546        Recent  Literature  Relating  to  Pharmacy.    { Af0VJe0mber,hS' 
The  presence  of  tartaric  acid  was  also  suspected,  and,  on  submit- 
ting the  article  to  the  test  outlined  by  the  U.S. P.  for  detecting  this 
acid,  its  presence  was  indicated.  But  a  microscopical  examination 
of  the  small  crystals,  which  were  supposed  to  be  potassium  acid 
tartrate,  showed  that  the  crystalline  structure  did  not  correspond  to 
that  of  potassium  bitartrate.  Further  examination  proved  the  pre- 
cipitate to  be  potassium  sulphate.  Potassium  sulphate  being  mod- 
erately insoluble  in  water,  the  addition  of  potassium  acetate  to  a 
saturated  solution  of  the  effervescing  salt,  containing  an  abundance 
of  sulphate,  naturally  favored  the  production  of  the  above  chemi- 
cal. The  pharmacopceial  test  for  tartaric  acid  cannot,  therefore,  be 
applied  to  effervescing  magnesium  citrate  containing  much  sul- 
phate. 
RECENT  LITERATURE  RELATING  TO  PHARMACY. 
A  STUDY  OF  ALOIN. 
The  work  of  Tschirch  and  Pederson,  in  tracing  the  analogy  of 
aloin  to  the  oxy-methyl-anthraquinones,  received  confirmation  in  an 
investigation  reported  by  O.  A.  Oesterle  (Arch,  der  Pharm.,  1899,  81). 
He  mixed  an  alcoholic  solution  of  aloin  (which  had  been  freed  from 
emodin  by  ether  extraction)  with  concentrated  aqueous  hydrochloric 
acid  and  heated  mixture  from  eighteen  to  twenty-four  hours  on  a 
water-bath  in  a  flask  with  return  condenser.  After  standing  some 
weeks,  a  crystalline  substance,  giving  that  cherry  coloration  so 
characteristic  of  the  natural  oxymethyl  anthraquinones,  separated 
from  this  mixture. 
The  crude  product,  purified  by  sublimation,  or,  better,  by  crystal- 
lization from  toluol,  after  decolorizing  with  animal  charcoal,  melted 
at  232°-233°  C.,  and  corresponded  on  analysis  to  the  formula 
An  acetyl  derivative  was  prepared  by  boiling  an  hour  with  acetic 
anhydride  and  sodium  acetate,  and  analysis  of  the  purified  product, 
which  melted  at  iyy°-iyS°C>  indicated  a  di-acetyl  body  of  for- 
mula C)5H8(C,1  LOjoO-.  The  three  emodins  from  frangula,  rhubarb 
and  aloes,  respectively,  show  the  formula  C15H10O5,  and  of  these, 
aloe-emodin  melts  most  nearly  the  new  product.  To  confirm  iden- 
tity, the  writer  prepared  the  acetyl  derivative  of  aloe-emodin,  and 
found  it  the  same  as  that  obtained  above,  hence  he  decides  that  hy- 
