The  temperature  of  the  room  during  the  experiment  was  10** ;  for
the  trials  at  the  higher  temperature,  the  flask  containing  the  indigo
and  nitrate,  and  the  test-tube  containing  the  oil  of  vitriol,  were
placed  for  some  time  in  a  water  bath  at  22 — 23**  previously  to  being
mixed.
Indigo  Solution  Standardized  with  10  r.c.  of  Nitre  Solution.
of  nitre
solutioii.
At  10".
At  22'


i  Standard


ft
ft

if


Indigo
required
(actual).
c.c.
10-28
4-97
2-30
0-99*


Indigo

calculated

from  two

extremes.
c.c.
10-28
4-97
2-82
099


Indigo
required
(actual).
c.c.
9-76
4-78
218
0-96


Indigo

calculated

from  two

extremes.
c.c.
9-76

4-73

2-22

0-96


Standardized  with  20  c.c.  of  Nitre  Solution,


i  Standard
^1


it
a


1

Hi


a


10-26
4-84
2-21
0-99


10-26
4-96
231
0-99


974

9-74

4-65

4-74

2-21

2-24

0-99

0-99

•  It  must  not  be  supposed  that  it  was  i)Ofl8iblo  to  work  to  one-hundredth  of  a  cubic
centimeter ;  in  all  the  figures  given  the  errors  shown  br  calibrating  the  measuring
vessels  employed  have  been  taken  account  of,  and  minute  fractions  thus  introduced.
§  67.  VOLUMETRIC   ANALYSIS.  221

It  is  seen  that  a  rise  of  1 2*"  in  temperature  diminishes  the  indigo
consumed  by  about  5  pet  cent,  in  the  case  of  the  stronger  solutions
of  nitrate ;  it  is  evident,  therefore,  that  the  indigo  solution  should  be
standardized  at  nearly  the  same  temperature  at  which  it  is  to  be
used.
