Mercury Arc Rectifier. Value?

[Richard_FM]

Originally Posted by Richard

Hi

Somewhere I have got a puzzle containing a blob of mercury instead of the normal ball bearing, bought it at a car boot sale years ago.
Looks like this, about 4" across.

Richard

I've heard of these before, a bit risky if the plastic case is broken.

[The Philpott]

Metallic Mercury being the least toxic form, there is however for the information of all, an interesting paper (from the year 1926) by Alfred Stock, loosely translated as 'The Dangerousness of Mercury Vapor.' It concerns the experiences of persons working with Hg in an everyday role, but the symptoms are worthy of note due to their insidious/ambiguous nature.

I am very conscious of the risk/s and this thread has included musings i hadn't considered before. Did i potentially invalidate my car insurance by transporting a MAR? Possibly. Would a collision which ruptured the MAR have crushed me beyond caring about the environmental discharge? Again, possibly. By way of perspective I recall the M25 Hydrogen Peroxide incident from some years ago. 90% pure, and one of the canisters leaked onto the wooden bed of the lorry. Anyone who dismisses oxidising agents as less dangerous than explosives should have been there. Things got airborne! When the underwriters from Royal Sun heard it was 90% pure they...erm....re-wrote the policy.

Dave

[Refugee]

I can remember a bloke that filled a 13 amp socket with mercury.
After it went bang his hand was silver.

[turretslug]

Lucien's mention of cabinet contamination makes me wonder how often they failed (as in envelope rupture) during use. The very idea of a large glass bulb with sticky-out limbs and what was effectively a conformal dead-blow hammer inside seems like asking for trouble! Could they have failed at bulb-to-limb joints through excess heating or uneven cooling, or been more vulnerable to later failure as a result of unsympathetic handling at installation? Also, bigger ones would have had a lot of current passing through the limb glass-to-metal seals, so connections must have been dependably good to avoid hot-spots. All-in-all, they seemed to have been something of a masterpiece of glassware, but not without a lot of caveats.

[Scaleyback]

The Isle of Man railway uses mercury rectifiers...
https://youtu.be/yjMZ5qtyCUc

[Argus25]

All the talk of mercury reminds me of a story involving it.

Some years ago one of my daughters was given a science project, the topic being to investigate an old fashioned material that got replaced with a modern one and to compare and contrast the materials. Many students did plastic vs glass or wood and vinyl vs leather but two students did amalgam fillings vs modern composite materials. One was my daughter (the other classmate was the daughter of a dentist!).

In any case when the assignment was done (supported by much google searching as this is how homwork seems to be done) my daughter showed me the assignment. Everything you could think of about the two materials, hardness, wear properties, thermal conductivity etc etc was covered and it was very well presented.

But then I thought of electrical conductivity (and the composite material an electrical insulator) and demonstrated it with the meter probes on a somewhat large amalgam filling in one of my lower molars. Suitably impressed with the beep from the Fluke digital meter she added it to the list and blow me down got the prize for the best assignment.

[factory]

Originally Posted by Scaleyback

The Isle of Man railway uses mercury rectifiers...
https://youtu.be/yjMZ5qtyCUc

They may still be on the island, but they built a new substation to replace the last MAR one.

http://isleofman.com/News/details/56...splay-tomorrow

http://www.britishtramsonline.co.uk/news/?p=4705

http://www.britishtramsonline.co.uk/news/?p=4909

David

[Scaleyback]

I never knew it had been unplugged. It was a big blue sparkly thing that you could read the paper by...
They used to have them on the southern railway. there is still a building at Chislehurst junction where they were installed. A big thing with large windows.

[factory]

Originally Posted by McMurdo

Can't quite remember but ISTR either Crich Tram Museum or the Black Country Museum using one for their tram or trolleybus, I forget.

I don't know about the Black Country Museum, but the Crich tramway uses some solid state transformer rectifier sets acquired from the Walsall trolleybus system, before that they used various diesel generators.
More information on the early years of the Crich tramway including the power supplies used can be found in the three part blog linked below (picture of the ex-Walsall transformer rectifiers in part three)

http://tramways.blogspot.com/p/crich-1959-1969.html

David

[julie_m]

Originally Posted by turretslug

Sorry, but messing around with mercury is like messing around with radium paint or blue asbestos- it's dumb, just don't do it!

I was all set to say "you'd be mad as a hatter to try it", but I see someone else got in with that before me.

Originally Posted by Richard

Somewhere I have got a puzzle containing a blob of mercury instead of the normal ball bearing, bought it at a car boot sale years ago.

I think I still have one of those plastic maze puzzles with a blob of mercury in it, somewhere. If you crash hard into a corner, you can split the blob into two, and then you have to try to get them back together. And at least one mercury-filled tilt switch.

I also saw a nice demonstration in which someone filled a mould with mercury, held a wooden handle upright in the middle of the mould, poured liquid nitrogen over the mould to freeze the mercury solid; then withdrew from the mould a hammer with a head of solid mercury, which they used to knock several large nails into a piece of wood. It really brought home how mercury is just a metal, albeit one with a very low melting point, but still a metal like any other metal. Molten solder behaves similarly to mercury while it is still liquid; and there are (or at least, there used to be; they may have contained one or more ingredient considered too dangerous today) special, low-melting point metal alloys which can be melted in the hand, or by breathing on them.

[Argus25]

I'm saving a jar of mercury I have to make a Faraday motor. The one where the edge of the slowly rotating copper disc spins in a pool of it. The current passes from the axle to the edge and a big U magnet's field crosses the disc.

[dseymo1]

I too have one of those puzzles and a few tilt switches and mercury-wetted relays, a couple of Hg thermometers and possibly a sphymomanometer at the back of a cupboard too.
As previously mentioned, there must be a lot of mercury tucked away in private hands.

[M0FYA Andy]

Originally Posted by Argus25

I'm saving a jar of mercury I have to make a Faraday motor. The one where the edge of the slowly rotating copper disc spins in a pool of it. The current passes from the axel to the edge and a big U magnet's field crosses the disc.

I made one of those as a youngster, the name I have heard is 'Barlow's Wheel'.
At the time (early 60s) I had a jam-jar full of mercury recovered from some relays which were due to be scrapped where my father worked. It was later sold to the local scrap-merchant for £65!

Andy

[Malcolm G6ANZ]

A long time age ,when my children were in junior school, the discussed subject was electricity. I made a replica of the Farady motor to demonstrate magnetism etc. Not having mercury to hand I improvised with a salt solution. This actually worked and the rod rotated in the bath of saline.

Malcolm

[trobbins]

Originally Posted by The Philpott

I am very conscious of the risk/s and this thread has included musings i hadn't considered before. Did i potentially invalidate my car insurance by transporting a MAR? Possibly. Would a collision which ruptured the MAR have crushed me beyond caring about the environmental discharge? Again, possibly.

For the emergency services people, I hope you would be concious enough to tell them that the blazing car and smoke may be worth taking extra special care with.

[The Philpott]

A valid point and i can't argue..but i can imagine with the blend of plastics in modern construction a vehicle fire is something they would already treat with great respect as regards the black smoke, and also alloy cylinder heads which have been known to explode. (Several horror stories circulate regarding the combustion products of certain synthetic rubbers, ie hydroflouric acid, which eat flesh and according to Haynes manuals 'may ultimately involve amputation of the limb concerned') On the rare occasions i see a category A burn-out in the middle of nowhere i think of this and 'phone it in asap.

There is another trick which can be done with amalgam fillings which is definitely not recommended- i once ate a kit-kat with a fragment of aluminium foil on it, and received a direct electric shock in the nerve.

Dave

[AC/HL]

Originally Posted by Russbrown

I recently came across a mercury arc rectifier in a friend's warehouse and he was looking to sell it. It is unused and in the original packaging crate which stands about 6 feet tall. Seen in photo attached.

Please could anyone give me some advice on who might buy it and what it is worth?

Thanks.

The consensus would appear to be that far from having a value, it is a liability. Your friend would be best advised to seek professional help, to avoid serious, possibly legal, difficulties in the future.

This is one official publication, there are probably others!

https://www.gov.uk/government/public...ive-precursors