Computer Science
Scientific paper
Jan 1961
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1961gecoa..21..182l&link_type=abstract
Geochimica et Cosmochimica Acta, Volume 21, Issue 3-4, p. 182-198.
Computer Science
26
Scientific paper
Silica walls of diatoms, prepared by digesting cultured cells with nitric acid, dissolved more rapidly in media of higher pH or at higher temperatures. Most of the studies reported here were carried out in Tris buffer at pH 9·0 9·3 and at 19°C. The rate of dissolution under these conditions was slightly less than in sea water at pH 8·0, since NaCl accelerates the dissolution of silica. The silica from cleaned diatom walls dissolved in Tris buffer until, after 3 4 weeks, the solution had become saturated at 40 50 mg Si/l. (85 110 mg SiO2/l.). The rate of solution decreased with time, probably due to the presence of silica in different states of hydration. Living cells suspended in buffer in darkness remained viable for many weeks during which time very little silicon dissolved from their walls. However, every treatment which killed the cells (heat, protein-denaturing agents, organic solvents, breakage) resulted in an increase in the rate of silica dissolution, although this rato was never as great as from acid-cleaned walls. Experiments with EDTA indicated that a cationic inorganic factor was retarding silica dissolution from killed cells. Protreatment of cleaned silica walls with salts of Al, Be, Fe, Ga, Gd, Sc, Ti, Y and Yb at pH values between 2·0 and 9·0, and with Mn at pH values between 4·0 and 11·0, had various effects on the subsequent rate of dissolution of the silica at pH 9·0. At certain pH values each of these elements can evidently-combine superficially with amorphous silica and thereby retard its rate of dissolution. Pretreatment of cleaned silica walls with salts of La, Mo, Cr, at pH values between 2·0 and 9·0, and with Ca and Mg at pH values between 4·0 and 11·0, had no effect on their subsequent dissolution at pH 9·0, Al, Be, Fe, Ga, Gd and Y were all capable of combining with silica walls at pH 8·0, which is the pH of sea water, and thereby retarding their subsequent dissolution. A single determination showed that the walls adsorbed Al equivalent to 1 per cent of their weight. In retarding dissolution of the silica, Al was as effective on killed, but intact, cells as on acid-eleaned walls. The silica of nine samples of untreated diatomaceous earth of fresh-water and marine origins, ranging in age from Upper Cretaceous through Pliocene, was essentially insoluble under these conditions. Digestion in strong nitric acid freed only a small fraction of the silica for dissolution. The factor which retarded the initial dissolution of silica from natural marine phytoplankton could be removed completely by pretreating the cells with a chelation mixture of EDTA and oxalate. DHEG, which is reported to complex certain cations such as Fe, but to have no effect on Ca, or Mg, was equally effective. It can be concluded that certain adsorbed inorganic cations decrease the rate of dissolution of diatom-aceous silica. In living diatom cells there may be an additional mechanism for stabilizing silica walls.
No associations
LandOfFree
The dissolution of silica from diatom walls does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with The dissolution of silica from diatom walls, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and The dissolution of silica from diatom walls will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1671513