PRODUCTION  OF  VALUABLE  MANURE  FROM  THE  AIR.  547 
of  the  highest  interest  to  agriculture.  But  to  arrive  at  this 
result  it  is  necessary  to  obtain  the  nitrogen  elsewhere  than  in 
nitrogenous  matters  ;  which  may,  for  the  most  part,  be  employed 
directly  as  manures,  and  of  which  the  limited  quantities  and 
elevated  price  permits  in  any  event  only  restricted  and  costly 
manufacture. 
Atmospheric  air  is  an  inexhaustible  and  gratuitous  source  of 
nitrogen.  However,  this  element  presents  so  great  an  indiffer- 
ence in  its  chemical  reactions,  that,  notwithstanding  the  nume- 
rous attempts  which  have  been  made,  chemists  have  not  hereto- 
fore succeeded  in  combining  it  with  hydrogen  so  as  to  produce 
ammonia,  artificially.  This  result,  so  long  desired,  has  been 
reserved  for  MM.  Margueritte  and  De  Sourdeval,  who  have  ob- 
tained it  by  employing  an  agent  of  which  the  remarkable  pro- 
perties and  neat  and  precise  reactions  have  permitted  them  to 
succeed  where  all  others  have  failed.  This  agent  is  baryta,  of 
which  notice  has  recently  been  taken  on  account  of  the  recent 
applications  that  M.  Kuhlmann  has  made  of  it  in  painting,  but 
of  which  no  person  suspected  the  part  that  it  was  to  be  called 
to  play  in  the  development  of  the  agricultural  riches  of  our 
country.  The  manufacture  of  ammonia  is  based  on  a  fact  en- 
tirely new,  the  cyanuration  of  barium.  It  had  been  believed 
until  the  present  time  that  potash  and  soda  alone  had  the  pro- 
perty of  determining  the  formation  of  cyanogen  ;  that  the  earthy 
alkaline  bases — baryta,  for  example,  could  not,  in  any  case, 
form  cyanides. 
Messrs.  Margueritte  and  De  Sourdeval  have  ascertained  that 
this  opinion  is  entirely  erroneous,  and  that  baryta,  much  better 
than  potash  or  soda,  fixes  the  nitrogen  of  the  air  or  of  animal 
matters  in  considerable  proportions.  It  is  already  understood 
that,  for  the  preparation  of  Prussian  blue,  the  cyanide  of  barium 
presents  great  advantages  over  that  of  potassium,  for  the 
equivalent  of  baryta  costs  only  about  the  one-seventh  of  that  of 
potash.  Thus  do  we  find  practically  and  really  obtained  the  result 
first  announced  by  Desfosses  and  vainly  pursued  in  France  and 
England,  the  manufacture  of  cyanides  from  the  nitrogen  of  the 
atmospheric  air.  This  solution,  so  important,  depends  on  the 
essential  difference  which  exists  between  the  properties  of  baryta 
and  those  of  potash ;  the  first  is  infusible.^  fixed,  porous,  and 
