254  Tincture  of  Ginger  U.  S.  P.       t^Aprif"  i^Srm" 
for  obtaining  the  water-soluble  solids  While  the  U.  S.  P.  states  the 
amount  of  water  with  which  the  solids  are  to  be  treated,  it  does  not 
state  the  length  of  time  which  the  water  is  to  remain  in  contact  with 
the  solids  and  whether  it  is  to  be  5,  10,  or  15  minutes,  1  hour,  2 
hours,  or  three  hours  or  longer,  is  left  entirely  to  the  discretion  of 
the  analyst,  and  as  the  amount  of  water-soluble  solids  will  vary 
with  the  length  of  time  the  water  is  left  in  contact  with  the  solids, 
it  should  be  definitely  stated  how  long  this  should  be.  From  the 
fact  that,  after  adding  water  to  the  solids,  a  sticky  gummy  mass  re- 
sults, the  average  chemist  would  probably  leave  it  in  contact  with 
the  water  for,  at  least,  a  couple  of  hours,  and  rub  it  frequently  with 
a  rubber-tipped  rod. 
Since  we  have  been  finding  that  several  of  the  tinctures  of 
ginger  have  yielded  by  our  interpretation  of  the  water-soluble 
method  of  the  U.  S.  P.  results  higher  than  15  per  cent.,  it  has  oc- 
curred that  it  might  be  advisable  to  consult  available  literature  upon 
the  subject,  prepare  samples  and  make  a  general  investigation. 
Street  and  Morrison,  Bulletin  137,  U.  S.  P.  Dept.  of  Agriculture, 
give  the  following  method  for  determining  water-soluble  solids : 
"  Add  15  to  20  Cc.  of  water,  at  room  temperature,  to  the  residues  ob- 
tained in  the  total  solids  determination.  Stir  with  a  glass  rod  at 
frequent  intervals  during  the  three  hours.  Because  of  the  gummy 
character  of  many  residues,  it  is  sometimes  difficult  to  secure  con- 
tact with  the  solvent.  Wash  into  a  50  Cc.  flask  with  water  and  make 
up  to  the  mark.  Filter  this  solution  through  a  dry  plaited  filter  and 
evaporate  an  aliquot  of  25  Cc.  and  dry  to  constant  weight  in  a  water 
oven." 
The  U.  S.  P.  excludes  this  method  of  Street  &  Morrison,  when 
it  specifies  only  20  Cc.  of  water,  for,  of  course,  the  residue  could 
not  then  be  washed  with  sufficient  water  to  bring  it  up  to  50  Cc. 
Street  and  Morrison  prepared  one  sample  of  tincture  of  ginger 
and  determined  the  total  solids  to  be  1.43  per  cent.,  14.7  per  cent, 
of  which  was  soluble  in  water  by  the  method  given  above.  From 
the  results  of  this  one  tincture  of  ginger  they  concluded  that  prop- 
erly prepared  tincture  of  ginger  should  show  a  specific  gravity  of 
about  0.82  and  contain,  at  least,  93  per  cent,  of  alcohol  by  volume, 
from  one  or  two  per  cent,  of  solids,  practically  all  of  which  is  sol- 
uble in  alcohol,  and  not  over  15  per  cent,  soluble  in  cold  water. 
Street  and  Morrison,  in  drawing  conclusions  from  one  sample  of 
tincture  of  ginger,  have  at  least  very  little  scientific  data  to  base  their 
