AmAp0r^r;l?ohl?^m•}  Production  of  Nitric  Acid.  171 
The  process  proposed  is  to  dissolve  I  gramme  mastic  in  50  c.c. 
benzine,  add  10  c.c.  decinormal  alcoholic  and  10  c.c.  decinormal 
aqueous  potassium  hydrate  solution  and  put  aside  for  twenty-four 
hours  in  a  closely  stoppered  bottle,  occasionally  shaking.  At  the 
end  of  this  time  the  mixture  is  titrated  with  decinormal  sulphuric 
acid,  using  phenolphtalein  as  indicator,  but  adding  no  water.  The 
difference  between  20  and  the  number  of  cubic  centimetres  of  deci- 
normal sulphuric  acid  used  multiplied  by  28  gives  the  acid  number. 
This  method  was  used  in  the  examination  of  the  mastic  samples 
above  referred  to. 
No.  1  was  a  blank  experiment  made  without  the  addition  of  any 
mastic  and  required  19  9  c.c.  sulphuric  acid  for  neutralization,  and 
this  number  was  used  in  place  of  20  mentioned  above. 
No.  2  was  the  white  sample  referred  to  in  the  beginning  and  re- 
quired 17-85  c.c.  sulphuric  acid  ;  19-9  —  17*85  =  2-05  X  28  =  57-4. 
No.  3  was  of  a  pale  yellowish  tint  and  required  17-4  c.c.  sulphuric 
acid  ;  19-9  —  17-4  =  2-5  X  28  =  70. 
No.  4  was  like  No.  3  in  color,  a  pale  yellow,  and  required  17-8 
c.c.  sulphuric  acid  ;  1.9-9 —  l7'%  —  21  X  28  =  58-8. 
No.  5  was  of  a  deep  yellow  color  and  required  17  8  c.c.  sulphuric 
acid;  19-9 — 17-8  =  2-1  X  28  =  58-8. 
These  acid  numbers  are  similar  to  that  obtained  by  Dieterich  for 
Levantine  mastic,  and  the  samples  behaved  with  alcohol  like  true 
mastic. 
THE  PRODUCTION  OF  NITRIC  ACID  FROM  ATMOS- 
PHERIC NITROGEN. 
By  M.  I.  Wii^BERT. 
It  does  not  seem  to  be  generally  understood  that  the  production 
of  nitric  acid  and  the  various  nitrates  by  the  combustion  of  atmos- 
pheric nitrogen  is  one  of  the  immediate  possibilities  of  the  future. 
Text-books  on  chemistry,  when  speaking  of  the  chemical  properties 
of  nitrogen,  usually  content  themselves  by  asserting  that  nitrogen 
is  neither  combustible  nor  is  it  a  supporter  of  combustion.  And 
while  this  is  true  in  the  ordinary  sense  of  the  word,  or  under  ordi- 
nary conditions,  nevertheless,  it  has  be^n  known  for  many  years 
that  nitrogen  is  combustible  under  favorable  conditions,  and  the 
only  reason  why  we  are  not  enveloped  in  a  sea  of  nitric  acid,  instead 
ora  mixture  of  nitrogen  and  oxygen,  is  because  the  ignition  point 
of  nitrogen  is  higher  than  the  temperature  of  its  flame. 
