NEW  MODE  OF  PREPARING  RED  OXIDE  OE  IRON. 
69 
due  dissolved  in  a  small  quantity  of  boiling  alcohol,  and  filtered. 
The  filtrate  was  allowed  to  evaporate  nearly  to  dryness,  when 
yellowish-colored  crystals  were  deposited.  These  were  pressed 
between  folds  of  bibulous  paper  and  recrystallized  out  of  spirits 
of  wine,  when  they  were  rendered  perfectly  colorless.  After 
being  dried  on  the  water-bath,  they  were  weighed,  when  the 
twenty-five  grammes  gave  1.260  grammes,  equal  to  5.04  per 
cent. 
A  second  determination,  in  which  fourteen  grammes  were  used, 
gave  0.715  grammes,  equal  to  5.1  per  cent. 
Average  of  the  two  determinations,  5.07  per  cent. 
In  addition  to  theine,  guarana  contains  a  coloring  matter,  ap- 
parently analogous  to  the  tannin  in  cinchona  bark,  and  likewise 
a  fatty  matter  which,  like  the  fat  of  chocolate,  does  not  appear 
to  become  rancid  by  keeping. 
From  an  inspection  of  the  subjoined  table,  it  will  be  seen  that 
guarana  is  the  richest  known  source  of  theine  : — 
Per  cent,  of  Theine. 
Guarana       ...         ...  5.07 
Good  Black  Tea    .  ...  2.13 
Black  Tea  from  Kemaon,  E.  I.        .       .  1-97 
Various  samples  of  Coffee  Beans,  from  0-8  to  1.00 
Dried  Coffee  Leaves,  from  Sumatra         .  1.26 
Paraguay  Tea,  from  Ilex  Paraguay ensis  1-2 
Pharmaceutical  Journal,  October,  1856. 
ON  A  NEW  MODE  OF  PREPARING  RED  OXIDE  OF  IRON 
("ROUGE")  FOR  POLISHING  GLASS  AND  METALS. 
By  M.  A.  Vogel,  Jim.,  of  Munich. 
We  ordinarily  use  for  polishing  glass  and  metals,  red  oxide  of 
iron  (colcothar,  caput  mortuum  vitrioli),  which  is  procured  in 
various  ways,  either  by  heating  sulphate  of  iron  alone  or  previ- 
ously mixed  with  common  salt,  or  by  several  other  means.  All 
these  processes  have,  however,  the  inconvenience,  that  it  becomes 
indispensable  to  wash  the  powder  for  a  long  time,  in  order  to 
separate  the  finer  from  the  coarser  and  harder  parts.  Even  by 
long  continued  washing,  it  is  difficult  to  arrive  at  absolute  secu- 
rity in  using  it,  without  running  the  risk  of  wasting  the  labor  of 
