Magnesium dispersions

Gum ghatti is the calcium and magnesium salt of a complex polysaccharide which contains L-arabinose, D-galactose, D-mannose, and D-xylose and D-glucuronic acid (48) and has a molecular weight of approximately 12,000. On dispersion in water, gum ghatti forms viscous solutions of viscosity intermediate between those of gum arabic and gum karaya. These dispersions have emulsification and adhesive properties equivalent to or superior to those described for gum arabic. 

The dispersion of amphiboles in concentrated HQ. solutions also leads to partial leaching, the rate of which depends on the metal cations present. With crocidoHte, only small amounts of magnesium and sodium are extracted in these conditions, whereas amosite Hberates substantial quantities of iron and magnesium. Overall, tremoHte appears to exhibit the highest resistance to acid leaching. 

A sohd solution of a pure magnesium aluminate spiael (MgAl20 with MgO is an effective metal oxide adsorbent (43). Such a soHd solution (Mg2A10 ) does not destroy the spiael framework the MgO adsorbs SO and the adsorption activity of the dispersed MgO ia the spiael is much greater than that of pure MgO itself (43). 

Calcium carbonate is controlled with poly(maleic acid) (26) and organic phosphonates. Dispersants designed to control silica and magnesium silicate (7,27,28) have been introduced. 

Seawater Distillation. The principal thermal processes used to recover drinking water from seawater include multistage flash distillation, multi-effect distillation, and vapor compression distillation. In these processes, seawater is heated, and the relatively pure distillate is collected. Scale deposits, usually calcium carbonate, magnesium hydroxide, or calcium sulfate, lessen efficiency of these units. Dispersants such as poly(maleic acid) (39,40) inhibit scale formation, or at least modify it to form an easily removed powder, thus maintaining cleaner, more efficient heat-transfer surfaces. 

DihydroxyanthraquiQone (anthranifin) [117-12-4] (47) is an important iatermediate for manufacturiag disperse blue dyes, eg. Cl Disperse Blue 73 (113), and is prepared from anthraquiQone-l,5-disulfonic acid by heating with an aqueous suspension of calcium oxide and magnesium chloride under pressure at 200—250°C (67). Alternative methods have been proposed, ie, direct replacement of the NO2 groups of 1,5-dinitroanthraquiaone (49) (68) or the route via 1,5-dimethoxyanthraquiaone [6448-90-4] (48) and subsequent hydrolysis (69). 

Dispersing Agents and Grinding Aids There is no doubt that grinding aids are helpful under some conditions. For example, surfactants make it possible to ball-mill magnesium in kerosine to 0.5- Im size [Fochtman, Bitten, and Katz, Ind. Png. Chem. Prod. Res. Dev., 2, 212-216 (1963)]. Without surfactants the size attainable was 3 [Lm, and of course the rate of grinding was very slow at sizes below this. Also, the water in wet grinding may be considered to act as an additive. 

Internal surfaces were covered with a tan deposit layer up to 0.033 in. (0.084 cm) thick. The deposits were analyzed by energy-dispersive spectroscopy and were found to contain 24% calcium, 17% silicon, 16% zinc, 11% phosphorus, 7% magnesium, 2% each sodium, iron, and sulfur, 1% manganese, and 18% carbonate by weight. The porous corrosion product shown in Fig. 13.11B contained 93% copper, 3% zinc, 3% tin, and 1% iron. Traces of sulfur and aluminum were also found. Near external surfaces, up to 27% of the corrosion product was sulfur. 

Seawater muds are commonly used on offshore locations, which eliminate the necessity of transporting large quantities of freshwater to the drilling location. The other advantage of seawater muds is their inhibition to the hydration and dispersion of clays, because of the salt concentration in seawater. The typical composition of seawater is presented in Table 4-48 most of the hardness of seawater is due to magnesium. 

Another excellent but expensive acrylic acid terpolymer is Acumer 5000, a silica and magnesium silicate dispersant. Although this polymer remains effective well above 600 psig (42 bar), it is recommended that at or above this pressure, FW silica should be removed at source, using DI or some other appropriate external treatment process. 

It is possible to separate a soap-LSDA dispersion by ultrafiltration through a polymeric membrane [33]. The filtrate contained sodium and some magnesium ions but no calcium soaps or LSDA. The separated substances on the membrane could be readily dispersed in water in which they retained a high degree of surface activity. 

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