Am'sipt.?i887arm"}       Estimation  of  Glycerin  in  Fats.  465 
The  ferrous  solution  is  exactly  standardized  upon  the  chromate  so- 
lution, and  the  glycerin  value  of  the  chromate  (contents  of  K2Cr207 
divided  by  7*486)  is  calculated. 
The  chromate  solution  used  in  my  experiments  standardized  as  fol- 
lows : — 
2*8412  grms.  iron-wire  =  2*8327  pure  iron,  required  33*94  c.c.  bi- 
<;hrome.    1  c.c.  ===  '07333  bichrorue,  or  "009796  glycerin. 
2*7078  grms.  iron-wire  =  2*6997  iron  used  32*3  c.c.  bichrome. 
1  c.c.  ==  *07344  bichrome,  or  "009810  glycerin.  Average  1  c.c.  bi- 
chrome =  *07338  grms.  bichrome  or  .009803  glycerin. 
Test  experiments. — Glycerin,  specific  gravity  1*2572,  containing  ac- 
cording to  Lenz's  tables,  95*55  per  cent,  of  pure  anhydrous  glycerin 
— was  taken,  a  solution  of  12*5798  grms.  per  litre,  corresponding  to 
12*0200  grms.  of  pure  glycerin,  being  used.  25  c.c.  of  this  solution, 
equal  to  *3005  glycerin  were  taken  in  each  of  the  following  experiments. 
25  c.c.  heated  with  40  c.c.  bichromate,  without  further  dilution  for 
two  hours  to  near  the  boiling  point :  30*41  c.c.  bichromate  were  con- 
sumed, corresponding  to  *2981  grms.  glycerin,  or  99*2  per  cent,  of  the 
glycerin  taken. 
25  c.c,  heated  with  bichrome  and  25  c.c.  strong  hydrochloric  acid 
for  one  hour,  consumed  31*16  c.c.  bichrome,  equal  to  "30546  grms.  or 
101*6  per  cent. 
25  c.c,  diluted  with  500  c.c.  of  distilled  water,  reduced  in  three 
hours  23*93  c.c  bichromate,  equal  to  "23458  grms.  or  78*1  per  cent, 
of  glycerin. 
The  same  quantity,  diluted  with  500  c.c  of  water,  plus  25  c.c 
strong  hydrochloric  acid,  heated  for  one  hour,  reduced  22*3  c.c.  bi- 
chrome, indicating  *2186  grms.,  or  72*7  per  cent. 
25  c.c,  diluted  with  500  c.c.  of  water,  plus  25  c.c.  sulphuric  acid, 
consumed  in  one  hour  29*34  c.c.  bichrome,  =  *2876  grms.,  or  95*7 
per  cent,  of  the  glycerin  taken. 
Conditions  the  same  as  in  the  previous  experiment,  only  the  heat- 
ing continued  for  two  hours.  Bichromate  consumed  29*89  c.c.  =  *2930 
grms.,  or  97*5  per  cent,  of  glycerin  taken. 
25  c.c  were  diluted  to  about  300  c.c,  the  solution  evaporated  to 
about  one  half  upon  the  water-bath,  and  then  heated  with  25  c.c. 
strong  sulphuric  acid  and  chromate.  After  two  hours  30*54  c.c  bi- 
chromate were  found  to  be  reduced,  corresponding  to  *2994  grms.  or 
9 9' 6  per  cent,  of  glycerin. 
