Filtering while it is hot, an operation of solid-liquid separation in chemical experiments. It is different from "filtering while it is hot". Hot filtration refers to direct filtration of high-temperature solid-liquid mixture by conventional filtration operation; Thermal filtration refers to the filtration process of keeping the temperature of solid-liquid mixture within a certain range by using instruments different from conventional filtration. If the solute in the solution is easy to precipitate a large number of crystals when the temperature drops, but it is not expected to remain on the filter paper during filtration, then thermal filtration is necessary.

Potassium ferric oxalate is the main raw material for preparing supported active iron catalyst, and it is also a good catalyst for some organic reactions, which has industrial production value. There are many technological routes to synthesize potassium ferrous oxalate. For example, iron can be used as raw material to prepare ammonium ferrous sulfate, and potassium oxalate can be added to prepare ferrous oxalate and then oxidized to prepare iron (III) potassium oxalate; Either ferric sulfate and potassium oxalate are used as raw materials to directly synthesize potassium ferrous oxalate, or ferric chloride and potassium oxalate are used to directly synthesize potassium ferrous oxalate. In this experiment, potassium oxalate was added to ferrous sulfate to form ferrous oxalate, and then oxidized and crystallized to obtain tribasic potassium oxalate.