| Cyanide in excess | 6 c.c. | 4 c.c. | 8 c.c. | 12 c.c. | 25 c.c. |
| Nickel found | .0434 | .0436 | .0440 | .0442 | .0444 |
Although the difference between the highest and lowest of these results is only 1 milligram, their meaning is quite obvious. The excess of cyanide should not be less than 20 c.c.
Effect of varying the quantity of Soda.—There were two series of experiments, one with 2 c.c. of nickel solution (= .0044 gram of nickel), the other with 20 c.c. The conditions were as before, except that the quantity of soda was varied.
| Soda added | 5 c.c. | 15 c.c. | 30 c.c. | |
| Nickel found, | 1st series | .0037 | .0042 | .0045 |
| " " | 2nd series | .0444 | .0444 | .0442 |
These show that the presence of much soda, though it has only a small effect, is beneficial rather than otherwise. Ammonia has a bad effect, if present in anything like the same quantities.
Effect of varying the Nickel.—In experiments with 10, 20, and 40 c.c. of the nickel solution, the results were:—
| Nickel present | .0222 | .0445 | .0890 |
| Nickel found | .0220 | .0442 | .0884 |
Effect of Zinc.—In these experiments 20 c.c. of nickel solution (= .0445 gram of nickel), 10 c.c. of soda, 6 drops of potassium iodide and water to 100 c.c. were used. The excess of cyanide was purposely kept at from 10 to 15 c.c., which is hardly sufficient.
| Zinc added | 0 | .25 gram. | .5 gram. |
| Nickel found | .0442 | .0440 | .0407 |