Will a Sprengel Pump Work?

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Max Stevens
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Will a Sprengel Pump Work?

Post by Max Stevens »

The sprengel pump may have been the original high vacuum pump. Apparently, it achieves high vacuum by trapping air in between drops of liquid. When properly designed, a sprengel pump will theoretically pump to the vapor pressure of the liquid used. It looks easy enough to rig for cheap. Such a liquid would usually be mercury, which would pump fast and has a low vapor pressure. However, silicone oil has a lower vapor pressure, and is easy to buy. The problem is that I am not sure if it would pump at all, if not very slowly compared to mercury. Just a few questions: Could it reach the needed vacuum, would the leftover mercury/silicone oil vapor work for plasma without deuterium, and is there be a place to buy mercury?
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Re: Will a Sprengel Pump Work?

Post by John Futter »

Yes it would work albeit very slowly
The drop tube would have to be very high nearly 30 feet due to the lower density of the fluid
also the viscosity of the oil is going to make it 10 -100 times slower than the mercury version
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Rich Feldman
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Re: Will a Sprengel Pump Work?

Post by Rich Feldman »

Welcome, Max. Most of your questions aren't hard to answer using Internet searches, and searches of this forum. That includes acquisition of mercury.

John mentioned the tall column required for a Sprengel pump using low-density fluids. A backing pump can greatly reduce the height requirement. I wonder what tube materials aren't wetted by oil? So falling droplets would be like short plugs of mercury in glass, without a film coating the whole I.D. , not that that's necessarily a problem.

One historical article says: The Sprengel pump was so fast and so efficient - Sprengel’s earliest attempts could completely evacuate a half litre vessel in 20 minutes - that everyone working with vacuum used them. William Crookes used the pumps in series in his studies of electric discharges. William Ramsay used them to isolate the noble gases. But, most significantly, Swan and Edison evacuated their new carbon filament lamps with Sprengel pumps. https://www.chemistryworld.com/opinion/ ... 41.article

Chilling the apparatus can reduce the vapor pressure of mercury, from order of 1e-3 torr at room temperature to order of 1e-6 torr at Hg freezing point. Moisture in the gas being pumped would tend to freeze in the pump.
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Re: Will a Sprengel Pump Work?

Post by Silviu Tamasdan »

You need a liquid that doesn't wet the glass or whatever tube you're using. Else you could make one with any other metal that is liquid at room temperature, such as galinstan. You could make galinstan work, but you need special coatings on the inside of the tubes.

video on building and operating a Sprengel pump: https://www.youtube.com/watch?v=viJ3T-1KZqY
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Max Stevens
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Re: Will a Sprengel Pump Work?

Post by Max Stevens »

I just did a little more research, and i found that elemental gallium has an extremely low vapor pressure in liquid form. It is also easily found online. A minor setback would be warming the metal through its cycle, but I could deal with that. It is also about 3/5 the density of mercury, so the pump would maybe even fit indoors!
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Re: Will a Sprengel Pump Work?

Post by Silviu Tamasdan »

Yes gallium will work if you find a way for it to not wet the glass. As long as it adheres to the glass (and it does it very well) you won't be able to get it to move along the capillary tube.
Same problem with galinstan, which contains gallium and is liquid at room temperature. But it wets glass very well.

(NB there are ways to prevent gallium-to-glass adhesion but I'm not sure they are feasible at amateur level; they involve special coatings of the glass)
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Re: Will a Sprengel Pump Work?

Post by Richard Hull »

If you are really serious about a Sprengel pump, and I mean really serious............Belly up to the bar and use the true, he-man's mercury in it as it was designed. It is the smallest Sprengel pump you can make. If you are going to do it, do it up right and never mind the mercury spill possibilities and the low vapor pressure leaving unseen mercury films all over the place. Man up!

It will help if you have a mercury "still" to warrant absolutely clean mercury for your project. I was offered one for free a few years back. All I had to do was pick it up. You could, of course, make your own Hg still, assuming you can make a Sprengel pump. Where there is a will there is a way.

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Re: Will a Sprengel Pump Work?

Post by Max Stevens »

I guess I didn't realize that gallium would wet the glass. Thank you for reminding me of that. At this point, I am just doing research on buying mercury in sufficient quantities. I have a furnace that could vaporize mercury already, so distillation wouldn't require much more than tubing and containers. Another acquisition method would be to roast cinnabar and something like zinc in such a distillation apparatus, but at this point, I don't know which method will be cheaper. If I could find my own ore, than home synthesis would be the way to go. However, as far as I have seen, cinnabar is almost the same cost as mercury for what it is worth.
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Rich Feldman
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Re: Will a Sprengel Pump Work?

Post by Rich Feldman »

There are much easier ways.
ebm.JPG
(kind of overpriced)
ebm2.JPG
(let's watch this one)
I hope those sellers aren't shipping by U.S.P.S., which is against the rules. Other parcel services can transport packages with < 1 pound of mercury, without hazmat documentation & fees.
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Dennis P Brown
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Re: Will a Sprengel Pump Work?

Post by Dennis P Brown »

Hold on here a minute - mercury being heated? That means a LOT of vapor released (even room temperature mercury releases a significant amount of vapor.) You had better have a good fume hood - mercury vapor is one of the worse substances to breath - over 50% (close to 70%) inhaled remains in your blood stream! It is a powerful neurological toxin and better not have any children breath this vapor.

Tripled distilled is as pure as anyone needs and is available - distilling it yourself is, again, dealing with significant quantities of Hg vapor.

Disposal is an issue - make sure that any company you buy it from allows return for disposal - that is an extremely toxic and hazardous material to dispose of relative to the environment and you must follow all local laws.

That all said, why would you want to create a vacuum using such a primitive system? A cheap, simple diffusion pump using oil is far, far better, and much faster as well as perfectly safe.
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Rich Feldman
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Re: Will a Sprengel Pump Work?

Post by Rich Feldman »

Yes, and Sprengel pumps were superseded by diffusion pumps driven by boiling mercury.

In the 1960's, Scientific American's classic Amateur Scientist columns had several projects for skilled, well-equipped amateur glassblowers.
Including a Hg-vapor diffusion pump.

I couldn't immediately find a picture of that, but here's a contemporary glass diffusion pump you can buy from svpneon.com.
StandardDP.jpg

Here's one homebrew Sprengel pump running on youtube.
https://youtu.be/viJ3T-1KZqY?t=641
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Re: Will a Sprengel Pump Work?

Post by Silviu Tamasdan »

That's the same video I linked to earlier in the thread. Cody has several other interesting videos, including running a mercury still. Somehow he manages to do it safely without exposing himself too much to mercury (another video has his own toxicology test results for heavy metals in the body including mercury and lead).
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Rich Feldman
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Re: Will a Sprengel Pump Work?

Post by Rich Feldman »

Silviu did post that video link first, and I'm sorry not to have noticed sooner.

Here's my account of cleaning "dirty" mercury, obtained through craigslist from a local resident about 5 years ago. Since then the street price has gone way up. I think after a USA-and-Europe export ban, to discourage unhealthy and wasteful use by very poor people extracting gold in far-away countries.

Looks like some previous owner had been collecting Hg metal from various sources. Floor sweepings? Came to me in a factory-printed "Mercury, 10 lbs" bottle (about the size of a 12 oz soda can), mostly full. I bet the shrink seal on its cap was put on to discourage friends or children from playing with it.

It looked too scummy to behave well in glass capillary tubes, such as McLeod gauges. I found online links to many references, dating back more than a century, about cleaning and purifying mercury. Bet it still deserves the title "the purest metal" in commerce.

I cleaned about a pound of mercury by shaking, in a thick plastic bottle with corrugated sides and stoutly-threaded screw cap. Starting with soapy water or ammonia, then vinegar, maybe even dilute HCl, till the wash water was clear. The metal looked mirror-clean after that, and "pinholing" (look it up). I never made it fall in fine drops through a tall column of dilute nitric acid, nor distilled any under vacuum. (Hulett's method mitigates the problem of dissolved zinc coming over with the Hg.) Nor, yet, has any of my mercury entered a McLeod gauge, or even a thick-walled glass capillary tube procured for resistivity measurement.

Mercury is traded and priced by the 76-pound iron flask (since 19th century) and by the metric ton.
flasks.jpg
Who wants to compute the size of a metric ton, in a cylinder whose height and diameter are the same?
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Silviu Tamasdan
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Re: Will a Sprengel Pump Work?

Post by Silviu Tamasdan »

1t=1000000g; divided by 13.53g/cm3 makes 73909.83cm3. V=pi*r^2*h; if h=d=2r, then V=pi*r^2*r/2=(pi*r^3)/2
r^3=2*V/pi, solve for V=73909.53, r=36.1cm or d=h=72.2cm.
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Re: Will a Sprengel Pump Work?

Post by Rex Allers »

I think you made a mistake. You said
h=d=2r
but then you substituted r/2 for h
seems correct formula should be
r^3=V/(2*pi)
giving
d=h=45.5 cm
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Rich Feldman
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Re: Will a Sprengel Pump Work?

Post by Rich Feldman »

Silviu Tamasdan wrote: Sat Nov 18, 2017 4:04 pm 1t=1000000g; divided by 13.53g/cm3 makes 73909.83cm3. V=pi*r^2*h; if h=d=2r, then V=pi*r^2*r/2=(pi*r^3)/2
r^3=2*V/pi, solve for V=73909.53, r=36.1cm or d=h=72.2cm.
Is that your final answer? :-)
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Re: Will a Sprengel Pump Work?

Post by Rex Allers »

Rich,

Dang, even knowing what I was looking for, it took several tries on searches to find that container diagram. Nice work to find that.

Did you choose to ignore the correction I made for Silviu's simple mistake? His calculation seems right except for when he ignored his own value for h when he substituted.

From container dimensions: 508 - 2*10 = 488 mm = 48.8 cm
My corrected value was 45.5

If you are building a container, better to spec it a little big.

Hg ton contain.png
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Dennis P Brown
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Re: Will a Sprengel Pump Work?

Post by Dennis P Brown »

Yes, a long detailed series of posts on this thread relative to Hg and its distillation and or/availability and weight/volume; uh, why again, one asks? Are we getting to be a Hg forum? ;)
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Re: Will a Sprengel Pump Work?

Post by Silviu Tamasdan »

LOL that is why I usually triple-check my calculations. I didn't for this one. :)

And I feel that discussions of Hg in a vacuum subforum are A-OK. Hg is a useful metal if used wisely. Unfortunately I don't have any.
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Rich Feldman
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Re: Will a Sprengel Pump Work?

Post by Rich Feldman »

Rex, I think we both hit Send at about the same time. I wasn't responding to your answer. Didn't figure it out myself, or find that dimensioned diagram, until seeing the first answer (which is correct size for 4 metric tons).

The most recent round is doubly relevant at fusor.net. The big boys at Oak Ridge N. L. investigated mercury storage in preparation for their Spallation Neutron Source. Most productive in the world, excluding nuclear fission reactors. A search for ornl spallation will do. My initial search was metric ton mercury container.

The 76-pound "flask" unit of measurement probably dates to long before the 19th century. I bet it's connected to an early Spanish or even Roman unit for commerce, used long ago around the Almaden mines in Spain.
https://minerals.usgs.gov/mineralofthemonth/mercury.pdf
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Re: Will a Sprengel Pump Work?

Post by Doug_Gourlay »

Dennis P Brown wrote: Thu Nov 16, 2017 4:23 pm (even room temperature mercury releases a significant amount of vapor.) Y
If mercury did release significant amounts of vapor at room temperature, the Sprengel Pump wouldn't work.
The high vacuum that results is due to the low vapor pressure of mercury, at room temperature.

Depth of vacuum is, in part a function of the vapor pressure of the material used to create the vacuum.
I used to use Santovac, many years ago. The vapor pressure of Santovac 5 at 25 degrees C determined by extrapolation of higher temperature data is 4 x 10-10*

Doug

*https://www.sisweb.com/vacuum/sis/satovc5.htm
mercury is 2.58×10 −6 atm
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Re: Will a Sprengel Pump Work?

Post by Richard Hull »

Santovac is great stuff if you have hundreds of dollars for your diff pump fill up. This now ancient post got a restart with the thoughts of $400 santovac refill suggestions.

I am stunned this topic and its related ancient pump topic relaunched.

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Re: Will a Sprengel Pump Work?

Post by Alex Aitken »

I did a lot of searching, I assume before this thread existed because I haven't read it before. I think it was in response to the French guy that made vacuum triodes with a Sprengel pump.

Low melting alloys stick because of an oxide layer that forms on the liquid metal. Additives, like antimony can help but not stop this. They universally destroy the pump when they freeze. Some alloys that are documented to freeze without an increase in volume actually do initially expand and then the solid shrinks over a few hours. There is a 'magical' galinstan that is supposed to freeze at -19C or thereabouts, but the company that makes it for thermometers doesn't sell that version only the normal one. -19C is only claimed to work in a vacuum, so it may be supercooled and not a real freezing point. The method used to stop it sticking to the glass is to make sure no oxygen enters the system, there is no coating.

Organic/Fluorine based liquids dissolve gasses quite well, especially oxygen. To me this suggests organic liquids are not workable.

The tube in a Sprengel pump does not last, the point at which the falling drop hits the liquid is subjected to a lot of stress and it fatigues and ultimately breaks.

Pumping speed is very very low. Operating a fusor by pumping at the same time as bleeding in deuterium to keep the gas clean and flush out crap in the chamber doesn't sound feasible.

It's a cool and simple design but there is nothing special about a Sprengel pump, it's classed as a mercury sealed mechanical pump, it's just that the pistons are a drop of mercury.

I do not want to use mercury, and I gave up trying to find an alternative in the lit.
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Re: Will a Sprengel Pump Work?

Post by Chris Seyfert »

Since this thread was resurrected, for historical and educational purposes I've attached an excellent paper on a particular variant of the Sprengel pump. It also goes into the history of vacuum pumping and why the Sprengel pump in general fell rapidly out of favor.
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1972 Myer forgotten Sprengel pump.pdf
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