^'"''ocuiij^^''^'}  Contributions  from  the  School  of  Pharmacy,  etc.  455 
gutta  percha  on  the  filter.  At  92°  F.  the  deposit  dissolved.  (This 
deposition,  at  about  60°  and  more  rapidly  at  lower  temperatures,  occurs 
with  ether  and  essential  oils,  but  not  with  bisulphide  of  carbon  or 
chloroform.)  The  solution  required  17  c.c.  (4  fluidrachms  and  35 
minims)  of  alcohol  for  complete  precipitation.  The  precipitate  was  drained, 
washed  with  a  little  alcohol  (which  facilitates  its  collection),  and 
collected  into  a  compact  mass,  which  was  stirred  for  a  short  time  in  an 
evaporating  dish  over  the  water-bath,  when  it  was  nearly  or  quite  free 
from  benzole.  When  42  grains  of  this  purified  gutta  percha  were 
dissolved  in  i  troyounce  of  chloroform  (the  pharmacopoeial  proportion),, 
a  clear  solution  of  a  light  brown  color  was  obtained.  It  was  of 
thicker  consistence  than  the  pharmacopoeial  solution,  and  this  will 
always  be  observed  when  pure  gutta  percha  is  taken  and  the  lead 
clarification  omitted.  In  subsequent  operations  with  benzole,  it  was 
found  that  by  addition  of  animal  charcoal  to  the  solution  before  filtra- 
tion, a  colorless  preparation  was  obtained.  The  benzole  used  in  these 
operations  was  mostly  recovered  from  its  mixture  with  alcohol,  by 
adding  sufficient  water,  setting  aside  in  a  cylindrical  vessel  and  drawing 
off  the  upper  liquid.  It  was  then  somewhat  turbid,  but  after  distilling 
from  a  water-bath,  it  was  as  pure  as  before  use. 
In  purification  with  bisulphide  of  carbon,  120  grains  of  gutta  percha 
required  4  troyounces  of  this  solvent  (i  to  16).  The  solution,  filtered 
under  a  bell-glass,  remained  clear,  and  was  somewhat  less  colored  than 
the  benzole  solution.  It  required  between  four  and  five  times  its. 
volume  of  alcohol  for  complete  precipitation.  The  precipitate  was 
gathered  on  a  pill-tile  and  pressed  with  the  spatula  into  as  thin  a  sheet 
as  possible.  After  the  evaporation  of  all  the  liquids,  the  gutta  percha 
was  a  milk-white  compact  sheet,  and  weighed  80  grains.  Of  this  42 
grains  were  dissolved  in  a  troyounce  of  chloroform,  giving  a  clear 
solution,  very  slightly  colored.  By  subsequent  operations  it  was  found 
that  by  adding  animal  charcoal  to  the  bisulphide  of  carbon  solution,  the 
filtrate  is  obtained  colorless.  The  bisulphide  of  carbon  and  a  portion  of  the 
alcohol  were  recovered  as  follows  :  The  mixture  of  bisulphide  of 
carbon  and  alcohol  was  subjected  to  fractional  distillation,  and  the 
distillate,  containing  a  very  little  alcohol,  was  washed  with  water, 
drawn  off  and  then  filtered.  The  alcohol  left  by  the  distillation  was 
filtered  and  used  in  another  operation. 
From  these  and  other  concordant  experiments,  it  was  fully  decided 
that  bisulphide  of  carbon  is  generallv  preferable  to  benzole  as  a  purifying 
