Amongst the properties of nitrous gas noticed by its great discoverer,
is that of absorbability by water.
In exposing nitrous air to distilled water, Dr. Priestley found a
diminution of the volume of gas, nearly equal to one tenth of the bulk
of the water; and by boiling the water thus impregnated, he procured
again a certain portion of the nitrous gas.
Humbolt, in his paper on eudiometry, mentions the diminution of
nitrous gas by water. This diminution, he supposes to arise from the
decomposition of a portion of the nitrous gas, by the water, and the
consequent formation of nitrate of ammoniac.[108]
[108] He says, “On a observé, (depuis qu’on travaille sur le pureté de
l’air) que le gaz nitreux, secoué avec l’eau, en souffre une diminution
de volume. Quelques physiciens attribuent ce changement à une vraie
absorption, à une dissolution du gaz nitreux dans l’eau; d’autres
à l’air contenu dans les interstices de tous les fluides. Le cit.
Vanbreda, à Delft, a fait des recherches très-exactes sur l’influence
des eaux de pluie et de puit, sur les nombres eudiométriques; et les
belles expériences du cit. Hassenfratz, sur l’abondance d’oxygène,
contenue dans les eaux de neige et de pluie, sont supposer que l’air
des interstices de l’eau joue un rôle important dans l’absorption
du gaz nitreux. En comparant ces effets avec les phénomènes observé
dans la decomposition du sulfate de fer, nous supposâmes, le cit.
Tassaert et moi, que le simple contact du gaz nitreux avec l’eau
distillée pourroit bien causer une décomposition de ce dernier. Nous
examinâmes soigneusement une petite quantité d’eau distillée, secouée
avec beaucoup de gas nitreux trés-pur, et nous trouvâmes, au moyen de
la terre calcaire, et l’acide muriatique, qu’il s’y forme du _nitrate
d’ammoniaque_. L’eau se décompose en cette opération, par un double
affinité de l’oxygene pour le gaz nitreux, et de l’hydrogène pour
l’azote; il se forme de l’acide nitrique et de l’_ammoniaque_; et,
quoique la quantité du dernier paroisse trop petite pour en évaluer
exactment la quantité, son existence cependant se manifeste, (à ne pas
sans douter) par le dégagement des vapeurs, qui blanchissent dans la
proximité de l’acide muriatique. Voilá un fait bien frappant que la
composition d’une substance alcaline par le contact d’une acide, et de
l’eau.”
Annales de Chimie, t. xxviii. pag. 153.
I confess, that even before the following experiments were made, I
was but little inclined to adopt this opinion: the small diminution
of nitrous gas by water, and the uniform limits of this diminution,
rendered it extremely improbable.
_a._ To ascertain the quantity of nitrous gas absorbable by pure water,
and the limits of absorption, I introduced into a glass retort about 5
ounces of water, which had been previously boiled for some hours. The
neck of the retort was inverted in mercury, and the water made to boil.
After a third of it had been distilled, so that no air could possibly
remain in the retort, the remainder was driven over, and condensed in
an inverted jar filled with mercury. To three cubic inches of this
water,[109] confined in a cylinder graduated to,05 cubic inches, 5
cubic inches of nitrous gas, containing nearly one thirtieth nitrogene,
were introduced.
[109] Which was certainly as free from air as it ever can be obtained.
After agitation for near an hour, rather more than ⁴/₂₀ of a cubic inch
appeared to be absorbed; but though the process was continued for near
two hours longer, no further diminution took place.
The remaining gas was introduced into a tube graduated to,02 cubic
inches. It measured ¹⁴/₅₀; hence ¹¹/₅₀ had been absorbed.
Consequently, 100 cubic inches of pure water are capable of absorbing
11,8 of nitrous gas. In the water thus impregnated with nitrous gas I
could distinguish no peculiar taste;[110] it did not at all alter the
color of blue cabbage juice.
[110] Dr. Priestley found distilled water, saturated with nitrous air,
to acquire an astringent taste and pungent smell. In some unboiled
impregnated pump water, I once thought that I perceived a subacid
taste; but it was extremely slight, and probably owing to nitrous acid
formed by the union of the oxygene of the common air in the water, with
some of the nitrous gas.
_b._ To determine if the absorption of nitrous gas was owing, to a
decomposition of it by the water, as Humbolt has supposed, or to a
simple solution; I procured some nitrous gas from nitrous acid and
mercury, containing about one seventieth nitrogene. ,5 cubic inches
of it, mingled with ,25, of oxygene, from sulphuric acid and manganese
left a residuum of,03. 5 cubic inches more were introduced to 3 of
water, procured in the same manner as in the last experiment, in the
same cylinder. After the diminution was complete, the cylinder was
transferred in a small vessel containing mercury, into a water bath,
and nearly covered by the water.
As the bath was heated, small globules of gas were given out from the
impregnated water, and when it began to boil, the production of gas was
still more rapid. After an hour’s ebullition, the volume of heated gas
was equal to 1,4 cubic inches nearly.
The cylinder was now taken out of the bath, and quickly rendered cool
by being placed in a water apparatus. At the common temperature the gas
occupied, as nearly as possible, the space of,5 cubic inches: these,5
mingled with,25 of oxygene, of the same kind as that employed before,
left a residuum nearly equal to,03.
From this experiment, which was repeated with nearly the same results,
it is evident,