Barium sulfate crystallization

Liu, S.T., Nancollas, G.H. and Gaseichi, E.A. (1976) Scanning electron microscopic and kinetic studies of the crystallization and dissolution of barium sulfate crystals. J. Cryst. Growth, 33, 11-20. 

When you add barium sulfate crystals to water, barium ions and sulfate ions leave the surface of the solid and enter the solution. Initially, the concentration of these ions is very low. Thus, the forward change, dissolving, occurs at a greater rate than the reverse change ... 

In another paper (N5), Nielsen reports further kinetic studies of barium sulfate crystal growth, followed turbidimetrically and conducti-metrically. When the concentrations of Ba++ and S04 were larger... 

Leung, W. and Nancollas, G.H. Nltrilotri (methylenephosphonlc acid) adsorption on barium sulfate crystals and its influence on crystal growth. J. Crystal Growth 44, 163-167 (1978). ... 

The vigorous mixing regime in the thin films of the SDR has also been exploited for crystallization processes.Homogeneous nucleation in the thin films results in a narrow crystal size distribution for crystals formed in the SDR. Uniformly shaped barium sulfate crystals of 0.5-1 pm have been produced with a reasonably low power dissipation of 115W/kg.f ... 

ASTM C 471 recommends use of SO mL of 1 + 5 hydrochloric acid (sp gr 1.19) as solvent for a 0.5-g gypsum sample and 20 mL of 10% barium chloride as precipitant. This results in too high a concentration of acid and chloride ions in reaction solution before and after precipitation, justifiable only for dissolution of impute gypsum samples and formation of coarse barium sulfate crystals to give rapid filtering. The method is silent about the final volume to be made of reaction solution, which determines the acidity before precipitation. It is also silent about the use of and the type of filtering crucibles. 

The conductivity can go down to zero if an insoluble salt is produced by the neutralization reaction. If one carries out a conductivity titration of barium hydroxide solution with diluted sulfuric acid, it is possible to observe a decrease in electrical conductivity (see E7.15). However, because additional white barium sulfate is precipitating, conductivity goes down to almost zero Ba2 + ions and S042 ions do not remain mobile, but form the ion lattice of barium sulfate crystals. 

Both strontium and barium are deposited as crystals in a range of organisms. These crystals may have both structural and functional properties. Some green algae such as the desmids deposit barium sulfate crystals, though it is unclear how much biological control is involved in the determination of the crystal structure which results [10]. 

Such crystals are employed in a number of relatively primitive species to exploit gravity. In desmids the weight of the dense barium sulfate crystals forces the organism into the deeper anoxic layers of their fieshwater habitat and protects them from predators [11]. In higher species such as... 

Loxedes barium sulfate crystals are employed to control balance or orientation when the dense crystal deflects, displaces, or distorts a sensory device under the influence of gravity [11]. 

A 25.0-mL sample of sodium sulfate solution was analyzed by adding an excess of barium chloride solution to produce barium sulfate crystals, which were filtered from the solution. 

A metal, M, was converted to the sulfate, M2(S04)3. Then a solution of the sulfate was treated with barium chloride to give barium sulfate crystals, which were filtered off. 

---