Am.  Jour.  Pharm.' 
May,  1886.  / 
Dderinination  of  Glycerin. 
249 
oxalic  acid  determined,  and  the  equivalent  quantity  of  glycerin  calcu- 
lated therefrom. 
We  carry  the  process  out  as  follows : 
The  aqueous  solution  of  glycerin  ■  which  should  not  contain  more 
than  0*25  gm.  C3H803)  is  made  strongly  alkaline  by  adding  5*0  gms. 
of  solid  caustic  potash ;  powdered  permanganate  of  potash  is  then  grad- 
ually added  until  the  solution  is  of  a  permanent  pink  color:  the  solu- 
tion is  now  kept  at  the  boiling  point  for  half  an  hour,  and  then  the  excess 
of  K2Mn2(X  decomposed  with  sulphurous  acid,  either  in  solution  or 
the  gas  may  be  used.  The  solution,  which  should  now  be  colorless,  is 
filtered  from  the  precipitated  oxide  of  manganese,  and  made  acid  with 
acetic  acid  and  boiled  :  a  lime  salt  is  added,  and  the  resulting  oxalate 
collected  on  a  filter  and  thoroughly  washed  with  boiling  water.  As 
the  precipitate  is  not  pure  oxalate  of  lime,  we  determine  the  oxalic 
acid  in  the  lime  salt  by  titrating  with  standard  K2Mn2Oi  in  the  usual 
way ;  with  a  moderate  amount  of  care  this  process  is  very  accurate : 
the  difference  in  several  experiments  should  be  under  a  half  per  cent., 
and  Messrs.  Benedikt  and  Zigmondy.  since  we  suggested  the  process, 
have  obtained  very  satisfactory  results,  which  they  publish  in  the 
Jloniteur  Scientifique  QuesneciJle.  vol.  xv.;  October,  1885. 
In  the  saponification  of  fats  in  which  it  is  proposed  to  estimate  the 
glycerin,  care  should  be  taken  to  have  the  whole  of  the  alcohol  driven 
off,  as  dilute  alcohol  treated  with  alkaline  permanganate  gives  oxalic 
acid.  It  may  be  mentioned  that  the  acids  of  the  acetic  series  do  not 
oxidize  to  oxalic  acid  with  alkaline  permanganate,  whilst  those  acids 
of  the  acrylic  series  do. — Chem.  Xeics,  January  8,  1886,  p.  15. 
Laboratory,  4.  Great  Tower  St.,  E.  C,  December  29, 1885. 
Phenolphthalein  as  an  Indicator. — By  E.  Leger  (J.  Pharm. 
[5],  xi,  125-428). — The  author  has  observed  that  certain  organic 
alkaloids  have  no  action  on  phenolphthalein;  thus  the  presence  of 
morphine,  qpiinine,  etc.,  does  not  interfere  with  the  titration  of  sul- 
phuric acid,  the  same  holds  true  with  regard  to  hydrochloric  and 
nitric  acids.  Cicutine  and  codeine  are  two  organic  bases  which  have 
been  found  to  affect  this  indicator.  The  author  details  experiments  and 
concludes  that — (1.)  It  is  possible  to  estimate  an  acid  volumetric-ally 
as  easily  when  combined  with  certain  alkaloids  as  when  in  the  free 
stat^.  (2.i  This  estimation  may  serve  within  certain  limits  to  indicate 
the  purity  of  a  salt  of  the  alkaloid. — Jour.  Chem.  Soc,  1885,  p.  931. 
