Magnesia is obtained by exposing carbonate of magnesium to a red heat, and thus expelling all of the carbonic acid, which is shown by a want of effervescence on the addition of dilute sulphuric acid. It is very light, and of a white color and odorless, and in the form of powder, with an earthy taste, and slightly soluble in water, more so in cold than in hot water.

Medical Properties And Action

Magnesia is antacid and laxative, its laxative effect being the result of the combination it forms with the three acids of the stomach and intestines. After its effects are exerted in the intestinal canal, it becomes absorbed and renders the urine alkaline. Large doses, when administered for a considerable time, may accumulate in the bowels; such an effect may be avoided by administering it with lemonade, which renders it more soluble. Being mild and unirritating, it is well adapted for children, and is an excellent remedy for great acidity in the stomach. It is the antidote for poisoning by the mineral acids.

Therapeutic Uses

Magnesia is administered in acidity of the stomach, heartburn, sick headache and kidney affections, as an antacid, and in combination with other agents in the diarrhoea of children. It is also an efficient aperient, alone or in a little milk.


Of magnesia, as a laxative, gr. x to Dose 1188 ; as an antacid,

Of a preparation known as " Henry's," the dose is half the quantity just given.

Dental Uses

Magnesia is employed in dental practice, chiefly for its antacid properties, as an ingredient of dentifrices ; in solution in the form of a gargle, to counteract the effect of acid medicines upon the teeth; also as an ingredient of remedies for infantile diarrhoea during the period of dentition; and also to change an acid condition of the oral fluids, by being rubbed between the teeth and permitted to remain for a short time.

Magnesium Hydrate

Dr. E. C. Kirk recommends Phillips' Milk of Magnesia, which consists of precipitated magnesium hydrate held in suspension in water, for contracting the injurious action of acid secretions, especially in erosion cases. It is applied in the same way that lime-water or precipitated chalk is used for the purpose of bringing about an alkaline condition of the oral fluids, by neutralizing the excess of acids present. A teaspoonful of the preparation taken into the mouth and allowed to float around over the teeth coats them with a slight film of magnesium hydrate, which protects the tooth-surface from the acid action for a number of hours. It should be used three times daily, after meals, and for erosion, night and morning.

Dental Formulae

For Infantile Bilious Diarrhoea.


Magnesia calc. . . . gr.xxiv - iij

Ipecacuanha .... gr.ij - iij Ext. hyoscyami . . . gr.iv-vj. M.

F. ch. No. xij.


One to be given every 2 or 3 hours.

Signa 1190

For Infantile Mucous Diarrhoea. Eherle.

Magnesise calc. . . . gr.x

Bals. copaibae . . .

Spir. aether nit. . . .

Sacch. alb......

Aq. cinnamon .... Signa. - A teaspoonful every 2 or 3 hours; each dose to be followed in the course of an hour by the fifth of a grain of Dover's Powder.

Signa 1191Signa 1192