418 
Valuation  of  Tartar  Emetic. 
(  Am.  Jour.  Pharm. 
X     August,  1884. 
of  about  2°  Twaddell.  The  value  of  the  hypochlorite  can  be  found 
by  using  a  standard  solution  of  sodium  arsenite.  The  sodium  arsenite 
is  the  usual  decinormal  solution,  made  by  dissolving  4*95  grams  of 
pure  arsenious  acid  in  a  solution  of  sodium  carbonate,  and  when  cool 
diluting  to  1  litre.    About  25  grams  of  sodium  carbonate  are  required. 
1  cc.=-00355  grams  of  CI,  or  -0061  grams  Sb. 
The  usual  potassic  iodide  and  starch  paper  are  needed.  The  process  is 
conducted  as  follows  :  A  weighed  portion  of  the  tartar  emetic  is  dis- 
solved, assisted  by  heat,  cooled,  and  made  alkaline  with  sodium  carbo- 
nate. A  known  amount  of  the  calcium  hypochlorite  solution  is  added 
in  excess,  this  being  shown  by  the  blue  color  which  a  drop  of  the  liquid 
gives  to  the  starch  paper.  The  excess  of  calcium  hypochlorite  is  now 
found  by  titrating  with  the  standard  sodium  arsenite,  until  the  liquid 
ceases  to  give  the  blue  color  to  the  starch  paper.  The  value  of  the 
hypochlorite  added  is  found  by  taking  an  amount  equal  to  that  put  to 
the  tartar  emetic,  or  an  aliquot  portion  may  be  taken,  making  alkaline 
as  before  and  titrating  with  standard  arsenite,  Penot's  method.  If  an 
aliquot  part  is  taken,  the  value  of  the  whole  is  then  to  be  calculated. 
The  worth  of  the  total  hypochlorite  added  being  known,  and  that  of 
the  excess  also  known,  the  amount  of  hypochlorite  and  therefore 
chlorine  used  to  oxidize  the  antimony  is  thus  obtained  by  difference. 
This  also  gives  the  amount  of  antimony.  The  reaction  that  takes 
place  is  as  follows  : — 
Sb203 + 2  Cl2  +  4  NaHO  =  Sb2Os + 4  NaCl  +  2  H20  . • .  7 1  CI  =  1 22  Sb. 
This  process  is  rapid,  and,  for  all  practical  purposes,  accurate,  the  end 
of  the  reaction  being  sharp,  and  denoted  at  once,  which  with  the  iodine 
process  is  both  tardy  and  tiresome. 
The  calcic  hypochlorite  solution,  the  value  of  which  should  be  found 
at  least  once  a  day  when  required,  must  be  kept  in  a  stoppered  bottle 
in  a  dark  place,  as  it  decomposes  quickly  if  exposed  to  light  and  air. 
Even  then  it  will  not  be  of  use  long,  but  a  fresh  solution  can  easily  be 
made. 
The  following  are  the  results  obtained  by  this  process,  along  with 
those  obtained  by  the  iodine  method,  showing  comparison : 
Iodine  Process.  Chlorine  Process. 
No.  1.  Mean  of  3  trials  33.41  per  cent,  Sb.  33*29  percent.  Sb. 
37-048       "        "  36-944  " 
No.  2  36-896       "        "  36'820 
37-000       "        "  37-020 
Mean  36-981  per  cent.  Sb.  36*928  per  cent.  Sb. 
