~--In these
experiments the bulk before titration was 50 c.c. except in the last, in
which it was 70 c.c. With less than 5 c.c. of strong hydrochloric acid
the finishing point is indistinct and prolonged.
Strong hydrochloric
acid present 5 c.c. 10 c.c. 20 c.c. 30 c.c. 50 c.c.
Stannous chloride
required 21.1 " 21.1 " 21.2 " 21.8 " 22.2 "
~Effect of Free Sulphuric Acid.~--In these experiments 20 c.c. of
hydrochloric acid were present, and the bulk was 50 c.c.
Strong sulphuric acid
present -- c.c. 3 c.c. 5 c.c. 10 c.c.
Stannous chloride
required 21.6 " 22.3 " 22.9 " 23.1 "
This interference of strong sulphuric acid may be completely
counteracted by somewhat modifying the mode of working. Another
experiment, like the last of this series, required 21.6 c.c.
~Effect of Foreign Salts.~--Experiments in which 10 grams of various
salts were added showed them to be without effect. The results were as
follows:--
Salt present -- AmCl Am_{2}SO_{4} MgCl_{2}
Stannous chloride required 21.6 c.c. 21.6 c.c. 21.6 c.c. 21.6 c.c.
Salt present CaCl_{2} FeCl_{2} Al_{2}Cl_{6}
Stannous chloride required 21.8 c.c. 21.6 c.c. 21.6 c.c.
~Effect of Varying Iron.
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