There are various types of salt in Japan.
Among them, table salt new cooking salt, cooking salt, and refined salt is smooth because sodium chloride is 99% or more and magnesium carbonate that prevents condensation is added.
It is good to use in finished cooked products, but magnesium carbonate is difficult to dissolve in water, so it becomes cloudy when used in clear soup.
Also, when you go to a restaurant, you may find roasted rice in a salt bottle.
The reason for this is that the heated starch, which is a component of roasted rice, has the property of absorbing water, so it is devised to increase hygroscopicity and prevent it from hardening.