II. Analysis of Nitrous Gas by Charcoal.
A quantity of nitrous gas was procured in a water apparatus, from the decomposition of nitrous acid by mercury. A portion of it was transferred to the mercurial trough. After the mercury and the jar had been dried by bibulous paper, 40 measures of this portion were agitated in a solution of sulphate of iron. The gas remaining after the absorption was complete, filled about a measure and half; so that the nitrous gas contained nearly ¹/₂₆ nitrogene.
Thermometer being 53°, a small piece of well-burnt charcoal, the weight of which could hardly have equalled a quarter of a grain, was introduced ignited, into a small cylinder filled with mercury, graduated to,10 grain measures; to this, 16 measures, equal to 160 grain m. of nitrous gas, were admitted. An absorption of about one measure and half took place. When the focus of a lens was thrown on the charcoal, a slight increase of the gas was produced, from the emission of that which had been absorbed.
After the process had been carried on for about a half an hour, the charcoal evidently began to fume, and to consume very slowly, though no alteration in the volume of the gas was observed.
The sun not constantly shining, the progress of the experiment was now and then stopped: but taking the whole time, the focus could not have been applied to it for less than four hours. When the process was finished, the gas was increased in bulk nearly three quarters of a measure.
A drop of water was introduced into the cylinder, by means of a small glass tube, on the supposition that the carbonic acid, and nitrogene, might be capable of holding in solution, more water than that contained in the nitrous gas decomposed; but no alteration of volume took place.
When 20 grain measures of solution of pale green[100] sulphate of iron were introduced into the cylinder, they became rather yellower than before, but not dark at the edges, as is always the case when nitrous gas is present. On agitation, a diminution of nearly half a measure was produced, doubtless from the absorption of some of the carbonic acid by the solution.
A small quantity of caustic potash, much more than was sufficient to decompose the sulphate of iron, was now introduced. A rapid diminution took place, and the gas remaining filled about 8 measures. This gas was agitated for some time over water, but no absorption took place. Two measures of it were then transferred into a detonating cylinder with two measures of oxygene. The electric spark was puffed through them, but no diminution was produced. Hence it was nitrogene, mingled with no ascertainable quantity of hydrogene: consequently little or no water could have been decomposed in the process.
Now supposing, for the greater ease of calculation, each of the measures employed, cubic inches.
16 of nitrous gas—¹/₂₆ = 15,4 were decomposed, and these weigh, making the necessary corrections, 5,2; but 7,4 nitrogene were produced, and these weigh about 2,2. So that reasoning from the relative specific gravities of nitrous gas and nitrogene, 5,2 grains of nitrous gas will be composed of 3 oxygene, and 2,2 nitrogene.