Full resolution (JPEG) - On this page / på denna sida - Sidor ...
<< prev. page << föreg. sida << >> nästa sida >> next page >>
Below is the raw OCR text
from the above scanned image.
Do you see an error? Proofread the page now!
Här nedan syns maskintolkade texten från faksimilbilden ovan.
Ser du något fel? Korrekturläs sidan nu!
This page has never been proofread. / Denna sida har aldrig korrekturlästs.
temperature [Ti = — 0°... C] of nearly pure ice. Water can
not absorb or develop the same quantity of latent heat at two
different temperatures. Besides, the presence of salt in freezing
water has the property of diminishing its latent heat, at least
if the solidification, as always in nature, takes place a few
degrees below zero. 1 2 or 3 p.c. of salt dissolved in pure
water has the same depressing influence on its latent heat
and likewise on its freezing temperature as an increase of
pressure amounting to some hundreds of atmospheres.
From these premises we can draw the following
conclusions :
1. In the imagined example a complete cycle2 of heat
takes place. The quantity of ice (= 1 kgrm), which was
supposed to melt in the warm water of the Gulf-stream, is also
supposed to return to its original point of depart, in its initial
state of pure or nearly pure ice.
2. Meanwhile it undergoes the following transformations:
it melts at — 0°.. [absolute temperature T = 273°].
Thereby it absorbs the latent, heat Q,................................................. tjv
it mingles with the surrounding ocean-
water and thereby absorbs heat, qi.............................
of sea-water. But in those parts ot the ocean, where a real melting of
sea-ice takes place, the temperature never sinks so low. That part of the ice,
which is first liquefied, forms a stratum of fresh water around the ice-floe
wherein the rest of the ice liquefies at its ordinary melting point. Very
often the fresh or diluted sea-water in the vicinity of melting ice is found
to be of surprisingly high temperature. The lowest temperature observed
on the bank of New-Foundland during 5 years was — 0°.9 R, the mean
temperature was + 3°.oi R. [Proceedings of R. S. 1869. JW 3.] On the other
hand the temperature of freezing sea-water has never been found to be
higher than the ordinary freezing point of the water. See the observations
of Scoresby 1810—1817 and those of the Vega-expedition in Sept. 1878 a. O.
1 I consider this reservation to be necessary, because the temperatures
of the freezing experiments, enumerated in table 2 of this chapter, do
not exceed the limits — 9° 0 and — 3° C. Having no experiments to rely
upon at lower or higher temperatures, I do not wish to extend the rule
beyond the dominions of experience.
2 In order to prepare the application of Carnot’s theorem to the
example in question, I denote the quantities of heat absorbed or developed
by the water at every one of these secondary changes by >q» and in the
case of ice by >r>. The corresponding absolute temperatures are T, Ti,
To... T’, Tt,... Thus we may form the quotients 3J, 3?... JL , li etc...
1 T, ’ Ta T,’ Ti’
[»die Aequivalenzwerthe> of Clausius].
<< prev. page << föreg. sida << >> nästa sida >> next page >>
