But 8,7 of carbonic acid were produced, which weigh 4,1 grains, and consist of 2,9 oxygene, and 1,2 charcoal.[101] Consequently, drawing conclusions from the quantity of carbonic acid formed, 5,2 grains of nitrous gas will consist of 2,9 oxygene, and 2,3 nitrogene. [101] That is, carbon, or oxide of diamond. The difference in these estimations is much less than could have been expected; and taking the mean proportions, it would be inferred from them, that 100 grains of nitrous gas, contain 56,5 oxygene, and 43,5 nitrogene. I repeated this experiment with results not very different, except that the increase of volume was rather greater, and that more unabsorbable gas remained; which probably depended on the decomposition of a minute quantity of water, that had adhered to the charcoal in passing through the mercury. As nitrous gas is decomposable into nitrous acid, and nitrogene, by the electric spark; it occurred to me, that a certain quantity of nitrous acid might have been possibly produced, in the experiments on the decomposition of nitrous gas, by the intensely ignited charcoal. To ascertain this circumstance, I introduced into 12 measures of nitrous gas, a small piece of charcoal which had been just reddened. The sun being very bright, the focus of the lens was kept on it for rather more than an hour and quarter. In the middle of the process it began to fume and to sparkle, as if in combustion. In three quarters of an hour, the gas was increased rather more than half a measure; but no alteration of volume took place afterwards. The mercury was not white on the top as is usually the case when nitrous acid is produced. On introducing into the cylinder a little pale green sulphate of iron, and then adding prussiate of potash, a white precipitate only was produced. Now, if the minutest quantity of nitric acid had been formed, it would have been decomposed by the pale green oxide of iron, and hence, a visible quantity of prussian blue[102] produced, as will be fully explained hereafter. [102] That is, blue prussiate of iron. III. _Analysis of Nitrous Gas by Pyrophorus._ I placed some newly made pyrophorus, about as much as would fill a quarter of a cubic inch, in a jar filled with dry mercury, and introduced to it, four cubic inches of nitrous gas, procured from mercury and nitric acid. It instantly took fire and burnt with great vividness for some moments. After the combustion had ceased, the gas was diminished about three quarters of a cubic inch. The remainder was not examined; for the diminution appeared to go on for some time, after; in an half hour, when it was compleat, it was to 2 cubic inches. A taper, introduced into these, burnt with an enlarged flame, blue at the edges; from whence it appeared, that they were composed of nitrogene and nitrous oxide.