on counterpoised filters, wash with water, then with alcohol, then with carbon tetrachloride, and again with alcohol. Dry at 110°C. and weigh.

Each Gm. U.S.P. bichloride =0.8568 Gm. HgS. For details see U.S.P., p. 214. Ammoniated Mercury. Accurately weigh about 0.5 Gm. ammoniated mercury and dissolve it in hydrochloric acid and water by aid of gentle heat, then dilute with water and proceed as in the assay of corrosive mercuric chloride.

Each Gm. U.S.P. ammoniated mercury =0.9047 to 0.9279 Gm. HgS. For details see U.S.P., p. 221.

Poison Tablets of Corrosive Mercuric Chloride.-Like that of the salt itself. For minor differences see U.S.P., p. 470.

THE OFFICIAL URANIUM ASSAY

Uranium Nitrate.-Accurately weigh about 0.4 Gm. uranyl nitrate, dissolve it in distilled water, heat to boiling, add ammonia water, collect the precipitate of uranium oxide, wash it with a 1 per cent. solution of ammonium nitrate, ignite at moderate heat and weigh as urano-uranic oxide.

Each Gm. U.S.P. nitrate=0.548 Gm. U3O.. For details see U.S.P., p. 483.

THE OFFICIAL BISMUTH ASSAYS

Bismuth Betanaphthol.-Accurately weigh about 2 Gm. bismuth betanaphthol, incinerate, dissolve the residue in nitric acid, evaporate the solution to dryness, carefully ignite and then weigh the resulting bismuth oxide.

Each Gm. U.S.P. compound =0.730 to 0.780 Gm. Bi2O3. For details see U.S.P.,

p. 79.

The following bismuth compounds are assayed in a similar manner.

The following ignition assay is self explanatory.

Tincture of Iodine (for potassium iodide).—Evaporate 10 mils of the tincture on a water-bath, then volatilize the iodine by gentle heat and weigh the residue. Each 1 mil of tincture =0.045 to 0.055 Gm. K.I. For details see U.S.P., p. 458.

SPECIAL MERCURY ASSAYS

The assays for mercurial ointment and diluted mercuric ointment consist in dissolving out the fat with petroleum benzin and then weighing the residual mercury. (See p. 552.)

Before closing the subject of gravimetric assays attention must be called to the eight assays of this character in which the alkaloids are extracted from salts by the "shaking out" process and then weighed. A typical one is the following:

Iron and Quinine Citrate (assay for quinine).-Accurately weigh about 1 Gm. double citrate, dissolve in 20 mils of water, pour into a separator, add ammonia water and then shake out with three portions of chloroform. Evaporate the chloroformic extracts, redissolve residue in alcohol and then evaporate to dryness and weigh. Each Gm. U.S.P. citrate=0.115 Gm. quinine. For details, see U.S.P., p. 168. The others, which have already been given on previous pages of this book are caffeine citrate (p. 680) effervescent caffeine citrate (p. 680), caffeine

sodio-benozate (p. 679), codeine phosphate (p. 824), quinine and urea-hydrochloride (p. 812), quinine tannate (p. 814) and theobromine sodio-salicylate (p. 680). Lastly the collodion assay for pyroxylin (p. 213) might be considered as a gravimetric process.

VOLATILE AND NON-VOLATILE EXTRACTIVE DETERMINATIONS

In the case of spices, the determination of the volatile and non-volatile extractive matter is of value in deciding quality.

The present pharmacopoeia (Part 2, Tests 12 and 13) has two monographs on the subject which may be summarized as follows:

Determination of Volatile Extracture.-Extract 2 gm. drug with anhydrous ether in a continuous extraction (Soxhlet) apparatus. Dry in a desiccator over sulphuric acid and weigh. This gives the total ether extract. Then heat the residue to constant weight at 110°C. The loss in weight represents the ether-soluble volatile extractive; while the weight after heating at 110°C. is non-volatile ether-soluble extractive. For details see U.S.P., pp. 591 and 592.

The spices for which these tests are produced are as follows:

This form of analysis is performed by liberating certain gases from appropriate substances by chemical action, measuring amount of gas obtained in a nitrometer (Fig. 239) or other measuring tube for gases; from the volume of the gas calculate its weight, and from its weight calculate the amount of chemical from which the gas was liberated. Only two official chemicals are assayed by this process-spirit of nitrous ether and amyl nitrite-and as the principle of assay was explained in the discussion of the preparation first mentioned (p. 596), it is unnecessary at this place to do more than insert a summary of the pharmacopoeial description of the process.

The monograph describes the nitrometer, states how it should be filled with a saturated aqueous solution of sodium chloride, and points out the precautions necessary in running the reagents (potassium iodide and H2SO4, V.S.) as well as the chemical solution that is to be tested.

It emphasizes the necessity of careful observation, not only of the volume of gas evolved, but also of the temperature and of the barometric pressure. It gives tables of correction for temperatures ranging from 15° to 35°C. and for barometric pressure ranging from 540 to 790 mm.; as well as examples of the calculations of such corrections.

It states that 1 liter of NO gas weighs 1.3406 Gm. at 0°C. and 760 mm. and 1.2281 Gm. at 25°C. and 760 mm. It also gives the equivalent factors for amyl nitrite both at 0°C. and at 25°C. For details see U.S.P., p. 600.

Colorimetric Assays.-In those cases where the quantity of substance is too small to determine either gravimetrically or volumetrically recourse is had to the fact that the intensity of a color reaction is proportional to the amount of the chemical present. Thus on p. 449 it was stated that Nessler's reagent was used to estimate minute amounts of ammonia present in water, space prevents extended description of this method of assay and the reader is referred to the articles by the author and his co

workers on the subject. (Proc. Eighth Int. Cong. App. Ch., 26, 1912, 319; Dr. Circ., 57, 1914, 131; Jl. Frank Inst. 180, 1915, 199; Jl. A.Ph.A., 4, 1915, 1294; Jl. Ind. Eng. Ch., 8, 1916, 309).

One such colorimetric test has been introduced with the present pharmacopoeia:

Dried Suprarenals.-Mix 0.01 Gm. dried suprarenals with 0.005 Gm. manganese dioxide and 10 mils of water, shake well, filter and compare the color of the filtrate with the color of mixtures of gold chloride T.S. and cobaltous chloride T.S. The pharmacopoeia gives receipes for the gold-cobalt mixtures corresponding in color to 0.2, 0.4, 0.6 and 0.8 of 1 per cent. of epinephrin and states that the maceration of 0.01 Gm. dried suprarenals in 10 mils of distilled water, as outlined above, should show them to contain from 0.4 to 0.8 per cent. epinephrin. For details see U.S. P., p. 424.

Electrolytic Assays.-On p. 352 it was 'stated that when a current of electricity was passed through a solution of certain metallic salts, dissociation took place and the metallic ions migrate toward the negative pole where they lose their electric charge and deposit as the metal. If the proper conditions of temperature, time, strength of solution and of current are observed the metal deposits quantitatively and from its weight can be deduced the quality of the salt. The present pharmacopoeia permits, as an optional method, the electrolytic assays of mercury and zinc salts. It gives (Part 2, Test 4) a detailed account of the proper manipulation, to which the reader is referred.

Polariscopic Assays.—We have already learned (p. 735) that the purity of many organic substances may be determined by estimation of their optical rotation. To this fact we must now add the statment that the rotation of a solution of an optically active substance-say, sugar or camphor-is directly proportional to the strength of the solution. Thus the polariscope is not only of service in detecting impurities, but it can also be used in assaying the strength of preparations containing optically active chemicals. Two such polariscopic assays are provided in the present pharmacopoeia; one for liniment of camphor; the other for spirit of camphor. The student should refer to these assays as given in the pharmacopoeia and should also read the general explanation of optical activity found on page 602 of that work.

Biological Assays. On page 646 an outline of the principles of biological or physiological assays was given. Here it will be merely mentioned that in the present pharmacopoeia such assays are compulsory as far as cannabis, extract of cannabis, fluidextract of cannabis and tincture of cannabis are concerned; while they are optional in the cases of aconite, extract of aconite, fluidextract of aconite, tincture of aconite, digitalis, fluidextract of digitalis, tincture of digitalis, squill, fluidextract of squill, tincture of squill, strophanthus, tincture of strophanthus and dried suprarenals. Details of manipulation to be followed in each of these assays are given in the pharmacopoeia (page 604).

PART VI

THE DISPENSING OF PRESCRIPTIONS

CHAPTER LVII

THE PRESCRIPTION

HAVING covered the entire field of special pharmaceutic operations and preparations, we can proceed to dispensing pharmacy and to that climax of the pharmaceutic art, the dispensing of prescriptions. Very properly, the prescription is the last topic studied in a course on pharmacy, for the preparation of prescriptions calls into play all the knowledge that belongs to an educated pharmacist. Not only must the prescriptionist know pharmaceutic manipulations and be well acquainted with all pharmaceutic preparations, but he must, moreover, be thoroughly familiar with all possibilities of chemical reaction, with the constituents of crude drugs, and, of course, must be well up on posology-dosage. However, we will leave the important topic of prescription criticism for subsequent pages, and this chapter will be devoted to the generalities of dispensing and to a discussion of the general character of the prescription -its composition, translating, and dispensing.

The prescription is an order written by the physician calling for medicines to be compounded and dispensed by the pharmacist.

Technically, the ideal prescription is supposedly divided into several parts, which can best be explained after presentation of a typical prescription.

Ideal Prescription

August 6, 1916

(Date.)

(Name of Patient.)

FOR MRS. JONES

Taking up the parts of the prescription in regular order, the following information may be of service.

The date of a prescription is rarely written by the physician, but is of value in establishing its identity.

The name of the patient should always be written by the physician, and especially the information as to whether the patient is an infant, child, or adult. If the doctor omits this important datum, the pharmacist should supply it by writing the name and address on the prescription or on the card to which it is attached. There is usually little difficulty in persuading the patient to furnish name and address. To this may be added the emphatic statement that whenever the name does appear, it should be written on the label. Suppose, in handing the medicine to two customers, an exchange is effected, and Mrs. Smith gets the remedy intended for Mrs. Jones. If the label bears the inscription "For Mrs. Jones," that inscription might prove a warning and secure the return of