^\lT,'il]'t''^'}  Chemical  Examination  of  Cincho-^inine,  157 
the  mixture  to  cool,  the  solution  formed  will  be  saturated  for  both  alka- 
loids, if  both  have  been  used  in  excess.  If,  however,  one  of  the  alka- 
loids is  present  in  smaller  quantity  than  the  water  is  capable  of  holding 
in  solution,  such  quantity,  if  unknown,  may  be  ascertained  by  evapor- 
ating the  aqueous  solution  to  dryness,  weighing  the  product  obtained, 
and  deducting  from  this  product  the  amount  of  that  alkaloid  which  was 
held  in  saturated  solution. 
For  example  :  We  have  a  substance,  which  requires  100  parts  of 
water  for  complete  solution,  and  we  have  a  substance,  5,  which  re- 
quires 10  parts  of  water  for  complete  solution.  We  have  a  mixture  of 
these  two  substances,  and  wish  to  ascertain  the  proportions  of  ad- 
mixture. We  apply  the  solvent  test  as  follows  :  We  take,  say  10 
parts  of  the  mixture,  digest  it  with  100  parts  of  water,  filter  the  solu- 
tion, and  evaporate  it.  We  obtain  5  parts  of  product.  Had  the  sub- 
stance consisted  of  ^  alone,  we  should  have  obtained  but  i  part  of  pro- 
duct ;  had  it  contained  of  B  alone,  or  contained  but  one-tenth  of  its 
weight  of  the  entire  substance  would  have  been  dissolved,  and  we 
would  have  obtained  10  parts  of  product.  But  we  have  obtained  5 
parts,  and  consequently  have  obtained  a  saturated  solution  of  the  sub- 
stance y/,  containing  all  of  the  substance  B  that  had  been  contained  in 
the  10  parts  of  mixture.  The  product  was  consequently  composed  of 
I  part  of  the  substance  J  and  4  parts  of  the  substance  B ;  and  the 
mixture  tested  was  composed  of  6  parts  of  J  and  4  parts  of  B. 
We  have  been  thus  explicit  in  order  that  our  method  of  determining 
the  quinia  in  the  ethereal  residue  of  No.  i  and  No.  4  may  be  clearly 
understood  ;  and  it  only  remains  now  to  give  some  consideration  to  the 
relative  solubility  of  the  two  alkaloids  in  cold  water  : 
1.  ^inta  is  soluble  in  364  parts  of  cold  water,  Duflos^  v'lde^  "  Gme- 
lin's  Handbuch  der  Chemie,"  vol.  7,  part  2,  page  1697  ;  in  480  parts, 
Ahl^  Ibid;  in  400  parts,  vide^  "  U.  S.  Dispensatory,"  13th  Ed.,  p.  297  j 
in  about  400  parts,  vide^  "  Pereira's  Materia  Medica,"  abridged  Ed., 
1872  ;  in  350  parts,  vide,  "Gottlieb's  Chemie,"  Ed.  1869,  vol.  2,  p. 
443- 
2.  ^inidia  is  soluble  in  1500  parts  of  cold  water.  Van  He'in'ingen^ 
De  Vrij^  vide^  "  Gmelin's  Handbuch  der  Chemie,"  vol.  7,  part  2,  p. 
1720  ;  in  2580  parts,  Leers^  vide^  "  U.  S.  Dispensatory  "  and  "  Pereira's 
Materia  Medica;"  in  2000  parts,  O.  Hesse^  vide^  "  Jahresberichtvder 
Pharmacie,"  1868,  p.  294;  in  1500  parts,  vide^  "Gottlieb's  Chemie," 
Ed.,  1869,  vol.  2,  p.  449. 
