[richu_z]

Hi, I'm doing a research project in which I am testing the zinc content of soil using EDTA titration with Eriochrome Black T as an indicator. I've been doing a lot of research but, as a high school student, the majority of the information is difficult to understand.

I do have three questions regarding the set up of my experiment:

-Firstly, everything that I read used a liquid as a sample, and since my sample will be soil I was wondering if there is anything special that I would need to do to prepare the soil sample. I was planning on just mixing it with water but my concern was that I would not be able to see the color change of the indicator.

-Secondly, I am going to add zinc to the soil for part of the project and I do not know what type of zinc salt to add. I was thinking maybe zinc oxide?

-And lastly, does anyone know where I can get Eriochrome Black T? I guess it is difficult to store, so no one wants to sell it.

[Borek]

Zinc in soil with EDTA? Doesn't sound good. How are you going to separate calcium and magnesium - there will be plenty of both in your samples.

[richu_z]

Oh sorry, I wasn't clear. I was going measure the total content but manipulate it by changing the only the zinc each time.

[Borek]

Zinc oxide is not a salt. OTOH adding salts can change pH of the soil, that's not good.

Eriochrome Black T should not be difficult to get. First of all - you need a very small amount. Second - it is not an expensive chemical, but as far as I know it is not widely used for other purposes. Either you need to check with some lab suppliers, or - and it can be much easier - ask in the college/uni close to you. You need just a pinch.

http://www.titrations.info/EDTA-titration-zinc

[walterVB]

The Zn-content in soils is very low, and measuring this content by titration is not a good idea. You should  better analyse it by atomic absorption or ICP, after dissolution of the soil sample.