[targe]

Hi,
I would like to test for the carbonate (limescale) content in the scale deposit sample using acid digestion with hydrochloric acid. I have a very small amount of scale deposits. The sample is dry and it is from the incoming water mains, it is also brown so I am assuming that there is iron. What should be the procedure for testing the sample? I would generally weigh the sample and then I would add hydrochloric acid to see if it fizzes and weigh it after it is finished. Should I rinse the sample with DI water to remove the unreacted hydrochloric acid and dry it or can I weigh it after digestion omitting the rinsing step? Not sure how should I finish this test to have a correct result and looking for some advice. Basically, I would like to find how much of the sample has reacted and weigh it afterward.
The equipment in my lab is very limited, the acid is the only reagent I have, but I do have a vacuum filtration kit. Look forward to hearing from you.

[Borek]

First of all - what it is that you want to measure? "Carbonate content" - do you mean total CO₃^2- in all different carbonates present in the scale? It is most likely a mixture of carbonates, basic carbonates, hydrated oxides and what not.

If so probably the best approach would be to measure volume of the CO₂ evolving during dissolution. Doable, but tricky, especially if the sample is small.

[marquis]

Are you feeling with boiler residue?