Am.  Jour.  Pharm. 
Feb.,  1883. 
I     CrysUtlline  Comfituent  of  Jafferahad  Aloes, 
93: 
the  aloiii  a  copious  yellow  precipitate  fell.  This  was  collected  after 
having  been  in  contact  with  excess  of  bromine  water  for  an  hour, 
washed,  dried,  and  crystallized  three  times  from  spirit.  The  bromi- 
nated  aloin  was  in  beautiful  yellow  crystals,  which  were  rather  soluble 
in  cold  alcohol,  and  were  somewhat  more  stable  than  the  aloin  itself. 
It  retained  only  a  trace  of  water  when  dried  in  a  vacuum  over  sul- 
phuric acid,  which  was  given  off  on  heating  to  100°  C.  to  110°  C. 
•2526  gram  of  the  perfectly  dry  substance  gave  -2539  gram  of  silver 
bromide,  corresponding  to  42*75  per  cent  of  bromine. 
In  1875  Dr.  Tilden  proposed,  as  the  result  of  the  cdnsideration  of  a 
number  of  analyses  of  aloins  and  their  derivatives  made  by  himself 
and  others,  that  the  aloins  obtained  from  Barbadoes  and  Zanzibar  aloes 
might  be  considered  isomeric  bodies,  with  the  empirical  formula 
C^eHigOy,  which  also  agrees  closely  with  the  results  of  his  analyses  of 
nataloin.  This  formula  requires  59'()2  per  cent,  of  carbon  and  5*59 
per  cent,  of  hydrogen.  Its  tribromo  derivative  requires  42*93  per 
cent,  of  bromine. 
No.  \a. 
No.  15. 
No.  2. 
It  will  be  seen  that  of  the  numbers  obtained  in  niy  analyses  those 
for  the  hydrogen  and  bromine  agree  very  closely  with  these,  and  that 
the  proportion  of  carbon,  though  a  little  high,  also  agrees  fairly  well. 
The  water  of  crystallization  found,  16  per  cent.,  is  rather  more  than 
the  amount  which  would  correspond  to  three  molecules,  i.  e.,  14*3  per 
cent.  The  difficulty  of  getting  air-dried  aloin  of  constant  composition, 
however,  is  so  great  that  the  result  is  not  of  much  value. 
Dr.  Tilden  found  that  air-dried  zanaloin  when  dried  over  sulphuric 
acid  in  a  vacuum,  gave  off  about  14  per  cent,  of  water. 
In  addition  to  the  above  work,  the  following  comparative  observa- 
tions were  made;  in  making  them  some  of  my  aloin  from  Jafferabad 
