Am.  Jour.  Pharm. 
November,  1919. 
Purified  Ether. 
741 
utes  over  a  flame,  to  decompose  and  dissolve  the  precipitate.  Care 
must  be  taken  to  see  that  the  whole  is  taken  up ;  with  the  larger 
quantities  particles  sometimes  remain  persistently  insoluble  unless 
rubbed  down  with  a  glass  rod.  The  solution  becomes  colorless,  and, 
after  cooling,  is  titrated  with  the  sulphocyanide  as  already  described, 
using  the  iron  alum  as  indicator.  A  deduction  of  o.i  to  0.2  Cc.  may 
be  made  for  the  amount  required  to  give  a  satisfactory  end  point, 
but  each  experimenter  should  determine  this  for  himself. 
Each  milligram  of  mercury  represents  0.058  Mgm.  of  acetone. 
The  following  trials  were  made.  A  dilute  acetone  solution  was  pre- 
pared and  its  apparent  strength  determined  by  taking  10  Cc.  to- 
gether with  40  Cc.  of  water,  and  50  Cc.  of  the  reagent. 
Determinations  were  then  made  by  taking  4  Cc.  of  an  ether  and 
different  quantities  of  the  acetone  solution,  and  proceeding  as  de- 
scribed above  for  the  ether  test.  After  making  the  necessary  deduc- 
tion for  the  "  blank  "  of  the  ethers,  the  results  were  as  follows : 
Acetone  Taken.    Milligrams.       Acetone  Found,    Milligrams.  Deviation. 
Fifty  Cc.  each  of  reagent  and  filtrate  being  used.  It  will  be 
noticed,  consequently,  that  in  the  last  test  the  reagent  is  insuffi- 
ciently in  excess  for  the  quantity  taken.  These  results  were  consid- 
ered good  enough  for  the  comparisons  desired,  and  the  estimations 
were  proceeded  with.  But  it  is  believed  that  for  absolute  accuracy 
it  would  be  necessary  to  keep  to  a  fixed  ratio  of  reagent  to  solution, 
and  prepare  a  scale  for  different  acetone  concentrations. 
This  work  was  done  in  the  Liverpool  Laboratory  of  Messrs. 
Evans  Sons,  Lescher  and  Webb,  Limited. 
0.46 
0.874 
0.92 
1.84 
2.76 
0.516 
0.893 
0.986 
1.91 
2.65 
+  11% 
+  2% 
+  7% 
+  4% 
-  4% 
