266  .         Commercial  Aloes.  { AmjuZ'i903arm" 
notannalester  of  cinnamic  acid.  This  same  subject  has  also  been 
reported  on  by  Professor  Tschirch  in  a  more  recent  article. 
CHEMICAL  TESTS. 
These  modern  developments  in  the  chemical  composition  of  aloes 
give  us  some  more  definite  knowledge  of  the  applicability  and  uses 
of  the  various  tests  lor  aloes. 
It  has  been  known  for  a  long  time  that  not  any  of  these  different 
tests  were  applicable  to  all  varieties  of  aloes.46  While  considerable 
work  must  still  be  done,  before  we  are  assured  of  reliable  quantita- 
tive tests  for  the  various  chemical  constituents  or  products  of  aloes, 
we  have  at  the  present  time  several  fairly  reliable  qualitative  tests. 
According  to  Tschirch,47  the  well-known  test  for  Barbadoes  aloes, 
deep  red  color  on  the  addition  of  a  small  fragment  of  aloes  to 
strong  nitric  acid,  is  really  a  test  for  iso-barb-aloin,  and  that  the 
resulting  aloin  red  is  a  characteristic  oxidation  product  of  the  iso- 
barb-aloin.  Klunge's  reaction48  is  another  reliable  and  readily  applied 
color-test  for  iso-barb-aloin;  it  is  rather  a  sensitive  one  and  is 
applied  as  follows : 
"  Dilute  a  freshly  prepared  aqueous  solution  of  aloes,  or  aloin, 
until  it  is  nearly  colorless,  then  add  one  drop  of  a  10  per  cent,  solu- 
tion of  cupric  sulphate;  the  solution  becomes  intensely  yellow.  On 
the  further  addition  of  a  few  drops  of  solution  of  sodium  chloride  or 
potassium  bromide  and  a  few  cubic  centimeters  of  alcohol,  or,  in  lieu 
of  the  alcohol,  on  boiling  the  mixture,  a  deep  red  color  indicates 
presence  of  iso-barb-aloin." 
For  the  physiologically  active  portion  of  aloes  we  have  an  effi- 
cient, reliable  and  comparatively  sensitive  test  in  the  well-known 
Borntraeger's  test  for  emodin.49  This  is  usually  directed  to  be 
applied  as  follows  : 
"  A  solution  of  aloes  or  aloin  is  shaken  with  an  equal  quantity  of 
petroleum  benzine,  and  the  mixture  allowed  to  stand;  when  it  has 
separated  into  two  distinct  layers,  a  portion  of  the  supernatant  clear 
benzine  solution  is  decanted  into  a  test  tube  and  one  drop  of 
stronger  solution  of  ammonia  is  added,  well  shaken,  and  the  mix- 
ture again  allowed  to  stand ;  on  separating,  it  will  be  found  that  the 
ammonia  has  assumed  a  deep  rose-red  color  if  emodin  is  present." 
A  modification  of  this  test,  using  stronger  ether  for  the  petroleum 
benzine,  will  usually  be  found  to  work  more  rapidly  and  to  give 
equally  as  reliable  results. 
