154  Standardisation  of  Sodium  Thio sulphate.  {Am\J°nrmh5arm' 
The  nature  of  the  sodium  carbonate  fraction  in  the  case  of  aloes, 
and  that  of  the  ammonium  carbonate  fraction  in  all  cases  are  among 
the  interesting  points  suggested  by  the  experience  herein  described, 
to  which  we  hope  to  give  further  attention. 
Analytical  Laboratory, 
Connecticut  Agriculture  Experiment  Station, 
New  Haven,  Conn. 
STANDARDIZATION  OF  SODIUM  THIOSULPHATE 
VOLUMETRIC  SOLUTION.1 
By  Joseph  L.  Mayer. 
A  reference  to  page  563  of  the  U.  S.  P.  will  show  that  the  official 
method  of  standardizing  sodium  thiosulphate  V.  S.  is  to  employ  a 
decinormal  solution  of  potassium  dichromate,  proceeding  as  follows: 
"To  a  solution  of  about  1  Gm.  of  potassium  iodide  (Potassii 
Iodidum,  U.  S.  P.)  in  10  Cc.  of  diluted  sulphuric  acid  contained  in  a 
flask  of  about  500  Cc.  capacity,  add  slowly,  from  a  burette,  20  Cc. 
of  tenth-normal  potassium  dichromate  V.  S.,  shaking  after  each 
addition.  Place  a  watch-glass  on  the  mouth  of  the  flask  and  allow  it 
to  stand  for  five  minutes,  then  dilute  the  solution  with  about  250  Cc. 
of  distilled  water,  add  some  starch  T.  S.,  and  then,  from  a  burette, 
the  trial  solution  of  sodium  thiosulphate,  in  small  portions  at  a  time, 
shaking  after  each  addition,  and,  toward  the  end  of  the  operation, 
reducing  the  flow  to  drops,  until  the  blue  color  of  the  mixture  changes 
to  a  light  green  ;  note  the  number  of  cubic  centimetres  of  the  trial 
sodium  thiosulphate  solution  consumed.  Then  dilute  the  sodium 
thiosulphate  solution  so  that  equal  volumes  of  it  and  the  tenth- 
normal potassium  dichromate  V.  S.  will  exactly  correspond  to  each 
other  under  the  above  conditions  at  25 0  C.  (770  F.)." 
On  page  549  of  the  U.  S.  P.  volumetric  iodine  solution  is  directed 
to  be  made  by  the  following : 
"  Tenth-normal  iodine  V.  S.  may  be  prepared  according  to  eithei 
of  the  following  methods  : 
"  1.  Dissolve  12.59  Gm.  of  pure  iodine  (see  below)  in  a  solution 
of  18  Gm.  of  potassium  iodide  in  300  Cc.  of  water.  Then  add 
sufficient  water  to  make  the  solution  measure,  at  250  C.  (770  F.), 
1Read  before  the  Kings  County  Pharmaceutical  Society,  March  9,  1915. 
