Silicate magnesium

Very pure, white platelet magnesium silicate (talc) is used to reinforce and nucleate partially crystalline thermoplastics, especially polypropylene and polyamide. It is used more as a reinforcement, giving good stiffness and dimensional stability. 

Type Surface modified Relative tint reduction (approx.) pH value (approx.) Density Weather resistance Light fastness 

Rutile chloride AhOj Si02 org. 102 8 4.0 Very good Very good 

Rutile AhOj SiOi org. 90 8 4,0 Good Very good 

Depends on system very good in polyamides and meiamine/formaldehyde mouidingcompounds. Source Sachtleben 

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Florisil Trade name of a magnesium silicate used for chromatography, especially of fluorine-containing compounds. 

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. 

A hydrated magnesium silicate in fibrous form. The fibres are believed to be the more hazardous component of asbestos dust. 

A hydrous magnesium silicate used in ceramics, cosmetics, paint and pharmaceuticals, and as a filler in soap, putty and plaster. 

Fig. 7.8. High temperature conversion of a-silicon nitride with an MgO additive to the p-pha.se is thought to be a consequence of dissolution of the a phase in a magnesium silicate with subsequent recrystallization from the melt. Enhanced dissolution rate should then strongly influence a. p conversion [84B01].

The separation capacity of a TLC method can be easily improved by use of a two-dimensional high performance TLC technique (2D HPTLC). Various plant essential oils (menthae, thymi, anisi, lavandulae, etc.) have been analysed by 2D TLC with florisil (magnesium silicate) as the adsorbent, using dichloromethane/ -heptane (4 6) in the first direction and ethyl acetate/n-heptane (1 9) in the second direction (69). 

Alternatively, as described in U.S. Patent 3,341,557, 6-dehydro-17-methyltestosterone may be used as the starting material. A mixture of 0.4 g of cuprous chloride, 20 ml of 4 M methylmagnesium bromide in ether and 60 ml of redistilled tetrahydrofuran was stirred and cooled in an ice bath during the addition of a mixture of 2.0 g of 6-dehydro-l 7-methyl-testosterone, 60 ml of redistilled tetrahydrofuran and 0.2 g of cuprous chloride. The ice bath was removed and stirring was continued for four hours. Ice and water were then carefully added, the solution acidified with 3N hydrochloric acid and extracted several times with ether. The combined ether extracts were washed with a brine-sodium carbonate solution, brine and then dried over anhydrous magnesium sulfate, filtered and then poured over a 75-g column of magnesium silicate (Florisil) packed wet with hexanes (Skellysolve B). The column was eluted with 250 ml of hexanes, 0.5 liter of 2% acetone, two liters of 4% acetone and 3.5 liters of 6% acetone in hexanes. 

Four 250-ml fractions were collected followed by 150 ml fractions. The residues from fractions B to 16 were combined and rechromatographed over a 125-g column of magnesium silicate. The solumn was eluted with 6% acetone in hexanes which was collected in 150 ml portions. Fractions IB to 29 were combined and dissolved in acetone, decolorized with charcoal, and recrystallized from acetone. One gram of a crystalline mixture of the 7-epimers of 7,17-dimethyltestosterone was obtained melting at 120° to 140°C. 

The residue was redissolved in methylene chloride and chromatographed over 500 g of Florisil anhydrous magnesium silicate. The column was eluted with 1 liter portions of hexanes (Skelly-solve B) containing increasing proportions of acetone. There was so eluted 6a-fIuoro-9/3,1113-epoxy-16a-methy 1-17a,21 -d I hydroxy-1, 4-pregnad ene-3,20-dione-21-acetate which was freed of solvent by evaporation of the eluates. 

This reaction mixture is kept between 0°C and -i-5°C for six hours, with agitation and under an inert atmosphere, then 5 cc of a 0.2N solution of acetic acid in toluene are added. The mixture is extracted with toluene, and the extracts are washed with water and evaporated to dryness. The residue is taken up in ethyl acetate, and then the solution Is evaporated to dryness in vacuo, yielding a resin which is dissolved in methylene chloride, and the solution passed through a column of 40 g of magnesium silicate. Elution is carried out first with methylene chloride, then with methylene chloride containing 0.5% of acetone, and 0.361 g Is thus recovered of a crude product, which is dissolved in 1.5 cc of isopropyl ether then hot methanol Is added and the mixture left at 0°C for one night. 

The methyl benzoate thus formed is eliminated by steam distillation, and 2.140 g of crude product are obtained, which are dissolved in 20 cc of methylene chloride. This solution is passed through 10 parts of magnesium silicate, elution being performed with 250 cc of methylene chloride containing 5% of acetone. After evaporation of the solvent 2.050 g of product is recovered, which is recrystallized from isopropyl ether. 

Fibers in this category are composed of naturally occurring materials. A good example is asbestos. The most common type is chrysotile, representing more than 95% of world asbestos production. Chemically it is magnesium silicate (Mg6(OH)4 Si205). Today, use of this fiber is limited because long exposure to it may cause bronchial cancer. 

Vermiculite is a naturally occurring group of hydrated aluminum-iron-magnesium silicates having a laminate structure. When subjected to direct heat in a furnace, the pulverized material exfoliates or expands in size, and then consists of a series of parallel plates with air spaces between. 

At pH levels above 9.0, there is an increased tendency for the soluble silica to form silicate anions and react with magnesium (and to a lesser extent with calcium) to form insoluble forms of magnesium silicate that precipitate to form crystalline scales and sludge. 

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. 

Other anticaking ingredients include ferric ammonium citrate, silicon dioxide, sodium ferrocyanide, magnesium silicate, magnesium carbonate, propylene glycol, aluminum calcium silicate, sodium aluminosilicate (also called sodium silicoaluminate), and calcium phosphate. 

Higher resolution aluminium-27 and silicon-29 NMR spectroscopy of glasses and crystals along the join calcium magnesium silicate-calcium aluminium silicate (CaMgSijOj-CaAljSiO,). American Mineralogist, 71, 705-11. 

The stabilizing effects of methylcellulose and hydrated magnesium silicate were applied to calamine lotion. Sample 1 was the U.S.P. XV calamine lotion, and sample 2 the U.S.P. XV calamine lotion with 0.5% of methylcellulose. Sample 1 showed 50% separation, while sample 2 showed 12% separation after 24 hours at room temperature. 

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