existed as permanent gas, and might be either nitrogen, carbon monoxide, or hydrogen which had escaped combination in the relatively large excess of oxygen which usually was present in the final explosion. In all probability this is the real explanation of the permanent gas found, as the apparent impurity was almost always larger when the excess of oxygen was large than when it was small and was roughly in proportion
Fig. 5.
General view of apparatus from back, with barometer turned round.
to it. This will be easily seen on inspection of the table of results. Taking a few examples in Series IIc, we have
| Residue. | Impurity. |
| 10.2 | .3 |
| 28.9 | .5 |
| 41.1 | .8 |
There are, no doubt, exceptions to this, but it seams to hold generally that the larger the oxygen residue the larger the impurity found as shown above. The other explanation which might account for the same thing is, that carbon monoxide might be given off easily (from the pyrogallol) to the small extent usually found,
| .3 corresponding to an impurity of about | 134,000. |
| 1.0 corresponding to an„ impurity„ of about„ | 110,000. |
