^""'Mar '"ifs'a^'""* }  RelaHon  of  Acids  of  Nitrogen  to  Sulphuric  Acid,   1 5 1 
one  hour  ;  any  free  nitrogen  tetroxide,  if  it  were  present,  must  have 
been  thus  expelled.  When  the  temperature  rose  to  200°,  a  little  red 
vapor  was  evolved,  and  the  liquid  acquired  a  golden-yello color  ;  but 
on  cooling,  it  again  became  colorless. 
On  analysis  the  author  calculated  that  77*9  per  cent,  of  the  nitrogen 
present  existed  as  N2O3,  and  21 'i  per  cent  as  HNO3;  there  is  conse- 
quently, he  says,  a  large  amount  of  the  nitric  acid  driven  off  and  another 
part  changed  into  nitrous  acid. 
(11.)  On  continuing  to  heat  for  one  hour  longer,  a  further  change 
took  place  of  the  same  kind,  and  94*5  per  cent,  of  the  nitrogen  remain- 
ing existed  as  N2O3,  in  combination  with  the  sulphuric  acid  forming 
nitrosulphuric  acid  ;  whilst  5*5  per  cent,  remained  as  HNO3,  and  18 
per  cent,  of  the  nitrogen  originally  present  having  been  expelled  by  the 
heating. 
(III.)  Another  experiment  was  made  by  adding  pure  nitric  to  pure 
sulphuric  acid,  and  analyzing  the  resulting  mixture,  but  no  change  was 
found  to  have  taken  place. 
(IV.)  On  boiling  the  mixtures  for  half  an  hour,  however,  red  fumes 
were  given  ofF,  and  the  whole  of  the  nitrogen  present  was  converted 
into  nitrous  acid,  which  was  found  in  combination  with  the  sulphuric 
acid. 
That  nitric  acid  is  thus  broken  up  has  also  been  demonstrated  in 
another  way  by  Winkler,  who  collected  the  oxygen  which  was  evolved 
from  the  decomposition. 
The  author  did  not  find  the  same  result  as  Winkler  with  sulphuric 
acid  of  66°B.  above  mentioned,  and  he  explains  this  hyy  assuming  that 
Winkler  employed  so  much  nitrogen  tetroxide  that  it  left  a  large  excess 
beyond  that  which  could  combine  with  the  sulphuric  acid  as  nitrous 
acid  :  hence  the  sudden  and  violent  ebullition  and  liberation  of  nitrogen 
tetroxide  on  heating  the  mixture. 
2  cc.  nitrogen  tetroxide  added  to  sulphuric  acid  of  1*805  specific 
gravity  was  broken  up  into  practically  the  same  proportions  of  nitrous 
and  nitric  acids  as  in  the  first  experiment,  with  acid  of  1*84  specific 
gravity. 
Other  experiments  are  described  in  which  sulphuric  acid  of  1*75 
specific  gravity  was  mixed  with  nitrogen  tetroxide  and  then  heated  (^7),  so 
that  the  vapor  evolved  might  at  once  escape,  and  {f)  where  a  long  tube 
was  attached  to  the  flask  in  which  the  mixture  was  heated,  so  that  the 
vapor  might  condense  and  flow  back  again  to  the  acid  in  the  flask.  In 
