Am.  Jour.  Pharm.\ 
Nov.,  1888.  j 
New  Constituent  of  Liver  Oil. 
571 
mained  a  brown  residue,  having  a  metallic  lustre.  This  dissolved  in 
alcohol  with  a  dark  brown  color,  and  the  solution  was  colored  gray- 
brown  by  ammonia.  By  this  last  reaction  this  constituent  of  liver  oil 
soluble  in  water  is  distinguished  from  varieties  of  gum,  since  gum 
gives  with  orcin  a  green  residue,  that  dissolves  in  alcohol  with  a  green- 
ish-yellow color,  and  this  solution  when  treated  with  ammonia  is  col- 
ored yellow,  with  a  tinge  of  greenish  violet. 
According  to  the  rotatory  power  of  the  new  substance  and  its  behavior, 
towards  Fehling's  solution  it  might  have  been  supposed  to  be  gum,  or 
an  albuminoid  or  a  sugar.  For  its  qualitative  distinction  from  any  of 
these  compounds  the  author  found  the  orcin  test  most  suitable,  and 
he  therefore  describes  the  reaction  somewhat  in  detail. 
Orcin  is  the  chromogen  of  various  coloring  matters,  and  is  obtained 
from  species  of  Roecella  and  Variolaria  by  boiling  with  milk  of  lime, 
and  extraction  of  the  neutralized  and  evaporated  filtrate  with  alcohol 
from  which  it  crystallizes  out  in  colorless  crystals.  The  orcin  is  freely 
soluble  in  water,  and  is  readily  altered  on  the  addition  of  hydrochloric 
acid.  Upon  evaporating  such  a  solution  on  a  water-bath  the  residue 
is  of  a  beautiful  red  color  ;  this  residue  dissolves  in  alcohol  with  arose 
color,  which  is  changed  to  a  very  beautiful  violet  upon  the  addition  of 
a  few  drops  of  ammonia  solution.  Small  quantities  of  organic  sub- 
stances modify  these  color  reactions  very  considerably,  so  that  orcin 
constitutes  an  important  reagent  for  such  bodies,  especially  for  carbo- 
hydrates. 
Constant  colorations  are  also  obtained  upon  boiling  a  dilute  solution 
of  a  carbohydrate  with  an  equal  volume  of  hydrochloric  acid  and  about 
one  per  cent,  of  orcin,  and  afterwards  adding  alcohol  and  ammonia. 
But  these  reactions  do  not  take  place  so  smoothly  as  those  obtained 
when  evaporation  is  practised. 
The  author  prepared  a  solution  of  one  gram  of  orcin  in  100  cc.  of 
pure  hydrochloric  acid,  of  which  he  placed  about  0*5  cc.  upon  a  por- 
celain dish,  then  added  about  an  equal  quantity  of  the  substance  to  be 
tested,  and  evaporated  upon  a  water-bath.  As  soon  as  this  small 
quantity  of  liquid  became  warm  the  color  reaction  began,  the  evapo- 
rated layer  becoming  colored  at  the  margin.  When  it  was  dry  alcohol 
was  added,  which  dissolved  the  residue  more  or  less  completely.  This 
alcoholic  solution  had  a  constant  color  for  each  substance,  which  upon 
the  addition  of  a  few  drops  of  ammonia  solution  was  altered  more  or 
less.    Strong  oxidizing  agents,  such  as  nitric  acid,  give  very  strong 
