@Hoves How do you measure 100g of Cl-, a chloride ion, in some rustic small town shop? Chlorine (Cl
2) is a gas in all the conditions available for some random old times shop. Although I suppoe magic could solve that if the shopkeeper was a magician and knew what they were doing. Chloride ion is exceptionally common in nature, in solutions that is. However, you aren't specifically weighing chloride ions when you are measuring amounts of solution, even though you'd know much of those you'd get as well if you knew the concentration (for example, if you had a bottle of HCl of a known concentration).
You know, sometimes people aren't just writing random stuff in the comments. For what it's worth, I'm never writing anything just to supposedly appear wiser among manga readers. I'm far too old for shit like that. I just enjoy pointing out funny or weird details. If a manga annoys me, I do it as a form of complaining. I expect most of the readers to recognise them as well, should the details catch their attention.