Acidum Phosphoricum Dilutum

Diluted Phosphoric Acid is the principal form in which phosphoric acid is employed in medicine.


H3Po4. Sp. gr., 1.056.


Phosphorus, a non-metallic element, obtained from bones, is a translucent, nearly colorless, wax-like solid, without taste, and emitting white vapors when exposed to the air. Sp. gr., 1.8.

It is insoluble in. water, but soluble in ether and in hot oil of turpentine, and has a peculiar smell. It is nervine, tonic and stimulant, and in over-doses, poisonous. The vapor is irritating to the conjunctiva and bronchial mucous membrane.

Diluted Phosphoric Acid is prepared by boiling phosphorus with nitric acid and distilled water until it is dissolved, evaporating and rediluting it. It may also be obtained by dissolving an ounce of glacial phosphoric acid in three ounces of distilled water, afterward adding forty grains of nitric acid, boiling to a syrup, and diluting with water until the solution measures twelve and a half ounces.

Medical Properties And Physiological Action

It is tonic and refrigerant, and, in large doses, is a powerful stimulant to the nervous and vascular systems. It can be detected in the blood, owing to its absorption, and, in large doses, is an irritant poison.

Therapeutic Uses

Diluted phosphoric acid is employed in scrofula, dropsy, hemoptysis, calculous disease, diabetes and car-dialgia. Externally, it has been employed as a local application in the treatment of caries of the bones and osseous tumors.


Of dilute phosphoric acid, gtt. ij-xv, diluted in sugar and water.

Dental Uses

As a local application in the treatment of caries of the maxillary bones and osseous tumors of the jaws. Internally, it has been administered with a view of supplying a deficiency of phosphoric acid in the teeth. (See Hypophosphites of Lime.)

Dental Formulae

For Caries of the Maxillary Bones and Osseous Tumors of the jaw.

Acidi phosphor. dilut. . I part Aquae destillatae 8 to 10 parts. M.


Apply as a lotion or injection.

Sign A 498

For Ulcers Over Carious Bones.

Acidi phosphorici gla-cialis ......

Aquae destillatae . . . Fiat Solutio. Signa. - To be applied on compresses to ulcers situated over carious bones.

Sign A 499Sign A 500

Phosphoric Acid in the Anhydrous State consists of one equivalent of phosphorus to five equivalents of oxygen (Po5), and it is obtained by the direct union of its constituents, which takes place when phosphorus is burned in perfectly dry oxygen gas.

Thus procured it is in the form of a white amorphous powder, extremely deliquescent, volatilizable at a red heat, and assumes, when it cools, after fusion, a vitreous appearance.

Glacial Phosphoric Acid, or monohydrated phosphoric acid, concentrated phosphoric acid, is readily obtained from calcined bones, by first heating them with sulphuric acid, which produces an insoluble superphosphate of lime; then dissolving out the latter salt, and saturating it with carbonate of ammonia, which generates phosphate of ammonia in solution, and finally obtaining the phosphate of ammonia by evaporating it to dryness, and then igniting it in a platinum crucible. The ammonia and all of the water, except one equivalent for each equivalent of the acid, are driven off, and the glacial phosphoric acid remains, the formula of which is HO,Po5, and contains 11.2 per cent. of water. It is a white, transparent fusible solid, generally in the form of sticks, inodorous and sour to the taste. It slowly deliquesces, and is sparingly soluble in water, but freely soluble in alcohol.

Dental Uses

Glacial phosphoric acid and white oxide of zinc formed into an anhydrate, give the plastic material for filling teeth, known as oxyphosphate of zinc. The powder or solid portion of this preparation is prepared by packing pure oxide of zinc in a clay crucible and subjecting it to almost a white heat for two hours, when it will have been reduced in bulk fifty per cent. It is then pulverized in a mortar to an almost impalpable powder. The burning of the oxide of zinc colors it to a light yellow, and it is now in a condition for use, and may be kept in a covered vessel for any length of time.

The liquid portion of this filling material being glacial phosphoric acid, is prepared by dissolving the acid in pure water until a saturated solution is obtained, when it is reduced by boiling in a glass vessel until it is of the consistency of glycerine, in which operation it loses one-third in bulk. It is now ready for use, and must be kept in a close glass-stoppered bottle.

Formulae for Fletcher's and Weston's preparations of oxyphosphate of zinc filling materials:



Phosphoric acid. Phosphate of alumina.

Solid. Basic oxide of zinc.



Phosphoric acid. (See Oxide of Zinc.)


Basic oxide of zinc - 80 per cent Silicate of alumina - 20 " "

Medicated Oxyphosphate Fillings

Dr. Chas. B. Atkinson claims the following advantages for such filling materials:


A remedial agent in constant contact with the walls of the cavity.


Germicidal action of the filling on the tissue with which it comes in contact.


A neutral influence resisting solution.


Increased hardness, varying somewhat with the agent used. The medicaments for oxyphosphate fillings are: 1. Creasote and oil of cloves, equal parts; 2. Eugenol; 3. Deliquesced Carbolic acid; 4. Oil of cinnamon; 5. Oil of cloves; 6. Creasote, pure; 7. Creasote, oil of cloves and iodoform ; 8. Creolin; 9. Campho-phenique; 10. Potassium chlorate (powdered); II. Salicylic acid; 12. Camphor (pulverized); 13. Stick sulphur (pulverized); 14. Iodoform; 15. Oil of wintergreen. The first seven have been fairly tested by Dr. Atkinson and were found to be equal in durability, manipulative qualities and time of setting. He employs them also in retaining inlays, in setting retaining-fixtures in pyorrhoea cases, in setting crowns, etc. In capping pulps he always employs a mixture of oxide of zinc, creasote and oil of cloves, and adds a remedial agent to the oxyphosphate filling. He employs mostly the first named on the list. If the medicament is a liquid he adds about an equal quantity of the medicament and phosphoric acid; if a powder, about equal parts of the medicament and oxide. The proportions may be varied as required. The average time of setting is about ten minutes.