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I have been planning on an experiment for quite some time now (as part of my after-school chemistry club), but I still feel like I am missing something.

Due to my family's calcium deficiency, I decided to measure calcium content in various foods. It's something rather personal, therefore it will make the experiment more interesting overall.

At first I wanted to choose dietary supplements since they can dissolve easily, though then I realised how flawed of an idea that is, since the contents are usually given on the package in full detail anyway. In then moved onto fruit and other various foods, though it all seemed rather messy/ hard to achieve.

I then realised I could measure the calcium content in cashews. I was thinking about using EDTA and Eriochrome Black T, as well as methyl orange. Here is where I hit my first struggle - how do I dissolve the nuts in the first place? I thought about acids, such as hydrochloric acid, though that would as a result affect the pH of the solution (which, I am not sure, could have an effect on the way the titration procedure functions).

I'd use methyl orange together with Eriochrome as the transition is much clearer since it goes green then grey, whereas the transition from purple to blue is rather subtle - in my opinion this would increase the accuracy of my experiment.

Alternatively, I could use absorbance technique to determine the calcium content - would it be more appropriate for this scenario? I could use a stock solution to find for example the absorbance of 10ppm before calculating the absorbance of the cashew. Does this sound more appropriate?

Any input would be greatly appreciated! These can be hints, I definitely want to work through the issue myself as much as possible. I just seem to be stuck and don't know where to go from there!

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  • $\begingroup$ I would recommend you try any procedure with chemicals that you know the content of already to determine the accuracy of your experiment (blind test). If I remember correctly, calcium itself was not easy to determine, especially in presence of other elements. Also the overall concentration on cashews might not be enough to be suitable for titration. $\endgroup$ – Martin - マーチン Aug 6 '17 at 16:19

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