TARTRATE  OF  LIME  AND  A  REACTION  OF  TARTARIC  ACID.  53 
ON  TARTRATE  OF  LIME  AND  A  REACTION  OF  TARTARIC  ACID. 
By  Arthur  Casselmann. 
The  author,  when  occupied  in  the  examination  of  Alexandrian 
senna,  found  that  the  aqueous  extract  deposited  the  lime  salt  of 
au  organic  acid  on  evaporation.  This  salt  possessed  a  remarkable 
property  ;  when  gradually  heated,  after  the  addition  of  ammonia 
and  nitrate  of  silver,  it  covered  the  sides  of  the  test-glass  with  a 
metallic  speculum  of  silver,  in  such  a  manner  that  the  reaction 
may  be  compared  with  the  reduction  of  nitrate  of  silver  by  al- 
dehyde-ammonia. Even  a  very  small  quantity  of  the  lime-salt 
was  sufficient  to  reduce  the  nitrate  of  silver  in  the  manner  above- 
mentioned,  but  only  when  the  nitrate  was  added  in  small  frag- 
ments, instead  of  in  solution.  If  it  were  added  in  solution,  the 
reduced  silver  was  deposited  in  the  form  of  a  gray  powder. 
When  the  hot  solution  of  the  lime-salt  was  mixed  with  neutral 
acetate  of  lead,  an  abundant  white  precipitate  was  obtained, 
which  however  always  contained  traces  of  the  lime-salt,  unless 
the  fluid  was  rapidl}r  altered  whilst  boiling.  This  precipitate  was 
decomposed  by  sulphuretted  hydrogen  ;  the  fluid  containing  the 
pure  acid  was  evaporated,  and  the  acid  was  obtained  as  a  syrupy 
sharply-acid  fluid,  which  exhibited  no  trace  of  crystallization  even 
after  standing  for  several  weeks. 
The  author  analysed  the  lead-salt  of  the  acid  ;  it  had  the 
composition  of  tartrate  of  lead.    Analysis  gave  : — ■ 
c 
13.5 
8 
=  48-0 
13-5 
H 
1.5 
4 
4-0 
11 
0 
22-7 
10 
80-0 
22-6 
PbO 
62-3 
2 
223-2 
62-8 
Comparative  experiments  with  artificially-prepared  tartrate  of 
lime  presented  the  same  behaviour.  The  remarkable  fact,  that 
tartaric  acid,  in  one  of  its  least  soluble  compounds,  possesses  the 
property  of  instantaneously  reducing  nitrate  of  silver,  might  be 
made  use  of  in  analysis  for  the  detection  of  minute  traces  of  this 
acid.  Racemic  acid,  however,  gives  the  same  reaction,  and  also 
produces  it  instantaneously  only  when  the  nitrate  of  silver  is 
added  in  the  solid  state. 
Tartrate  of  lime  occurs  in  considerable  quantity  in  senna- 
leaves  ;  but,  from  its  sparing  solubility,  is  not  obtained  from  them 
