RESEARCHES  ON  ALOETINE. 
545 
obtained  by  dessication  in  the  open  air,  and  without  the  aid  of 
heat ;  they  all  contain  crystallisable  aloetine. 
Messrs.  Smiths'  process  of  preparation  is  very  simple  in  prin- 
ciple, but,  in  practice,  it  is  troublesome  to  evaporate,  in  vacuo, 
large  quantities  of  liquid,  and,  moreover,  the  yield  is  very  tri- 
fling. I  endeavored,  therefore,  to  overcome  this  difficulty,  and, 
after  some  failures,  I  arrived  at  the  following  method,  which 
gives  about  15  per  cent,  of  product. 
Preparation  of  Aloetine. 
Distilled  water  is  boiled  for  an  hour,  in  order  to  expel  the  air, 
and,  when  cold,  2  kilogrammes  are  poured  on  1  kilogramme  of 
Barbadoes  aloes  in  powder,  which  is  kept  ready  in  a  dish.  By 
agitating  rapidly,  the  solution  is  effected  in  a  few  minutes  ;  the 
dish  is  covered  as  accurately  as  possible,  and  left  to  repose  for 
about  a  quarter  of  an  hour.  The  liquor  must  be  decanted  into  a 
conserve  glass,  of  such  a  size  as  to  exactly  contain  it ;  a  little 
ether  is  poured  in,  in  order  to  expel  the  air  as  much  as  possible, 
and  to  prevent  mouldiness ;  the  lid  is  immediately  fitted  on,  and 
carefully  luted.  It  only  remains  to  place  this  vessel  in  a  cool 
situation,  and  to  leave  it  to  itself  for  a  month.  It  is  then  open- 
ed, and,  after  having  separated  all  the  portion  still  remaining 
liquid,  we  find  its  interior  lined  with  a  compact  mass,  and,  as  it 
were,  covered  with  stalagmites.  These  concretions  are  no  other 
than  a  mixture  of  amorphous  aloetine,  foreign  earthy  matters, 
and  crystallisable  aloetine. 
Now,  as  the  latter  is  very  sparingly  soluble  in  cold  water,  and 
much  heavier  than  the  impurities  which  accompany  it,  it  is  easy 
to  separate  it,  mechanically,  by  simple  levigation. 
The  crude  aloetine  is  under  the  form  of  yellowish  and  radiated  • 
crystalline  grains,  giving  way  between  the  teeth,  like  wax,  and 
rapidly  turning  brown,  in  contact  with  nitric  acid,  and  even,  in 
damp  air.  To  purify  them  completely,  they  must  be  washed  in 
alcohol  of  56  centesimal  degrees  (22°  Beaume,)  until  this  liquid 
takes  a  straw-colored  tint,  without  any  red  in  it,  and  then  crys- 
tallised five  or  six  different  times  in  alcohol  of  86  per  cent.  (36° 
b.) 
Dr.  Pereira  has  described,  with  much  care,  a  new  variety  of 
Socotrine  aloes,  recently  imported  into  England,  and  which  is  no 
other  than  the  natural  juice  of  the  plant  which  has  undergone  no 
35 
