144 
ALOINE. 
publication  of  Messrs.  Smith's  paper,  first  suggested  an  inquiry. 
I  was  engaged  in  filling  a  small  pot  with  the  aqueous  extract  of 
Socotrine  aloes,  when  I  was  called  away  for  a  short  time,  and  on 
returning,  observed  that  a  bubble  of  considerable  size  had,  by 
the  gradual  subsidence  of  the  extract,  formed  on  its  surface. 
The  extract,  when  first  made,  had  been  perfectly  transparent, 
but  the  surface  of  the  bubble  I  observed  to  be  studded  with 
bodies  of  a  regular  shape,  which  unassisted  sight  enabled  me 
to  recognize  as  crystals  of  aloine — the  microscope  afforded  more 
certain  evidence. 
I  will  hear  observe  parenthetically,  that  by  cautiously  blow- 
ing a  bubble  of  a  suspected  extract,  a  very  trifling  amount  of 
crystallization  maybe  detected,  that  cannot  readily  be  discovered 
in  any  other  way. 
The  extract  that  afforded  this  indication  had  been  prepared 
by  exhausting  Socotrine  aloes  with  boiling  water ;  filtering  the 
cooled  liquor,  a  little  carbonate  of  magnesia  being  previously 
added  ;  and  evaporating  by  a  steam  heat.  The  exhaustion  re- 
quires a  little  knack.  The  aloes  should  be  closely  powdered,  and 
sifted  through  a  40-hole  brass  seive,  then  shaken  lightly  off  a 
wide  spatula  into  the  boiling  water,  kept  in  constant  agitation 
during  the  addition,  and  maintained  in  that  state  for  twenty 
minutes  after.  The  aloes  will  by  this  means  be  completely  ex- 
hausted, and,  by  allowing  the  liquor  to  stand  quiet  till  cold,  the 
resinoid  substances  will  deposit  and  adhere  to  the  bottom  and 
sides.  The  magnesia  is  added  without  decanting  the  liquor  from 
the  vessel.  It  filters  very  readily  through  serge,  affording  a 
perfectly  bright  liquid  and  extract.  It  is  rendered  turbid  by  the 
addition  of  acid. 
Aloine  has  not  been  permanently  introduced  into  medical 
practice  in  this  part  of  the  world,  so  that  I  had  no  inducement 
to  prepare  a  larger  quantity  than  sufficed  for  experiment.  In- 
deed, in  investigations  in  general,  the  smaller  in  reason  the  quan- 
tity of  material  operated  on,  the  greater  will  be  the  care  ex- 
pended on  it,  and  less  dubious  the  results  arrived  at — the  chief 
disadvantage  being  the  loss  occasioned  by  not  being  able  to 
economise  the  mother-liquors. 
One  ounce  of  Socotrine  aloes  was  therefore  powdered  and  ex- 
hausted as  previously  described.   When  cold,  hydrochloric  acid 
