From this we also see how
advisable it is to stir the liquid frequently during titration. Toward
the close of it, it is also advantageous, when the contents of manganese
are large, to warm the solution to about 50 deg. C., because the removal of
color is thereby hastened. When the fluid, which is well stirred after
each addition of chameleon, has obtained from it a perceptible color,
which does not disappear after several stirrings, the whole of the
manganese is precipitated and the color of the solution remains almost
unchanged after the lapse of at least twelve hours.
When the content of manganese is large the solution may be divided into
two equal portions, one of which is first to be roughly titrated to
ascertain its content approximately, after which the whole is to be
mixed together and the titration completed, which can thus be performed
with greater speed and certainty. If too much chameleon has been added,
one may titrate back with an accurately estimated solution of manganese,
which is prepared most easily by evaporating fifteen cubic centimeters
chameleon solution down to two or three cubic centimeters, boiling with
two to three cubic centimeters hydrochloric acid so long as the smell
of chlorine is observed, and then diluting the solution to ten cubic
centimeters, when one cubic centimeter of it corresponds to the same
measure of chameleon.
Pages:
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123