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18
ningspunctet’ fra begge Sider, idet jeg paa den ene Side
bar behandlet Vand. som paa Forhaand var utilstrækkeligt
mættet med Luft ved vedkommende Temperatur, og paa
deu anden Side først har mættet Vandet ved en betydelig
lavere Temperatur for derefter, som ovenfor beskrevet, at
ryste det med Luft ved den Temperatur, hvorved det
ønskedes mættet. Den Barometerstand, hvorved
Vandprøverne ere mættede, er altid bleven observeret, og ere de
uddrevne Gasmængd’er reducerede til Mætning ved 700""",
idet de absorberede Volumina ere satte proportionale med
Trykket. Resultaterne ere sammenstillede i nedenstaaende
Tabel, hvor Gasmængderne ere udtrykte som CC. pr. Litre
udkogt Vand reduceret til 0" og 760"" Tryk. De med
fede Typer trykkede Tal hidrøre fra de Vandprøver, der
i Forveien have været mættede med Luft ved en lavere.
Temperatur. Ved de med Klammer sammenføjede Tal ere
begge Luftprøver udkogte af samme Vandprøve.
o° C. 5°C- ’ lo-C. 15° C.
0 iV 0 N 0 1V 0 N
1 7-76 14-36 16.83 13.20 6.31 12.14 1 5-60 10.713
1 7-85 14-56 j 6.90 13-30 1 6.30 12.06 I 5-79 11.20
7-71 14-31 ( 6.97 13.16 1 6.25 12.04 5.70 11.04
— — 1 7.01 13 20 — — — —
Som Middelværdier erholder man heraf:
"C. 0 5 10 15
0 7-77 6-93 6.29 5-7°
N 14.41 13.22 12.08 11.01
0+ N= 100 0 »/„ 35-03 34-39 34-24 34-II
Til yderligere Control paa Rigtigheden af denne
Tabel hensattes en Vandprøve i uproppet Kolbe ved 0° i 7
Døgn, hvorpaa den deri opløste Luft udkogtes og
analyseredes, og viste den uddrevne Gas sig at være omtrentlig
af samme Sammensætning som ovenfor angivet nemlig
35.18 °/o Q mod 64.82 °/0 N. Af den samlede Luftmængde
erholdtes her ingen Maaling, da desværre en liden Blære
under Overfyldningen i Evdiometret gik tabt, den
resterende Del maalte 21.71 CC. Som man af denne Tabel
vil kunne se, er den Kvælstofmængde, som 1 Litre Søvand,
absorberer af den atmosphæriske Luft, ligetil proportional
med Temperaturen og lader sig udtrykt i CC. meget nøie
fremstille ved Formelen
N= 14.4 — 0.23 t,
hvoraf man istedetfor de
observerede Værdier . 14.41 13.22 12.08 11.01
kan beregne .... 14.40 13.25 12.10 10.95.
Hvad angaar den absorberede Surstofmængde, da er
Forholdet ikke længere saa simpelt, idet den Curve, der
betegner Variationen med Temperaturen, ikke længere er
en ret men en svagt krummet Linie, som paa Strøget fra
0 til 10". hvorom der her nærmest er Tale, lader sig
udtrykke ved Formelen
on the one hand, operating with water that has been
imperfectly saturated at a given temperature, and on the
other, saturating that water at a much lower temperature;
and not till then proceeding to shake it along with air at
the temperature for which saturation is sought to be
attained. The atmospheric pressure at which the samples of
water were saturated, was always noted down, and the
quantity of gas driven oft’ reduced to the point of
saturation at 760 mm, the volumes absorbed being put
proportional with the pressure. The results are set forth in
the following Table, the amounts of gas being expressed
in cubic centimetres per litre of the water examined,
reduced to a temperature- of 0° and a pressure of 760""".
The figures printed in thick type refer to samples of
water previously saturated with air at a lower
temperature: those in brackets are determinations performed with
the same sample of water.
0° C. 5" C. 10" C. 15° C.
0 V 0 N 0 iV 0 . A
17-76 14-36 ) 6.83 13.20 6.31 12.14 1 5-6O 10.79
17.85 ’4-56 1 6.90 ■3-30 1 6.30 12.06 ) 5-79 11.20
7-71 14-31 1 6.97 13.16 1 6.25 12.04 5.70 11.04
_ / 7.01 13.20 — — — ’ —
The mean proportions are accordingly: —
c. 0" 5° 10° _’5"
0 7-77 6-93 6.29 __5-70
A’ 14-41 I3-" 12.08 11.01
0 + iV= 100 0 p.ot. 35-03 34-39 34-24 34-n
"With the object of testing still further the accuracy
of this Table, a sample of water was allowed to stand over
in an open matrass at a temperature of 0° for the space
of 7 days, when the air absorbed by it was boiled out and
analysed; but the composition of the gas driven off proved
to be almost the same as that specified above, viz. 35.18
per cent oxygen and 64.82 per cent nitrogen. Of the total
amount of air no measurement was obtained, a small bubble
of gas having unfortunately escaped when transferring
the air into the eudiometer; the remaining portion
measured 21.71cc. As appears from this Table, the
quantity of nitrogen absorbed from the atmosphere by 1 litre
of sea-water is strictly proportional to the temperature,
and may be very accurately expressed in cubic centimetres
bv the formula —
N- 14.4 — 0.23t,
which, in place of
the values observed. 14.41 13.22 12.08 11.01
gives...... 14.40 13.25 .12.10 10.95
With regard to the amount of oxygen absorbed, the
proportion is less easily expressed, since the curve
indicating the variation with the temperature will no longer
be a straight, but a slightly curved line, which, from 0°
to 10", the interval most important here, may be
expressed by the formula —
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