NOMENCLATURE OF THE UNITED STATES PHARMACOPOEIA.

3

in expressing symbolic formula-the latter in italics-but the former is to be preferred.

The figures following the symbolic formulæ express the molecular weight (the sum of the weights of the atoms) of the chemical. For example, the molecular weight of Na,SO3 + 7H2O is 252. Na weighs 23; two atoms are employed, which equals 46. S weighs 32. O weighs 16; three atoms are employed, which equals 48. H weighs I; two atoms are employed, which equals 2. O weighs 16, which added to 2 equals 18. HO is taken 7 times; 7 times 18 equals 126. 46 + 32 +48 +126 252, the molecular weight of sulphite of sodium.

This matter of atomic and molecular weights can be made clear to the student by the following illustration: A pays B 100 sovereigns, English money, in sovereigns and half sovereigns, giving him 50 of the former and 100 of the latter; how much will the 100 Sovereigns of gold weigh?

I sovereign weighs 124 grains X 50=

62 66

X 100

=

6200 grains.
6200

66

Weight of 100 sovereigns in gold,

12400 grains.

In the same way the molecular weight of water (H2O) is 18.

H, Hydrogen atom, weighs IX 2 = 2
O, Oxygen atom,

66

16 XI = 16

Official Description.-Immediately following the official definition, there will be noticed in the Pharmacopoeia, in smaller types, what is termed the official description: of what does this description usually consist? (A) In drugs-I, a concise statement of physical characteristics 2, tests of identity; 3, description of adulterants. (B) In chemicals—1, statement of physical characteristics, as in case of drugs; 2, solubilities; 3, tests of identity and purity.

DISPENSATORIES.

;

What is a Dispensatory? A Dispensatory is a Commentary on a Pharmacopoeia.

What do Dispensatories aim to present? The Dispensatories generally aim to present information concerning important non-official drugs and those official in other Pharmacopoeias, as well as those of the U. S. P.

What Dispensatories have we in the U. S.? We have in this country The United States Dispensatory, National Dispensatory, and King's Dispensatory.

PART I.

METROLOGY.

WEIGHT, MEASURE, AND SPECIFIC GRAVITY.

What is weight? Weight is the difference between the attraction of the earth and that of surrounding bodies for bodies on the surface of the earth.

Upon what does the weight of a body depend? Upon its bulk and density. Density is the amount of matter in given bulks of bodies. What is meant by weighing? Balancing a body of known gravitating force with one whose gravity is not known, for the purpose of estimating the gravitating force of the latter, which is called its weight.

What are weights? Bodies of known gravitating force used for weighing.

What name is given to the apparatus used for weighing? Scales and weights.

What standards are used upon which to base the system of weights? The Grain and the Metre.

How was the grain weight derived? By act of Henry III of England, in 1226; "An English silver penny, called the sterling, round and without clipping, shall weigh thirty-two grains of wheat, well dried and gathered out of the middle of the ear.

What is a Metre? One 40 millionth of the circumference of the earth at its poles.

What systems of weights used in Pharmacy are based on the Grain? The Troy or Apothecaries' system and the Avoirdupois system. State the denominations of each. Troy or Apothecaries' Weight: 20 grains I scruple; 3 scruples : I drachm; 8 drachms I ounce ; 12 ounces I pound. Avoirdupois Weight: 4371⁄2 grains 16 ounces 1 pound. State the Symbols of each. Troy grain, or grains, gr.; scruple,; drachm, 3; ounce, 3. Avoirdupois : ounce, oz; pound, ib.

= I ounce ;

How many grains does the ounce of each system contain, respectively, and what is the difference in grains between the Troy and Avoirdupois ounce? Avoirdupois ounce = 4371⁄2 gr.; Troy ounce == 480 gr. Troy ounce 421⁄2 grains greater.

What is the difference in grains between the Avoirdupois and Troy pound? Avoirdupois pound, 7000 gr.; Troy pound, 5760. Avoirdupois pound, 1240 grains greater.

What is Measure? The bulk or extension of bodies.

What Systems of Measure are used in Pharmacy? Apothecaries' or Wine Measure, Imperial or British Measure, and the Metric System. State the denominations of each. Apothecaries' Measure: 60 minims I fluidrachm; 8 fluidrachms I fluidounce; 16 fluidounces = I pint; 8 pints I gallon. Imperial Measure: 60 Imperial minims I Imperial

fluidrachm; 8 Imperial fluidrachms = 1 Imperial fluidounce; 20 Imperial fluid ounces = I Imperial pint; 8 Imperial pints = I Imperial gallon. NOTE. The U. S. Fluidounce is equal to 480 U. S. minims, and to 500 Imperial minims. The Standard Imperial gallon is the volume of 70,000 grains, or IO avoirdupois pounds of pure water at + 62° F., barometer at 30 inches. One Imperial minim of pure water at + 62° F., only weighs

0.911458 grain.

State the Symbols of each. Apothecaries' Measure: Minim, m; fluidrachm, f3; fluidounce, f3; pint, O; gallon, Cong. Imperial Meas ure: Minim, min. ; fluidrachm, fl. dr.; fluidounce, fl. oz.; pint, O; gallon, C.

State the relations of Apothecaries' and Imperial Measures to Troy and Avoirdupois Weights. Apothecaries' Measure: The pint of distilled water at 15.6° C. (60° F.) weighs 7291.2 gr.; the fluidounce, 455.7 gr.; the gallon, 8.3328 pounds avoirdupois. Imperial Measure: pint weighs 8750 gr.; fluidounce, 437.5 (which is the same as the avoirdupois ounce, and 18.2 gr. less than that of the U. S. fluidounce of water at the same temperature); gallon, 10 pounds avoirdupois.

What is a Metre? The unit of length of the Metric, French, or Decimal system, from which all other denominations are derived.

How was it obtained? It was obtained by a measurement of the quadrant of a meridian of the earth, and is about 40000000 of the circumference of the earth at the poles.

What is it practically? Practically, it is the length of certain carefully preserved bars of metal from which copies have been taken.1

What is its equivalent in feet and inches ? It is equal to about 3 ft. 3 in. and 3% in.

What is the unit of surface, and how derived? The unit of surface is the Are, which is the square of ten metres (the square of a dekametre) a square whose side is II yards.

What is the unit of capacity, and how derived? The Litre, which is a cube of a tenth of a metre (the cube of a decimetre) = 2.1134 pints.

What is the unit of weight, and how obtained? The unit of weight is the Gramme, which is the weight of that quantity of distilled water, at its maximum density (4° C.) which fills the cube of the onehundredth part of the metre (cube of a centimetre, or, in other words, cubic centimetre, C.c.) 15.43235 grains, or about 151⁄2 grains.

How are the denominations of the Metric System multiplied and divided? They are multiplied by the Greek words, "Deka," Ten; "Hecto," Hundred; "Kilo," Thousand; and divided by the Latin words, "Deci," one-tenth; "Centi," one-hundredth ; 66 Milli," one

thousandth.

1 Accurate models or prototypes have been made of the principal units of linear measure, measures of capacity, and weights. These actual standards are usually legalized, are carefully preserved in the custody of governments, and serve as originals, of which copies are taken directly or indirectly for actual use.

Describe the use of the Gramme and Cubic Centimetre (fluigramme) as units of weight and measure. In the practical working of a laboratory, the gramme and its divisions are used for weighing, and the cubic centimetre (C. c. or fluigramme) for measuring liquids. A gramme and a cubic centimetre of distilled water are identical, but owing to greater or less density, cubic centimetres of other liquids weigh more or less than a gramme. But if the C.c. is taken as a unit of capacity only, and the gramme as the unit of weight, all difficulty is avoided. For example, dissolve I gramme of sugar in sufficient quantity of water to make 10 C.c. It is evident that each C.c. of this solution contains I decigramme of sugar. By keeping the C. c. intact and varying the strength of the solution, each C.c. can be made to contain any stated amount of sugar from saturation to infinity.

Explain the signification of the Micromillimetre and the Kilo. Micromillimetre (Mkm) is a term used in microscopy, and signifies the one-thousandth part of a millimetre. Kilo is merely an abbreviation of the word kilogramme, and is used for convenience and brevity.

How would you convert metric weights or measures into those in ordinary use? Multiply the metric quantities by the corresponding equivalent. Ex. To convert

How would you convert the weights and measures in ordinary use into metric weights and measures? Multiply the quantities by the corresponding metric equivalent.

Ex.

To convert

What is a Balance? An instrument for determining the relative weight of substances.

How many kinds of Balances are there? Five: 1. Single beam, equal arm. 2. Single beam, unequal arm. 3. Double beam, unequal arm. 4. Compound lever balances. 5. Torsion balances.

I.

Describe the construction, requirements, and tests of each. SINGLE BEAM, Equal Arm.-Construction.—A beam is suspended on a knife-edge, which divides it into equal arms; end knife edges are placed at each end of the beam, on the same plane and at equal distances from the point of suspension, for supporting the pans which carry the substances to be weighed.

Requirements.—I. "When the beam is in a horizontal position, the centre of gravity should be slightly below the point of suspension, or central knife-edge, and perpendicular to it." 2. "The end knife-edges must be exactly equal distances from the central knife-edge; they must all be in the same plane, and the edges absolutely parallel to each other." 3. "The beam should be inflexible, but as light in weight as possible, and the knife-edges in fine balances should bear upon the agate planes."

Test.-I. Sensibility with unloaded pans: I. Place the balance in position on a perfectly level counter or table; elevate the beam so that it is free to oscillate; when the balance comes to rest, place the smallest weight to which it is sensitive upon the right-hand pan, to which the balance should immediately respond. 2. Sensibility with loaded pans : Place the full weight the balance is designed to carry on the pans, then on one pan place the smallest weight, as before. The balance should respond in a decided manner. 3. Equality of arms: Load the pans to half their capacity, perfecting the equilibrium, if necessary, with a piece of tin-foil. Now reverse the weights, and if the equilibrium is still maintained, the arms of the beam are equal. 4. Parallelism in knife-edges: Moderately load and balance the pans. Now shift one of the larger weights in different positions on the edge of the pan, carefully noting any variation in equilibrium, if such occur. This variation indicates a want of parallelism in the knife-edges.

2. SINGLE BEAM, Unequal Arm.-Construction.—This can be seen by inspecting the well known Fairbanks scales. It depends on the principle in physics, "The power is to the weight or resistance in the inverse ratio of the arms of the lever." The longer arm of the beam is graduated for a movable weight, the use of which dispenses with small weights, which is a decided advantage.

3. DOUBLE BEAM, Unequal Arm.-Construction.-Same as the above,