690 
Examination  of  Camphor. 
(Am.  Jour.  Pharm. 
(  September,  1920. 
out  here  may  be  of  interest:  The  moisture  is  first  estimated  on  the 
well-mixed  sample,  then  loo  Gm.,  weighed  to  the  nearest  o.i  Gm., 
are  transferred  to  a  press  and  pressed  between  two  layers  of  lint. 
The  press  designed  for  this  work  has  a  steel  cylinder  2  inches  in 
diameter,  and  6  inches  deep,  and  is  furnished  with  a  movable  per- 
forated bottom  plate.  The  piston  is  operated  by  a  strong  screw 
thread.  The  sample  is  allowed  to  remain  in  the  press  under  pressure 
for  fifteen  minutes,  at  the  end  of  which  time  it  is  carefully  removed 
and  the  pressed  cake  weighed,  any  camphor  adhering  to  the  lint 
being  carefully  brushed  off  and  added  to  the  cake.  From  the  loss 
in  weight  the  amount  of  water  plus  oil  expressed  is  found. 
The  moisture  is  then  estimated  on  the  pressed  cake,  and  from  the 
difference  between  the  result  and  the  original  moisture  the  amount 
of  water  expressed  is  found,  and,  by  difference,  the  amount  of  oil 
in  the  expressed  liquid  is  found. 
It  is  then  assumed  that  the  water  still  remaining  in  the  pressed 
cake  is  associated  with  as  much  oil  as  that  in  the  expressed  liquid, 
and  the  total  oil  calculated  on  that  basis.  The  accuracy  of  this 
assumption  may  be  open  to  question,  but,  with  a  good  press,  very 
little  moisture  remains  in  the  cake,  while  the  m.  p.  of  the  pressed 
camphor  usually  indicates  a  fairly  high  degree  of  purity. 
Government  Laboratory, 
Hongkong. 
