PREPARATION  OF  THE  SULPHATE  OF  ALUMINA. 
45 
difficult  to  dissolve,  and  which  is  now  under  closer  examination. 
— Phar.  Jour,  from  Ann.  d.  Qhem.  und  Pharm.,  Bd.  lxxxi. 
ON  THE  PREPARATION  OF  THE  SULPHATE  OF  ALUMINA. 
By  MM.  Huria  and  Brunei,. 
Sulphate  of  ammonia  and  alumina  is  placed  in  shallow  earthen- 
ware vessels  in  a  drying  furnace.  When  it  has  lost  all  its  water 
of  crystallization,  it  is  powdered  and  placed  in  a  cast-iron  cylin- 
der, one  end  of  which  is  closed  with  an  iron  cover,  which  is  luted 
air-tight.  From  the  other  end  of  the  cylinder  a  bent  cast-iron 
tube  issues,  which  is  connected  with  leaden  tubes  perforated  with 
a  number  of  holes,  and  tying  horizontally  in  a  wooden  water- 
cistern  lined  with  lead;  the  water  must  absorb  the  gas  evolved. 
A  safety-tube  prevents  the  rising  of  the  water  into  the  cylinder. 
The  products  of  the  decomposition  of  the  sulphate  of  ammonia 
and  alumina  are  now  to  be  expelled  at  a  cherry-red  heat ;  the  sul- 
phate of  alumina  remains  in  the  cylinder.  The  sulphite  of  am- 
monia that  goes  over  serves  again  for  the  preparation  of  the  alum, 
after  being  changed  into  sulphate  of  ammonia  by  oxidation  in 
the  air.  The  drying-furnace  lies  above  the  furnace  in  which  the 
cylinder  is  heated  to  redness,  and  is  heated  by  it. — Bull,  de  la 
Soc.  d'  Encourag.,  1852,  p.  199,  and  Ohem.  Graz.,  Sept.  15. 
ON  THE  MrCPvOSCOPE,  AS  A  MEANS  OF  DETECTING  THE 
ADMIXTURE  OR  ADULTERATION  OF  DRUGS. 
"  You  are  doubtless  conversant  with  the  recent  very  extensive 
employment  of  the  microscope  for  disclosing  the  adulteration  of 
food.  No  less  useful—no  less  powerful  is  it  in  disclosing  the 
contamination  of  drugs  ;  and  I  cannot  too  strenuously  recommend 
you  to  employ  it."  Such  was  the  language  used  by  Dr.  Pereira, 
in  his  introductory  lecture  on  Materia  Medica,  delivered  this 
year  at  the  Pharmaceutical  Society. 
Many  persons  of  no  mean  skill  in  chemistry,  smiled  incredu- 
lously at  the  results  obtained,  when  they  ascertained  that  the 
principal  instrument  employed  by  Dr.  Hassal,  the  Lancet  com- 
missioner, in  detecting  the  adulteration  of  substances  used  as 
food,  was  the  microscope.    We  confess  that  we  entertained  con- 
