According to Baidu Encyclopedia, white portland cement refers to a kind of hydraulic cementing material made of white portland cement clinker with low iron oxide content, appropriate amount of gypsum and mixed materials (limestone and kiln ash), which is called white cement for short and code-named P W. According to its main components, it is actually calcium silicate and does not contain formaldehyde.

Formaldehyde, also known as ant aldehyde, is an organic compound with chemical formula of CH2O and relative molecular weight of 30.03. Colorless gas, with strong irritating and suffocating smell. Melting point -92℃, boiling point-265438 0℃. The relative density is 0.8 15g/cm3.