336        ON  THE  MANUFACTURE  OF  TARTARIC  ACID,  ETC. 
or  hydrochloric  acid  is  added  in  the  proportions  above  mentioned. 
The  bitartrate  of  potash,  which  is  precipitated,  is  allowed  to  set- 
tle, and  the  supernant  solution  is  decanted  or  filtered  from  the 
deposited  bitartrate  of  potash.  The  solution  separated  is  neu- 
tralized with  sulphide  or  sulphides  of  sodium,  and  concentrated 
by  evaporation,  when  sulphuric  or  hydrochloric  acids  are  to  be 
added  to  decompose  the  tartrate  of  potash  and  soda  existing  in 
the  concentrated  solution,  and  they  are  to  be  added  until  no 
further  precipitate  of  bitartrate  of  potash  is  occasioned  by  the 
addition  of  the  same  to  the  said  solution.  The  said  solution,  be- 
ing separated  from  the  precipitated  bitartrate  of  potash,  and  neu- 
tralized by  means  of  sulphides  of  sodium  as  before  mentioned,  is 
to  be  evaporated,  in  order  that  the  salts  of  soda  (sulphate  of  soda 
or  chloride  of  sodium)  may  be  separated  by  means  of  crystal- 
lization. The  mother-liquor  remaining  will  contain  a  small 
quantity  of  tartrate  of  potash  and  soda,  which  may  be  decom- 
posed by  means  of  sulphuric  or  hydrochloric  acid  as  before  men- 
tioned, or  may  be  mixed  with  mother-liquors  resulting  from  a 
subsequent  operation. 
Mr.  Gatty's  process  for  obtaining  tartrate  of  lime  to  be  used 
for  the  manufacture  of  tartaric  acid,  conjointly  with  carbonate  of 
soda  or  potash,  consists  in  decomposing  solutions  of  the  neutral 
tartrate  of  potash  and  neutral  tartrate  of  soda  by  means  of  car- 
bonic acid  gas  or  carbonate  of  lime,  and  is  performed  in  the  fol- 
lowing manner  : — Into  a  cylindrical  wooden  vessel,  of  the  capa- 
city of  about  400  gallons,  300  gallons  of  solution  of  neutral  tar- 
trate of  potash,  marking  5°  of  Twaddell's  hydrometer,  are 
introduced  through  an  opening  in  the  top  of  the  vessel.  34  gal- 
lons of  milk  of  lime,  each  gallon  containing  one  pound  of  lime, 
are  then  added,  and  the  opening  closed  by  means  of  an  air-tight 
cover.  Carbonate  of  lime,  or  a  mixture  of  carbonate  of  lime  and 
lime,  may  be  employed  instead  of  lime  only.  An  agitator,  pass- 
ing through  an  air  and  steam-tight  stuffing  box  in  the  top  of  the 
vessel,  is  then  set  in  motion,  and  a  current  of  carbonic  acid  gas 
passed  into  the  mixture  until  its  complete  saturation  is  effected. 
The  result  is,  that  bicarbonate  of  potash  and  tartrate  of  lime  are 
formed,  the  former  of  which  remains  in  solution,  whilst  the  lat- 
ter is  precipitated  to  the  bottom  of  the  vessel.  The  clear  solu- 
tion of  bicarbonate  of  potash  is  now  run  off,  and  the  tartrate  of 
