93 grains of the bright yellow acid of 1,5 became, when 6 cubic inches of gas had been passed through it, orange colored and fuming, whilst the undissolved gas increased in quantity so much as to render it impossible to confine it by the solution of potash. When 9 cubic inches had passed through, it became dark orange. It had gained in weight 2,75 grains, and was become of specific gravity 1,48 nearly. Hence it was evident that much nitrous gas had passed through it undissolved. 25 cubic inches more of nitrous gas were now slowly sent through it: it first became of a light olive, then of a dark olive, then of a muddy green, then of a bright green, and lastly of a blue green. After its assumption of this color, the gas appeared to pass through it unaltered, and large globules of fluid, of a darker green than the rest, remained at the bottom of the cylinder, and when agitated, did not combine with it. The increase of weight was only 1 grain, and the acid was of specific gravity 1,474 nearly. In this experiment it was evident that the unabsorbed nitrous gas had carried over with it a considerable quantity of nitrous acid. I endeavoured to correct the errors resulting from this circumstance, by connecting the curved tube first with a small water apparatus, and afterwards with a mercurial apparatus; but when the water apparatus was used, the greater part of the unabsorbed gas was dissolved with the nitrous acid it held in solution, by the water; and when mercury was employed, the nitrous acid that came over was decomposed, and the quantity of nitrous gas evolved, in consequence increased. As it was possible that a small deficiency of weight might arise from the red vapor given out during the processes of weighing and examining the acid in the last experiment, 35 cubic inches of nitrous gas were very slowly passed through 90 grains of pale nitrous acid, of specific gravity 1,5: it became of similar appearance to that just described, had gained in weight 6,75 grains, and was become of specific gravity 1,475.