-
定義
本品は、塩基性炭酸マグネシウム脱水物又は正炭酸マグネシウム含水物である。
-
性質
マグネサイトは、菱面体や三方晶の結晶構造を有したモース硬度は3.5〜4.5の炭酸塩鉱物です。純粋なものは透明〜白色を示し、ガラス光沢を有します。紫外線を照射すると、緑または青の蛍光およびりん光を発します。
モース硬度とは、主に鉱物に対して使われる単位の一種です。1〜10の数字で表され、あるもので引っかいたときに傷がつくかどうかの指標です。
また、マグネサイトを1,000ºC程度で焼成すると、主成分である炭酸マグネシウムからが脱離し、酸化マグネシウム (MgO) が得られます。主成分である炭酸マグネシウム (英: Magnesium carbonate) の化学式はMgCO3で表され、分子量は84.31です。
-
解説
菱苦土 (りょうくど) 鉱ともいう。 MgCO3 。炭酸マグネシウムを主成分とする鉱物。六方晶系，菱面体または柱状。白色，灰色，褐色など。透明または不透明で硬度 3.5～4.5，比重 3.0～3.12。熱塩酸には発泡して溶ける。普通，滑石片岩，蛇紋岩など，マグネシウムに富む岩石中に脈状に含まれて産出する。中国の東北地方，朝鮮などでは厚い層状をした鉱床がよくある。 煆焼 (かしょう) calcinationして，マグネシア (苦土) とし，金属マグネシウム，マグネシア耐火物 (苦土質煉瓦など) ，マグネシア・セメントなどの製造に使う。マグネサイト，MgCO3．りょう苦土石ともいう．蛇紋岩，かんらん岩などMgの多い岩石の変質により生成する．変成岩，たい積岩，熱水鉱脈中にも産出する．方解石族で，三方晶系，空間群 R3c，格子定数 a(rh) ＝ 0.5635～0.5648 nm．α ＝ 48°00′～48°03′．単位りょう面体格子中に2個の基本組成を含む．へき開{10
"1}完全．硬度3.75～4.25．密度3.00 g cm－3．紫外線により緑または青の蛍光およびりん光を発する．
-
製法
天然では、主に中国で産出されます。日本では、茨城県常陸太田市にある長谷鉱山や長崎県西海市および大分県豊後大野市にある尾平鉱山にて産出されていましたが、現在はどちらも閉山しています。
人工的には、マグネシウム蛇紋岩 (リザード岩) の炭酸化によっても合成可能です。しかし、本手法では炭酸マグネシウム三水和物 (ネスクホナイト) が生成します。
-
化粧品の成分用途
pH調整剤、不透明化剤、吸着剤、増量剤
-
主な用途／役割
エポキシ樹脂系接着剤、ゴム系接着剤に使用される。
-
説明
Magnesium carbonate is obtained mainly by mining
the natural mineral magnesite. The trihydrate salt,
MgCO3·3H2O, is prepared by mixing solutions of magnesium
and carbonate ions in the presence of carbon
dioxide.
-
化学的特性
Magnesium carbonate occurs as light, white-colored friable masses
or as a bulky, white-colored powder. It has a slightly earthy taste
and is odorless but, since it has a high absorptive ability, magnesium
carbonate can absorb odors.
The USP 32 describes magnesium carbonate as either a basic
hydrated magnesium carbonate or a normal hydrated magnesium
carbonate. However, the PhEur describes magnesium carbonate as
being a hydrated basic magnesium carbonate in two separate
monographs: heavy magnesium carbonate and light
magnesium carbonate. The molecular formulas for
heavy magnesium carbonate and light magnesium carbonate vary,
but heavy magnesium carbonate may generally be regarded as the
tetrahydrate [(MgCO3)3·Mg(OH)2·4H2O], while light magnesium
carbonate may be regarded as the trihydrate [(MgCO3)3·
Mg(OH)2·3H2O].
The molecular weights of the heavy and light forms of
magnesium carbonate are 383.32 and 365.30, respectively.
-
物理的性質
This material is available in a very light, fluffy grade which absorbs well. The before-mentioned qualities are why magnesium carbonate is often used to absorb perfume before incorporation into face powders.
-
使用
Some applications of magnesiumcarbonate are uses in
flooring, fireproofing and fire-extinguishing compositions;
as a filler material and smoke suppressant in plastics;
as a reinforcing agent in neoprene rubber; as a drying
agent and for color retention in foods; in cosmetics.
Magnesium carbonate is used as an antacid in medicine
and as an additive to table salt. Another important application
of magnesium carbonate is as a starting material in
producing a number of magnesium compounds.
Because of its water-insoluble, hygroscopic properties,
MgCO3 was first added to salt in 1911 to make the
salt flow more freely. Magnesium carbonate, most often
referred to as “chalk”, is used as a drying agent for hands
in gymnastics, weight lifting and rock climbing. Magnesium
carbonate is also used in taxidermy for whitening
skulls. It can be mixed with hydrogen peroxide to create
a paste, which is then spread on the skull to give it awhite
finish. Basic magnesium carbonate is used as a clay in
face masks and it has mild astringent properties and
helps to smooth and soften skin. It is recommended for
use on normal to dry skins.
-
定義
A whitecompound, MgCO3, existing in anhydrousand hydrated forms. The anhydrousmaterial (trigonal; r.d.2.96) is found in the mineral magnesite.There is also a trihydrate,MgCO3.3H2O (rhombic; r.d. 1.85),which occurs naturally as nesquehonite,and a pentahydrate, MgCO3.5H2O (monoclinic; r.d. 1.73),which occurs as lansfordite. Magnesiumcarbonate also occurs in themixed salt dolomite (CaCO3.MgCO3)and as basic magnesium carbonatein the two minerals artinite(MgCO3.Mg(OH)2.3H2O) and hydromagnesite(3MgCO3.Mg(OH)2.3H2O).The anhydrous salt can be formed byheating magnesium oxide in astream of carbon dioxide:
MgO(s) + CO2(g) → MgCO3(s)
Above 350°C, the reverse reactionpredominates and the carbonate decomposes.Magnesium carbonate isused in making magnesium oxideand is a drying agent (e.g. in tablesalt). It is also used as a medicalantacid and laxative (the basic carbonateis used) and is a componentof certain inks and glasses.
-
調製方法
Depending upon the manufacturing process used, the composition
of the magnesium carbonate obtained may vary from normal
hydrated magnesium carbonate to basic hydrated magnesium
carbonate.
Light magnesium carbonate may be manufactured by saturating
an aqueous suspension of dolomite, CaMg(CO3)2, with carbon
dioxide under pressure. On increase of the temperature, calcium
carbonate precipitates almost entirely. The filtered solution is then
heated to boiling; the magnesium bicarbonate in the solution loses precipitates.
Heavy magnesium carbonate may be manufactured by mixing a
hot concentrated solution of magnesium chloride or magnesium
sulfate with a solution of sodium carbonate. The heavy magnesium
carbonate may be either precipitated to produce a granular material
or spray-dried. Varying the temperature of the reaction solutions
produces heavy magnesium carbonate with differing physical
properties: e.g. material with a higher specific surface area is
produced at a lower reaction temperature. Low processing
temperature provided the largest surface area, which produced
optimum granules or spray-dried powder.If dilute magnesium
chloride or magnesium sulfate solutions are used for the reaction, a
less dense material is produced.
Magnesium carbonates in varying states of hydration are also
found as minerals in nature.
-
一般的な説明
White, yellowish, grayish-white or brown crystalline solid or crystalline powder. Density: 3-3.1 g cm-3. An important ore for magnesium. Used in the manufacture of materials capable of withstanding very high temperatures. Sometimes used to produce carbon dioxide.
-
反応プロフィール
Magnesium carbonate has generally low chemical reactivity. Non-flammable and non-combustible. Reacts with acids and acidic salts to generate gaseous carbon dioxide with effervescence (bubbling). The reaction may be rapid and exothermic with concentrated solutions of acids. The efferversence can create foaming. Incompatible with formaldehyde.
-
危険性
A nuisance particulate.
-
健康ハザード
Magnesite is considered to be a
nuisance dust.
-
使用用途
1. 酸化マグネシウムの原料
マグネサイトは、主に熱処理してを生成する用途に使われます。
2. 芸術作品
マグネサイトは、ビーズなどの原料として利用されます。色が付けやすい性質から、染色されてトルコ石やラピスラズリの代用品としたり、カットや穴あけ、研磨によってさまざまな装飾品に変化します。
3. その他
マグネサイトは、床材 (マグネサイトスクリード) のバインダー、合成ゴムの製造における触媒や充填材、工場で発生する排煙中に含まれるを除去する製品の原料としても使用されています。
-
取り扱い及び保管上の注意
ここでは、主成分である炭酸マグネシウムについて解説します。
取り扱い時の対策
取り扱う際は、側板付きの保護メガネ (必要に応じゴーグルまたは全面保護メガネ) と長袖の保護衣、保護手袋を着用します。局所排気装置内で使用してください。
火災の場合
熱分解で、一酸化炭素や二酸化炭素マグネシウム酸化物を生成するおそれがあります。現場状況と周囲の環境に適した消火方法を選択してください。
保管する場合
ポリエチレン製の容器に密閉し、直射日光を避けた換気が良く涼しい場所に保管してください。保管場所は必ず施錠します。
参考文献
-
农业用途
Hydromagnesite is a magnesium ore which occurs as a carbonate. Magnesium carbonate occurs in a mixed salt dolomite (CaCO3.MgCO3) and as basic magnesium carbonate in two minerals, namely, artinite (MgCO3.Mg(OH)2.3H2O) and hydromagnesite (3MgCO3.Mg(OH)2.3H2O).
-
応用例（製薬）
As an excipient, magnesium carbonate is mainly used as a directly
compressible tablet diluent in concentrations up to 45% w/w.
Heavy magnesium carbonate produces tablets with high crushing
strength, low friability, and good disintegration properties.
However, magnesium carbonate can have varying effects on
dissolution and stability.Magnesium
carbonate has been incorporated in microsphere formulations for
the purpose of stabilizing encapsulated proteins. It has also been
coencapsulated in poly(lactide-co-glycolide) microsphere formulations
to neutralize acidity and enhance the immunogenicity of a
contraceptive peptide vaccine. Magnesium carbonate is also used
to absorb liquids, such as flavors, in tableting processes.
Magnesium carbonate is additionally used as a food additive and
therapeutically as an antacid.
-
安全性
Magnesium carbonate is used as an excipient in oral solid-dosage
pharmaceutical formulations and is generally regarded as an
essentially nontoxic and nonirritant material. However, the use of
magnesium salts, such as magnesium carbonate, is contraindicated
in patients with renal impairment. In certain studies, magnesium
carbonate has been shown to be an effective phosphate binder in
short-term use for patients with chronic kidney disease, but the
effects of long-term use require further study.The probable oral
lethal dose in humans has been estimated at 0.5–5.0g/kg bodyweight.
On contact with gastric acid, magnesium carbonate reacts in the
stomach to form soluble magnesium chloride and carbon dioxide.
Magnesium carbonate should therefore not be used as an antacid by
those individuals whose stomachs cannot tolerate the evolution of
carbon dioxide. Some magnesium is absorbed but is usually
excreted in the urine. As with other magnesium salts, magnesium
carbonate has a laxative effect and may cause diarrhea.
Therapeutically, the usual dose of magnesium carbonate as an
antacid is 250–500mg, and 2.0–5.0g as a laxative.
-
貯蔵
Magnesium carbonate is stable in dry air and on exposure to light.
The bulk material should be stored in a well-closed container in a
cool, dry place.
-
不和合性
Incompatible with phenobarbital sodium,diazepam solution at
a pH≥5, some binary powder mixtures, lansoprazole,
and formaldehyde. Acids will dissolve magnesium carbonate,
with the liberation of carbon dioxide. Slight alkalinity is imparted to
water. Magnesium carbonate was also found to increase the
dissolution of acetazolamide formulations at a pH of 1.12; however,
dissolution was retarded at a pH of 7.4.
-
規制状況(Regulatory Status)
GRAS listed. Accepted as a food additive in Europe. Included in the
FDA Inactive Ingredients Database (oral capsules and tablets).
Included in nonparenteral medicines licensed in the UK.
