Am.  Jour.  Pharm. 
April,  1896. 
Opuntia  Vulgaris,  Mill. 
175 
hydrogen  sulphide  to  precipitate  the  excess  of  lead.  The  resulting 
lead  sulphide  was  removed  by  filtration,  the  precipitate  washed  and 
the  filtrate  and  washings  warmed  on  a  water  bath  to  expel  the 
excess  of  hydrogen  sulphide — lead  acetate  paper  being  used  to  deter- 
mine the  complete  expulsion  of  this  gas.  The  liquid  was  then 
allowed  to  cool  and  afterward  adjusted  to  a  definite  volume.  One- 
half  of  this  volume  was  made  slightly  alkaline  with  sodium  hydrate, 
then  warmed  gently  and  filtered.  The  filtrate  and  washings  of  the 
filter  were  mixed  with  an  equal  volume  of  Fehling's  solution,  and 
then  heated  on  a  water-bath  at  the  boiling  point  for  twenty  minutes. 
The  cuprous  oxide  which  had  separated  during  this  time  was  col- 
lected on  a  filter,  washed  with  hot  water  until  free  from  alkali  and 
soluble  copper  compounds,  then  dried  and  converted  into  the  more 
stable  cupric  oxide  by  igniting  until  a  constant  weight  had  been 
reached.  The  actual  weight  of  glucose  in  the  quantity  of  extract 
operated  on  was  calculated  by  taking  45  per  cent,  of  the  weight  of 
the  cupric  oxide  and  the  percentage  amount  by  simple  proportion, 
of  course,  to  the  weight  of  the  powdered  fruit  represented  by  the 
above  quantity  of  extract.  The  amount  of  glucose  found  in  the 
absolute  alcohol  extract  was  -83  per  cent.  To  determine  the  sac- 
charose, it  was  inverted  by  boiling  the  other  half  volume  with 
some  diluted  sulphuric  acid  for  an  hour,  and,  after  allowing  the  solu- 
tion to  cool  and  making  it  alkaline,  the  determination  was  proceeded 
with  as  in  the  foregoing  estimation  of  glucose. 
From  the  whole  quantity  of  glucose  indicated  by  the  weight  of 
cupric  oxide  obtained,  the  previously  determined  quantity  of  glucose 
was  deducted.  Of  the  remainder,  which  represented  the  amonnt  of 
glucose  produced  from  the  saccharose  by  inversion,  95  per  cent,  was 
taken  as' the  amount  of  saccharose  required  to  yield  it,  i.  e.,  the 
amount  of  saccharose  present.  Of  this  sugar  7  22  per  cent,  was 
found.  That  part  of  the  extract  which  was  undissolved  by  the 
water  was  found  to  be  soluble  in  solution  of  potassium  hydrate. 
When  its  solution  in  the  latter  solvent  was  acidified  with  diluted 
sulphuric  acid,  a  brownish  precipitate  was  produced.  An  alcoholic 
solution  of  some  of  that  part  of  the  extract  which  was  undissolved 
by  water  gave,  with  alcoholic  solution  of  lead  acetate,  a  brown  pre- 
cipitate, and  with  ferric  chloride  a  very  slight  precipitate. 
The  water  extract  of  the  powdered  fruit  amounted  to  16  59  per 
cent,  of  organic  solids.    This  amount  included  -92  per  cent,  of  glu- 
