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Volume 79: debated on Thursday 16 May 1985

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asked the Secretary of State for the Environment what is the full chemical breakdown of the substance or substances currently being used to fluoridate the public water supplies.

Hexafluorosilicic acid (H2SiF6) or disodium hexafluorosilicate (Na2SiF6) are currently used to fluoridate public water supplies. The chemical analysis of the former by weight is 80 per cent. water and 20 per cent. Na2SiF6, with minute traces of other substances such as phosphate and chloride. The chemical analysis of the latter by weight is at least 98 per cent. Na2SiF6 with traces principally of water and iron.