The hydrogene that I employed, was procured from the decomposition of
water by means of clean iron filings and diluted sulphuric and muriatic
acids. It was breathed in the same manner as nitrous oxide, in the
large mercurial airholder.
After a compleat voluntary exhaustion of my lungs in the usual
posture, I found great difficulty in breathing hydrogene for so
long as half a minute, so as to make a compleat expiration of it. It
produced uneasy feelings in the chest, momentary loss of muscular
power, and sometimes a transient giddiness.
In some of the experiments that I made; on account of the giddiness,
the results were rendered inconclusive, by my removing my mouth from
the mouth-piece after expiration, before the assistant could turn the
stop-cock.
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.
From the increase of volume, it would appear that a minute quantity
of gas had been generated during the respiration, and this was, as we
shall see hereafter, most probably carbonic acid.[196] Likewise there
is reason to suppose, that a little of the residual oxygene must have
been absorbed. Making allowances for those circumstances, it would
follow, that the 37,5 cubic inches of gas remaining in my lungs, after
a compleat expiration of atmospheric air at animal heat 98°, equal to
31,8 cubic inches at 59°, were composed of
Nitrogene 21,9
Carbonic acid 4,9
Oxygene 5,0
————
31,8
[194] Annales de Chimie, vol. 1, page 279.
[195] This is only an imperfect approximation; the ratio of the
increase of expansibility of gases to the increase of temperature, has
not yet been ascertained. It is probable that the expansibility of
gases is altered by their mixture.
[196] For there is no reason to suppose the production of nitrogene.
E. 2. I respired for near a half a minute in the mercurial airholder at
61°, 182 cubic inches of hydrogene; having made during this time, six
long inspirations. After the last expiration, the gas filled a space
nearly equal to 184 cubic inches, and analised, was found to consist of
Carbonic acid 4,8
Oxygene 4,6
Nitrogene 21,0
Hydrogene 153,6
—————
184,0
Now in this experiment, reasoning in the same manner as before, 28,4
cubic inches of hydrogene must have remained in the lungs, and likewise
5,5 of the atmospheric residual gas. Consequently, the whole residual
gas was nearly equal to 34 cubic inches at 61°, which at 98° would
become about 40,4 cubic inches. And reasoning as before, it would
appear from this experiment, that the quantity of gas remaining in my
lungs after a compleat voluntary respiration, equalled at 98, about 40
cubic inches, and at 61°, 34 nearly: making the necessary corrections;
that after common air had been breathed, these 34 cubic inches
consisted of
Carbonic acid 4,1
Oxygene 5,5
Nitrogene 24,4
_b._ It would have been possible to prove the truth of the postulate on
which the experiments were founded, by respiring common air or oxygene
after the compleat expiration of the hydrogene, for the same time as
the hydrogene was respired and in equal quantities.
For if portions of hydrogene were found in the airholder equal to
those of the residual gases in the two experiments, it would prove
that a _uniform_ mixture of residual gas with the gas inspired, was
produced by the respiration. That this mixture must have taken place,
appeared, however, so evident from analogous facts, that I judged the
experimental proof unnecessary.
Indeed, as most gases, though of different specific gravities, when
brought in contact with each other, assume some sort of union, it
is more than probable, that gas inspired into the lungs, from being
placed in contact with the residual gas on such an extensive surface,
must instantly mingle with it. Hence, possibly one deep inspiration
and compleat expiration of the whole of a quantity of hydrogene, will
be sufficient to determine the capacity of the lungs after compleat
voluntary exhaustion, and the nature of the residual air.
That two inspirations are sufficient, appears probable from the
following experiment.
E. 3. After a compleat voluntary expiration of common air, I made two
deep inspirations of 141 cubic inches of hydrogene. After the compleat
expiration, they filled a space equal to rather more than 142 cubic
inches, and analised, were found to consist of
Carbonic acid 3,1
Oxygene 4,5
Nitrogene 18,8
Hydrogene 115,6
—————
142,0
Now calculating on the exhausted capacity of my lungs from this
experiment, supposing uniform mixture, they would contain after
expiration of common air, about 30,7 cubic inches at 58°, equal to 36
at 98°, composed of about
Nitrogene 20,9
Oxygene 5,8
Carbonic acid 4,0
————
30,7
One should suppose a priori that in this experiment much less of the
residual oxygene of the lungs must have been absorbed, than in Expts. 1
and 2; yet there is no very marked difference in the portions evolved.
That a tolerably accurate mixture took place, appears from the quantity
of nitrogene. The smaller quantity of carbonic acid is an evidence in
favour of its evolution from the venous blood.
_c._ It is reasonable to suppose that the pressure upon the residual
gas of the exhausted lungs, must be nearly equal to that of the
atmosphere. But as aqueous vapour is perpetually given out by the
exhalents, and perhaps evolved from the moist coats of the pulmonary
vessels, it is likely that the residual gas is not only fully saturated
with moisture at 98°, but likewise impregnated with uncombined vapor;
and hence its volume enlarged beyond the increment of expansion of
temperature.
Considering all these circumstances, and calculating from the mean
of the three experiments on the composition of the residual gas, I
concluded,
1st. That the exhausted capacity of my lungs was equal to about 41
cubic inches.
2dly. That the gas contained in my bronchial vessels and fauces, after
a compleat expiration of atmospheric air, was equal to about 32 cubic
inches, its temperature being reduced to 55°.