AmAp°rnr;iP893arm'}    Determination  of  Calcium  Tartrate.  185 
grms.,  according  to  the  quantity  of  the  insoluble  matters,  and  filter. 
We  take  50  grms.  of  the  solution  when  cold,  and  pour  it  into  a  flask 
holding  about  90  cc.  We  add  2  cc.  of  solution  of  citric  acid  at 
25  per  cent,  and  then  10  cc.  of  solution  of  calcium  acetate  at  25 
per  cent.  (25  grms.  calcium  acetate  and  water  to  make  up  100  cc.) 
We  agitate  strongly,  when  crystals  of  calcium  tartrate  form  after  a 
few  minutes.  We  then  add  5  cc.  more  of  the  same  solution  of  calcium 
acetate,  agitate,  and  allow  it  to  settle  for  fifteen  or  thirty  minutes. 
All  the  tartar  is  precipitated  in  a  pure  state. 
We  pour  the  whole  upon  a  plain  filter  9  cm.  in  diameter,  detach 
the  tartar  adhering  to  the  flask  with  a  slender  piece  of  curved  wood, 
wash  the  flask  and  the  tartar  from  the  filter  with  30  cc.  of  water  in 
several  portions. 
The  filter  is  then  opened  and  laid  on  a  plate  of  copper  or  sheet- 
iron  above  a  water-bath.  The  paper  dries  enough  to  permit  the 
separation  of  the  tartar,  which  is  transferred  to  a  round  nickel 
capsule  9  cm.  in  diameter.  The  filter  is  dried  completely,  the 
tartar  is  detached  and  added  to  that  in  the  capsule. 
The  capsule  is  then  placed  on  the  water-bath  so  as  to  dry  the  cal- 
cium tartrate  completely.  The  desiccation  is  promoted  by  stirring 
the  mass  with  a  very  pliable  spatula.  We  cease  when  the  tartar, 
which  forms  clots  as  long  as  it  is  moist,  begins  to  flow  like  dry  sand. 
At  this  moment  we  wipe  the  capsule  and  weigh  the  tartar  obtained. 
The  result  found,  multiplied  by  twenty,  gives  the  standard  of  the 
tartar  if  we  have  operated  upon  5  grms.  of  substance.  To  this  must 
be  added  2  per  cent,  to  compensate  for  the  loss  on  the  filter  and  the 
solubility  of  calcium  tartrate. 
The  exact  moment  of  drying  must  be  seized  when  the  calcium 
tartrate  contains  4H20.  Each  additional  minute  causes  a  loss  of  010 
per  cent,  of  tartar,  but  as  the  point  is  easy  to  seize  (for  it  occurs 
suddenly  on  stirring  the  substance),  there  is  no  error  in  this  respect 
beyond  0  20  per  cent.,  which  may  be  neglected. 
By  this  process  there  are  formed  calcium  tartrate,  calcium  chloride, 
and  free  acetic  acid,  which  has  no  action  on  calcium  tartrate.  As 
the  precipitation  of  the  tartar  is  always  effected  in  a  very  acid 
liquid,  malic  acid,  if  it  is  present,  remains  in  solution  and  does  not 
falsify  the  results. 
The  object  of  the  citric  acid  is  to  dissolve  the  aluminium  phos- 
phate, which  forms  a  lake  with  the  coloring  matter,  and  which  the 
