416  Toxicological  Detection  of  Phosphorus.  \ A  sepH;  ml?"*' 
the  contents  of  the  stomach,  the  animal  having  been  killed  five  hours 
afterwards.  The  distillate  may  contain  granules  of  phosphorus  even 
when  none  can  be  recognized  in  the  matters  submitted  to  distillation. 
The  process,  however  delicate,  is  not  applicable  in  all  cases.  Certain 
products  of  putrefaction,  creasote,  sulphuretted  hydrogen,  alcohol, 
ether,  and  oil  of  turpentine  prevent  the  appearance  of  the  luminous 
vapors.  The  phosphorus  may  always  be  detected  when  in  quantity 
sufficient  to  separate  out  in  granules,  but  the  presence  of  these  foreign 
bodies  may  mask  mere  traces.  In  such  cases  the  distillate  is  subjected 
to  a  further  examination.  Scheerer  recommends  to  distil  in  a  current 
■of  carbonic  acid  gas,  in  order  to  prevent  any  of  the  phosphorns  being 
lost  by  oxidation.  By  this  method,  however,  the  valuable  character 
of  luminosity  is  sacrificed.  It  may  happen  that  all,  or  most  of  the 
phosphorus,  has  been  transformed  into  phosphorous  or  hypophospho- 
rous  acid,  in  which  case  little  or  no  luminous  vapor  can  be  detected  by 
the  above-mentioned  method.  The  vapors  of  phosphorous  and  hypo- 
phosphorous  acids  reduce  salts  of  silver,  and  consequently  blacken 
filter-paper  saturated  with  an  argentic  solution.  This  reaction  is  so 
sensitive  that  when  it  fails  we  may  be  sure  of  the  absence  of  phos- 
phorus. The  converse  unfortunately  does  not  hold  good,  since  many 
bodies  produce  a  similar  reaction,  e.  g.,  formic  acid  and  sulphuretted 
hydrogen.  Hence  Scheerer  recommends  the  simultaneous  employ- 
ment of  paper  soaked  in  acetate  of  lead,  which  is  blackened  by  sul- 
phuretted hydrogen,  but  not  by  the  acids  of  phosphorus.  Fresenius 
and  Neubauer  have  shown  that  ozone  may  give  a  brown  color  to  the 
lead-paper.  It  is,  therefore,  better  to  replace  the  lead  with  other  test- 
papers  prepared  with  nitro-prusside  of  sodium,  arsenious  acid,  and 
chloride  of  antimony.  The  simultaneous  coloration  of  these  papers 
will  show  the  presence  of  sulphuretted  hydrogen,  but  will  prove  noth- 
ing as  to  the  simultaneous  presence  or  absence  of  the  phosphorous 
acids.  Scheerer  proposes  to  search  for  phosphorus  in  the  silver  paper. 
It  is  to  be  washed  with  boiling  water,  the  silver  separated  with  hydro- 
chloric acid,  and  phosphoric  acid  determined  in  the  filtrate  by  means 
of  molybdate  of  ammonia.  It  is  better  to  dissolve  the  filter-paper  in 
aqua  regia.  The  only  drawback  to  this  process  is  the  difficulty  of 
procuring  filter-paper  absolutely  free  from  phosphates.  Dussard  and 
Blondlot  treat  the  homogeneous  mass  under  examination  with  pure 
zinc  and  sulphuric  acid.  The  gas  generated  contains  phosphides  of 
hydrogen,  and  burns  with  a  characteristic  green  flame.    The  gas? 
