354      THE  PROCESS  OF  PERCOLATION  OR  DISPLACEMENT. 
into  a  glass  flask,  furnished  with  a  gas-tube,  and  heated  it  over 
a  spirit-lamp.  The  sulphur  soon  melted,  and  in  a  short  time 
there  was  an  evolution  of  sulphurous  acid  which  was  conducted 
into  water.  The  evolution  was  very  uniform,  and  the  burning 
of  the  spirit-lamp  was  continued  until,  after  about  six  hours, 
there  was  only  a  comparatively  small  residue  in  the  flask. 
During  this  treatment  the  sulphur  constantly  floated  in  the 
form  of  a  transparent,  hyacinth-red,  thickly  fluid  mass  on  the 
hot  sulphuric  acid,  and  a  small  portion  of  it  sublimed ;  part  of 
this  condensed  again  in  drops  upon  the  walls  of  the  flask,  and 
flowed  back  into  the  acid,  whilst  another  part  was  deposited  in 
the  form  of  a  thin  crust  in  the  neck  of  the  flask.  Very  small 
quantities  of  sulphur  were  carried  further  mechanically  by  the 
sulphurous  acid,  and  deposited  in  the  conducting-tube,  and  the 
water  placed  to  absorb  the  gas. 
After  the  conclusion  of  the  process,  the  flask  contained  only 
4j  drachms  of  sulphuric  acid,  and 
32  grains  of  unaltered  sulphur. 
The  advantages  of  this  process  are  : — 
1.  That  it  furnishes  a  pure  product ; 
2.  That  it  is  easily  effected,  and  cheap; 
3.  That  the  evolution  of  sulphurous  acid  gas  is  very  uniform, 
the  reason  of  which  is  that  the  sulphuric  acid  always  acts  only 
upon  the  outer  surface  of  the  melted  sulphur,  and  this  always 
forms  a  coherent  mass  ;  and 
4.  That  no  solid  deposit  settles  to  the  bottom  of  the  vessel  of 
evolution,  which,  in  other  methods,  so  often  occasions  the  crack- 
ing of  the  vessel. — London  Chem.  Gaz.,  Mar.  15,  1859,  from 
Dingier  s  Polyt.  Journal  and  Chem.  Centralblatt. 
THE  PROCESS  OF  PERCOLATION  OR  DISPLACEMENT. 
{An  extract  from  a  paper  read  before  the  American  Pharmaceutical  Association,  and 
published  in  its  Proceedings  for  1858). 
By  Israel  J.  Grahame. 
The  author  after  alluding  to  the  history  of  the  process  in  its 
application  to  pharmacy,  and  reviewing  the  usual  modes  of  con- 
ducting it,  says  : 
