Australia's Science Forum

Calling all E&ES and Streamwatch people.
Does anyone use a meter for measuring dissolved Oxygen? We need to measure at different temperatures, and not sure if the colorimeter is the way to go.
Ellice.

Hi Ellice,

A colorimeter would not be the way to go A colorimeter measure the absorbance of a solution at a particular wavelength of light, whereas dissolved oxygen is a meassure of the amount of gaseous oxygen dissolved in an aqeuous solution (mg/L). To meassure dissolved oxygen you would need a DO meter, they are simple to use, much like a pH probe. The effect of DO and varying temp was a major part in my research...

Yep, I agree with Sassi! A DO meter is what we always used at uni too

Hi Ellice,
just to be different , I will give you one method for DO using colorimeter.
It is a streamwatch method, and uses 4 different chemicals to produce yellow coloured solution which you can measure at certain wawelenght. I have made up all the chemicals (can give you recipe if you wish), and then used streamwatch colorimeter to work at DO.
We also use a oxygen probe with Easy sense datalogger for a quick test.
Good luck, Lada

Hi All,
this is a scratchy area for me but I'll put my 2c in. The amount (concentration in mg/L) of dissolved oxygen in the water is a measurable quantity either by meter or colorimetric (winkler titration method). The temp affects the % saturation of the water. I think with a meter you can input the temperature so the meter gives you a result for % sat directly. with the colorimetric method, the result in mg/l is used with a conversion chart to manually calculate the % saturation.
I have a Waterwatch kit and it uses the colorimetric method and included is the conversion chart so i can record the % saturation & know if the water is good or oxygen deficient.

Hope this helps
Shas

Hi all,
Thanks for all the tips re DO. We already use the Streamwatch kit for DO, but this teacher wanted to watch the change in DO at different temperatures. Anyway, after all that, she's decided not to bother!!! Typical! We're going to look at %salt instead.
Lada, you mentioned you make your solutions yourself. We order in from Vendart at the moment, but it would surely save money if I made them up, as they come from USA!
Hope all are well.
Ellice