3i6 
A  Note  on  a  Source  of  Error. 
A.m.  Jour.  Pharm. 
July,  1907. 
sand  which  had  been  previously  treated  with  hot  hydrochloric  acid 
and  thoroughly  washed  with  water  and  dried,  it  was  found  that  after 
conducting  the  experiment  fourteen  hours  and  then  filtering  the 
liquid  through  a  fat-free  filter  and  evaporating  spontaneously  and 
over  sulphuric  acid  a  yellowish,  cosmoline-like  residue  weighing 
0-0138  gramme  remained. 
A  volume  of  200  c.c.  of  a  distillate  which  had  been  twice  distilled 
at  20°  to  500  C.  and  had  stood  215  days  in  a  flask,  as  above  described, 
left  on  evaporation  at  room  temperature  and  at  iOO°  C.  for  two  hours 
a  residue  of  0-0494  gramme.  The  residue  before  being  heated  at 
iOO°  C  was  yellowish  and  cosmoline-like  in  appearance,  but  on  being 
heated  to  I00°  C.  it  rapidly  turned  black  and  on  cooling  changed 
in  consistency  from  a  pasty  mass  to  a  hard  solid. 
A  volume  of  1 900  c.c.  of  a  distillate  which  had  been  twice  dis- 
tilled at  20°  to  500  C,  using  Glinsky's  fractionating  bulbs,  and  which, 
after  the  second  distillation,  had  stood  217  hours,  was  redistilled  at 
20°  to  500  C.  All  but  1 3 5  c.c.  distilled  over  at  the  temperatures  stated 
and  on  evaporating  this  spontaneously  a  yellowish,  cosmoline-like 
residue  remained  which,  on  being  heated  for  three  hours  at  1000  C, 
turned  black.  This  residue  while  hot  was  pasty  in  character  but 
when  cold  became  hard.  It  weighed  0*5062  gramme  so  that  this 
is  the  quantity  of  material  non-volatile  at  100°  C.  that  was  contained 
in  the  1900  c.c.  of  distillate. 
A  portion  of  distillate  from  the  above  stated  1900  c.c.  amounting 
to  a  volume  of  970  c  c.  was  put  aside  in  a  flask  for  a  period  of  twenty 
days  and  then  redistilled  at  20°  to  500  C,  using  Glinsky's  fractionating 
bulbs,  with  the  result  that  120  c.c.  refused  to  distil  over  at  a  tem- 
perature below  500  C.  The  120  c.c.  were  permitted  to  evaporate 
spontaneously  and  a  yellowish,  cosmoline-like  mass  remained  which 
on  being  heated  to  ioo°  C.  for  three  hours  turned  black  and  weighed 
0-0216  gramme. 
In  every  case  of  distillation  care  was  exercised  that  the  liquid  in 
the  distilling  flask  should  not  be  in  ebullition,  but  that  evaporation 
should  occur  in  such  a  manner  that  the  surface  of  the  liquid  in  the 
flask  remained  placid.  Weighings  were  made  until  constant  weight 
was  obtained.  The  cork  stoppers  employed  had  been  previously 
extracted  with  ethyl  ether.  In  every  case  there  was  an  open  space 
of  about  a  litre  above  the  surface  of  the  liquid  in  the  corked  storage 
flask  and  the  liquid  was  exposed  to  diffused  sunlight  at  room  tem- 
perature. 
