  be  treated  with  zinc  and  sulphuric  acid.    Phosphoric  acid  is 
27 
