EXAMINATION  OF  THE  SULPHATE  OF  QUINIA.  399 
salt  had  lost  -5431  gram.,  or  5-431  per  cent.  Then  exposed  to 
the  ordinary  atmosphere  for  five  hours,  the  pure  salt  regained 
its  original  weight  within  -0029  gram.,  while  the  impure  salt  was 
still  «0461  gram,  short. 
This  experiment  terminates  those  in  which  drying  was  resorted 
to  in  order  directly  to  estimate  the  amount  of  water  present ; 
and  the  concise  result  is  that 
Dried  by  exposure  at  ordinary  temperatures,  the  salt  loses       10-587  p.  c. 
do.  do.       212°  do.  15-11   p.  c. 
do.  do.       242°  do.  15-223  p.  c. 
Now  if  this  salt  was  pure  disulphate  of  quinia,  as  it  is  not ; 
and  if  the  final  heating,  had  perfectly  effloresced  it, — which  is 
not  prohable,  as  the  salt  did  not  fuse — it  should  still  have  con- 
tained 2  eqs.  or  4-128  per  cent  of  its  water  of  crystallization. 
But  in  drying  it  had  lost  within  1.29  per  cent,  of  all  the  water 
it  should  have  contained  as  the  chemically  perfect  salt  represented 
by  the  analysis  of  the  manufacturers. 
Dr.  Wood,  (Dispensatory,  10th  edition,  p.  1172),  Pereira, 
(Materia  Medica,  Am.  ed.,  vol.  2,  p.  694),  and  Brande,  (Manual 
Chem.  vol.  2,  p.  1436)  agree  that  the  crystals  in  efflorescing 
lose  one-half  their  water  of  crystallization.  But  if  we  double 
the  loss  this  salt  suffers  at  212°,  it  would  indicate  a  loss  which  I 
now  know  to  be  incorrect. 
These  authorities  (all  I  have  at  hand  that  are  definite  upon  the 
character  of  the  officinal  salt,)  all  quote  Soubeiran  in  brackets, 
or  Liebig,  as  giving  the  loss  by  efflorescing,  at  6  eqs.  or  three- 
fourths  of  the  water  of  crystallization  ;  and  this  latter  is  proba- 
bly the  true  loss  of  a  pure  salt  that  has  been  fused.  Brande, 
(op.  cit.  p.  1435),  says  the  pure  salt,  heated  to  212°,  should  lose 
only  8  to  10  per  cent,  in  weight,  and  I  believe  this  test,  as  a 
standard,  is  better  expressed  thus  than  by  the  U.  S.  and  London 
Pharmacopoeias.  In  my  single  comparative  •experiment  with 
what  may  be  considered  a  pure  disulphate  of  quinia,  it  held  4.57 
or  probably  4-59  per  cent,  of  water  above  the  2  eqs.,  or  4-128 
per  cent.,  at  ordinary  temperatures;  and  after  being  heated  to 
242°  regained  its  full  weight,  within  a  mere  fraction,  in  five 
hours. 
These  deductions  from  the  results  of  the  foregoing  experi- 
ments are,  however,  very  much  confused  by  the  results  that  fol- 
low : 
