The purity of the hydrogene was ascertained immediately before the experiment by the test of nitrous gas, and by detonation with oxygene or atmospheric air; generally 12 measures of atmospheric air were fired with 4 of the hydrogene, and if the diminution was to ten or a little more, the gas was judged to be pure. After the experiment, when the compleat expiration had been made and the common temperature restored; the volume of the gas was noticed, and then a small quantity of it thrown into the mercurial apparatus by means of the conducting tube, to be examined. The carbonic acid was separated by from it by means of solution of potash or strontian; the quantity of oxygene it contained, was ascertained by means of nitrous gas of known composition; the superabundant nitrous gas was absorbed by solution of muriate of iron; and the proportions of hydrogene and nitrogene in the remaining gas, discovered by inflammation with atmospheric air or oxygene in the detonating tube by the electric spark. _a._ The two following experiments made upon quantities of hydrogene, equal to those of the nitrous oxide respired in the experiments in the last section, are given as the most accurate of five. E. 1. I respired at 59° 102 cubic inches of hydrogene apparently pure, for rather less than half a minute, making in this time seven quick respirations. After the complete expiration, when the common temperature was restored, the gas occupied a space equal to 103 cubic inches nearly. These analised were found to consist of Carbonic acid 4,0 Oxygene 3,7 Nitrogene 17,3 Hydrogene 78,0 ————— 103,0 Now as in this experiment, the gas was increased in bulk only a cubic inch; supposing that after the compleat expiration the gas in the lungs, bronchia and fauces was of nearly similar composition with that in the airholder, and that no hydrogene had been absorbed by the blood, it would follow that 24 cubic inches of hydrogene remained in the internal organs of respiration, and consequently, by the rule of proportion, about 7,8 of the mixed residual gas of the common air. And then the whole quantity of residual gas of the lungs, supposing the temperature 59°, would have been 31,8 cubic inches; but as its temperature was nearly that of the internal parts of the body, 98°, it must have filled a greater space; calculating from the experiments of Guyton and Vernois,[194] about 37,5[195] cubic inches.