620  Salicin  Content  of  British  Willows.      { AmseJp°tur'i92iarm' 
The  bark  from  the  following  species,  Salix  Nuttallii,  Salix 
Hookeriana,  Salix  sitchensis,  Salix  lasiandra,  Salix  purpurea,  Popu- 
lus  trichocarpa  and  Populus  tremuloides,  were  analysed.  We  wish 
to  thank  Professor  John  Davidson  for  his  kindness  in  providing  the 
various  samples. 
METHOD  OF  ANALYSIS. 
The  bark  was  dried  for  forty-eight  hours  at  a  temperature  of 
about  no  degrees.  Two  samples  of  each,  weighing  twenty  grams, 
were  taken,  and  digested  separately  for  three  hours  with  boiling 
water  and  the  solution  filtered.  Two  grams  of  lead  acetate  were 
then  added  to  the  nitrate  to  precipitate  the  proteins,  which 
were  removed  by  filtration.  The  excess  of  lead  was  then  precipitated 
by  the  addition  of  the  required  amount  of  sulphuric  acid,  and  the 
liquid  filtered.  To  this  filtrate  was  added  100  cc.  of  the  emulsin  of 
almonds  solution  and  the  mixture  allowed  to  stand  sixty  hours,  at 
which  time  the  solution  was  diluted  to  two  litres  and  two  portions  of 
100  cc.  were  taken  for  analysis  with  Fehling's  solution.  The  weight 
of  glucose  present  being  found  by  reference  to  Munson  and  Walker's 
tables.4   One  mole  of  salicin  gives  on  hydrolysis  one  mole  of  glucose. 
The  emulsin  of  almonds  solution 5  was  prepared  from  sweet 
almonds,  from  which  the  oil  had  been  pressed,  as  follows  :.The  press 
cake  was  macerated  for  twenty-four  hours  with  water,  to  which  a 
small  amount  of  chloroform  was  added.  The  mixture  was  then 
strained  through  a  cloth  and  two  drops  of  acetic  acid  were  added  per 
too  cc.  of  the  liquid  for  the  precipitation  and  removal  of  the  proteins. 
To  the  filtrate  was  then  added  an  equal  volume  of  alcohol,  50  cc.  at  a 
time,  which  caused  the  enzyme  to  come  down  as  a  fine  precipitate, 
which  was  filtered  off,  washed  with  alcohol  and  immediately  re-dis- 
solved in  water,  to  which  a  small  amount  of  toluene  had  been  added. 
The  solution  of  emulsin  of  almonds  so  obtained  was  tested  by  treat- 
ing solutions  containing  known  amounts  of  pure  salicin.  It  was  found 
that  the  hydrolysis  was  complete  after  sixty  hours.  The  results  ob- 
tained were  correct  to  within  less  than  1  per  cent. 
As  is  seen  from  the  following  table  of  determinations  the  dupli- 
cate analyses  are  in  close  agreement,  whilst  the  salicin  content  of  the 
various  species  of  willow  and  poplar  show  a  considerable  variation. 
4  "Food  Inspection  and  Analysis,"  Leach. 
5  Allen's  Comm.  Organic  Analysis,  vol.  8,  p.  6. 
