204  EXAMINATION  OF  BITARTRATE  OF  POTASSA. 
EXAMINATION  OF  BITARTRATE  OF  POTASSA. 
By  John  M.  Maisch. 
In  a  former  paper  I  have  pointed  out  the  necessity  and  import- 
ance of  subjecting  the  commercial  drugs  and  chemicals  to  an 
analysis,  at  least  so  far  as  those  impurities  and  adulterations  are 
concerned,  that  are  common  to  the  substances  in  question.  Cream 
of  tartar  is  among  those  articles  which  at  present  command  a  very 
high  price,  and  to  the  adulteration  of  which,  it  might  seem,  there 
is  much  inducement.  Tartrate  of  lime  2CaO,  C8  H4  O10  +  8HO 
is  always  to  be  found  in  the  commercial  cream  of  tartar,  and  can 
not  wholly  be  separated  from  it,  as  it  is  soluble  in  water,  requiring 
about  600  parts  of  boiling  water  to  effect  its  solution.  As  cream 
of  tartar  is  dissolved  by  about  15  parts  of  boiling  water,  it  is 
obvious,  that  the  best  article  of  it  will  still  contain  about  3  per 
cent,  of  the  lime  salt.  Besides  this,  cream  of  tartar  sometimes 
contains  copper,  from  the  copper  vessels  in  which  it  had  been 
purified. 
The  best  way  to  find  these  impurities,  is  by  incineration  in  a 
crucible,  and  extracting  the  residue  with  hydrochloric  acid,  when 
the  chlorides  of  potassium,  calcium,  &c,  will  be  dissolved  ;  from  the 
solution,  copper  will  be  precipitated  by  hydrosulphuric  acid.  Five 
specimens  which  I  have  analysed  were  free  of  copper,  and  I  deter- 
mined the  quantity  of  tartrate  of  lime  by  adding  ammonia  in  excess 
to  the  acid  solution,  precipitating  the  lime  by  oxalate  of  ammonia, 
and  heating  the  obtained  oxalate  of  lime  carefully,  in  order  to 
destroy  the  oxalic  acid  without  expelling  any  carbonic  acid. 
Of  two  specimens,  the  quantity  of  lime  was  determined  by  dis- 
solving the  obtained  chloride  of  calcium  in  alcohol,  and  adding 
sulphuric  acid  diluted  with  some  water,  which  will  precipitate  the 
lime  as  sulphate;  this,  after  separation  and  washing  with  alcohol, 
was  heated  so  as  to  leave  the  anhydrous  sulphate  of  lime, 
CaO  S03. 
From  the  weight  of  the  obtained  carbonate  and  sulphate  of  lime, 
the  amount  of  tartrate  of  lime  was  calculated  in  accordance  with 
the  following  weights  of  equivalent : 
CaO,  C02  50,  CaO,  S03  68,  2  CaO,  C8  H4  Oj0  +  8  HO  260. 
