Sciencemadness Discussion Board - Water BP seems lower with copper salts

Water BP seems lower with copper salts

RogueRose - 5-12-2016 at 09:22

I've tried to reach saturation points of copper sulphate and copper acetate solutions (salt + H2O) and in both instances the BP seems much lower than standard 212. I'm getting about 181-183 with acetate and about 188 with sulphate. These salts are very pure (99+ I would guess).

Is this a normal reaction and if so, do other metal salts act similarly? Does this have a name in chemistry that I can look up to see how other salts behave?

The strange thing is that in Wiki, both salts are listed with solubility amounts at 100C but I can't get any where near that temp without boiling over.

I have tried heating on a hot plate as well as a microwave. I'm at 800 ft above sea level and everything else is pretty normal atmosphere wise.

DraconicAcid - 5-12-2016 at 09:51

Solutes should raise the boiling points. Weird. Try with a condenser and good stirring; it shouldn't boil over with that.

WGTR - 5-12-2016 at 13:55

With such a result, did you try measuring the temperature of boiling water for reference? Maybe there's something off with your measurement apparatus.

aga - 5-12-2016 at 15:58

Quote: Originally posted by RogueRose

I've tried to reach saturation points of copper sulphate and copper acetate solutions (salt + H2O) and in both instances the BP seems much lower than standard 212. I'm getting about 181-183 with acetate and about 188 with sulphate.

Finally ! I got all of those ! Woohoo !

Heater, Thermometer(s) Water, Copper sulphate, Copper acetate, glass pot, pen, paper, hands and eyes.

Maybe i can replicate your (presumed) experiment(s) to verify.

Are they degrees C or F ?

How are you determining 'saturation point' to within 2 degrees ?

DraconicAcid - 5-12-2016 at 16:09

Quote: Originally posted by aga

Are they degrees C or F ?

If it's boiling slightly below 212 oC, we've got bigger problems.

RogueRose - 5-12-2016 at 16:29

Quote: Originally posted by WGTR

With such a result, did you try measuring the temperature of boiling water for reference? Maybe there's something off with your measurement apparatus.

I'll do that. I didn't measure it this last time with Cu acetate because I had when I was working with the sulphate and the water was boiling at 210 on one of my infra-red thermometers and 211.8 on my wired temp probe on my multimeter.

Well I thought NaCl (and maybe other chloride salts) raised BP of water but didn't know if it was different for other types of salts like sulfates or acetates.

Could the color of the sulphate and acetate (both being a dark blue at saturation and at water BP) be effecting an IR thermometer?

RogueRose - 5-12-2016 at 16:38

Quote: Originally posted by aga

Quote: Originally posted by RogueRose

Finally ! I got all of those ! Woohoo !

Heater, Thermometer(s) Water, Copper sulphate, Copper acetate, glass pot, pen, paper, hands and eyes.

Maybe i can replicate your (presumed) experiment(s) to verify.

Are they degrees C or F ?

How are you determining 'saturation point' to within 2 degrees ?

Still have your doubts, ehh? IDK what I have to do (not that I really care) to make you "believe"...

Saturation wasn't measured to "perfect" accuracy. I added an excess (by 40-50%) of acetate than what would be needed to reach the listed solubility at 100C. Then heated the solution, stirred for awhile - repeat 2-3x. Then poured off solution to new container while filtering out excess acetate crystals and weighed to see amount dissolved (roughly).

Hot solution was then slowly cooled to room temp allowing crystals to form on various items inserted into the solution. It's amazing how fast the crystals grow after 3-4 cooling cycles. I'm finally getting some really nice size and shape crystals!

Sulaiman - 6-12-2016 at 01:28

I would get a conventional thermometer, e.g. http://www.ebay.co.uk/itm/Glass-Celsius-Temperature-Thermome...

gYAAOSwH71XPBaI
then calibrate 0 and 100 C with melting and boiling water.
(ideally using distilled water and compensation for local atmospheric pressure)
Use Celcius rather than Farenheight to make life easier.
i.r. thermometers are accurate when calibrated for a particular surface, otherwise use caution.
i.r. thermometers get 'confused' by 'looking' through glass.
i.e. do not expect accurate readings.
e.g. measure the temperature of 'outdoors' through a window, then open the window and measure,
or measure the temperature of the sky, clear vs. cloudy ......

[Edited on 6-12-2016 by Sulaiman]

XeonTheMGPony - 6-12-2016 at 04:29

IR probes are utter shit to measuring fluids, and same with the thermal couples on multi-meters, they are just for ruffing and a quick general reference.

For proper measures you need to use a narrow range thermal couple and a dedicated reader or a thermister type unit, or good old mercury therm!

a fine crushed mixture of distilled water and ice, wrap in towel, let sit for a couple minutes for every thing to normalize then calibrate your zero point in C

Amos - 6-12-2016 at 07:56

Yeah, IR is not going to cut in in this case. Use that for opaque surfaces only, and even then, that's just going to be a ballpark figure if you're trying to apply it to the inside of a container or something.

RogueRose - 6-12-2016 at 21:15

Wow, I thought the temp probe on the multi-meter was supposed to be very accurate. That's good to know.

I had tested the IR and probe on 65 degree tap water and they were about .4F degrees different. After reading some suggestions on this thread I tested hot tap water and the probe read 130 (which is the water heating setting) and 120 for the IR device. So 10 degrees difference (reading taken from top of beaker, directly on water). I then put the water in the microwave to boil. The IR read 181 and the probe read 211.8.

So, it looks like the IR is programmed at or around room temp and there seems to be something wrong with the increments between temps (maybe wavelenth multiplier??).

I'll have to check for temps below freezing b/c I had some very odd cold readings that didn't seem proper.

Thanks to those who pointed out the issues with IR thermometers.

are Laser thermometers any different or better? I've seen ones that shine a red laser on a target and give a temp reading. IDK if these use an IR thermometer and an optical laser to show where it is pointed, or if it is some kind of laser other than IR (not sure there are any though..).

WGTR - 7-12-2016 at 10:18

I agree that IR thermometers aren't that great for this kind of application, at least not without thorough calibration.

The type K thermocouples are generally pretty accurate, but for liquids you need to use the thermocouple with a shroud, not with just the bare junction. I've put them into small glass tubes, where the bottom end of the tube was sealed, and then injected some heat sink compound into the bottom of the glass tube. The junction can then be placed down into there. The glass tube protects the thermocouple from chemical attack.

They can also be obtained with stainless steel shrouds, which seem to be compatible with a variety of chemicals and situations.

Make sure that the meter is set up for whatever type thermocouple you are using (there are various ones out there).

Regardless of the shroud material, there is a certain minimum insertion depth into the material being measured. I usually stick my thermocouple probes a couple of inches into a liquid, etc. If the insertion is too shallow, the temperature can read lower than expected.

[Edited on 12-8-2016 by WGTR]

XeonTheMGPony - 7-12-2016 at 14:29

Quote: Originally posted by RogueRose

Wow, I thought the temp probe on the multi-meter was supposed to be very accurate. That's good to know.

I had tested the IR and probe on 65 degree tap water and they were about .4F degrees different. After reading some suggestions on this thread I tested hot tap water and the probe read 130 (which is the water heating setting) and 120 for the IR device. So 10 degrees difference (reading taken from top of beaker, directly on water). I then put the water in the microwave to boil. The IR read 181 and the probe read 211.8.

So, it looks like the IR is programmed at or around room temp and there seems to be something wrong with the increments between temps (maybe wavelenth multiplier??).

I'll have to check for temps below freezing b/c I had some very odd cold readings that didn't seem proper.

Thanks to those who pointed out the issues with IR thermometers.

are Laser thermometers any different or better? I've seen ones that shine a red laser on a target and give a temp reading. IDK if these use an IR thermometer and an optical laser to show where it is pointed, or if it is some kind of laser other than IR (not sure there are any though..).

No optical therms will never be all that good at accurate readings, and you are using very lose and flaky methods for testing the calibration range.

Distilled water at 14.5psiA will boil at 100c, distilled water slush will read at 0c at any pressure

A good quality mercury therm will give you the most accurate reading, it is the oldest and best understood technology.

A narrow range quality thermalcouple will give you pretty good readings too to within .0x degrees but you're geting up there in cost, the closest degree is plenty.

But any non contact therm or built in multimeter are just meant to be ruff guess, not for any thing requiring such accuracy as chemistry or for even tuning an hvac system!

When adjusting TXV's on a refer system we use contact thermal probs that clamp to the pipe.

Sulaiman - 8-12-2016 at 03:57

distilled water slush will be 0C at 1 kPa to 1 MPa pressure - but not at higher pressure.

Quote: Originally posted by XeonTheMGPony

Distilled water at 14.5psiA will boil at 100c, distilled water slush will read at 0c at any pressure