[time-nuts] OT, looking for a good science forum

Bob Camp lists at rtty.us
Sat Jan 26 15:48:44 EST 2013


Hi

If the intent is to come up with a triple point cell to calibrate your thermometer, acetone's triple point (at 178.5K) is a bit low. I still think I'd go with ammonia. 

Bob

On Jan 26, 2013, at 2:51 PM, Graham / KE9H <timenut at austin.rr.com> wrote:

> On 1/26/2013 1:29 PM, Paul Amaranth wrote:
>>> Message: 4
>>> Date: Sat, 26 Jan 2013 16:28:19 +0100
>>> From: Fabio Eboli <FabioEb at quipo.it>
>>> To: Discussion of precise time and frequency measurement
>>> 	<time-nuts at febo.com>
>>> Subject: Re: [time-nuts] OT, looking for a good science forum
>>> Message-ID: <5ef3f142b075fcab38182666a4e5073b at quipo.it>
>>> Content-Type: text/plain; charset=UTF-8; format=flowed
>>> 
>>> Il 2013-01-26 14:58 Bob Camp ha scritto:
>>>> Hi
>>>> 
>>>> Platinum RTD's are a pretty good bet for -80C, they hold up well down
>>>> there. For calibration, ammonia and acetylene both have triple points
>>>> in the vicinity. I'd probably try ammonia first, but not for any good
>>> Doesn't acetylene have a bad habit of dissociate when pure liquid?
>>> 
>>> Fabio.
>>> 
>> Yes, it's normally stored disolved in acetone.  It also spontaneously dissociates
>> if pressures exceed 15 psig or 30 psi absolute.  That could put a real damper on your day.
>> 
>> 
> Just pure acetone works well at dry ice temperatures.  We used crushed dry ice
> in acetone as an alternative when the liquid nitrogen truck was late making its delivery
> for the cryro lab.
> 
> --- Graham / KE9H
> 
> ==
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