Synthetic magnesium silicates are white, odorless, finely divided powders formed by the precipitation reaction of water-soluble sodium silicate (water glass) and a water-soluble magnesium salt such as magnesium chloride, magnesium nitrate or magnesium sulfate. The composition of the precipitate depends on the ratio of the components in the reaction medium, the addition of the correcting substances, and the way in which they are precipitated.
When used as a food additive, it is safe to ingest synthetic magnesium silicate. In 1990, the safety of synthetic magnesium silicate was reviewed by the Scientific Committee on Food (SCF) together with that of silica and the other metal alkali silicates. The SCF noted that “the available data, including a number of short-term studies in two species, appear to substantiate the biological inertness of those compounds”. The SCF established a group Acceptable Daily Intake (ADI) not specified for silicon dioxide and the alkali metal silicates.