When you boil a pot of water until it all boils off, what is the whitish, dusty residue that remains on the bottom of the pan?

Question

Is it just minerals/other impurities in the water?

In: Chemistry

Answer 1

The technical term for this is “Total Dissolved solids” (this assumes the water went through a filter at some point to strain out any sediment or fish or whatever, but in tap water it you _should_ be just getting dissolved stuff).

Exactly what makes up TDS in your water varies from region to region, but it’s usually calcium and magnesium and carbonates. Calcium/magnesium carbonate is the most common source of “white stuff”. It also makes for “hard water”. There may be more sodium and chloride if you are close to the ocean and getting a teeny bit of seawater inflow. Sulfides are common in well water in some areas…you will usually smell them if they are present.

All in all, this stuff isn’t harmful unless there’s a huge amount of it…honestly it’s probably a net benefit to get a bit of calcium and magnesium from your water. Straight up totally pure water also tends not to taste great.