*51 
et Thermometer, inddelt i Delstreger af Yærdi 0.‘2 med 
en Længde af O-Ofr"""., hvis CoiTectioner bestemtes ved 
gjentagne Sammenligninger med det herværende meteoro- 
logiske Instituts Normalthermometer. som til det Brug 
velvillig blev mig laant af Iiistitutots- Bestyrer. Professor 
Dr. Molm. 
Af Observationerne 32' til 37 kan først Udvidelsen 
af det til Pyknometrenc benyttede Glasrør beregnes, og 
man erholder, naar de af Wiillner 1 beregnede Yærdier for 
Ivviksolvets 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 For- 
bindelse med 24 og 25 til Be-regning af Glassets Udvidelse 
og erholder, naar man anvender de [af Hallstrom- og Ro- 
setti 3 bestemte Yærdier for Yandets Udvidelse. meget vel 
overensstemmende Tal, som i Middel ' fastsætte Glassets 
midlere Udvidelsescoefficient mellem 0° og 17.°5 til 0.0000275. 
Efterat man heraf har bestemt en passende Yærdi for Glas- 
sets Udvidelse, hvorved naturligvis de med Kviksølv ud- 
førte Bestemmelser fortrinsvis maa komme i Betragtning, 
kan man nu skride til Udledelsen af de videre Resultater 
af Forsøgene. Man maa imidlertid her 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 Y ægt, hvad der rimeligvis skriver sig fra Op- 
løsuiug af en Del af Glasset paa de ydre Vægge paa 
Grund af den stadige Omrøring i Badet. Den herved 
foraarsagede tJsikkerhed kan dog betydelig reduceres, naar 
man beregner Pyknometrets Vægt til enhver Tid under 
Forudsætning af, at Vægttahet er proportionalt med Ob- 
servationernes Antal, idet Usikk.erheden da knapt nok vil, 
influere paa 5te Decimal. Under denne Forudsætning har 
jeg senere beregnet følgende Resultater, idet jeg paa en- 
kelte Steder har tilladt mig smaa Aproximationcr, som 
imidlertid kim kan virke paa de endelige Yærdier med en 
liden Feil i 6te Decimal. 
Egen vægt ved j- 
• 17.°5 
17. "5 
17.5 
1 7.5 
0 ° 
w 
af ril 1.01739. 
af YH 1,02669. 
af I 1.02691. 
af I 1.02845. * 
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 mm , 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. Molm, 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 Wiillner 1 
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 Hallstrbm* * 
and Rosetti 3 for the expansion of water, very closely 
agreeing results will he obtained, the figures expressing 
the average mean coefficient of expansion of the glass be- 
tween 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 he given to the de- 
terminations performed with mercury, we may proceed 
to deduce the further results of the experiments. Mean- 
while. regard must be had to the fact, of. which the obser- 
vations 1. 2. 10. 26, 27, 28. and 29 afford conclusive proof, 
that the pycnometer had lost about 0.7 m ‘ ?r in weight during 
tlu* 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 instru- 
ment when in the water-bath. The uncertainty this occa- 
sions may however be very considerably reduced by com- 
puting 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 assump- 
tion, I subsequently computed the following results, intro- 
ducing, 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. •' 
of vn 1.02669. 
I 1.02691. 
I 1.02845. 
1 7.°o . 
17.°5 
it. ;> 
0 ° 
0 ° 
of 
of 
1 Pogg. Ann. 153 — 440. 
x Disse Yærdier ere ogsaa af Ekman benyttede til Bestemmelse 
af Udvidelsen af det Dilatometer, som denne til sine Forsøg over Sø- 
vandets Udvidelse har anvendt. 
* Ann. Chim. Phys. [4] — IT — 372. 
1 Pogg. Ann. 153, p. 440. 
* 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], IT, p. 372. 
