346 
TARTARIC  ACID  FROM  SUGAR  OF  MILK,  ECT. 
the  mother  liquor  yields  the  fine  needle-like  crystals  of  the 
saccharate  of  potash. 
Two  analyses  of  the  artificially  formed  bitartrate  gave  the 
following  results  : 
Calculation 
I. 
II. 
C8  H5  KOla. 
Potash  . 
24-5 
24.3 
25-06 
Tartaric  acid  . 
75.5 
75.7 
74.94 
100-0 
100-0 
100-00 
By  adding  nitrate  of  silver  to  the  neutral  potash  salt,  a  white 
precipitate  is  thrown  down,  which  quickly  turns  black  in  the 
light.  On  igniting  the  dry  precipitate,  59  per  cent,  of  metallic 
silver  is  left  behind. 
By  neutralising  the  acid  potash  salt  with  soda,  and  slowly 
evaporating  the  solution,  very  beautifully  formed  crystals  of 
Rochelle  salt  are  obtained.  After  digesting  the  acid  potash 
salt  with  antimonic  oxide,  well  defined  crystals  of  tartar  emetic 
are  deposited. 
After  these  results,  we  can  have  no  doubt  of  the  formation  of 
tartaric  acid  by  the  oxidation  of  milk  sugar.  It  is  also  obtained 
when  gum  arabic  is  treated  with  nitric  acid  in  the  same  way. 
Besides  mucic,  saccharic,  and  tartaric  acids,  some  oxalic  acid 
is  formed.  The  saccharic  acid  is  in  largest  proportion  immedi- 
ately after  the  separation  of  the  mucic  acid;  but  by  longer  boil- 
ing with  fresh  additions  of  nitric  acid  it  becomes  decomposed, 
and  the  amount  of  tartaric  acid  in  the  residue  increases. 
A  long  illness  has  prevented  Liebig  from  carrying  out  a  series 
of  experiments  to  decide  the  question  whether  the  tartaric  and 
saccharic  acids  are  formed  simultaneously,  or  first  saccharic  and 
then  tartaric  acid.  He  conjectures,  however,  that  the  latter 
is  the  fact — that  the  tartaric  is  formed  from  the  saccharic 
acid. 
From  grape  and  cane  sugar  Liebig  could  not  obtain  tartaric 
acid,  but  as  a  small  per  centage  of  saccharic  acid  was  formed 
from  both,  he  believes  the  reason  of  his  failure  was  the  small 
quantities  operated  on. 
On  subtracting  the  formula  of  tartaric  from  that  of  saccharic 
