1 86  Determination  of  Calcium  Tartrate.  {^m±^:\m*m' 
acetic  acid  does  not  dissolve.  It  is  also  without  action  upon  calcium 
tartrate.  It  is  preferable  to  precipitate  in  two  portions,  since  the 
crystals  of  tartar  are  thus  coarser,  which  renders  it  easier  to  seize 
the  exact  moment  when  the  moisture  is  expelled. 
If  we  wish  to  determine  the  total  acidity  of  any  tartar  we  must 
operate  in  the  same  manner,  adding  25  cc.  of  solution  of  calcium 
acetate  in  two  portions.  This  quantity  is  sufficient  for  5  grms.  pure 
potassium  bitartrate,  and  consequently  the  process  is  general. 
The  calcium  tartrate  must  be  washed,  collected,  and  weighed. 
We  have  then  to  add  2  per  cent,  to  the  amount  found,  and  on  mul- 
tiplying the  calcium  tartrate  by  0*576  we  have  the  value  in  tartaric 
acid. 
Second  Process. — We  take  50  grms.  of  the  solution  of  tartar, 
which  is  poured  into  a  porcelain  capsule  and  heated  to  ebullition. 
We  add  then  some  drops  of  solution  of  phenolphthalein,  and  then 
gradually,  and  with  continual  stirring,  a  clear  milk  of  lime  which 
has  been  strained  through  silk.  The  source  of  heat  is  extinguished 
or  removed  as  soon  as  "  bumping"  sets  in;  the  saturation  is  con- 
tinued, giving  the  calcium  tartrate  time  to  subside  after  each  addi- 
tion of  lime,  and  ceasing  when  neutrality  is  reached,  which  requires 
about  five  minutes.  We  add  then  to  the  liquid  2  cc.  of  the  citric 
solution  at  25  per  cent.,  stir  and  allow  it  to  subside.  After  some  min- 
utes, the  temperature  is  500  to  6o°,when  we  decant,  pour  the  tartar 
upon  a  plain  filter  of  0-09  metre,  and  wash  with  30  cc.  of  water. 
The  calcium  tartrate  is  dried  as  above,  taking  care  not  to  break 
the  filter.  To  the  result  obtained  we  add  4  per  cent,  for  the  solu- 
bility of  the  substance  in  the  liquid  and  the  loss  on  the  filter.  Even 
if  the  quantity  of  malate  exceeds  20  per  cent.,  which  is  a  very  rare 
case,  we  need  add  only  3  per  cent,  for  accuracy,  as  the  solubility  is 
then  lower.  The  quantity  of  malate  is  found  by  the  deficiency  of 
the  result  plus  the  insoluble  matters  to  make  up  IOO.  On  operating 
thus  on  pure  calcium  tartromalate,  or  on  a  mixture  of  the  two  salts 
in  equivalent  proportions,  we  find  99  50  per  cent,  of  calcium  tartrate 
almost  free  from  malate. 
This  process  has  the  advantage  of  serving  for  industrial  refining. 
In  place  of  adding  citric  acid  we  leave  a  slight  acidity,  which  dis- 
solves the  alumina  and  the  phosphates.  The  tartar  obtained  is  pure 
if  the  liquid  is  decanted  whilst  lukewarm,  for  complete  refrigeration 
precipitates  the  calcium  tartromalate  to  the  extent  of  about  10  per 
