482 
Laboratory  Notes. 
{  Am.  Jour.  Pharm. 
\       Oct.,  1877. 
pitant,  with  the  common  salt  of  the  alkaloid.  From  an  experiment  by 
Mr.  Lobb  it  appears  that  solution  of  sodium  sulphate  has  practically 
neither  more  nor  less  solvent  power  than  pure  water.  A  precipitate 
of  0*280  gram  of  the  alkaloid  was  washed  with  500  cc.  of  a  half- 
saturated  solution  of  sodium  sulphate,  dropped  from  a  burette  on  the 
filter  during  i\  hours,  and  then  washed  with  pure  water  (214  cc.)  until 
free  from  sulphate,  when  0*1375  gram  of  alkaloid  remained.  There- 
fore, of  the  714  cc.  of  sodium  sulphate  solution  and  pure  water,  aver- 
aged together,  each  cc.  dissolved  0*0002  gram  of  alkaloid,  a  result  prac- 
tically the  same  as  the  0*000216  gram  dissolved  by  a  cc.  of  pure  water. 
Of  course,  solubility  in  washing  precipitates  must  fall  below  solubility 
of  saturation.  The  latter  is  given  for  quinia,  at  1667  parts  of  water  of 
68°F.  (Sestini),  in  which  proportion  1  cc.  of  water  dissolves  0*0006 
gram  of  the  alkaloid,  nearly.  J.  Regnault  found  2024  parts  of  water 
at  I5°C.  to  dissolve  1  part  of  pure  quinia. 
Evidently,  the  precipitation  of  quinia  as  a  free  alkaloid  is  inaccurate 
in  quantitative  work,  under  any  circumstances,  and,  if  there  is  much 
dissolved  matter  in  the  filtrate  to  be  washed  away,  the  operation  gives 
no  result  of  even  approximate  quantity.  By  measuring  the  filtrate 
with  the  washings,  some  notion  of  the  loss  may  be  gained,  but  this 
loss  is  varied  by  proportion  of  the  precipitant,  and  may  be  varied  by 
other  dissolved  bodies  in  the  filtrate.  Moreover,  the  precipitation  of 
quinia  by  alkali,  in  the  preparation  of  citrate  of  iron  and  quinia,  is 
wasteful  and  inaccurate. 
II.  Gravimetric  Determination  of  Quinia,  as  a  Precipitate  by 
Potassium  Mercuric  Iodide. 
The  value  of  this  precipitate,  washed  and  dried  at  2I2°F.,  was  found 
to  be  2*900  grams  for  1  gram  of  quinia,  dried  at  the  same  temperature. 
This  finding  was  the  mean  of  three  determinations,  using  Mayer's 
solution  upon  an  acidulate  sulphate  solution  of  alkaloid,  the  results 
being  respectively  o*8oi,  0*824  anc^  0*812  of  precipitate  from  0*280  of 
alkaloid.  Just  26  cc.  of  Mayer's  solution  were  required  for  the  full 
precipitation  of  each  portion  (26x0*0108=0*2808),  after  which  4  cc. 
of  the  standard  solution  were  added  in  each  portion,  to  represent  an 
excess  of  the  reagent,  as  convenient  in  a  gravimetric  operation.  The 
quinia  taken  was  Powers  &  Weightman's  "  pure  quinia,"  which  was 
found  to  lose  6|  per  cent,  at  2I2°F.,  so  0*300  gram  was  weighed  in 
