36 
A  few  Notes  an  Aloes. 
f  Abi.  Jour.  Pharm. 
\     Jan.  2, 1871. 
redissolved  in  water,  and  this  operation  repeated  several  times,  but  the 
aloin  undergoes  but  slight  change  of  color,  and  will  still  crystallize  on 
letting  the  solution  stand  for  an  hour  or  two,  or  almost  immediately 
on  stirring.  The  transparent  yellow  varnish  left  by  evaporating  solu- 
tions of  it  consists  merely  of  anhydrous  aloin  ;  treatment  with  water 
restores  to  it  its  crystalline  state.  It  is  of  course  already  known  that 
if  kept  in  a  moist  state  on  a  water-bath  for  some  time,  the  pure  sub- 
stance becomes  gradually  brown,  and  assumes  the  appearance  of 
Socotrine  aloes  ;  but  this  is  a  comparatively  slow  process,  and  even 
after  some  time  a  considerable  quantity  of  the  aloin  is  still  capable  of 
crystallizing. 
A  further  illustration  of  its  stability  is  exhibited  in  the  following 
experiment  and  accompanying  specimen.  About  ten  years  ago,  a 
paper  by  Kosmann  appeared  in  the  Journal  de  Pharmacie^  the  object 
of  which  was  to  show  that  aloes  was  a  mixture  of  glucosidic  bodies. 
The  experiments  by  which  grape  bugar  was  obtained,  and  its  presence 
indicated  by  the  asserted  production  of  alcohol  and  carbonic  acid, 
were  performed  by  Kosmann  solely  upon  Cape  aloes.  I  have  made 
a  number  of  experiments  which  convince  me  that  he  is  quite  incorrect 
in  his  statements,  but  as  I  hope  to  reproduce  the  subject  at  a  future 
meeting,  I  will  cite  only  one  experiment  made  with  pure  aloin.  Some 
aloin  was  dissolved  in  about  an  equal  weight  of  oil  of  vitriol  (it  forms 
a  clear  orange  syrup)  ;  the  solution  was  gently  heated  for  a  few  min- 
utes, and  then  poured  into  water  and  kept  boiling  for  about  two  hours. 
Saturated  by  excess  of  pure  carbonate  of  barium,  filtered  and  evap- 
orated on  a  water-bath,  a  minute  quantity  of  barium  retained  in  solu- 
tion precipitated  by  dilute  sulphuric  acid  and  the  liquid  further  con- 
centrated, unaltered  aloin  was  deposited  in  yellow  crystals.  A  part 
of  the  solution  which  had  been  thus  treated  was  submitted  to  the  fer- 
mentation test.  Three  tubes  full  of  mercury  were  inverted  in  a  small 
mercurial  trough.  Into  the  first  was  introduced  some  washed  yeast 
and  distilled  water.  Into  the  second  some  washed  yeast  and  a  weak 
solution  of  sugar.  Into  the  third  some  yeast  and  the  boiled  solution 
of  aloin.  The  first  and  third  gave  no  bubbles  of  gas  larger  than  a 
pin's  head  ;  the  second  tube  was  completely  filled  with  COg  in  half  an 
hour. 
To  ascertain  if  the  aloin  prevented  fermentation,  two  similar  tubes 
were  set  up.  The  first  contained  yeast,  distilled  water  and  sugar; 
the  second  had  in  addition  a  portion  of  the  solution  which  had  been 
