Am.  Jour.  Pharm.  i 
Aug.,  1880.  J 
Chemical  Notes, 
399 
become  affected  to  a  depth  equal  to  the  thickness  of  a  finger,  the  iron 
being  changed  into  a  friable  mass,  which  consist  essentially  of  dark 
bluish-violet  crystalline  scales.  Two  samples  of  these  were  found  to 
consist  of:  ^ 
Ferric  oxide,  .  .  .    88  01  87*92 
Manganic  oxide,  .  .  1*61  i*66 
Water,        ....    loii  10-30 
corresponding  to  the  formula  H2Fe204. — Ber.  der  Chem.  Ges.^  xiii,  p. 
725- 
Purification  of  Sulphuric  Acid  from  Arsenic. — According  to  F.  Selmi, 
sulphuric  acid  can  be  readily  freed  from  arsenic  if  the  sulphuric  acid, 
diluted  with  half  its  bulk  of  water,  be  distilled  after  addition  of  some 
plumbic  chloride.  All  the  arsenic  goes  over  with  the  first  portions  of 
the  distillate  as  arsenic  chloride. — /^/V.,  p.  206. 
Preparation  of  Phosphoric  Acid. — Phosphoric  acid  may  be  readily  pre 
pared  by  covering  a  stick  of  vitreous  phosphorus  with  water,  adding  a 
crystal  or  two  of  iodine  and  some  nitric  acid,  and  allowing  the  mixture 
to  stand  for  24  to  36  hours.  After  the  oxidation  is  complete  the  solu- 
tion is  evaporated  and  treated  as  the  Pharmacopoeia  directs.  The 
advantages  presented  by  this. method  are  economy  of  material  and  con- 
sequent safety,  and  the  indefinitely  large  quantities  of  phosphorus  which 
can  be  oxidized  by  a  very  small  quantity  of  iodine.  The  theory  of  the 
process  is  based  on  the  discovery  of  Brodie  ("Jour.  Chem.  Soc,"  1852, 
p.  289),  that  the  iodine  converts  the  vitreous  phosphorus  into  the  amor- 
phous variety  which  is  oxidized  by  the  nitric  acid.  This  method  differs 
from  that  of  Pettenkolfer,  who  treats  phosphorus  iodide  with  water,  and 
obtains  phosphorus  acid  which  is  oxidized  by  nitric  acid. — Phar.  four, 
and  Trans.  [3],  lO,  p.  468. 
Preparation  of  Phosphates. — A  great  technical  advance  frequently 
carries  with  it  minor  improvements  in  its  wake.  Such  is  the  case  with 
the  newly-devised  process  of  the  English  metallurgist,  Sidney  Gilchrist 
Thomas,  for  dephosphorizing  iron  ores.  The  elimination  of  the  phos- 
phorus from  the  cast-iron  in  this  process  is  effected  by  lining  the  fur- 
naces with  a  very  basic  fire-brick,  rich  in  magnesia.  Thomas  has  just 
patented  in  England  a  process  for  recovering  from  the  slags  all  the 
phosphate  so  formed.  The  slags  are  broken  up  and  treated  with 
hydrochloric  acid.  The  filtered  solution  is  then  evaporated  and  the 
residue  calcined  at  low  temperatures  to  drive  out  the  adhering 
hydrochloric  acid,  without  decomposing,  however,  the  ferric  or  man- 
