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51
et Thermometer, inddelt i Delstreger af Værdi 0.°2 med
en Længde af 0.68""".. hvis Correctioner bestemtes ved
gjentagne Sammenligninger med det herværende
meteorologiske Instituts Normalthermometer. som til det Brug
velvillig blev mig laant af Institutets Bestyrer. Professor
Dr. Mohn.
Af Observationerne 32 til 37 kan forst Udvidelsen
af det til Pyknometrene benyttede Glasror beregnes, og
man erholder, naar de af Wüllner1 beregnede .Værdier for
Kviksølvets Udvidelse lægges til Grund, som Udtryk for
Glassets midlere Udvidelsescoefficient mellem 0° og 15°
0.0000267 og mellem 0° og 20° 0.0000274. Man kan
desuden ogsaa benytte Observationerne 3, 4 og 5 i
Forbindelse med 24 og 25 til Beregning af Glassets Udvidelse
og erholder, naar man anvender de af Hällström- og
Rosette bestemte Værdier for Vandets Udvidelse, meget vel
overensstemmende Tal. som i Middel fastsætte Glassets
midlere Udvidelsescoefficient mellem O" og 17.°5 til 0.0000275.
Efterat man heraf har bestemt en passende Værdi for
Glassets Udvidelse, hvorved naturligvis de med Kviksølv
udførte Bestemmelser fortrinsvis maa komme i Betragtning,
kan man nu ski-ide til Udledelsen af de videre Resultater
af Forsøgene. Man maa imidlertid lier tage Hensyn til,
at Observationerne 1. 2, 10, 26, 27. 28 og 29 tydeligt
bevise, at Pyknometret under Forsøgene har tabt omkring
0.7 Mgr. i Vægt, hvad der rimeligvis skriver sig fra
Opløsning af en Del af Glasset paa de ydre Vægge paa
Grund af den stadige Omrøring i Badet. Den herved
foraarsagede Usikkerhed kan dog betydelig reduceres, naar
man beregner Pyknometrets Vægt til enhver Tid under
Forudsætning af. at Vægttabet er proportionalt med
Observationernes Antal, idet Usikkerheden da knapt nok vil
influere paa 5te Decimal. Under denne Forudsætning har
jeg senere beregnet følgende Resultater, idet jeg paa
enkelte Steder liar tilladt mig smaa Aproximationer, som
imidlertid kun kan virke paa de endelige Værdier med en
liden Feil i 6te Decimal.
Egenvægt ved af III 1.01739.
11 .°o
af vn 1.02669.
11 ."o
U^i af [ 1.02691.
1 <.°5
af I 1.02845.
1 Pogg. Ann. 153 — 440.
2 Disse Værdier ere ogsaa af Ekman benyttede til Bestemmelse
af Udvidelsen af det Dilatometer. som denne til sine Forsøg over
Søvandets Udvidelse bar anvendt.
3 Ann. Chim. Phys. [4] — 17 — 372.
too. at least once for every other determination,, and again
filled with the sea-water the volume of which had to be
■found. These observations were in no case considered
satisfactory unless the temperature of the water-bath had
been kept comparatively uniform for at least 15 minutes,
the greatest variation indicated by the thermometer during
that interval never having exceeded 0.°1. For reading the
temperature of the water-bath, a thermometer graduated
in divisons of 0.°2. measuring each 0.68""", was made use
of. the instrument having been previously corrected by
frequent comparison with the standard thermometer of the
Norwegian Meteorological Institute, which the Director.
Professor H. Mohn, had kindly lent me for that purpose.
Nos. 32—37 are the first of the observations by
which the expansion of the glass in the pycnometer may
be computed; and. taking the values found by AVüllner1
for the expansion of mercury as the basis of calculation,
the mean coefficient of expansion of the glass between 0° and
15° will be 0.0000267. and between 0° and 20°, 0.0000274.
Moreover, Nos. 3, 4. and 5. in conjunction with Nos. 24 and
25, will also serve for determining the expansion of the
glass; and, adopting the values computed by Hällström
-and Rosetti3 for the expansion of water, very closely
agreeing results will be obtained, the figures expressing
the average mean coefficient of expansion of the glass
between 0° and 17.°5 being 0.0000275. After a proportionate
value of the expansion of the glass . has been found,
for computing which preference should be given to the
determinations performed with mercury, we may proceed
to deduce the further results of the experiments.
Meanwhile. regard must be had to the fact, of which the
observations 1. 2. 10. 26, 27, 28, and 29 afford conclusive proof,
that the pycnometer had lost about 0.7m♂r in weight during
the progress of the experiments, some portion of the outer
surface of the glass having probably been dissolved, a result
of the constant motion of the water surrounding the
instrument when in the water-"bath. The uncertainty this
occasions may however be very considerably reduced by
computing the weight of the pycnometer for every experiment
on the assumption that the loss of weight is proportional
to the number of observations; in that case it will hardly
influence the 5th decimal. On the basis of this
assumption. I subsequently computed the following results,
introducing here and there slight approximations, which, however,
can affect the final result only by occasioning a small error
in the 6th decimal.
Specific Gravity at of III 1.01739.
1 1 < .°o
, of VII 1.02669.
1 < .’o
of I 1.02691.
1 <.°o
° of I 1.02845.
1 Pogg. Ann. 153, p. 440.
2 These values were also adopted by Ekman for determining the
expansion of the dilatometer which he used when investigating the
expansion of sea-water.
3 Ann. Chim. Phys. [4], 17, p. 372.
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