Oven thermostats

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resabed01

Well-known member
Joined
Sep 6, 2009
Messages
467
Location
Alberta
I've been harvesting switch and relay contacts from washers, dryers and stoves. One thing I've noticed and found interesting is the oven thermostats.
The old mechanical type that have a bulb and capillary tube attached to the switch housing. When I harvest these I just remove the switches and take them home to bust open for the contacts.
So I usually cut the wires and cut the capillary tube as well. I noticed inside the bulb and tube is a silvery metal liquid. When this liquid comes in contact with water it erupts into flame.
Kinda like one would expect from elemental sodium, potassium or rubidium. It's a liquid at and below room temperature so maybe it's some kind of alloy?
Does anybody know what this liquid is and it's toxicity? Google didn't help me this time.
 
resabed01 said:
I've been harvesting switch and relay contacts from washers, dryers and stoves. One thing I've noticed and found interesting is the oven thermostats.
The old mechanical type that have a bulb and capillary tube attached to the switch housing. When I harvest these I just remove the switches and take them home to bust open for the contacts.
So I usually cut the wires and cut the capillary tube as well. I noticed inside the bulb and tube is a silvery metal liquid. When this liquid comes in contact with water it erupts into flame.
Kinda like one would expect from elemental sodium, potassium or rubidium. It's a liquid at and below room temperature so maybe it's some kind of alloy?
Does anybody know what this liquid is and it's toxicity? Google didn't help me this time.

If the humidity in the air is high, this sets them alight as well.
 
Im sure i read somewhere that this liquid, in older model ovens, is mercury amalgum of some form. Could be wrong, butt safer than sorrier or is that sorryer, hmmmm????. :p

Deano
 
Here is a guide to compliance for our California members.

http://www.dtsc.ca.gov/HazardousWaste/Mercury/upload/HWMP_POL_Guidance_Mercury_Appliances.pdf
 
These mercury switched came from some very old electric ranges.

100_7056.jpg
 
mercury is used in rocker switch's and contactor relays.

http://www.google.com/search?hl=en&q=mercury%20contactor%20relay&rlz=1R2RNQN_enUS457&psj=1&bav=on.2,or.r_gc.r_pw.&bpcl=38626820&biw=1024&bih=539&wrapid=tlif135286724427710&um=1&ie=UTF-8&tbm=isch&source=og&sa=N&tab=wi&ei=zR2jUJ2TMI_oiwKlxYC4Dw#um=1&hl=en&tbo=d&rlz=1R2RNQN_enUS457&tbm=isch&sa=1&q=mercury+contactor+relay+switch&oq=mercury+contactor+relay+switch&gs_l=img.3...18329.24110.0.24454.9.6.0.0.0.0.1109.1327.2-1j7-1.2.0...0.0...1c.1.dul0Kb7VO_4&bav=on.2,or.r_gc.r_pw.&fp=b2dd49b947988cff&bpcl=38626820&biw=1024&bih=539

http://www.google.com/search?hl=en&q=mercury%20contactor%20relay&rlz=1R2RNQN_enUS457&psj=1&bav=on.2,or.r_gc.r_pw.&bpcl=38626820&biw=1024&bih=539&wrapid=tlif135286724427710&um=1&ie=UTF-8&tbm=isch&source=og&sa=N&tab=wi&ei=zR2jUJ2TMI_oiwKlxYC4Dw#um=1&hl=en&tbo=d&rlz=1R2RNQN_enUS457&tbm=isch&sa=1&q=+mercury+switch&oq=+mercury+switch&gs_l=img.3..0j0i24l9.47312.67765.0.68625.31.2.0.0.0.0.625.625.5-1.1.0...0.0...1c.1.MsKs7QAlxe0&bav=on.2,or.r_gc.r_pw.&fp=b2dd49b947988cff&bpcl=38626820&biw=1024&bih=539
 
I found this that said it's possibly a Gallium alloy of some kind but the details are not there. The possibility of a Mercury amalgam being used is true considering some of the switches I'm scrapping may date back to the 70s.

http://en.wikipedia.org/wiki/Liquid_metal

Still having difficulty finding specific information about how these thermostats were constructed and with what materials.
If the alloy does contain Mercury, it would not be the bulk of the material considering how this liquid behaves.
When exposed to atmosphere it almost instantly skins over from silver to dull grey. And as rusty mentioned, if the humidity is high enough, it will erupt into flame like one would expect from a metal from the alkali group.
Safety is my concern with this stuff. Not just from poisoning but from the potential of starting fires because it's so reactive and unpredictable.
 
The mercury acting as a switch, would oxidize easily from the arc created, the mercury in in a glass tube evacuated of air (oxygen) to help slow down the oxidation of the mercury in the arc created with current in the switch,another gas may be used in the switch or it may just be in a vacuum, after a period of use some of this mercury will still oxidize, and limit the life of the switch.

opening this tube of mercury to air could oxidize some of the mercury.

I do not know if your switch was mercury or not.

gallium indium tin is replacing mercury:

http://blogs.indium.com/blog/gallium-alloy

http://www.chemicalonline.com/doc.mvc/Nontoxic-Liquid-Metal-Alloy-Could-Substitute-0001

http://www.google.com/#sclient=psy-ab&hl=en&tbo=d&rlz=1R2RNQN_enUS457&q=gallium+indium+tin&rlz=1R2RNQN_enUS457&oq=gallium+indium+tin&gs_l=serp.3..0l3j0i30l7.24359.40063.1.40734.15.13.0.0.0.1.1969.8969.4-2j0j4j2j1.9.0.les%3B..0.0...1c.1.YBhZsLAdEw8&psj=1&bav=on.2,or.r_gc.r_pw.&fp=349c1040e4b0bea2&bpcl=38626820&biw=1024&bih=539

http://www.youtube.com/watch?v=VZC_bCwiVOA

Gallium is one of the metals (with caesium, rubidium, mercury and likely francium) which are liquid at or near normal room temperature, and can therefore be used in metal-in-glass high-temperature thermometers
 
Did anyone get an answer
Do any of the metals butcher mentions
React to water like sodium

I found some lights a while back, they
Had liquid metal in them I think when I
look it up they came back as lithium
or something of that nature

I think the reason it reacts with water
Was due to hydrogen gas it produced

Any ways just curious

Steyr223 rob
 
Just to support this, needed a volume estimation, like by pouring into a graduated cyllinder and weighing before and after filling
 
The only metal I have seen burst into flame on contact with water is sodium.
And they still make and sell them with sodium:

74005019: THERMOSTAT FOR WHIRLPOOL OVEN
240 VOLTS 27 AMPS 8 TERMINALS
replace PS2082816, AP4094393, 778549, (275-3369-03, 7404P130-60)
2 REAR SWITCHES
48'' SODIUM FILLED CAPILLARY
HYDRAULIC SELF CLEAN THERMOSTAT (EATON)
 
Cesium will ignite in air.

If it is a liquid at room temperature and spontaneously flammable with air, then it is sodium-potassium alloy.

NaK is the worst of the worst. Worse than Cs because it makes far more H2 gram for gram with less surface tension
 
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