Common air was now thrown into the globe till the residual gases of the experiment were judged to be displaced; it weighed 2106,5 grains, that is, 40 grains more than it had weighed when filled with common air before the experiment.[22]
And if from those 40 grains we take 13 for the solution of ammonia introduced, the remainder, 27, will be the quantity of solution of nitrous acid in water remaining in the globe, which added to 54, equals 81 grains, the whole quantity formed; but if from this be taken 41 grains, the quantity of water, the remainder 40 grains, will be the quantity of nitrous acid gas absorbed in the solution.
To find the absolute quantity of nitrous acid formed, we must find the specific gravity of that absorbed; but as during, and after its absorption, 17 grains of air, equal to 53,2 cubic inches entered, it evidently filled such a space. 53,2 cubic inches of it consequently weigh 40 grains, and 100 cubic inches 75,17 grains. Then,75 cubic inches weigh,56 grains, and this added to 40, makes 40,56 grains, equal to 53,95 cubic inches, the whole quantity of aëriform nitrous acid produced.
But the quantity of nitrous gas entering into this, allowing for the nitrogene it contained, is 27,6 grains, equal to about 80,5 cubic inches; and the oxygene is 40,56-27,6 = to 12,96 grains, or 36,9 cubic inches.
V. There could exist in this experiment no circumstance connected with inaccuracy, except the impossibility of very minutely determining the quantities of common air which entered with the gases from the stop-cocks. But if errors have arisen from this source, they must be very inconsiderable; as will appear from a calculation of the specific gravity of the nitrous acid gas, founded on the volume of the gases that entered the globe.
| The air that remained in the globe | ||
| after exhaustion was 15 grains= | 47[23] | cub. in. |
| The nitrous gas introduced was | 82 | |
| Common air | 13 | |
| Oxygene | 70 | |
| Common air | 1 | |
| —— | ||
| Whole quantity of air thrown into the globe | 213 | |
| From which subtract its capacity | 148 | |
| —— | ||
| The remainder is | 65 | |
And this remainder taken from 80,5 nitrous gas + 36,9 oxygene, leaves 52,4 cubic inches, which is the space occupied by the nitrous acid gas, and which differs from 53,95 only by 1,55 cubic inches.
I ought to have observed, that before this conclusive experiment, two similar ones had been made. In comparing the results of one of them, performed with the assistance of my friend, Mr. Joseph Priestley, Dr. Priestley’s eldest son, and chiefly detailed by him in the journal, I find a coincidence greater than could be even well expected, where the processes are so complex. According to that experiment, 41,5 grains of nitrous acid gas fill a space equal to 53 cubic inches, and are composed of nearly 29 nitrous gas, and 12,5 oxygene.
We may then conclude, First, that 100 cubic inches of nitrous acid, such as exists in the[24] aëriform state saturated with oxygene, at temperature 55°, and atmospheric pressure 30,1 weigh 75,17 grains.
Secondly, that 100 grains of it are composed of 68,06 nitrous gas, and 31,94 oxygene. Or assuming what will be hereafter proved, that 100 parts of nitrous gas consist of 55,95 oxygene, and 44,05 nitrogene, of 29,9 nitrogene, and 70,1 oxygene; or taking away decimals, of 30 of the one to 70 of the other.