438 
NOTE  ON  BLOOD-STAINS. 
NOTE  ON  BLOOD-STAINS. 
By  M.  Guibourt. 
One  of  the  problems  of  chemical  jurisprudence  most  frequent- 
ly presenting  itself  is  that  of  determining  the  nature  of  supposed 
spots  of  blood,  and  one  of  the  most  usual  methods  consists  in 
treating  the  spots  in  a  manner  accurately  described  in  special 
works  with  a  small  quantity  of  distilled  water.  This  water,  in  the 
case  supposed,  dissolves  the  coloring  matter  of  the  blood,  leav- 
ing the  fibrin  on  the  spot.  The  liquid,  which  is  red  and  trans- 
parent, loses  its  color  by  boiling,  and  forms  a  gray  coagulum, 
which  a  small  quantity  of  caustic  potash  will  re-dissolve.  The 
liquid,  again  become  transparent,  appears  either  reddish  or  green 
according  to  the  manner  of  looking  at  it. 
Let  us  suppose  an  operation  carried  on  in  a  straight  glass 
tube  closed  at  one  end.  The  alkaline  liquid  prepared  as  is  about 
to  be  ascribed,  will  appear  green  by  transmitted  light ;  that  is 
to  say,  when  the  tube  is  placed  between  the  eye  and  the  day- 
light. If,  on  the  contrary,  the  experimenter  stands  between 
the  tube  and  the  light,  the  liquid  appears  reddish,  the  color 
being  perceived  from  the  same  side  as  the  reflected  rays. 
M.  Picquot,  junior,  a  pharmaceutist  Bar-le  Due,  when  called 
upon  to  decide  whether  the  spots  found  on  some  planks  in  the 
house  of  a  suspected  murderer  were  spots  of  blood,  after  having 
obtained  the  preceding  results,  was  much  puzzled  by  reading 
in  M.  Devergie's  "  M^docine  Legale"  that  the  sanguineo-alka- 
line  liquid  is  green  seen  by  reflection  and  rose  colored  by  refraction 
(Yo\.  iii.  p.  822).  M.  Gaultier,  of  Claubry,  is  even  more  posi- 
tive. In  his  "  Chimie  Legale,"  p.  7,  he  says  : — "  The  liquid 
takes  then  a  green  tint  seen  by  reflection  and  rose  by  refraction. 
*  *  *  *  The  green  coloration  by  reflection,  rose  or  reddish  by 
refraction,  is  a  certain  proof  of  the  presence  of  blood."  M, 
Picquot  finds  here  a  confusion  of  words,  and  I  quite  agree  with 
him.  First,  the  green  color  seen  by  transmitted  light  on 
placing  the  tube  between  the  eye  and  the  light  is  evidently  not  a 
reflected  color.  Again,  this  same  green  color  is  refracted,  since 
the  luminous  rays  cannot  traverse  the  liquid  without  undergoing 
refraction  on  entering  the  liquid  and  again  on  emerging  from  it. 
Only  the  reddish  color  seen  from  the  side  whence  the  light 
proceeds  simultaneously  with  the  reflected  rays  can  be  said 
