AmNo0v.r;i877arm"}    Goa-powder  and  Chrysophanic  Acid.  545 
commerce.  Water  is  added  from  time  to  time  to  keep  the  crude  in  a 
soft  consistence,  for  when  it  becomes  too  thick  it  takes  longer  to  boil, 
thereby  injuring  the  product.  The  water  is  added  through  an  opening 
in  the  still  head.  After  nearly  all  the  oil  has  been  extracted  the  head 
of  the  still  is  taken  off,  and  a  stop-cock,  which  is  situated  near  the  bot- 
tom of  the  still,  is  opened,  and  the  residue,  which  is  rosin,  flows  out 
and  passes  through  three  or  four  large  strainers,  the  bottom  one  being 
covered  with  cotton  batting,  into  a  large  trough,  from  where  it  is  dipped 
into  barrels  made  for  that  purpose  ;  said  barrels  contain  between  280 
and  400  lbs.  As  stated  before,  care  must  be  taken  to  keep  sufficient 
water  in  the  still,  otherwise  the  rosin  becomes  charred  black.  The 
rosin  of  the  first  years'  dip  is  the  best,  and  is  consequently  worth  the 
most  ;  the  opaqueness  of  rosin  is  caused  by  too  much  water  being  left 
in  the  still.  The  rosin  for  the  first  part  of  the  season  of  the  first  year's 
product  is  very  light-colored  and  transparent,  like  "  window  glass." 
Each  succeeding  year  the  color  becomes  darker,  and  finally  the  rosin  is 
black  or  nearly  so,  and  there  is  a  very  small  yield  of  the  oil.  We  often 
obtain  rosin  which  is  very  soft,  owing  to  too  much  of  the  oil  being  left 
to  run  out  with  the  rosin. 
The  method  of  obtaining  tar,  as  practised  by  the  manufacturers,  is  very 
simple.  A  large  hole  is  dug  in  the  ground,  in  which  are  placed  pieces 
of  pine,  one  on  the  other.  After  a  sufficient  quantity  has  been  placed 
therein  they  are  slowly  burnt,  when  the  tar  exudes  and  flows  through 
a  trench  into  a  trough,  where  it  is  ladled  out  into  barrels  ;  in  this  way 
it  is  generally  contaminated  with  chips,  dirt,  etc.  This  product  is  capa- 
ble of  being  distilled,  when  some  pyroligneous  acid  and  an  oil  of  tar  are 
obtained,  and  what  is  left  is  pitch. 
GOA  POWDER  AND  CHRYSOPHANIC  ACID. 
By  Charles  Bullock. 
[Read  0  the  Pharmaceutical  Meeting  October  16.) 
In  asking  your  attention  to  the  specimens  of  Goa-powder  and  chryso- 
phanic acid,  I  have  nothing  new  to  communicate  regarding  them  ;  but  as 
the  literature  of  the  subject  is  somewhat  scattered,  a  resumi  of  what 
has  been  already  published  may  not  be  without  interest  to  those  present 
at  this  meeting. 
The  first  notice  we  have  of  Goa  was  in  1874,  in  a  paper  from  Dr. 
35 
