}   ^^^^  Physical  Properties  of  ^inia.  1 2  5 
corresponding  to  15*2  per  cent.  (Schlimpest),  mentioned  by  Dragen- 
dorfF,  is  evidently  erroneous. 
Solubility  in  Sulphuric  Ether. — The  ether  used  in  these  experiments 
was  entirely  free  from  aldehyde,  alcohol  and  water. 
Ether  saturated  at  15°  C.        Quinia  dried  at  110°  C. 
1st  Experiment,        .        .        .        Z'^'ZSA-S  grams.  i-399o  grams. 
2d         "  ...    18-6590     "  0.7965  " 
Or  a  mean  equal  to  4*23 14  of  quinia  to  each  100  grams  of  solution. 
From  which  the  author  concludes  that  the  co-efficient  of  quinia  in  pure 
sulphuric  ether  at  15°  is  i  in  22*632.  This  value  is  very  different 
from  that  indicated  by  Dragendorff,  who,  according  to  Pettenkofer, 
supposes  that  100  grams  of  ether  dissolve  i"66  grams  of  quinia,  or 
equal  to  i  in  60,  instead  of  i  in  22. 
Observations  upon  Aqueous  Solution  of  ^uuiia. — The  determination  of 
the  exact  composition  of  the  aqueous  solution  afforded  the  author  op- 
portunities for  making  numerous  experiments  upon  some  of  the  reac- 
tions of  this  alkaloid.  The  solution  of  i  part  in  2  000  is  bitter,  and 
presents  very  clearly  the  emerald-green  coloration  under  the  influence 
of  chlorine  and  ammonia.  Gallo-tannic  acid  causes  an  abundant  pre- 
cipitate. By  means  of  mixtures  consisting  of  definite  proportions  of 
this  solution  and  distilled  water,  the  author  ascertained  that  it  is  neces- 
sary to  dilute  one  part  of  this  solution  of  i  in  2,000  with  ten  parts  of 
distilled  water  before  the  opalescence  resulting  from  the  formation  of 
the  tannate  ceases  to  be  visible  in  the  sunlight,  gathered  in  the  focus  of 
a  convergent  lens  ;  i  part  in  20,000  is  therefore  the  extreme  limit  of 
the  sensitiveness  of  this  reagent.  This  experiment  shows  that  the 
solubility  at  a  temperature  between  10°  C.  and  20°  C.  is  extremely 
slight,  and  that  some  statements  that  have  been  made  upon  this  point 
are  incorrect. 
The  fluorescence  of  the  aqueous  solution  of  i  part  of  pure  quinia 
in  2,000  is  almost  invisible  if  the  solution  be  examined  in  the  direct 
sunlight.  It  is,  however,  perceptible  up  to  an  extreme  limit  of  i  in 
20,000,  if,  according  to  the  method  proposed  by  Stokes,*  the  rays 
converging  from  a  lens  or  a  concave  metallic  mirror  be  thrown  upon  it. 
It  is  known  that  the  presence  of  an  excess  of  sulphuric  acid  increases 
the  fluorescent  power  of  quinia,  and  the  author  has  found  that  this 
singular  influence  renders  the  solution  of  i  in  20,000  twenty  times 
more  energetic.     In  fact,  he  has  found  that  a  solution  of  i  part  of 
*  "  Philosophical  Transactions,"  1852,  p.  463. 
