Re: experimental latent heat of evaporation

[Bernard Cleyet <anngeorg@PACBELL.NET>]

Four terminal measurement of R is always recommended even tho typical
inexpensive (Radio Shack) DMM have ~ 100 Ohm R in the low mA ranges and
< ~ 0.1 Ohm in the A ranges.  This will ensure detection of poor
connections.

W/ out seeing the xpt.  [photo' and send me an attachment?] I wonder *
if not water isn't lost (boiled out as liquid).   I'm trying the xpt. in
the kitchen using methane just to dtmn. how vigorous is the boiling.

I'm surprised by the inefficiency of a gas burner.  A small one boils
water at the rate of only ~ 350 W!  This is not very vigorous, but if
the mouth is small and the liquid level high, liquid will be lost.

Millikan [Millikan - Gale - Bishop, Laboratory Physics  1914] does this
xpt. while measuring the gas flow.  [Efficiency of a gas stove p. 49].
This is after an xpt.. to detmn. the "heat" content of the gas.

To not worry about ripple and also convenient, a dime store immersion
heater plugged into a Variac would do the job.

*  However, unless I'm  confused, your error is on the "wrong direction"
for this to have occurred.

bc

p.s. You're performing the only practical method I can think of to find
L at other than "100 deg."


Ludwik Kowalski wrote:

> Not knowing what the "d.c." means (in the context of my power supply),
> and suspecting the worse, I used the oscilloscope. The amplitude of 60

cut