[MCL99]

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]

Chances are there will be nothing left to weigh.

In general procedures in such a case call for dissolution in acid and for analysis of the liquid for whatever ion it can contain, by any means (gravimetry, titration, instrumental analysis). If you have very tiny sample and very limited lab you can be out of luck, generally the smaller the sample and the lower the concentration the more challenging (in terms of glassware, hardware and reagents) the analysis is.