| Temperature | 15° C. | 30° C. | 70° C. | 100° C. |
| "Ferrocyanide" required | 20.6 c.c. | 20.3 c.c. | 20.3 c.c. | 20.3 c.c. |
The solution can be heated to boiling before titrating without interfering with the result; but it is more convenient to work with the solution at about 50° C. Cold solutions must not be used.
Effect of Varying Bulk.—These were all titrated at about 50° C., and were like the last, but with varying bulk.
| Bulk | 25.0 | c.c. | 50.0 | c.c. | 100.0 | c.c. | 200.0 | c.c. |
| "Ferrocyanide" required | 20.2 | " | 20.4 | " | 20.3 | " | 20.4 | " |
Any ordinary variation in bulk has no effect.
Effect of Varying Hydrochloric Acid.— With 100 c.c. bulk and varying dilute hydrochloric acid the results were:—
| Acid added | 0.0 | c.c. | 1.0 | c.c. | 5.0 | c.c. | 10.0 | c.c. | 20.0 | c.c. |
| "Ferrocyanide" required | 24.4 | " | 20.2 | " | 20.3 | " | 20.3 | " | 20.7 | " |
Effect of Foreign Salts.—The experiments were carried out under the same conditions as the others. Five grams each of the following salts were added:—
| Salt added | Ammonic chloride. | Ammonic sulphate. | Sodium chloride. | Sodium sulphate. |
| "Ferrocyanide" required | 20.3 c.c. | 20.5 c.c. | 20.6 c.c. | 20.4 c.c. |
| Salt added | Potassium Nitrate. | Magnesium sulphate. | Nil. | |
| "Ferrocyanide" required | 20.2 c.c. | 20.4 c.c. | 20.4 c.c. |
In a series of experiments in which foreign metals were present to the extent of 0.050 gram in each, with 20 c.c. of zinc solution and 5 c.c. of dilute hydrochloric acid, those in which copper sulphate, ferrous sulphate, and ferric chloride were used, gave (as might be expected) so strongly coloured precipitates that the end reaction could not be recognised. The other results were:—