398  The  Chemistry  of  Aloes.  {Amj£^m.^ 
of  potassium  hydrate.  Another  way,  suggested  by  Dr.  Charles 
Rice,  consists  in  precipitating  the  potassium  cobaltic  nitrite  from  a 
concentrated  solution  of  the  sample,  collecting  on  counterpoised 
filters,  drying  and  weighing,  another  sample,  containing  a  known 
quantity  of  potassium  being  treated  in  exactly  the  same  manner^ 
and  the  weights  of  the  two  precipitates  compared.  A  large  excess 
of  reagent  is  required  to  obtain  a  maximum  precipitation,  enough 
to  give  the  supernatant  solution  a  dark  brown  color.  The  precipi- 
tate is  appreciably  soluble  in  water  and  should  therefore  not  be 
overwashed.  Both  samples  should  be  washed  with  the  same  quan- 
tity of  water.  As  the  composition  of  the  precipitate  is  somewhat 
variable  and  the  conditions  governing  the  variability  have  not  been 
determined,  sodium  cobaltic  nitrite  cannot  at  present  be  used  for 
accurate  estimations  of  potassium. 
Pharmaceutical  Laboratory  of  the 
New  York  College  of  Pharmacy,  July,  1898. 
u 
THE  CHEMISTRY  OF  ALOES. 
By  Alfred  R.  L.  Dohme,  Ph.D.1 
Aloes  is  the  concentrated  juice  of  the  plants  of  the  genus  Aloe, 
principally  the  varieties  Aloe  Socotrina,  Aloe  ferox,  Aloe  plicatilis, 
Aloe  vulgaris,  Aloe  Africana  and  Aloe  Perryi.  Strange  to  say,  the 
much-talked-of  and  official  Socotrine  aloes  does  not  grow  on  the 
island  of  Socotra,  this  variety  being  Aloe  Perryi,  named  after  our 
famous  Commodore  Perry,  who  observed  it  on  the  island  in  1878. 
Commercially  speaking,  the  varieties  of  aloes  are  Socotrine,  Cura- 
coa, Barbadoes,  Natal,  Cape  and  Indian  aloes.  In  England  they  pre- 
fer Barbadoes  aloes ;  in  Germany,  Cape  aloes,  and  in  this  country, 
Socotrine  and  Curacoa  aloes.  A  correct  and  reliable  division  and  clas- 
sification of  the  varieties  of  this  important  drug  is  as  yet  only  a 
wished-for  but  not  by  any  means  realized  fact.  Much  of  the  Soco- 
trine aloes  we  buy,  and,  apparently  knowing,  label  ''True  Socotrine 
Aloes,"  is  a  mixture  containing  various  varieties,  and  no  doubt 
largely  Curacoa  aloes.  As  we  all  know,  Socotrine  aloes  costs  about 
25  cents  a  pound,  while  Curacoa  aloes  costs  only  about  3  cents  a 
1  Read  at  the  meeting  of  the  Maryland  State  Pharmaceutical  Association  at 
Blue  Mountain  House,  Maryland,  on  June  23,  1898. 
