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54
stemme de her beskrevne Resultater kun maadeligt overens.
Ifølge den af Wackerbarth efter Ekmans Observationer
beregnede Formel er Temperaturen for Tæthedsmaximum
hos Søvand af Egenvægt 1.02707 = — 4.°04, medens Lig-
ningen ’V = 0 med de af mig fundne Coefficienter giver
at
Temperaturen —4.° 45.
Paa Grund af denne gjennemførte Overensstemmelse
mellem Ekmans og mine Resultater, har jeg ikke fundet
det fornødent at bestemme Udvidelsen af Vandprøver af
lavere Egenvægt, men har uden videre anvendt Ekmans
Observationer paa de faa Puncter, hvor jeg til Reduction
af de paa den norske Nordhavsexpedition aflæste
Egenvægter har havt Brug for dem. Ved Hjælp af de ovenfor
opførte Værdier for Søvandets Volumina ved forskjellige
Temperaturer kan man nu beregne de Correctioner,
hvormed de ved vilkaarlige Temperaturer aflæste Egenvægter
17.°5
maa forbedres forat reduceres til . _ . . Correctionerne.
1 / .°o
hvori ogsaa indgaar et Led. der afhænger af Aræometrenes
Udvidelsescoefficient,1 findes sammenstillede i nedenstaaende
Tabel.
t° Correction t° Correction
o —0.00224 12 —0.00104
2 —0.00214 14 —0.00069
4 —0.00201 16 —0.00031
6 —0.00183 18 0.00011
8 —0..00161 20 0.00056
IO —0.00134
Hvor den Temperatur, hvorved Aflæsningen ’foretages,
ikke fjerner sig meget fra Normaltemperaturen 17."5. kan
disse Correctioner. der strengt taget kun gjælde for Søvand
af Egenvægt omkring 1.027. ogsaa uden mærkelig Feil
anvendes for Vandprøver af en derfra temmelig forskjellig
Egenvægt. Hvor derimod den Temperatur, hvorved
Aflæsningen foretages, ligger langt fra 17.°5, ere disse
Correctioner kun gyldige for et meget begrændset Interval.
Efterat saaledes de aflæste Egenvægter ved
Anbringelse af disse Correctioner ere reducerede til
Normaltemperaturen. staar det endnu tilbage at befrie dem for de ved
de benyttede Aræometre heftende constante Feil.
Til Aflæsning af saa godt som alle paa Expeditionen
bestemte Egenvægter benyttedes kun 3 Aræometre. to paa
første Togt og et paa de to sidste. Af de to først nævnte,
der af Svendsen før Udreisen vare udvalgte af de øvrige,
foreli de havde vist sig at stemme særdeles vel overens, er
desværre det ene senere bleven knust, det andet er endnu
i Behold og er sammen med det paa sidste Togt benyttede
bleven corrigeret af mig.
A. Wackerbarth from Ekman’s observations, the
temperature for the maximum density of sea-water with a specific
gravity of 1.02707 is—4.p04, whereas the equation ^ =0
gives, with my coefficients, a temperature of —4.°45.
Relying, then, on the close agreement between
Ekman’s results and my own, I have not determined
the expansion in samples of sea-water with a lower
specific gravity, but have adopted Ekman’s observations,
for reducing, when needful, the specific gravities read on
the Norwegian North-Atlantic Expedition. By means of
the values, tabulated above, for the volume of sea-water at
different temperatures, the corrections which serve to reduce
. 17.°5
specific gravities read at any given temperature to ^ ti_
may be computed. These corrections, into which the
coefficient of expansion of the areometer1 enters as a factor,
are given in the following Table.
t° Corrections t° Corrections
0 —0.00224 12 —0.00104
2 —0.00214 14 —0.00069
4 —0.00201 16 —0.00031
6 —0.00183 18 0.00011
8 —0.00161 20 0.00056
10 1 —0.00134
When the temperature is not far removed from the
normal temperature. 17.°5. these corrections, which, strictly
speaking, apply only to sea-water with a specific gravity
of about 1.027. may, without involving any appreciable
error in the result, be likewise adopted for samples of
water whose specific gravity differs considerably from that
expressed by the above formula; but when, on the other
hand, the temperature at which the specific gravity is read
and that of 17."5 lie far apart, the interval for which these
corrections will serve is but very limited.
After reducing by means of these corrections the
specific gravities to the normal temperature, there still
remains to eliminate the constant error of the areometer.
For reading almost all of the specific gravities
determined on the Expedition, only 3 areometers were made use
of, two on the first cruise and one on the two last. Of
the two former, which, having been found to agree
uncommonly well, Mr. Svendsen had selected previous to his
departure, one was unfortunately afterwards broken; the
other is still in perfect order, and was, together with that
made use of on the last voyage, corrected by myself.
1 Som saadan benyttedes 0.000026.
1 That adopted was 0.00002G.
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