140  INDUSTRIAL  APPLICATION  OF  BARYTA. 
and  chloride  of  barium  treated  in  the  same  way  furnishes  this 
sulphate  and  muriatic  acid. 
The  nitric  acid  furnished  by  the  new  process  marks  10°  B., 
and  may  be  employed  directly  in  the  preparation  of  certain  ni- 
trates ;  the  muriatic  acid,  although  its  density  does  not  exceed 
6°  B.?  may  find  numerous  applications,  besides  its  employment 
in  the  production  of  certain  chlorides ;  it  may  be  used  in  the 
acidification  of  bones,  in  washing  animal  charcoal,  in  the  compo- 
sition of  acid  bleaching  baths,  &c. 
With  the  view  of  ascertaining  the  limits  within  which  the 
concentration  of  these  acids  should  be  restrained  in  order  to 
avoid  loss  by  vaporization,  the  author  made  a  series  of  experi- 
ments, from  which  it  appears — -1st,  that  the  dilute  nitric  acid 
cannot  be  directly  concentrated  beyond  20°  or  25°  B. ;  and 
2ndly,  that  the  direct  concentration  of  the  muriatic  acid  cannot 
exceed  14°  B.,  and  that  it  is  better  to  stop  below  this  limit. 
The  maximum  fixity  of  hydrochloric  gas  in  solution  is  at  a  density 
of  14°  B. ;  its  boiling-point  is  then  228°  F. 
Manufacture  of  tartaric  acid. 
Tartaric  acid  is  prepared  from  bitartrate  of  potash  by  satu- 
rating the  excess  of  acid  of  that  salt  with  native  carbonate  of 
baryta,  and  decomposing  the  neutral  tartrate  by  means  of  chloride 
of  barium.  The  ebullition  of  a  solution  of  bitartrate  of  potash 
with  native  carbonate  of  baryta  produces  a  liquid  which  is  per- 
fectly neutral,  and  may  even  be  slightly  alkaline. 
The  tartrate  of  baryta  thus  obtained  is  well  washed  with  cold 
water,  heated,  and  decomposed  with  dilute  sulphuric  acid,  in 
sufficient  quantity  to  remove  the  whole  of  the  baryta  of  the  tartrate. 
The  solution  furnishes  tartaric  acid,  the  whole  of  which  crystal- 
lizes readily ;  the  deposit  of  very  heavy  sulphate  of  baryta  is 
washed  by  decantation,  and  the  washing-waters  may  be  used  to 
dilute  the  sulphuric  acid  intended  for  new  operations.  This 
substitution  of  baryta  for  lime  in  the  manufacture  of  tartaric 
acid  has  the  advantages  that  the  base  employed  is  used  in 
the  form  of  artificial  sulphate  of  baryta,  and  this  sulphate 
separates  from  the  tartaric  acid  with  greater  rapidity  than 
sulphate  of  lime,  which  is  very  bulky,  and  is  moreover  very 
soluble  in  acid  liquids. 
