546 
RESEARCHES  ON  ALOETINE. 
manipulation.  It  is  a  chestnut  brown  liquid,  with  a  powerful 
odor  of  black  currant,  in  which  float  a  great  number  of  silky 
crystals  of  aloetine. 
It  would  appear,  at  first  sight,  that  nothing  is  easier  than  to 
prepare  aloetine  from  this  natural  juice :  simple  pressure  between 
folds  of  bibulous  paper,  and  several  crystallisations  in  alcohol, 
ought  to  be  sufficient.  But  this  is  not  the  case,  and  the  portion 
of  this  juice  which  has  become  altered  in  the  air,  suffices  for  pre- 
venting the  crystallisation  of  the  aloetine  from  remaining  intact ; 
at  any  rate,  a  large  portion  is  lost.  The  process  which  is  the 
least  disadvantageous,  is  the  following  : — the  liquid  juice  of  So- 
cotrine  aloes  is  diluted  with  distilled  water,  to  which  10  or  12 
drops  of  liquid  ammonia  have  been  added  per  litre.  The  resinous 
portion  of  the  juice  is  first  dissolved  by  the  alkali,  and,  if  we  ope- 
rate very  quickly,  the  portion  still  unaltered  may  be  separated 
by  filtration.  Two  or  three  crystallizations  in  alcohol  are  then 
sufficient  for  arriving  at  complete  purification.  However,  this 
method,  however  rapidly  we  operate,  never  gives  more  than  4  or 
5  per  cent,  of  aloetine. 
Pure  aloetine  occurs  under  the  form  of  prismatic  needles,  of  a 
fine  sulphur  yellow.  At  the  temperature  of  10°  C.  (50°.  F.,)  1 
part  of  aloetine  requires,  for  its  solution,  10  parts  of  water,  2 
parts  of  alcohol,  of  36°  B.,  and  8  parts  of  ether  of  66°  B.  It  is 
impossible  to  determine,  exactly,  its  solubility  at  the  boiling 
points  of  these  liquids,  because  heat  alters  it  more  or  less  pro- 
foundly. 
Owing  to  its  sparing  solubility  in  water,  aloetine  has  scarcely 
any  taste,  but  its  characteristic  bitterness  is  speedily  developed. 
The  mucilaginous  pulp  of  the  leaves  of  aloes  contains  a  pecu- 
liar matter,  which  is  colorless  in  the  plant,  but  which  rapidly  ac- 
quires a  violet  red  color  in  contact  with  the  air.  This  may  easily 
be  perceived  by  suddenly  tearing  one  of  these  leaves,  when  the 
central  part  rapidly  becomes  colored.  This  substance,  whatever 
may  be  its  nature,  accompanies  aloetine  in  its  last  purifications ; 
I  have  ascertained  that  to  it  was  due  the  property  of  being  color- 
ed red  by  nitric  acid,  attributed  by  Messrs.  Smith  to  aloine. 
Without  heat,  pure  aloetine  should  color  nitric,  sulphuric  and 
hydrochloric  acids,  of  a  citron  yellow.  When  it  is  boiled  for 
about  half  an  hour,  with  concentrated  nitric  .  acid,  we  obtain  a 
