506  EXAMINATION  OF  THE  SULPHATE  OP  QUINIA. 
Under  these  circumstances,  I  shall  be  much  obliged  to  you  for 
a  little  additional  space  to  set  forth  more  clearly  these  points, 
and  make  myself  understood. 
Messrs.  Powers  &  Weightman  say  that  I  acknowledge  the 
statement  made  in  my  first  communication  to  have  been  practi- 
cally and  technically  incorrect.  This  is  exactly  what  I  did  not 
intend  to  do.  The  statement  was  technically  incorrect,  but  not 
practically  incorrect,  and  the  whole  object  of  my  last  paper  was 
to  exhibit  the  fact,  that  there  was  not  10  per  cent,  of  uncom- 
bined  water  in  the  preparation,  but  that  the  preparation  was 
more  than  10  per  cent,  deficient  in  crystallized  disulphate  of 
quinia,  or  about  10  per  cent,  deficient  in  quinia. 
Messrs.  Powers  &  Weightman  regret  that  I  did  not  push  my  ex- 
periments still  farther  to  ascertain  whether  the  two  atoms  of  water, 
calculated  as  remaining  after  complete  dessication,  wTere  really 
there.  The  regret  is  misplaced,  for  the  3d,  4th  and  5th  experi- 
ments of  my  paper  are  directed  mainly  to  this  very  point ;  and 
a  comparison  of  their  results  shows  that  the  same  impure  efflor- 
esced sulphate  of  quinia,  which,  when  dried  at  242°,  lost  5.431 
per  cent.  (Exp.  3.)  yielded  on  subsequent  analysis  8.50  per  cent, 
of  water.  (Exps.  4th  and  5th.) 
Then  8.53—5.431  —  3.099  =  the  percentage  amount  of 
water  still  retained  by  the  salt  when  dried  at  242°. 
This  3. 009  per  cent,  of  water  happens  to  be  exactly  1.5  equi- 
valents. With  the  pure  recrystallized  sulphate  the  results  were 
very  different.  In  it  "  nearly  the  whole  of  the  water  of  crystal- 
lization "  was  "  driven  off  at  a  temperature  short  of  fusion." 
(Exps.  3d,  6th  and  7th.) 
All  authorities  agree  that  crystallized  disulphate  of  quinia 
requires  30  times  its  weight  of  boiling  water  for  complete  solu- 
tion, whilst  this  commercial  salt  is  soluble  in  20.96  times  its 
weight,  or  less.    (Exp.  2d.) 
The  influence  of  air  and  a  temperature  of  242°,  does  not  alter 
quinia  when  in  combination  with  a  fixed  acid,  and  not  in  solution. 
If  the  simple  processes  of  an  examination  under  the  influences 
of  heat  and  air  are  inadmissible,  we  must,  of  course,  give  up 
research  into  the  purity  of  the  preparation. 
If  my  statements  with  regard  to  the  impurities  of  the  mother 
liquor  are  "  very  indefinite  "  to  Messrs.  Powers  &  Weightman,  it 
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