80  Gleanings  from  the  German  Journals.  { AmFeb*i$i&Tm' 
tion,  60  grams  in  one  liter  95  per  cent,  alcohol ;  iodine  solution,  50 
grams  in  one  liter  95  per  cent,  alcohol;  thiosulphate  of  sodium 
solution,  24  grams  of  the  crystallized  salt  in  one  liter  distilled  water  ; 
potassium  iodide  solution,  10  per  cent.;  potassium  bichromate  solu- 
tion, 3-874  grams  pure,  dry  salt  in  one  liter  water ;  chloroform  : 
dilute  hydrochloric  acid. 
To  standardize  the  thiosulphate  solution — 10  cc.  potassium  iodide 
solution,  5  cc  dilute  hydrochloric  acid,  20  cc.  potassium  bichromate 
solution  and  150  cc.  water  are  placed  in  a  stoppered  flask  of  300  cc. 
capacity  and  well  agitated ;  to  the  red  solution  which  contains 
exactly  0-2  gm.  free  iodine,  is  added  the  thiosulphate  solution  from 
a  burette  until  a  faint  bluish-green  color  due  to  the  chromium  salt 
results  (the  addition  of  starch  is  not  necessary  and  besides  is  con- 
sidered a  source  of  error,  as  the  albuminoids  generally  present  in 
starch  liberate  iodine).  One  cc.  thiosulphate  solution  corresponds 
generally  to  I2-I4mg.  iodine;  by  keeping  in  well-stoppered  bottles 
very  little  change  in  the  strength  of  this  solution  takes  place.  To 
standardize  the  iodi7ie  solution — 10  cc.  each  of  the  iodine  and  mercuric 
chloride  solutions  are  placed  in  the  flask,  20  cc.  potassium  iodide 
solution  and  150  cc.  water  added;  after  thorough  agitation  the 
thiosulphate  is  added  until  the  liquid  becomes  colorless.  The  deter- 
mination  of  the  iodine -absorption  of  the  oil  presupposes  that  the 
nature  of  the  oil  is  known ;  if  unknown,  a  preliminary  determination 
must  be  made.  0-2-0-3  gram  of  the  oil  to  be  examined  is  weighed 
into  the  flask,  dissolved  in  20  cc.  chloroform,  a  quantity  of  iodine 
solution  added,  which  contains  four  times  as  much  iodine  as  is  likely 
to  be  absorbed,  previously  mixed  with  an  equal  volume  of  the 
mercuric  chloride  solution ;  in  a  second  flask  are  placed  the  same 
quantities  of  chloroform,  iodine  and  mercuric  chloride  solutions ; 
after  standing  two  hours  the  proper  quantity  of  potassium  iodide 
solution  (for  each  gram  iodine  about  four  grams  potassium  iodide) 
and  50-100  cc.  water  are  added,  and  the  mixture  titrated  with  the 
thiosulphate  solution;  the  difference  between  the  two  represents 
the  iodine  absorbed  by  the  oil.  In  the  examination  of  olive  oil 
which  has  an  iodine-absorption  of  about  84  for  one  gram  oil,  3-360 
gm.  iodine  should  be  added ;  in  the  case  of  linseed  oil,  one  gram 
requires  7*20  grams  iodine  to  be  added  because  180  is  the  iodine- 
absorption  figure. 
To  keep  drugs,  which  are  easily  attacked  by  insects,  R.  Idelson 
