| Temperature | 15° | 30° | 70° | 100° |
| Stannous chloride required | 22.8 c.c. | 22.0 c.c. | 22.1 c.c. | 22.0 c.c. |
The finishing point, however, is more distinct the hotter the solution; so that it is best in all cases to run the standard into the boiling solution.
Effect of Varying Bulk.—Solutions containing the same quantity of iron and acid as the last, but diluted to various bulks, and titrated while boiling, gave the following results:—
| Bulk | 30 c.c. | 100 c.c. | 500 c.c. |
| Stannous chloride required | 21.5 " | 21.7 " | 24.3 " |
Effect of Varying Quantities of Hydrochloric Acid.—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:—