236         ON  THE  EXTRACTION  OF  POTASSA  FROM  MARL. 
poisonous  metal,  the  nitric  acid  may,  and  the  muriatic  acid  must, 
contain  the  same.  But  its  absence  in  two  or  three  samples  does 
not  prove  yet  that  it  may  not  be  found  in  the  fourth  one.  The 
only  way  to  get  at  positive  results  is,  to  subject  every  sample 
to  a  rigid  examination,  which  is  at  once  a  very  interesting  and 
a  very  easy  process  of  manipulation. 
The  decision,  however,  at  which  we  arrive  from  these  experi- 
ments is,  that  acids  of  American  manufacture  are  of  the  same 
purity,  as  far  as  arsenic  is  concerned,  as  those  of  foreign  origin. 
While  I  have,  on  former  occasions,  occasionally  met  with  arsenic 
in  American  oil  of  vitriol,  yet  this  metal  does  not  constitute  one 
of  the  impurities  of  every  sample,  and  the  acids  produced  by 
the  same  manufacturer  are  likely  to  vary  considerably  in  this 
respect. — Proceed.  Amer.  Pharm.  Assoc.,  1863. 
ON  THE  EXTRACTION  OF  POTASSA  FROM  MARL. 
By  George  J.  Scattergood. 
The  green  sand  or  marl  of  New  Jersey,  according  to  analysis, 
contains,  among  other  constituents,  from  10  to  12  per  cent,  of 
potassa.  Query.  "  Can  this  potassa  be  economically  extracted 
sufficiently  pure  for  pharmaceutical  and  commercial  use,  so  as 
to  compete  in  price  with  that  derived  from  wood  ashes  ?  " 
The  experiments  -which  have  been  performed  in  reference  to 
this  question  require  that  it  should  be  answered  decidedly  in 
the  negative.  The  small  proportion  of  potassa,  and  the  very 
insoluble  form  in  which  it  exists  in  the  green  sand,  are  insuper- 
.  able  obstacles  to  the  latter  ever  becoming  a  cheap  source  of 
commercial  potash.  The  results,  however,  which  have  been  ob- 
tained are  not  entirely  devoid  of  interest,  since  they  show  the 
effects  of  certain  agents  upon  a  substance  whose  chemical  na- 
ture is  as  yet  but  little  known. 
The  earlier  analyses  of  green  sand  have  shown,  as  above 
stated,  the  large  amount  of  10  or  12  per  cent,  of  potassa.  But 
later  investigations,  performed  by  improved  methods,  have  not 
confirmed  their  accuracy ;  but,  on  the  contrary,  have  pointed  to 
the  fact,  that  the  alkali,  previously  estimated  as  potassa  only,  is 
in  part  soda,  and  that  the  average  amount  of  the  former  through- 
out the  green  sand  formation  in  New  Jersey  does  not  probably 
average  more  than  5  per  cent. ;  and  from  but  few  specimens  can 
