288        Pharmaceutical  Notes  from  Purdue  University.  {Amju°nUe^iS6arm' 
The  so-called  "Commercial  Saltpetre" — The  wide  range  of  prices 
among  the  several  brands  of  genuine  saltpetre  is  insufficient  to 
meet  all  demands,  and  venders  of  horse  medicine  require  a  cheaper 
article  to  mix  with  their  "  black  antimony/' 1  etc.  Nitrate  of  sodium 
(which  is  largely  imported  from  Chili,  as  a  fertilizer)  is  naturally  sug- 
gested as  a  substitute.  The  deliquescent  character  of  this  salt  is  well 
known,  making  it  unfit  for  ordinary  gunpowder.  It  would  probably 
be  unsatisfactory  in  curing  meat,  and  should  not  on  any  account  be 
substituted  for  nitrate  of  potassium  in  filling  prescriptions.  Number 
9  consists  of  coarse  lumps  or  crystals  of  this  salt,  many  of  them  show- 
ing plainly  in  crystalline  form  that  they  are  not  the  genuine  or  "  pris- 
matic" saltpetre.  Some  pieces  were  white,  others  were  stained  on  the 
outside  with  a  reddish  tinge,  but  both  kinds  were  nearly  free  from 
chloride. 
Number  10  was  given  to  me  with  the  statement  that  it  was  merely 
rock  salt,  used  as  a  substitute  for  saltpetre.  It  proved,  however,  to 
contain  two  distinct  materials  in  coarse  lumps  mixed  together.  Some 
of  these,  which  could  easily  be  distinguished  by  their  similarity  to 
number  9,  proved  to  be  nitrate  of  sodium.  After  careful  washing, 
these  were  dissolved,  and  gave  a  mere  turbidity  with  nitrate  of  silver 
and  very  slight  opalescence  with  oxalate  of  ammonium.  The  other 
material,  which  gave  no  reaction  for  nitric  acid,  was  chloride  of 
sodium,  with  traces  of  sulphate  of  calcium.  Many  imperfect 
crystals  were  marked  by  faces  meeting  at  right  angles.  After 
careful  sampling  number  10  was  found  to  contain  75'4  per  cent,  of 
chloride. 
Number  11  consisted  of  rock  salt  alone,  Avith  a  less  proportion  of 
calcium  sulphate  than  the  lumps  of  salt  in  number  10. 
The  samples  of  nitrate  of  sodium  were  also  tested  for  iodine  with 
negative  results. 
Conclusions. — So  far  as  observed,  the  goods  offered  as  pure  salt- 
petre contain  no  impurities  which  are  likely  to  be  hurtful,  but  druggists 
should  be  careful  to  purchase  from  reliable  houses,  and  never  to  dis- 
pense as  saltpetre  that  which  will  impart  a  yellow  color  to  an  alcohol 
flame. 
Those  who  have  occasion  to  use  "commercial  saltpetre"  should  note 
whether  it  is  nitrate  or  chloride  of  sodium,  or  a  mixture  of  both. 
1  See  report  on  Antimonii  Sulphidum,  above. 
