Studies in the Use of Sodium Silicates

Iron Salts as Coagulants

“…This applies to a lesser extent to ferrous sulfate, but silicates were found to be of little value when used with ferric salts. Similar conclusions were reached by Lordley and Smith (6) following their studies in the use of sodium silicate.…”

Water Purification Methods Involving Sodium Silicates

“…It has been shown that waters in which substantial pH variations occur respond more uniformly to coagulation involving silica sol addition, than to iron or alum coagulants. The value in low temperature and low turbidity waters has been demonstrated by several investigators (21,22) . A water which had previously been difficult to flocculate because most of the suspended matter was of organic nature improved with the addition of silicate (7).…”

“…Baylis found (21) that silicon tetrachloride added to water containing alum aided flocculation, but no effect was obtained if introduced prior to the alum. Lordley and Smith (22) report "silicic acid," alone or treated with caustic to 1,200 ppm. alkalinity, had no value.…”

“…The second critical article (22) emphasizes that an acid-treated silica coagulant aid appears deterimental to floc formation with ferric salts and appears limited to conditions of low temperature and low turbidity for the water tested. No exception is taken to to these laboratory studies as restricted to the one water investigated.…”