The N. F. previously gave formulas for two petroxolins, but the number has been increased to twenty. Two petroxolins are solid.

COMMENTS

Petroxolinum Hydrargyri, Mercury Petrox, N. F. This is a solid preparation in which mercury is present in a finely divided metallic condition.

Petroxolinum Iodi, N. F. Following the directions given, there is undoubtedly some reaction between iodine and ammonia, ammonium iodide and ammonium iodate being formed. These are perhaps later decomposed by the excess of acid. Some of the iodine combines slowly with oleic acid, making an addition product. Oleic acid and ammonia unite to form an oleate.

Petroxolinum Liquidum, Liquid Petrox, N. F. This is used as the base for several other petroxolins. There is a small excess of acid used. Heating on a water-bath for onehalf to two hours may be necessary before a clear liquid is obtained. Probably most of the alcohol and a part of the water is evaporated.

Petroxolinum Sulphuratum, N. F. Sulphur must be heated with linseed oil for several hours before it is dissolved, and the heating darkens the preparation. During the heating a small amount of liquid will be seen to have separated from the oil; this is melted sulphur.

SPRAYS

Sprays are liquid preparations in which the base is light liquid petrolatum, containing a volatile oil, phenol, ketone or similar compound, and intended to be used with an atomizer. This class is not recognized by the U. S. P.,

and was not in the previous edition of the N. F. Most sprays are simple solutions, and are easily made. Liquid petrolatum is a solvent for a limited number of substances. Sometimes the medicinal agent, if insoluble in liquid petrolatum, can first be dissolved in a fixed oil or in liquid petroxolin, and then in the liquid petrolatum. Small amounts of free alkaloids can be dissolved in liquid petrolatum, but it is often better to convert them into oleates, which are more soluble in this liquid.

INFUSED OILS

This class is recognized by the N. F. but not by the U. S. P., and the N. F. gives only a general formula. Infused oils are generally made from drugs containing alkaloids. Most alkaloids exist naturally in combination with an acid, and these salts are not soluble in oil. Ammonia is used to liberate the bases and make them soluble in oil. Alcohol is used because it penetrates the drug better and dissolves out the alkaloids more completely. The alcohol and ammonia are later evaporated, leaving the alkaloids dissolved in the oil.

LOTIONS

Definition. Lotions are liquid preparations for external application in which the liquid is water, or water with glycerin. In many commercial face lotions a small amount of tragacanth (1 per cent) or mucilage of quince seed is used. Tragacanth contains two gums; one is soluble in water, and the other is not soluble but swells in water. Enough of tragacanth should be used to keep the insoluble portion suspended, but not enough to make it too thick.

The amount of glycerin should not be so much as to leave the face and hands sticky. If quince seed is used, care should be taken not to use that which has been eaten by bugs, as little particles of the dark coat are liable to get into the finished product and are difficult to remove. Lotions should not be filtered. The N. F. recognizes four, and the U.S. P. none. A "shake well" label should be used with each.

COMMENTS

Lotio Ammoniacalis Camphorata, Sedative Water, N. F. A small amount of camphor is precipitated. Camphor, being lighter than water, is difficult to keep suspended.

Lotio Flava, Yellow Wash, Aqua Phagedænica Flava, N. F. The solution of mercuric chloride is poured into the lime water, not the lime water into the mercuric chloride, so as to have an excess of calcium hydroxide. If the lime water is weak or is not in excess, a red-brown basic chloride of mercury is formed instead of the yellow oxide.

HgCl2+Ca(OH)2 = HgO+CaCl2+H2O.

Mercuric

Calcium Mercuric Calcium Water
chloride

chloride hydroxide oxide

Lotio Nigra, Black Lotion, Aqua Phagedanica Nigra, N. F. The following reaction takes place, the black precipitate being mercurous oxide:

Lotio Plumbi et Opii, Lead and Opium Wash, N. F. Some of the lead is precipitated as the sulphate, and some as the meconate, because of the sulphuric and meconic acids with which the alkaloids of opium are combined. Some of the resinous matter of the tincture is precipitated, but the

alkaloids remain in solution. Physicians frequently prescribe tincture of opium with solution of lead subacetate (laudanum with lead water), and the alkaloids are precipitated here because the solution of lead subacetate is alkaline.

COLLODIONS

Definition. Collodion is a solution of pyroxylin in a mixture of alcohol and ether, which mixture is a better solvent than either alone. Pyroxylin or gun cotton is made by treating purified cotton with a mixture of sulphuric and nitric acids, and is chiefly cellulose tetranitrate. Pyroxylin is also used with camphor in making celluloid. When the solvent in collodion has volatilized there is left a thin membrane which is impervious to air and water and which contracts. The five N. F. collodions are simple solutions of medicinal agents in flexible collodion. Bottles containing collodion should be kept tightly stoppered, and after some has been poured out the neck of the bottle should be wiped off to prevent the cork from sticking.

COMMENTS

The

Collodium Cantharidatum, Blistering Collodion. Spanish flies are extracted with acetone acidified with glacial acetic acid, and the solvent is evaporated; the residue makes a nearly clear solution with flexible collodion. If the flies were macerated with collodion it would be difficult. to remove the insoluble part. It is said that the extract made with acetone gives a more permanent collodion than when made with chloroform, which was formerly used.

Collodium Flexile. The residue from flexible collodion, containing camphor and castor oil, does not contract as much as that from plain collodion, and is not as stiff.

Collodium Salicylici Compositum, N. F. This is similar in composition to many of the liquid corn remedies on the market, though perhaps not quite as strong.

SOLID PREPARATIONS FOR LOCAL APPLICATION

OINTMENTS

Definition. An ointment is a solid preparation for external application with friction, and of such consistency that it will generally melt at or below the temperature of the body. Ointments are used for their local or their systemic effects, and to get the best results a knowledge of the bases is required. The articles most commonly used as bases are petrolatum, wool fat, lard, lard with wax, sodium stearate, casein, and glycerite of starch.

Bases. Petrolatum is a mixture of hydrocarbons obtained from petroleum by distilling off the more volatile and liquid portions, and deodorizing and decolorizing the residue. Petrolatum is not readily absorbed, and agents mixed with it are not readily absorbed, consequently it is good as a protective agent and for the application of antiseptics, but not good for systemic remedies. It does not become rancid or change quickly. It can be made to take up about 5 per cent of water, but the addition of 5 per cent of beeswax enables considerably more water to be taken up. When a watery or alcoholic preparation is to be mixed with petrolatum, the liquid can first be mixed with wool fat and then with petrolatum. It melts between 38° and 54° C., and should be free from acids or chemicals used in purifying it. In warm weather it may be stiffened by adding some paraffin.

Wool fat is a complex mixture of which cholesterin is an