Re: temp. calibration

[PHRP@FHSUVM.FHSU.EDU (Roger A. Pruitt)]

My 1958-1959 edition of the Handbook of Chemistry and Physics discusses stem
correction for liquid in glass thermometers on p. 2323. There is a formula
which is 
T_c = T_o + F*L(T_o - T_m)
where T_c is the corrected temperature,
T_o the observed temperature,
T_m the mean temperature of the exposed stem,
L the length of the exposed stem in degrees above the surface of the
substance whose temperature is being determined, and
F the correction factor.

A table of F values are given and depend on the liquid as well as the type
of glass used in the stem.

T_m determined by fastening the bulb of a second termometer against the
midpoint of  the exposed liquid column.

I don't know the derivation of this formula but hopes it helps.

Roger Pruitt

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> On Mon, 6 Jan 1997, James Mclean wrote:
>
> > Michael N. Monce says:
> > > calibration curve.  More accuarcy can be obtained by correcting the data
> > > for stem effects, etc. on the Hg thermometer.
> > This sounds interesting.  What are "stem effects" on a thermometer?
>
>
> 	These are corrections due to the stem of the thermometer not being
> in contact with the same substance as the bulb.  For example, if the bulb
> is placed in water but the stem is in air, then the expansion of the Hg
> will be different from the case when the entire thermometer was immersed.
> Very similar to some of the corrections necessary when making pressure
> measurements with a McLeod gauge.  I don't recall details off the top of
> my head; I think you would have to look back into the literature from the
> 50's.  I do recall a paper I have buried somewhere from circa 1950 which
> describes such corrections, especially in the Hg column on a McLeod gauge.
>
>
> 				Mike Monce
>        			Connecticut College