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PRODUCTION  OF  NITRE  IN  INDIA. 
OBSERVATIONS  ON    THE   PRODUCTION   OF  NITRE  IN 
INDIA. 
By  Dr.  J.  W.  Palmer. 
The  native  "sorawallahs  "  make  it  the  business  of  their  lives 
to  search  for  saline  incrustations  in  and  around  the  mud  walls 
which  enclose  the  primitive  dwellings  of  the  inhabitants  of  the 
north-western  provinces  of  India.  When  the  appearance  of  the 
soil  indicates  the  existence  of  nitre  they  scrape  off  a  thin  layer 
of  the  impregnated  earth  and  lixiviate  it  in  clay  vessels,  either 
with  water  alone  or  with  the  last  washings  of  a  previous  opera- 
tion, the  solution  thus  obtained  being  poured  into  shallow  pans 
of  unglazed  earthenware,  and  there  left  exposed  to  the  sun  and 
hot  winds  of  a  tropical  climate,  until  the  nitre  crystallizes  out. 
The  crude  product  is  then  partially  purified  by  being  again  dis- 
solved and  recrystalllzed.  The  saltpetre  is  recovered  in  the  form 
of  dingy  prismatic  crystals,  and  common  salt  to  the  amount  of 
from  one  to  nine  per  cent,  is  left  in  the  mother  liquors,  which 
upon  evaporation  to  dryness  is  recovered  and  separately  collected. 
The  sorawallah  makes  periodical  visits,  and  secures  fresh  collec- 
tions of  nitre  from  the  same  spots  of  ground  week  after  week, 
the  rate  of  production  remaining  constant  whilst  the  dwellings 
are  inhabited,  but  decreasing  gradually  if  from  any  cause  the 
villages  are  deserted.  The  physical  features  of  the  nitre-pro- 
ducing regions  were  then  described,  and  the  author  referred  to 
the  conditions  under  which  most  nitre  seemed  to  be  obtained ; 
these  were  dependent  upon  the  existence  in  the  plains  of  India 
of  a  friable,  nodular,  calcareous  rock  called  "  kunkur,"  and  water 
must  not  occur  nearer  the  surface  than  twenty  feet ;  but  it  was 
remarked  that  the  largest  yield  of  nitre  was  furnished  in  the  four 
months  of  the  year  constituting  the  rainy  season,  the  heavy  tro- 
pical rains  having  the  effect  of  washing  the  salt  from  the  depths 
of  the  soil  to  the  surface,  rather  than  of  dissolving  it  out  entirely 
and  carrying  it  into  the  rivers.  The  process  of  nitrification  com- 
menced with  the  conversion  of  urea,  &c,  into  nitrate  of  lime, 
under  the  combined  influences  of  heat,  moisture,  and  of  the  be- 
fore-mentioned calcareous  rock  ;  whilst  the  practice  of  the  natives 
of  throwing  their  wood  ashes  into  the  common  drains  supplied  the 
carbonate  of  potash  from  which,  by  double  decomposition,  the 
