I Fordunstningsmaaleren B begynder Forsøget med 
en Vandmængde af 263 cbem. eller en Vægt af 270 Gram, 
der indeholder 9.56 Gram Salt. Den største Fordunstnings- 
mængde, der er maalt, er 60 chem. Ved Forsøgets Slutning 
indeholder Skaalen 270 minus 60 eller 210 Gram Vand, 
der holder 9.56 Gram Salt eller 4.55 pro Cent. Den spe- 
cifiske Vægter voxet fra 1.027 til 1.0347, altsaa mere end 
i det foregaaende Exempel. 
Fordunstningshastigheden er, cæteris paribus, propor- 
tional med Forskjellen mellem Vanddampenes Maximums- 
tryk (£) over den fordunstende Vædske og Vanddampenes- 
Tryk i Luften (e). Kaldes den i Tidsenheden fordunstede 
Vandmængde f, og er @ en Constant, saa har man 
Jf = 4 (LE). 
Antages e constant, har man 
hvor df er den Correction, som skal lægges til f, naar H 
gaar over fra Æ til E + dE. Trykket H over Saltvand 
kan ifølge Wiillners Lov! sættes 
13} = 19) | — & 4 
a 
hvor Æ, er Maximumstrykket af Dampene over rent Vand, 
a en Constant (der for Chlornatrium er 0.601), y Mæng- 
den af Salt og « Mængden af rent Vand. I vort Exem- 
pel fra Fordunstningsmaaleren B have vi Temperaturen af 
Fordunstningsvandet 79.6, hvortil svarer H) = 7.”"78 og 
Middelværdien af e = 5.”"15 efter Psychrometret. Man 
faar saaledes iølgende Regning. 
Ved Begyndelsen. 
(At Commencement). 
Y= 9:56 
w = 270—9.56 = 260.44 
_ 0.0367 
æ 
a? = 0.02206 
G6 
y 
l—e@2= : 
OF 0.97794 
B= 7:62793 
1 Annalen, Bd. 
Poggendorffs 103. 
143 
evaporating dish. These 515 grammes of water contain the 
whole amount of salt, 22.65 grammes, or the proportion of 
salt is 4.40 per cent. Hence, the specitic gravity of the 
water has increased from 1.027 to 1.0336. 
In the atmometer 4, the experiment begins with a 
volume of water of 263 cem., or a weight of 270 grammes, 
containing 9.56 grammes of salt. The greatest evaporation 
At the end of the experiment, the 
evaporating dish contained 270 minus 60, or 210 grammes 
measured was 60 cem. 
of water, with 9.56 grammes of salt, or 4.55 per cent. 
Hence, the specitic gravity had increased from 1.027 to 
1.0347, a greater value, therefore, than in the case given 
above. 
The rate of evaporation is, ceteris paribus, proportion- 
ate to the difference between the maximum tension of the 
aqueous vapour (#7) above the evaporating fluid and the 
tension of the aqueous vopour (e) present in the air. Let 
the quantity of water evaporated in the unit of time be f 
and å be a constant, we have then, f = a (#—e). 
Supposing e to be constant, 
df representing the correction to be applied to / when # 
changes from Hto H+ dE. The tension Æ above the salt 
water can, according to Wiillner's law,' be put — 
H=B,|1—« Å 
Då 
E, representing the maximum tension of the vapour above 
fresh water, @ a constant (which for chloride of sodium 
is 0.601), y the amount of salt, and x the quantity of 
fresh water. In the example from the atmometer BD, the 
mean temperature of the evaporating water was 7°.6, 
corresponding to Æ, = 7.”"78, and the mean value of 
e = 5.""15, by the psychrometer. 
these data is as follows: — 
The computation from 
Ved Slutningen. 
(At End). 
9:56 
210—0.56 = 200.44 
0.0476 
0.02861 
0.97139 
7:57684 å 
1 Poggendorffs Annalen, Bd. 103. 
