366 
Detection  of  Blood. 
Am.  Jour.  Pharm. 
August,  1899. 
towards  giiaiacnm  tincture  being  previously  stated')  is  carefully  added 
without  mixing  ;  then  an  intensely  blue  and  rapidly  increasing  zone 
appears,  with  extraordinary  sensibility,  in  the  place  of  contact  and 
diffusion  of  the  two  solutions,  while  by  sudden  mixture  a  less 
pure  blue  coloration  of  the  liquid  results. 
By  the  way,  it  may  be  mentioned  that,  after  my  experience  con- 
firmed by  other  observers,  the  method  may  also,  in  suitable  cases, 
be  so  modified  that  the  blood  solution  is  first  mixed  with  H'une- 
felds  liquid  and  then  added  to  the  guaiacum  solution.  This  pro- 
cess can  just  as  well  be  conducted  to  obtain  a  zone  reaction  or 
also  a  capillary  reaction. 
In  cases  of  extraordinary  small  blood  stains,  so  as  to  necessi- 
tate, in  a  certain  measure,  a  microchemical  operation,  or  where  the 
respective  residue  of  blood  has  to  be  tested  on  its  natural  place, 
it  is  advisable  to  digest  the  stain  on  a  flat  porcelain  dish  with 
strong  chloral  solution  (v.  s.),  having  first  moistened  with  a  small 
drop  of  acetic  acid,  and,  after  half  an  hour's  contact,  to  pour  on 
the  digested  spot  first  a  corresponding  small  quantity  of  guaia- 
cum chloral  solution,  and  then,  after  having  thoroughly  mixed,  a 
few  drops  of  the  one  or  other  liquid  containing  the  peroxide. 
With  this  method  also  a  more  or  less  intense  blue  coloration  is 
seen  to  appear  on  the  light-colored  underground.  Experience 
has  shown  me  that  even  very  old  blood  stains  and  exceedingly 
small  parts  of  such  may  be  identified  in  this  manner,  provided  a 
sensible  guaiacum  chloral  solution,  prepared  with  quite  fresh  resin, 
and  at  the  same  time  a  liquid  of  Hiinefeld  or  hydric  peroxide 
solution  of  right  composition4  and  controlled  in  regard  to  their 
activity  are  used.  The  zone  reaction  surpasses  the  other  older  . 
methods  of  testing  by  special  purity  of  the  blue  color  resulting 
from  the  formation  of  the  so-called  "  guaiacum  blue;  "  besides 
that  this  purer  color  is  more  durable,  according  to  the  fact 
that  in  the  measure  of  progressive  mixtion  of  the  active  sub- 
stances of  the  two  layers  (hematin  as  the  oxygen-transferring 
body,  hydric  peroxide  or  essential  oil  as  the  source  of  oxygen 
4  A  solution  of  Hiinefeld  suitable  for  the  purpose  may  easily  be  prepared, 
mixing  f.  i.  15  c.c.  of  turpentine  oil,  exposed  to  light  and  air  for  a  certain  time 
(but  which  ought  not  to  change  directly  blue  in  the  guaiacum  tincture),  or 
15  c.c.  of  a  3  to  5  per  cent,  hydric  peroxide  solution,  free  from  acids,  with  25 
c.c.  of  alcohol,  5  c.c.  of  chloroform  and  1*5  c.c.  of  glacial  acetic  acid. 
