Silicum tonic Silicum tonic is a Finnish silica gel preparation. Contains silica and carmellose gels which work well together. Microscopically small silica crystal and carmellose particles are film-forming colloids.  Silica In nature, silica is in an oxygen-bound form e.g. plants, seawater and bedrock. Silica also occurs as pure silica crystal. Carmellose Carmellose is a water-soluble structural fibre of spruce, pine and cotton. Colloidal carmellose is water-soluble, odourless, and slightly alkaline.