330         OX  THE  MANUFACTURE  OP  TARTARIC  ACID,  ETC. 
quantity  to  effect  the  decomposition  of  the  sulphate  of  potash. 
The  solution  thus  obtained  yields  crystals  of  binoxalate  of  potash 
on  evaporation.  The  residuary  mother-liquor  is  dilute  sulphuric 
acid. 
In  these  cases  the  advantage  sought  to  be  obtained  is,  the  use 
of  a  salt  in  the  manufacture  of  binoxalate  of  potash,  yielding  that 
alkali  at  a  more  economical  rate  than  carbonate  of  potash, 
(pearlash),  which  has  hitherto  been  employed  for  this  purpose. 
"  Suppose,  for  instance,'"'  says  Mr.  Firmin,  "100  lbs.  of  cream  of 
tartar  to  contain  25  lbs.  of  potash,  this  I  do  not  value  at  more 
than  2.?.,  after  deducting  the  loss  of  ouantitv  owing:  to  the  difficult 
solubility  of  the  sulphate  (into  which  it  is  converted),  and  the 
cost  of  evaporation,  vrhich,  owing  to  the  same  cause,  is  very  great, 
"while  it  would  require  50  lbs.  of  pearlash,  at  a  cost  of  12s.  6c?., 
to  produce  the  same  quantity,  independently  of  the  gain  upon 
the  purification  of  the  cream  of  tartar  precipitated.  Or  100  lbs. 
of  sulphate  of  potash,  of  SO  per  cent.,  at  8s.  per  cwt.,  will  yield, 
independently  of  sulphuric  acid,  4-1  lbs.  of  potash,  against  88  lbs. 
of  pearlash,  costing  22s." 
Dr.  Price's  improvements  in  obtaining  and  refining  bitartrate 
of  potash  consist  in  rendering  the  bitartrate  of  potash,  contained 
in  crude  argol  and  crude  tartar,  more  soluble,  by  combining  the 
said  bitartrate  of  potash  with  potash,  soda,  or  ammonia,  and  ob- 
taining soluble  double  and  neutral  tartrates  (tartrate  of  potash 
and  soda,  tartrate  of  potash  and  ammonia,  or  tartrate  of  potash) 
which  said  tartrates,  being  separated  from  the  insoluble  impurities 
contained  in  the  said  impure  bitartrate  of  potash,  are  decomposed 
by  means  of  acids  or  acid  salts,  as  after  mentioned,  and  purified 
bitartrate  of  potash  is  obtained  more  economically  and  expedi- 
tiously than  by  the  methods  now  generally  employed.  To  effect 
this  the  following  process  is  adopted: — Crude  argol,  or  crude 
tartar,  or  impure  bitartrate  of  potash,  is  placed  in  a  closed  vessel, 
with  one  or  more  exit  pipes,  capable  of  allowing  any  gas  that 
may  be  generated  to  escape,  or  to  be  conducted  away,  and  into 
such  vessel  is  run  a  solution  of  sulphide  or  sulphides  of  sodium, 
sufficient  to  neutralize  the  bitartrate  of  potash.  The  vessel  is  so 
arranged,  that  artificial  heat  may  be  applied  by  steam  or  other- 
wise, or  that  a  jet  of  steam  may  be  admitted:  the  bitartrate  of 
potash  decomposes  the  sulphide  or  sulphides  of  sodium,  forming 
