Am.  Jour.  Pharm.  1 
Jan.  2,  1871.  J 
A  few  Notes  on  Aloes.  ^ 
35 
2.  Crystallized  or  hydrated  aloin. 
3.  Resin. 
4.  Aloesic  acid ;  supposed  by  some  to  be  gallic  acid. 
Experiments  made  by  myself,  in  addition  to  those  already  published 
by  Mr.  Groves  and  other  chemists,  induced  me  to  adopt  an  opinion  re- 
specting the  constitution  of  aloes  somewhat  modified  from  the  fore- 
going. 
I.  Aloetin. — The  first  of  these  bodies  certainly  forms  a  constituent 
very  important  as  to  quantity  of  all  the  varieties  of  aloes.  There  can 
be  no  doubt  that  it  is  the  product  of  the  alteration  of  crystallizable 
aloin,  partly  by  the  action  of  heat,  partly  by  the  oxidizing  action  of 
the  air.  I  regard  it  as  a  mixture  of  anhydrous  aloin,  which  is  capa- 
ble in  the  presence  of  water  of  recovering  its  crystalline  condition, 
and  the  brown  oxidized  substance  referred  to  further  on. 
II.  Crystallizable  aloin  is  the  body  to  w^hich  especially  all  the  va- 
rieties of  aloes  owe  their  bitterness.  Its  isolation  is  usually  thought 
to  be  a  matter  of  some  difficulty,  but  the  following  simple  process  will 
furnish  any  desired  quantity, — pounds  if  necessary. 
Select  a  specimen  of  Barbadoes  aloes,  the  most  powerfully  odorous 
that  can  be  procured,  bright-looking,  and  not  the  most  waxy  ;  break 
it  up  and  dissolve  it  in  a  quantity  of  boiling  distilled  water,  to  which  a 
few  drops  of  sulphuric,  sulphurous,  or  hydrochloric  acid  have  been 
added.  The  proportions  employed  may  be  those  of  the  Pharmacopoeia 
for  Extractum  Aloes,  viz.  one  pound  to  a  gallon.  Let  the  liquid  stand 
a  night  to  deposit  resin,  then  pour  it  off  and  evaporate  quickly  till,  if 
1  lb.  of  aloes  have  been  used,  about  2  lbs.  of  liquid  remain. 
This  left  for  twenty-four  hours  will  deposit  an  abundant  crop  of 
yellow  crystalline  matter.  The  fluid  portion  poured  of!'  and  duly  con- 
centrated yields  a  first-rate  extract.  The  yellow  crystals  must  be  w^ell 
drained  and  pressed,  and  will  yield  pure  aloin  by  recrystallization 
once  or  twice  from  water  mixed  with  a  small  proportion  of  rectified 
spirits.  If  the  selection  of  the  aloes  be  looked  to,  the  product  will 
amount  to  about  20  per  cent,  of  the  material  employed. 
Aloin  has  been  said  to  be  with  great  facility  decomposed  or  altered 
by  the  simple  application  of  heat  to  its  aqueous  or  alcoholic  solution. 
I  have  found,  however,  that  it  will  bear  without  appreciable  change 
comparative  rough  treatment  in  this  way,  provided  the  solution  is  quite 
neutral  or  slightly  acidified.  A  little  pure  aloin  dissolved  in  distilled 
water  may  be  evaporated  to  dryness  and  heated  till  it  fuses,  and  then 
