What is of, pertaining to, or designating, any one of a series of double acids of silicon and tungsten, known in the free state, and also in their salts (called silicotungstates) called?

silicotungstic — Of, pertaining to, or designating, any one of a series of double acids of silicon and tungsten, known in the free state, and also in their salts (called silicotungstates). (Webster's 1913.)

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