96 
Action  of  Nitrtc  Acid  on  Metals. 
i  Am.  Jour.  Pharm. 
t       Feb  ,  im. 
the  concentration  of  the  acid  increases;  nitric  peroxide  is  the  main 
gaseous  product  with  50  per  cent.  acid.  Neither  nitrogen  nor 
nitrous  oxide  is  formed. 
No  appreciable  amount  of  ammonia  is  produced  in  the  reaction 
between  copper  and  3  or  27-5  per  cent  nitric  acid.  Dilute  acid 
(below  30  per  cent.)  yields  only  nitric  oxide  and  nitrous  acid ;  with 
stronger  acid,  the  gas  evolved  is  principally  nitrogen  tetroxide,  but 
small  quantities  of  the  trioxide  are  also  formed.  With  acid  of  less 
than  30  per  cent,  concentration,  the  reaction  is  represented  by  the 
equation  Cu  +  3HNO3  =  Cu(N03)2  +  HN02  -  H20.  Nitric  oxide 
is  then  formed  in  accordance  with  the  equation  3HNCX  =  2NO  — 
HNO3  -}-  H20.  Nitric  peroxide  only  is  obtained  with  70  per  cent, 
acid. 
Below  1 50,  nitric  acid  of  all  concentrations  attacks  pure  lead  very 
slowly  ;  rather  dilute  acid  acts  the  most  rapidly.  Small  quantities 
of  ammonia  are  formed,  the  amount  being  greatest  with  weak  acid. 
The  action  of  nitric  acid  (27-5  and  70  per  cent.)  on  bismuth  yields 
neither  ammonia,  nitrogen,  nor  nitrous  oxide.  More  nitric  oxide  is 
obtained  with  dilute  than  with  concentrated  acid,  and  owes  its  origin 
to  secondary  action.  27-5  per  cent,  acid  gives  no  nitric  peroxide,  but 
this  gas  is  the  main  product  if  70  per  cent,  acid  be  employed. 
The  reaction  between  nitric  acid  and  aluminium  proceeds  very 
slowly;  with  27-5  per  cent,  acid  no  ammonia  was  obtained. 
Mercury  yields  no  ammonia  with  27  and  50  per  cent,  acid;  the 
quantity  of  nitric  oxide  produced,  diminishes  as  the  concentration 
increases.  27-5  per  cent,  acid  gives  no  nitric  peroxide,  but  stronger 
acid  yields  large  quantities  just  as  in  the  cases  of  copper  and 
bismuth.  Mercurous  nitrate  is  obtained  in  solution  on  operating 
with  25  per  cent,  acid ;  more  concentrated  acid  (50-70  per  cent.) 
gives  the  mercuric  salt. 
Nitric  acid  (27-5  per  cent.)  gives  no  ammonia  with  silver,  but  only 
nitric  oxide  and  nitrous  acid. 
The  amount  of  ammonia  produced  in  the  reaction  between 
magnesuim  and  nitric  acid  increases  with  the  concentration  of  the 
latter  until  40  per  cent,  acid  is  reached,  the  quantity  then  decreases. 
Much  hydrogen  is  formed ;  the  mixture  of  this  gas  and  nitric  oxide 
liberated  by  13  per  cent,  acid  may  be  exploded  by  an  electric  spark. 
Ammonia  is  produced  by  the  action  of  nitric  acid  on  manganese ; 
so  much  hydrogen  is  formed  that  the  evolved  gas  will  not  explode 
