Am.  Jour.  Pharm.  ) 
June,  1879.  / 
Saligenin  Test. 
chloric  or  nitric  acid,  and  the  cleansed  and  weighed  electrode  is  again 
dipped  into  the  solution  in  order  to  see  if  the  precipitation  was  com- 
plete. 
The  authors  give  an  analysis  of  zinc  sulphate,  and  one  of  brass,  to 
show  the  exactness  of  the  method. — Ber.  d.  Chem.  Ges.,  xii,  p.  446. 
THE  SALIGENIN  TEST  FOR  SALICIN. 
By  Dr.  A.  Senier,  F.I.C.,  F.C.S., 
Demonstrator  in  the  Laboratories  of  the  Pharmaceutical  Society. 
It  is  stated  in  text-books  of  chemistry  that  when  salicin  is  boiled 
with  water,  acidulated  with  hydrochloric  or  sulphuric  acid,  it  assimi- 
lates a  molecule  of  water  and  is  converted  into  glucose  and  saligenin. 
The  conversion  is  expressed  thus:  C13H1807  +  H20— C7H802+C& 
H12Oe.  This  reaction  is  usually  commended  as  a  test  for  salicin,  the 
glucose  to  be  detected  by  its  well  known  reducing  action  on  cupric 
potassium  tartrate  solution,  and  the  saligenin  by  neutralizing  and  adding 
solution  of  ferric  chloride,  with  which  it  gives  an  intense  blue  or  pur- 
plish blue  color. 
The  production  of  glucose  and  its  detection  as  just  indicated  is  a 
simple  and  certain  analytical  operation,  but  not  so  the  formation  of 
saligenin  and  the  color  which  it  gives  with  ferric  chloride.  I  have 
experimented  repeatedly  under  what  appeared  to  be  the  most  favorable 
conditions,  but  have  failed  to  obtain  a  color  with  ferric  chloride  at  all 
corresponding  to  that  described  in  the  text-books.  Using  a  tempera- 
ture of  8o°C.  instead  of  ioo°  a  somewhat  better  result  was  obtained, 
but  the  color  was  so  indistinct  and  its  production  so  uncertain  as  to  be 
useless  in  analysis. 
Upon  reference  to  the  original  memoir  upon  this  reaction,  I  was 
surprised  to  find  my  experience  both  anticipated  and  explained.  Piria^ 
in  1845,  says  tnat  although  saligenin  is  formed  together  with  glucose 
when  salicin  is  boiled  with  dilute  acids  it  is  nearly  as  soon  transformed 
into  a  resinous  substance,  saliretin.  Saliretin  is  insoluble  in  the  acid 
solution,  and  is  not  colored  blue  by  ferric  chloride.  It  is  formed  from 
saligenin  by  the  separation  of  a  molecule  of  water,  thus  :  C7H802= 
C7H60  +  H20.  . 
1  "Ann.  de  Chim.  et  de  Physique,1'  1845,  259>  2^°* 
