What is Milk of Magnesia?
Milk of magnesia, also known as magnesium dihydroxide or magnesium hydroxide, is a chemical compound with the formula Mg(OH)2. This chemical compound occurs naturally in the form of the mineral brookite. Under standard conditions for temperature and pressure, milk of magnesia is known as a white solid that exhibits very low solubility in water. It is important to note that milk of magnesia is an important ingredient in antacids and some laxatives.
Milk of magnesia is sold for medicinal use (often in flavored form) as chewable tablets, capsules, powders, and liquid suspensions. To neutralize stomach acid, and relieve indigestion and heartburn, milk of magnesia is often sold as an antacid. It is also a laxative that can be used to relieve constipation. The osmotic force of magnesia, as a laxative, acts to draw fluid from the body. High doses can cause diarrhea and deplete the body’s supply of potassium, often resulting in muscle cramps.
Preparation of milk of magnesia
Milk of magnesia can be prepared by mixing several solutions of magnesium salts with basic or alkaline water. The resulting chemical reaction usually involves precipitation of milk solids of magnesia. The ionic chemical reaction taking place here can be expressed as:
2OH– + Mg2+ → Mg(OH)2 [milk of magnesia]
However, production of milk of magnesia cannot be efficiently achieved on a commercial scale using the techniques described above. For the commercial production of magnesium hydroxide, seawater can be treated with calcium hydroxide (also known as lime). It is interesting to note that one ton of milk of magnesia can be obtained from six hundred cubic meters of sea water. The reason milk of magnesia solidifies in this reaction is that calcium hydroxide is more soluble in water than magnesium hydroxide.
Properties of Milk of Magnesia
The chemical formula of milk of magnesia can be shown as Mg(OH)2.
The molar mass of this chemical compound is equal to 58.3197 grams per mole.
Under standard conditions, this compound exists as a white solid with no characteristic odor.
The density of milk of magnesia, under standard conditions of temperature and pressure (STP), corresponds to 2.3446 grams per cubic centimeter.
The melting point of this compound may be around 350 degrees Celsius. However, it is important to note that this compound begins to decompose at this temperature gradient.
Milk of magnesia is not very soluble in water. At a temperature of 25 degrees Celsius, the solubility of this compound in water is equal to 0.00064 g/100 ml. When the temperature is raised to 100 degrees Celsius, the solubility of this compound in water increases to 0.004 g/100 mL.
It may be noted that magnesium hydroxide crystallizes in a hexagonal crystal lattice.
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