POLYMERIZATION OF SILICA IN ACIDIC SOLUTIONS: A NOTE OF CAUTION TO PHYCOLOGISTS.

Concentrated stock solutions of sodium metasilicate (Na[sub2]SiO[sub3]·9H[sub2]O). prepared in distilled-distilled water and acidified to pH 2 as suggested by McLachlan (1973), were found to be polymerized; stocks kept at their alkaline pH of dissolution were not polymerized. Depolymerization studies using the acidified stock added to deionized-dis. tilled water, 3% NaCl or artificial saltwater medium showed that complete depolymerization took longer than 2 days. Studies of Si uptake, using the marine diatom Tha-lassiosira pseudonana (Hust.) Hasle and Heimdal. showed that use of an acidified Si stock for experiments can lead to anomolous results. It is recommended that concentrated Si stocks be stored at their pH of dissolution and not be acidified prior to addition to media. In instances where the pH must be adjusted prior to addition (e.g. in some Si-uptake experiments), it may be necessary to take into account polymerization/depolymeriztion effects. [ABSTRACT FROM AUTHOR]