Physics boffins: conductivity of water at varying temperatures

Status
Not open for further replies.


Urban Silverback said:
From memory, conductivity will drop about 2% per degree C. I think de-ionised , or distilled water will have zero conductivity because there will be no dissolved salts resulting in charged ions to conduct electricity. Mind, I'm going back years so could be completely wrong here.
Click to expand...
Nay. pure/distilled/DI water is a much poorer conductor than normal tap water, but it still conducts by proton transfer between water molecules.
 
yyy said:
For reference (whipped from Wikipedia), conductivity of sea-water is typically 5 S/m (Siemens per metre), drinking water is typically in the range of 5-50 mS/m, while highly purified water can be as low as 5.5 μS/m (0.055 µS/cm), a ratio of ~1,000,000:1,000:1. This should allow you to predict the values you are after if coupled with the information in the paper.

Pure water is a poorer conductor than one with a solute in it. If you've highly deionised water, you could assume close to pure though I'd measure conductivity to be sure.
Click to expand...

Yeah, I've taken a reading of the de-ionised water as I realise it's probably not 100% pure. If I'm using it as a blank measurement I need to account for that. Apart from that I'm using conductivity as a proxy for cell death in plant tissue (ions leak into the water if cells are dying). I'm just getting quite variable results depending on whether I incubate in the cold room or at room temperature.
 
Melody Nelson said:
If it's important for an experiment you're planning, why not just measure it?
Click to expand...

I am/have.

I was just trying ascertain whether or not the conductivity meter I'm using is playing up or if temperature was responsible.

Either way, I've calibrated the fucker that many times today I've ran out of the standard calibration solution :lol:

zwartekat said:
Charming Man in desperate lunge for a podium place in the 100m Most Intelligent Poster dash.
Click to expand...

I was the first person @Her Ivory Tower listed iirc.

The thread actually alerted me to just how many people know a lot about physics on here so I thought I'd ask.
 
Charmless Man said:
Yeah, I've taken a reading of the de-ionised water as I realise it's probably not 100% pure. If I'm using it as a blank measurement I need to account for that. Apart from that I'm using conductivity as a proxy for cell death in plant tissue (ions leak into the water if cells are dying). I'm just getting quite variable results depending on whether I incubate in the cold room or at room temperature.
Click to expand...

What's your incubation time? Presumably the lower temperature would slow the release of ions from your cells to a degree anyway.

I wouldn't use deionised as your blank either. There must be some degree of background loss of ions from healthy plant cells and a background level of 'normal' cell death.

What happens to your reading if you incubate at RT then cool a sample the same solution rapidly?
 
Hammer said:
What's your incubation time? Presumably the lower temperature would slow the release of ions from your cells to a degree anyway.

I wouldn't use deionised as your blank either. There must be some degree of background loss of ions from healthy plant cells and a background level of 'normal' cell death.

What happens to your reading if you incubate at RT then cool a sample the same solution rapidly?
Click to expand...

4-6 hours. Doesn't seem to be much of a difference in leakage in that range.

The biggest 'noise' in the system probably comes from the fact that I'm floating leaf discs on the water, the discs are cut with a cork borer so some tissue damage round the periphery. I've checked tissue expressing no transgenes and tissue transformed with empty vectors as a control and it doesn't differ significantly from the water blank. Well, the completely untampered with leaf tissue doesn't. There's some enhanced leakage with empty vector controls.

Never tried it. Done it the other way round (cold to RT) and you get some enhanced conductivity but it never reaches the levels of discs that have been incubated at RT since harvest.
 
Charmless Man said:
4-6 hours. Doesn't seem to be much of a difference in leakage in that range.

The biggest 'noise' in the system probably comes from the fact that I'm floating leaf discs on the water, the discs are cut with a cork borer so some tissue damage round the periphery. I've checked tissue expressing no transgenes and tissue transformed with empty vectors as a control and it doesn't differ significantly from the water blank. Well, the completely untampered with leaf tissue doesn't. There's some enhanced leakage with empty vector controls.

Never tried it. Done it the other way round (cold to RT) and you get some enhanced conductivity but it never reaches the levels of discs that have been incubated at RT since harvest.
Click to expand...

Suggests to me that the change in temp is affecting something else in addition to conductivity then. Without knowing all the details, you'd guess that any processes going on would happen faster at RT though, no?

You could measure the effect of temp on the conductivity of your solution by taking any sample (ddH2O/negative control/etc) and measuring conductivity at a range of temps. If the effect you're seeing is bigger, then something else is going on.

What temp range does the tissue you're working with usually live at? You could repeat the experiment at more temps both inside and outside this range and see what happens. It might just be that there's an optimal temp for the process you're measuring and it's closer to RT than 4.
 
Occam's Razor said:
The good lady Razor is a geet expert in physics, with a degree and a frankly terrifying number of letters after her name and shit. I asked her about this but just received the reply, “Is this to do with that f***ing message board?” so I doubt any help will be forthcoming from that direction.
Click to expand...
And very eloquent too, I see
 
Charmless Man said:
Yeah, I've taken a reading of the de-ionised water as I realise it's probably not 100% pure. If I'm using it as a blank measurement I need to account for that. Apart from that I'm using conductivity as a proxy for cell death in plant tissue (ions leak into the water if cells are dying). I'm just getting quite variable results depending on whether I incubate in the cold room or at room temperature.
Click to expand...

Match temperatures mentioned in literature or opt for a standard temperature of 25°C. If you want to use another temperature, you need to justify that.
 
Hammer said:
Suggests to me that the change in temp is affecting something else in addition to conductivity then. Without knowing all the details, you'd guess that any processes going on would happen faster at RT though, no?

You could measure the effect of temp on the conductivity of your solution by taking any sample (ddH2O/negative control/etc) and measuring conductivity at a range of temps. If the effect you're seeing is bigger, then something else is going on.

What temp range does the tissue you're working with usually live at? You could repeat the experiment at more temps both inside and outside this range and see what happens. It might just be that there's an optimal temp for the process you're measuring and it's closer to RT than 4.
Click to expand...

The process leading to cell death would occur faster at higher temperatures up to a point as it rests on the activity of a protein kinase. So cold temperatures could be inhibiting enzyme activity easily. However, I'm harvesting 12h post vector induction which I've determined is more than enough time to accumulate the protein, phosphorylate downstream kinases and initiate cell death.

Tissue is (Nicotiana benthamiana) grown at 26/22 degrees C day/night cycle.

Either way, the results I've got for room temperature incubations match what I might expect from the literature. I was just interested in what was going on at colder temperatures.
 
Status
Not open for further replies.

Back
Top