Sulaiman
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usb m.p. determination discussion
On my wish-list is a cheap, simple, reliable, rapid, accurate melting point determination box.
There are of course many professional instruments, but nothing cheap on eBay.
I know that there are quite a few here who may have the interest and expertise to make such things,
and many willing to contribute,
so I would like to start a discussion of this topic,
in the hope that I will be able to buy a good cheap one from someone soon 
A m.p. determination of a synthesised product is rarely done by members here, even the YouTube publishers,
We know how useful m.p. determination is, we want to do it - but it is soo tedious that we rarely do it.
Once you have a usb device there is the potential for mission-creep and no result,
so no spectroscopy, colorimitry, densitometry .... PLEASE, just a m.p. box
... make a new topic for 'options' if necessary.
I suggest that the first constraint is that it can be powered by a usb port
. anyone interested has a usb power source
. there are no power related safety or liability problems.
. there is enough power for heating and instrumentation.
Accuracy: - more experienced members will hopefuly suggest an 'optimim'
I consider +/- 1oC purchaseable, +/- 0.1oC excellent ... tbd
So, does anyone here want to enter a niche market ?
CAUTION : Hobby Chemist, not Professional or even Amateur
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j_sum1
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So... what are you thinking here? A holder for a glass tube, glass tubes to hold your sample -- preferably of a standard size so you can buy a box of
1000 for $2 and call them disposable, a heating element, a window so you can see when melting occurs, a thermocouple and a digital readout. All
integrated. The size of a matchbox and able to plug into a 5.5V USB.
Both the electronics and fabrication are beyond my ability. But I would buy one in an instant if it was available and was halfway reliable. ATM I
don't even own a thiele tube. Maybe I should expend a couple of bucks on that first.
I love this idea -- that is if your idea is remotely similar to what I envisage. It is one of those things that should already have been done. It
would be fantastic if combined skills here could make this happen.
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Sulaiman
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I have all sorts of ideas, but I thought I'd see if anyone is willing and able to take on the actual work
. capillary tubes are disposably cheap so possibly a good choice maybe combined with an eyepiece/usb camera etc.
. but good thermal contact between sample and thermocouple or Pt temperature sensor is problematic - (or not ?)
. maybe just putting the raw material on a micro-hotplate is easier ?
(e.g. the ceramic side of a Pt film RTD combining heating and measuring)
should we detect melting by visual methods?
or by other means ?
e.g. the sensor from an optical mouse, a weighted lever on the crystals, detecting collapse, ... more brains = more options.
I'm just hoping for an enthusiast to take the bait 
EDIT: conversely, if we can produce a functional requirements specification, and a vague hope of a small market,
I think that I know members of other more electronics related forums that may be interested.
So rather than wait for a voulenteer, let's start with functional requirements, as a start, later we can look at methods.
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FUNCTIONAL REQUIREMENTS
Power Source: usb port
Temperature range: ambient to 300oC
Temperature accuracy: +/- 1oC
Temperature rate of change : 1oC/second
Mode :
automatic - A sample is inserted and after a time the m.p. is displayed.
and/or
manual - requires user observation of melting and temperature.
Options:
. auto-calibrate (probably requires at least two reference samples ?)
Please suggest changes to functional requirements with reasons.
__________________________________________________
EDIT: there is a related market for m.p. rreference samples,
e.g. I have paid more for callibration weights than for scales 
[Edited on 15-2-2017 by Sulaiman]
CAUTION : Hobby Chemist, not Professional or even Amateur
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wg48
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One minute determination time could be difficult if the max t is 300C. A fast ramp to the low limit of a selectable temperature range would help.
A calibration mode would useful.
The melting point can be determined by the heat flow or rate which would detect decomposition too. That could difficult but if you want automatic.
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Sulaiman
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Changed to 1oC per second
... open to debate, as is the 300oC upper limit .. all are up for discussion
Added potential for m.p. reference kit
let us do functional requirements first, then look at methods
... I get confused and side-tracked easily.
[Edited on 15-2-2017 by Sulaiman]
[Edited on 15-2-2017 by Sulaiman]
CAUTION : Hobby Chemist, not Professional or even Amateur
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Boffis
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If the thermometer and heavy paraffin in a test-tube or special Thiele tube isn't good enough then I think you will have to buy a second hand
electronic one off ebay. I got one for about £70 an old SM3. I had to calibrate it to check that it was giving me sensible numbers. It actually
turned out to be 2 degrees too low across the whole range from about 30 to 280 C. I recrystallised 6 compounds numerous times until they gave constant
MPs. The main problem I had was finding half a dozen compounds over the range that had melting points that most source could agree on! I use mine a
lot, like you say its a value piece of kit so I think it was worth it.
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Sulaiman
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my m.p. determinations have been few and crude, I'd rather not talk about them 
starting of course with thermometer callibration vs. reference samples. (thanks to DJF90)
but I do see/want the use of one.
I would expect a < $10 product if the Chinese like it, something like the pH probes etc.
My main reason for wanting m.p. determinations is to check if what I made is what I intended to make.
I don't mind failing, but I hate lack of certainty in my own results.
Anyway ....
Any comments on the functional requirements ?
[Edited on 15-2-2017 by Sulaiman]
CAUTION : Hobby Chemist, not Professional or even Amateur
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