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Siile
stillede jeg paa følgende Maade. Fordunstningsskaalen
holdtes tør. Et lidet Glas sattes op i den. og den
belastedes forresten med torre Vægter. Sand og Hagel, til den
kom paa Merke. De.t ydre Vand var ved Forsøgets
Begyndelse varmest, tildels opvarmet over Luftens
Temperatur. Dets Temperatur noteredes, hvorpaa jeg lod det
af-kjøle. enten i Luften eller ved Hjelp af Sne omkring det
ydre Kar. Paa forskjellige Stadier under denne Afkjøling
aflæstes Vandets Temperatur og Bøjen bragtes ned paa
Merke ved at helde rent. Vand fra en Burette i det lille
Glas. Efter hvert saadant Forsøg aftørredes Glasset
omhyggeligt. Den i Glasset heldte Vandmængde udviser
Forskjellen mellem Værdien af xt ved den oprindelige højeste
og ved de senere noterede lavere Temperaturer af det ydre
Vand. Jeg gjorde to saadanne Forsøgsrækker med hver
af Fordunstningsmaalerne. Af disse hidsættes de med B
gjorte, den förste i Christiania før Rejsen i 1877. den
anden i Tromsø samme Sommer.
object in view. I proceeded as follows: — The evaporating
dish was kept dry. A small glass vessel was put into the
dish, which, besides, was loaded with dry weights, sand
and shot, till the buoy had become depressed to the mark
on the stem. At the beginning of the experiment, the
outer water was warmest, being sometimes heated to a
higher temperature than that of the air. Its temperature
was noted, after which I let it cool, either by exposure to
the air or with snow surrounding the outer vessel. At
successive stages of the cooling, the temperature of the
water was read off. and the buoy brought down to the
mark on the stem by pouring fresh water from a burette
into the small glass vessel. After each experiment the
glass vessel was carefully dried. The quantity of water
poured into the glass vessel represents the difference
between the value of xt at the original (maximum)
temperature of the outer water and at the subsequently noted
(lower) temperatures. I made two such series of
experiments. with each of the atmometers. The following Table
gives the series with atmometer B, the first of which was
made in Christiania, previous to our departure on the
cruise in 1877. the second in Tromsø during the course of
the same summer.
Christiania.
Kubikcentimeter.
(Cubic Centimetres).
t x, r, ,—x, Obs. Diff.
■ 5"-o 4.18 0.00 0.0
12 .6 3.10 1.08 1.2 + 0.1
II .9 2.80 1.38 ’■5 + 0.1
II .6 2.68 1.50 1.6 + 0.1
9 -9 2.03 215 2.2 + 0.05
9 -5 1.90 2.28 2.2 — 0.1
Tromsø.
Kubikcentimeter.
(Cubic Centimetres).
t x, xa.-,—X, Obs. Diff.
8°.7 1.62 0.00 0.0
6 .2 0.92 0.70 0.7 0.0
5 ■> 0.67 0-95 0.9 0.0
4.6 0.56 i 06 0.4 — 0.7
i -9 0.16 1.46 1.1 - 0.4
■ -7 0.12 1.50 0.8 — 0.7
Forskjellerne mellem de observerede og beregnede
Værdier ere, som man ser, mindre end den Nøjagtighed,
som man kan opnaa i Søen.
4. Under Fordunstningen voxer Vandets
Saltholdighed, hvorved Fordunstningen bliver langsommere. For at
vise Virkningen heraf vil jeg tage et Exempel. Lad
Vandets specifiske Vægt være ved Forsøgets Begyndelse 1.027.
Vandet i Skaalen i A udgjør 023 cbcin., altsaa dets Vægt
623 X 1.027 eller 640 Gram. Til en specifisk Vægt af
1.027 svarer efter Prof. Karstens Tabeller 3.54 Procent Salt.
640 Gram Vand indeholder altsaa 22.65 Gram Salt. Den største
Fordunstningsmængde, der maaltes med A er 125 cbcm.,
eller 125 Gram rent Vand. Ved Forsøgets Slutning var
der altsaa 640 minus 125 eller 515 Gram Vand i Skaalen.
I disse 515 Gram Vand indeholdes den hele Saltmængde,
22.65 Gram, eller Saltholdigheden er 4.40 Procent.
Vandets specifiske Vægt er voxet fra 1.027 til 1.0336.
The differences between the observed and the computed
values are much below the limit of accuracy attainable
at sea.
4. During evaporation the saltness of the water
increases, thus retarding the evaporating process. To show
the effect of this phenomenon, I will give an instance in
point. Let the specific gravity of the water at the
beginning of the experiment be 1.027. The volume of the
water in the evaporating dish A amounts to 623 cubic
centimetres, and its weight is accordingly 623 X 1-027, or 640
grammes. To a specific gravity of 1.027 correspond,
according to Professor Karstens’s Tables. 3.54 per cent of
salt; hence, 640 grammes of water contain 22.65 grammes
of salt. The greatest evaporation found, in any one
experiment with atmometer A, was 125 ccm., or 125 grammes
of water. At the end of the experiment, there was
consequently 630 minus 125. or 515 grammes of water in the
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