Quite often when reading through some instructions or documentation or an outline that I've found online (EG: acid-base extractions), theres a step that involves using a "dilute hydrochloric acid solution", but oddly enough, it often doesn't detail exactly how diluted the HCl should be. Heres one example (little past half way into the 3rd paragraph)
Dilute hydrochloric acid is often used in the extraction of basic substances from mixtures or in the removal of basic impurities. The dilute acid converts the base such as ammonia or an organic amine into water soluble chloride salt.
So my question is: How does one know exactly how diluted the HCl should be? Is there a commonly used concentrated amount of HCl that I just don't know about? Sometimes it'll suggest using Muriatic acid instead, which I believe is basically 31.45% concentrated HCl, is that a commonly used concentration?