418         ON  THE  PREPARATON  OP  FUMING  NITRIC  ACID. 
phuric  acid,  which  must  be  added  very  slowly,  otherwise  the  heat 
produced  will  cause  the  spirit  to  boil  and  project  the  acid  vio- 
lently from  the  tube.  If  the  spirit  is  impure,  the  mixture  will 
immediately  become  colored,  and  if  but  slightly  so,  it  is  best  to 
examine  it  by  looking  down  through  the  open  end  of  the  tube. 
The  color,  if  any,  becomes  deeper  on  standing  some  hours,  but 
generally  a  few  minutes  will  suffice  to  determine  as  to  the  purity 
of  the  spirit  under  consideration. 
I  have  tried  the  above  test  on  spirits  of  different  strength,  from 
absolute  alcohol  to  proof  spirit,  and  find  that  the  water  in  the 
latter  does  not  perceptibly  affect  the  test,  when  the  quantity  of 
sulphuric  acid  used  is  equal  to  that  of  the  spirit  to  which  it  is 
added. — New  York  Journal  of  Pharmacy,  Aug.  1854. 
ON  THE  PREPARATION  OF  FUMING  NITRIC  ACID. 
By  Prof.  C.  Brunner. 
A  mixture  of  100  parts  of  crystallized  nitrate  of  potash  and  5 
parts  of  flowers  of  sulphur  is  put  into  a  retort,  and  100  parts  of 
English  sulphuric  acid  are  poured  over  it.  With  large  quantities, 
the  best  plan  is  to  add  the  acid  in  fractions,  as  the  mixture  be- 
comes considerably  heated.  It  is  now  distilled  with  a  gentle 
heat  into  a  well-cooled  receiver,  when  a  fuming  acid  of  a  strong 
red  color  passes  over  from  the  commencement.  After  a  time 
the  sulphur  separates  from  the  mixture,  and  floats  on  the  fluid 
with  a  pure  yellow  color.  From  this  time  little  more  fuming 
nitric  acid  passes  over,  its  place  being  taken  by  the  ordinary  acid. 
It  is,  therefore,  advisable  to  change  the  receiver.  If  about  50 
parts  of  the  above-mentioned  mixture  have  gone  over,  this  is 
about  the  right  proportion. 
The  acid  thus  obtained  is  very  strongly  fuming,  and  of  a  red 
color.  It  contains  a  considerable  portion  of  sulphuric  acid,  as 
may  be  shown  by  its  reaction  with  chloride  of  barium.  If  it  be 
again  distilled  by  itself  with  a  gentle  heat  in  a  retort  furnished 
with  a  long  tube  attached,  without  luting,  to  the  neck  of  the  retort, 
a  very  strongly  fuming  acid,  quite  free  from  sulphuric  acid,  passes 
over;  this  separates  into  two  strata,  of  which  the  upper  is  the 
fluid  substance  which  was  regarded  by  Berzelius  as  nitrate  of 
oxide  of  nitrogen,  by  others  as  hyponitrous  acid,  but  which  is 
