Well now, I cannot claim that I paid very close attention in Chemistry (and it
 is
going on ten years now <gulp>).  But any liquid will heat to the boiling point
 and
then the temperature will stay absolutely flat until all of the liquid is vapor
(gone).  At that point the temperature will shoot through the roof (assuming
 that
your temp probe is somehow coupled to the element when the liquid is gone).  If
memory serves me, an impure liquid, such as salt water, will not flatten off
perfectly but will have a gentle slope during the boiling process.  You may have
to prepare for boiling phases that are simply less sharp than the heating phase.
You may have to make some pretty intuitive software.  Wait! I know! use fuzzy
logic and just say 'look for the flat spot'.  Then you're problem is solved.
 Why
didn't we think of that sooner.

Chris Eddy
Pioneer Microsystems, Inc.

PHXSYS wrote:

> Hello everyone,
>
> I have a challenge!
>
> I need some ideas for measuring the boiling point of various fluids. The
> specific gravity of one fluid is approx 1.03, very close to water. The
> accuracy I am looking for is +/- 3 %. I am looking for creative options, the
> simplier the better.
>
> The boiling points may be as high as 500 degress F. A very small sample of
> fluid will be tested 3-10 ml. I believe I will use a small electric heating
> probe (hot wire) to quickly raise the temperature. The tesing time should be
> between 30-60 seconds. The higher the boiling point the longer the test.
>
> Can I look for the presence of vapor is a closed system; measure the current
> of the probe and watch for reaction at boiling point, measure pressure changes
> or pulsations as the fluid boils?
>
> I would appreciate any code snippits that help. Thanks in advance.
>
> Jon