[thorium]

Is there an adapter for bucner funnel Ground Joint?

is there an apparatus specially designed to measure Melting Point? Other than filling small cappilary pipettes with the substance then dipping it into H2SO4 with a thermometer and then watching it to melt? I mean is there an easier way? A machine designed to measure the M.P?

And what about claisen adapters? what size are the ground joints? Say I have 14/23 ground joint addition funnel and I want to use my 29/32 reflux condenser at the same time is there a Claisen adapter adapted to this?

[Arkcon]

is there an apparatus specially designed to measure Melting Point? Other than filling small cappilary pipettes with the substance then dipping it into H2SO4 with a thermometer and then watching it to melt? I mean is there an easier way? A machine designed to measure the M.P?

I felt the same way in college and asked the professor.  And he said no.  And in my experience in industry, he was right.  That is exactly how raw materials are identified.

In my day it was a thiele tube of cottonseed oil, you're using H2SO4, at work it was a synthetic high quality oil. In school we relied on a gentle bunsen burner flame, at work it's a thermostatically controlled electric heater for the oil bath. 

But in the end, it's a capillary of a tiny amount of solid, attached to a thermometer, a black background, and your eyes, that tells you the m.p.

[ARGOS++]

Dear Thorium;

What you may think about (Only as one Example):   "FP62 Melting Point Apparatus”


Good Luck!
                    ARGOS⁺⁺

[Arkcon]

Dear Thorium;

What you may think about (Only as one Example):   "FP62 Melting Point Apparatus”


Good Luck!
                    ARGOS⁺⁺

Ahhh...very nice.  That's what I was hoping for back in my college days.  It's about time they automated the process.  I don't want to seem lazy, but like the blurb says, it's nice to take the human bias out of the analysis.  Still, I'll bet that, at least once in a while, the instrument fails with some sample or another.

[enahs]

Is this good for a mixture where there might be a relatively large range?

[ARGOS++]

Dear Enahs;

Could this be a part of a possible answer for you?:   "FP62 Document 1”

And also:  "ftp://ftp.dep.state.fl.us/pub/labs/lds/sops/3744.pdf”

Good Luck!
                    ARGOS⁺⁺

[thorium]

And about the vacuum pumps. As I do see there're some pumps which reduces the pressure up to 0.0001 Torrs! This is really unbelieveable! Is 1Torr=1mmHg (SO THIS MEANS 0.0001mmHg) or am I REALLY mistaken? Can't the glassware implode under this pressure?

[Arkcon]

And about the vacuum pumps. As I do see there're some pumps which reduces the pressure up to 0.0001 Torrs! This is really unbelieveable! Is 1Torr=1mmHg (SO THIS MEANS 0.0001mmHg) or am I REALLY mistaken? Can't the glassware implode under this pressure?

The glassware has a pressure rating written on it, I assume the manufacturer disavows liability for exceeding it. 

As for the pumps, I don't know how accurate the gauge is. If it is a small benchtop oil valve pump then maybe not.  A washing machine sized pump attached to a freeze drier, on the other hand, might work to that low.

Given that I don't know how accurate the dial gauge on any lab pump is, you might wonder how I know if I'm over-evacuating glassware.  It could potentially be a problem, so diligence is in order, generally keeping all vacuum or pressurized glassware behind a shield, of some sort.

[thorium]

But there must be an adjustement valve on the machine. If not it wont work for all the glasswares! Is this right?

[Borek]

This is a little bit funny. Assuming external pressure of 760 mmHg difference in forces acting on glassware that has 5 mmHg inside or 0.0001 mmHg inside is in the range of 0.6%. If the glass is strong enough to be used at 5 mmHg it should be able to survive any level of vacuum. 50 mmHg vs 0.0001 mmHg is 7% difference in forces - still not that much, I suppose security margins are much higher.

[Arkcon]

But there must be an adjustement valve on the machine. If not it wont work for all the glasswares! Is this right?

Hmmm... adjustment valve on a vacuum pump, to set to a specific pressure, no that's not now the bench-top oil valve or diaphragm evacuation pumps work.  Pretty much what I'd used was, you evacuated to the pressure you wanted, then blocked the vac. source with a valve.  I've used screw-type pressure regulators, but not vacuum regulators, they may exist for some applications.

Time to clear this all up, Thorioum.  What do you have, and what do you need to do?

[ARGOS++]

Dear Thorium;

For Glassware: Forces in the direction of “Compressing” is very rarely a problem, more common are its problems for tractive power!, because the corresponding “e-Modules” differ by several factors.
As with a simple water-jet pump you can reach a vacuum of 8 till 11 Torrs (for distillation), so the additional difference is nearly marginal, as Mr. Borek pointed out. With well designed Oil pumps you can easily get low pressurs like 0.1 till 0.01 Torrs.
“Over-evacuating” is ‘not possible’ for usual laboratory glassware.

For PES or “Photon-Electron-Coincidence-Spectroscopy” such powerful pumps (LPP’s) are required to make measurement possible.
But for such low pressure a Lot of special designs are required and you have to overcome several hindrances.
You may know, that by lowering the pressure the “Freie Weglänge” (German, - in English maybe: “free length of path”) increases dramatically for every molecule you have to catch with this LPP’s!
That’s why the diameters of the metallic (Why?) tubings goes over 15 – 30 Centimeters!
Another problem is to get the whole apparatus “clean enough”! – A small forgotten fingerprint can be a disaster!


Good Luck!
                    ARGOS⁺⁺

[thorium]

I need a vacuum pump which can go below pressures 4-5 mmHg. I've found a website called Welch but I cannot understand the terms like

Ultimate Pressure (which is defined by Torr and I've found a vacuum which suits my needs => 2 Torr)

and

Maximum Vacuum (which is "Hg And at the same pump its => 29.85)

They're Reverse-Balanced (meaning that as the ultimate pressure drops Maximum Vacuum rises )

 If someone could explain these to me I'd be very happy . Which one (maximum pressure or maximum vacuum) should I look for (for the pressures that I want)?

[ARGOS++]

Dear Thorium;

NO!,  ─  That’s not an Antagonism!

Both values mean the limit of the pump on the “identical side” of pressure/vacuum.
But both scales start not at the same “origin”:

•   ─  “Ultimate/Absolute Pressure” is the absolute Pressure the pump can not go below in any case, but it is possible that you never will reach this low level.
•    ─  “Maximum Vacuum” is in real a Δ Pressure (= Vacuum), that means how far below you can pump “below” the ambient Pressure the pump has to work in (against).

You see if you would have to start in an environmental pressure, let say of 1.5 atm the “Maximum Vacuum” set you a higher “End”-Limit as the “Ultimate/Absolute Pressure” will do it.
But if you start at 0.5 atm. you can not pump to a lower value then the “Ultimate/Absolute Pressure”, even if you have not reached the “Maximum Vacuum”.

The Diagram on the left in the Attachment may help for understanding.

Take care there are other “parameters” which should influence your decision like:
Must your pump be solvent resistant (in a Lab.), then an Oil-Pump may be not the adequate devise, and so on.

I hope to have been of help to you.

Good Luck!
                    ARGOS⁺⁺

[thorium]

You're unexplainably kind and helpful Argos++
Argos++ I've read what you wrote several times but there's something that I can't understand If the pump has got a Max Vacuum value that is 29,85 does it mean that it will go just 29,85 "Hg down the Atmospherical pressure or is this JUST an upper limit?   
 
I want to learn something does the pump that I've found has the requirements that I desire?  

And a note: The very deep (0.0001 mmHg Absolute Pressure) vacuum oil pumps haven't got a maximum vacuum value why?

Thank you very much!