DETECTION  AND  ESTIMATION  OE  PHOSPHORUS,  ETC. 
461 
ON  THE  DETECTION  AND  ESTIMATION  OF  PHOSPHORUS  AND 
PHOSPHOROUS  ACID. 
By  Prof.  Scherer. 
Within  two  years  the  author  had  occasion  to  gather  much  ex- 
perience from  a  number  of  cases  of  poisoning  of  animals,  and  of 
two  men,  also  from  several  attempts  of  poisoning  by  phosphorus. 
In  one  case,  the  phosphorus  from  30  to  40  matches,  equivalent 
to  about  J  grain,  proved  fatal  to  a  woman  in  48  hours.  He  es- 
tablishes the  presence  of  phosphorus  by  Mitscherlich's  method, 
with  the  modification  of  filling  the  apparatus  with  carbonic 
acid,  generated  from  a  few  pieces  of  calcareous  spar  introduced 
into  the  acid  liquid.  No  luminous  vapors  are  obtained,  but 
little  of  the  phosphorus  is  oxidized,  and  if  the  tube  dips  into 
distilled  water,  this  is  phosphorescent  when  agitated  in  the  dark, 
and  its  vapor  blackens  nitrate  of  silver. 
To  estimate  the  phosphorus,  the  last  bottle  containing  the 
water,  is  connected  with  another  vial  containing  either  neutral 
or  slightly  ammoniacal  nitrate  of  silver,  which  absorbs  all  the 
phosphorous  vapors  that  have  not  been  retained  by  the  water. 
Any  globules  of  phosphorus  which  may  have  been  obtained,  are 
fused  together  and  weighed  ;  the  water  is  added  to  the  silver 
solution,  nitromuriatic  acid  is  added  and  then  evaporated,  the 
chloride  of  silver  is  filtered  off ;  the  phosphoric  acid,  which  is 
contained  in  the  filtrate,  is  estimated  in  the  usual  manner  and 
calculated  for  phosphorus. 
Very  minute  portions  of  phosphorus  may  be  recognized,  after 
first  ascertaining  the  absence  of  sulph-hydric  acid,  the  vapors  of 
which  will  turn  sugar  of  lead  paper  black,  and  paper  moistened 
with  nitroprusside  of  sodium  blue  ;  papers  moistened  with  ni- 
trate of  silver  are  suspended  over  the  acid  liquid,  which  is 
gently  heated ;  in  the  presence  of  phosphorus,  the  silver  will  be 
reduced  with  a  black  color.  The  papers  may  now  be  macerated 
in  chlorine  water  or  aqua  regia,  the  filtrate  will,  after  evapora- 
tion contain  phosphoric  acid,  to  be  recognized  as  ammonio-phos- 
phate  of  magnesia,  or  as  phosphomolybdate  of  ammonia. 
If  phosphorus  has  been  wholly  or  partly  converted  into  phos- 
phorous acid,  the  residue  from  the  first  distillation  is  heated  in 
Mitscherlich's  apparatus  with  sulphuric  acid  and  pure  zinc,  un- 
