Synthetic magnesium silicates are white, odorless, finely divided powders formed by the

precipitation reaction In an aqueous solution, precipitation is the "sedimentation of a solid material (a precipitate) from a liquid solution". The solid formed is called the precipitate. In case of an inorganic chemical reaction leading to precipitation, the chemic ...

of water-soluble

sodium silicate Sodium silicate is a generic name for chemical compounds with the formula or ·, such as sodium metasilicate (), sodium orthosilicate (), and sodium pyrosilicate (). The anions are often polymeric. These compounds are generally colorless tra ...

(water glass) and a water-soluble magnesium salt such as

magnesium chloride Magnesium chloride is an inorganic compound with the formula . It forms hydrates , where ''n'' can range from 1 to 12. These salts are colorless or white solids that are highly soluble in water. These compounds and their solutions, both of which ...

magnesium nitrate Magnesium nitrate refers to inorganic compounds with the formula Mg(NO3)2(H2O)x, where x = 6, 2, and 0. All are white solids. The anhydrous material is hygroscopic, quickly forming the hexahydrate upon standing in air. All of the salts are very ...

magnesium sulfate Magnesium sulfate or magnesium sulphate is a chemical compound, a salt with the formula , consisting of magnesium cations (20.19% by mass) and sulfate anions . It is a white crystalline solid, soluble in water but not in ethanol. Magnesi ...

. The composition of the precipitate depends on the ratio of the components in the reaction medium, the addition of the correcting substances, and the way in which they are precipitated.Ralph K. Iler, The Chemistry of Silica: Solubility, Polymerization, Colloid, and Surface Properties, and Biochemistry, John Wiley and Sons (1979)Krysztafkiewics, A., Lipska, L.K., Ciesielczyk, F., and Jesionowski, T. Amorphous magnesium silicate – synthesis, physicochemical properties and surface morphology. Advanced Powder Technol, 15, 549, 2004.Ciesielczyk, F., Krysztafkiewics, A., Jesionowski, T. Physicochemical studies on precipitated magnesium silicates. J Mater Sci. 42, 3831, 2007. The

molecular formula A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols, numbers, and sometimes also other symbols, such as paren ...

is typically written as MgO:XSiO₂, where X denotes the average mole ratio of SiO₂ to MgO. The product is

hydrated In chemistry, a hydrate is a substance that contains water or its constituent elements. The chemical state of the water varies widely between different classes of hydrates, some of which were so labeled before their chemical structure was understo ...

and the formula is sometimes written MgO:XSiO₂•H₂O to show the water of hydration.

Properties

Unlike natural magnesium silicates like

talc Talc, or talcum, is a clay mineral composed of hydrated magnesium silicate, with the chemical formula . Talc in powdered form, often combined with corn starch, is used as baby powder. This mineral is used as a thickening agent and lubricant ...

forsterite Forsterite (Mg2SiO4; commonly abbreviated as Fo; also known as white olivine) is the magnesium-rich Endmember, end-member of the olivine solid solution series. It is Isomorphism (crystallography), isomorphous with the iron-rich end-member, fayalit ...

, and

olivine The mineral olivine () is a magnesium iron Silicate minerals, silicate with the chemical formula . It is a type of Nesosilicates, nesosilicate or orthosilicate. The primary component of the Earth's upper mantle (Earth), upper mantle, it is a com ...

which are

crystalline A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macrosc ...

, synthetic magnesium silicates are

amorphous In condensed matter physics and materials science, an amorphous solid (or non-crystalline solid) is a solid that lacks the long-range order that is a characteristic of a crystal. The terms "glass" and "glassy solid" are sometimes used synonymousl ...

. Synthetic magnesium silicates are insoluble in water or alcohol.Condensed Chemical Dictionary, Eleventh Edition, Van Nostrand and Reinhold Co. Inc., New York, NY (1987) The particles are usually

porous Porosity or void fraction is a measure of the void (i.e. "empty") spaces in a material, and is a fraction of the volume of voids over the total volume, between 0 and 1, or as a percentage between 0% and 100%. Strictly speaking, some tests measure ...

, and the BET surface area can range from less than 100 m²/g to several hundred m²/g.

Applications

The very large active surface makes synthetic magnesium silicate useful for a wide variety of applications: purifying

adsorbent Adsorption is the adhesion of atoms, ions or molecules from a gas, liquid or dissolved solid to a surface. This process creates a film of the ''adsorbate'' on the surface of the ''adsorbent''. This process differs from absorption, in which a ...

(

polyols In organic chemistry, a polyol is an organic compound containing multiple hydroxyl groups (). The term "polyol" can have slightly different meanings depending on whether it is used in food science or polymer chemistry. Polyols containing two, thre ...

, animal and vegetable oils,

chromatography In chemical analysis, chromatography is a laboratory technique for the Separation process, separation of a mixture into its components. The mixture is dissolved in a fluid solvent (gas or liquid) called the ''mobile phase'', which carries it ...

, U.S. Silica, FLORISIL®
/ref> dry cleaning, sugar, resins, odors); filler (rubber, ceramics, paper, glass, refractories);

anti-caking agent An anticaking agent is an additive placed in powdered or granulated materials, such as table salt or confectioneries, to prevent the formation of lumps ( caking) and for easing packaging, transport, flowability, and consumption. Caking mechanism ...

(salt);

catalyst Catalysis () is the increase in rate of a chemical reaction due to an added substance known as a catalyst (). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycles quick ...

; catalyst carrier; filter medium.

In food

The U.S.

Food Chemicals Codex The Food Chemicals Codex (FCC) is a collection of internationally recognized standards for the purity and identity of food ingredients. Scope The FCC features more than 1,250 monographs, including food-grade chemicals, processing aids, foods (suc ...

,Food Chemicals Codex, Seventh Edition, United Book Press Inc., Baltimore, MD (2010) JECFA,Food and Agricultural Organization of the United Nations/World Health Organization Joint Expert Committee on Food Additives, 61st Session, published in NFP 52, Add 11, 2003. and other monographs for Food Grade synthetic magnesium silicate specify a mole ratio of 2MgO:5SiO₂ (or X=2.5 in the general formula). The most common use for Food Grade synthetic magnesium silicate is as an active filter aid for adsorption of color, free

fatty acids In chemistry, in particular in biochemistry, a fatty acid is a carboxylic acid with an aliphatic chain, which is either saturated or unsaturated. Most naturally occurring fatty acids have an unbranched chain of an even number of carbon atoms, ...

and other

polar Polar may refer to: Geography * Geographical pole, either of the two points on Earth where its axis of rotation intersects its surface ** Polar climate, the climate common in polar regions ** Polar regions of Earth, locations within the polar circ ...

compounds from used frying oils. ACE Filters International; Miracle FP
/ref>Michael D. Erickson (Editor), Deep Frying: Chemistry, Nutrition, and Practical Applications, 2ND Edition, AOCS Press (2007) Various national and international regulations allow use of this material as an anti-caking agent in a wide variety of powdered foods.Codex Alimentarius General Standard for Food Additives, Codex Alimentarius, Volume 1, General Requirements, 199121 CFR 182.2437, U.S. Code of Federal Regulations
/ref>European Union Commission Directive 2008/84/EC of 27 August 2008No. 98-90, Korea Food and Drug Administration Bulletin When used as a

food additive Food additives are substances added to food to preserve flavor or enhance taste, appearance, or other sensory qualities. Some additives, such as vinegar ( pickling), salt ( salting), smoke ( smoking) and sugar ( crystallization), have been used f ...

, it is safe to ingest synthetic magnesium silicate. In 1990, the safety of synthetic magnesium silicate was reviewed by the

Scientific Committee on Food The Scientific Committee on Food (SCF), established in 1974, was the main committee providing the European Commission with scientific advice on food safety. "Scientific Committee on Food - FOOD STANDARDS AGENCY" (overview), Gov.uk, F ...

(SCF) together with that of silica and the other metal alkali silicates. The SCF noted that “the available data, including a number of short-term studies in two species, appear to substantiate the biological inertness of those compounds”. The SCF established a group

Acceptable Daily Intake Acceptable daily intake or ADI is a measure of the amount of a specific substance (originally applied for a food additive, later also for a residue of a veterinary drug or pesticide) in food or drinking water that can be ingested (orally) daily ove ...

(ADI) not specified for silicon dioxide and the alkali metal silicates.

References

{{Reflist Silicon

Properties

Applications

In food

See also

References