Magnesia. MgO. Protoxide of Magnesia. A' compound of Magnesium 60, Oxygen 40, in 100 parts; or 1 Eq. Magnesium = 12, +1 Oxygen=8 = 20.

* Hufeland's Journ., vol. xxxvi Med. Times, vol. xvii. p. 211. Rat. Med., par. iii. p. 195; and par. iv. p. 250.

§ On Stomach and Renal Diseases, 3rd Ed., op. cit.

Magnesia Levis. MgO. Prepared by burning light Carbonate of Magnesia in a Cornish or Hessian Crucible at a red heat, as long as any of the powder effervesces with dilute Sulphuric Acid.

Med. Prop. and Action. Antacid, in doses of gr. x. - xx.; laxative, in doses of gr. xxx. - gr. lx. - gr. xc.; for a child the dose is from gr. ij. - x. It is supposed by Hufeland to possess, in addition to its antacid, a specific property of diminishing gastro-intestinal irritation, by a directly sedative action. As an antacid, it is preferable to the Carbonate, as the latter, when brought in contact with the acid of the stomach, gives rise to much flatulence. After exerting its antacid effects in the intestinal canal, it becomes absorbed, and renders the urine alkaline. It is, therefore, of use in increased excretion of uric acid and urates. As an aperient, it is mild and unirritating, and is well adapted for children: it may be given alone in a little milk, or combined with a few grains of Rhubarb. It is an antidote in poisoning by the mineral acids.

Offlc. Prep. of Magnesia Levis: Pulvis Rhei Compositus (Gregory's Powder) (Powdered Rhubarb oz. ij.; Light Magnesia oz. vj.; Powdered Ginger oz. j.). Dose, gr. lx. - gr. cxx.

Dose, of Magnesia or Magnesia Levis: as an antacid, gr. x. - gr. xx.; as a laxative, gr. xxx. - gr. xc.

Incompatibles. Acids; Acidulous Salts; Hydrochlorate of Ammonia; Metallic Salts; Alum.

1752. Therapeutic Uses

In Acidity of the PrimAe Vice, Car-dialgia, Sympathetic Vomiting, and some irritated states of the Stomach, Magnesia, in doses of gr. xv. - gr. xx., may be given with advantage. In the Heartburn of Pregnancy, Dr. Simms particularly recommends the following formula: - ℞ Magnes. Ust. 3j., Aq. Ammonise f3j., Spt. Cinnam. f3iij., Aq. fvss., M. Dose, two or three table-spoonfuls, immediately after every meal, or when required. (Dewees.*)

1753. In Eczema, Dr

J. Green states that of all applications none is so generally useful as 3j. of Calcined Magnesia, rubbed into ij. of melted Lard. The ointment, being a little warmed, is smeared over the surface, and then covered with tissue-paper, and the longer it can be allowed to remain on the better. It may be applied once or twice daily. (See also MagnesiAe Car-bonas.)