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Incoming links: Fluid drachm
Fluid ounce 2026-10-31
A unit of volume; the Imperial and United States measures differ. An Imperial fluid ounce contains 8 fluid drachms.
The 1864 solid units are the avoirdupois pound, avoirdupois ounce and grain; the liquid units are the Imperial measures. The grain is unchanged, while the old apothecaries' pound and ounce are not the units of the new formulary. [ref]
The Prescriber's Analysis of the British Pharmacopoeia by John Birkbeck Nevins (1864). pp. 16–17, change of weights and unchanged liquid measures
- one grain: , about ;
- one avoirdupois ounce: ;
- one avoirdupois pound: .
- one minim: ;
- one fluid drachm: ;
- one fluid ounce: ;
- one Imperial pint: ;
- one Imperial gallon: .
A millilitre is a cubic centimetre, and a litre is a cubic decimetre. These displayed equivalents are rounded; small differences from a period table's last digits reflect rounding and historical calibration conventions. A fluid ounce is a volume and an avoirdupois ounce is a mass. They cannot be interchanged for an arbitrary liquid without its density. Likewise, a drop is not a defined minim: its volume depends on the liquid and the dropper.
[ref]
NIST Guide to the SI. Appendix B.8, grain, avoirdupois pound and ounce, Imperial gallon and fluid measures; modern rounded metric conversions
The principal period groups were digitalis preparations, squill, broom, juniper oil, buchu, nitrous ether spirit, and several soluble potassium salts. They were grouped by observed promotion of urine flow, rather than by one common mechanism. The following are historical adult quantities per administration, expressed in the contemporary units; they are not present-day prescriptions.
- Digitalis preparations: powdered leaves, ½–2 grains; Infusum Digitalis, 2–4 fluid drachms; Tinctura Digitalis, 5–40 minims; digitalin, 1/40–1/10 grain in the period table. Historical digitalin was not simply a modern pure digoxin product.
- Squill: powder, 1–2 grains; Pilula Scillae Composita, 5–10 grains; Tinctura Scillae, 10–20 minims; Syrupus Scillae, ½–1½ fluid drachms.
- Broom: Decoctum Scoparii, 1–3 fluid ounces; Succus Scoparii, 1–4 fluid drachms.
- Buchu: powdered leaves, 20–40 grains; Infusum Bucco, 1–2 fluid ounces; Tinctura Bucco, 1–2 fluid drachms.
- Juniper oil: Spiritus Juniperi, 10–30 minims in the 1864 commentary. This unusually concentrated spirit contains one volume of juniper oil in ten; its dose must not be borrowed from a later, weaker formula.
- Nitrous ether spirit, Spiritus Aetheris Nitrosi: 30 minims to 2 fluid drachms.
- Potassium acetate: 10–20 grains; potassium citrate: 20–60 grains; potassium nitrate: 5–20 grains; potassium tartrate: 10–60 grains; potassium hydrogen tartrate: 20–60 grains.
- Ammonium acetate solution, Liquor Ammoniae Acetatis: 10–40 minims of the concentrated British preparation, diluted for administration.
[ref]
The Essentials of Materia Medica and Therapeutics by Alfred Baring Garrod (1865). Posological table: Digitalis, Infusum Digitalis, Scoparius preparations, Bucco preparations, Spiritus Aetheris Nitrosi, potassium salts and Liquor Ammoniae Acetatis; Liliaceae: squill preparations
[ref]The Prescriber's Analysis of the British Pharmacopoeia by John Birkbeck Nevins (1864). p. 61, Spiritus Juniperi, 1 in 10 and 10–30 minims
Other recognised period agents included dandelion and copaiba. The dandelion decoction was given in quantities of 1–2 fluid ounces, its soft extract in quantities of 10–30 grains, and its preserved juice in quantities of ½–2 fluid drachms. Copaiba was given in quantities of 15–30 minims, and copaiba oil in quantities of 5–20 minims. Their historical inclusion does not establish that they are suitable substitutes for current diuretic therapy. [ref]
The Essentials of Materia Medica and Therapeutics by Alfred Baring Garrod (1865). Posological table, Taraxacum preparations, Copaiba and Copaibae Oleum
The distinction between preparations matters more than a single “dose of the plant”: an infusion, tincture, juice and powder have different concentrations. Likewise, a salt's small historical diuretic dose is not its larger purgative dose. A modern explanation also separates a direct effect on renal tubules from improved cardiac output in appropriate heart failure: digitalis preparations cannot be understood simply as agents that make every kidney excrete more water. Modern digoxin is used for selected cardiac indications, rather than as a general treatment for low urine output. [ref]
Digoxin by MedlinePlus. Why is this medication prescribed?
The seven named mixtures of the 1864 British Pharmacopoeia are Mistura Ammoniaci, Mistura Amygdalae, Mistura Creasoti, Mistura Cretae, Mistura Ferri Composita, Mistura Guaiaci and Mistura Scammonii. Their compositions are as follows; avoirdupois ounces are used for solids and fluid ounces for liquids.
- Mistura Ammoniaci: ammoniacum ¼ avoirdupois ounce, distilled water 8 fluid ounces, rubbed together and strained. Its own gum helps disperse its resin; ammoniacum is not Ammonia. [ref]The Essentials of Materia Medica and Therapeutics by Alfred Baring Garrod (1865). Umbelliferae, part 2, Ammoniacum
- Mistura Amygdalae: compound almond powder 2½ avoirdupois ounces, distilled water 1 Imperial pint. The compound powder is made from sweet almonds 8 parts, sugar 4 parts and gum arabic 1 part by mass. Trituration produces an emulsion. [ref]The Essentials of Materia Medica and Therapeutics by Alfred Baring Garrod (1865). Rosaceae, continued, almond preparations
- Mistura Creasoti: creosote 16 minims, glacial acetic acid 16 minims, Spiritus Juniperi ½ fluid drachm, syrup 1 fluid ounce, distilled water 15 fluid ounces. Here the spirit has the particularly strong 1864 juniper oil content. [ref]The Essentials of Materia Medica and Therapeutics by Alfred Baring Garrod (1865). Hydrocarbons from the destruction of wood by fire, Mistura Creosoti
- Mistura Cretae: prepared chalk and powdered gum arabic, ¼ avoirdupois ounce each; syrup ½ fluid ounce; cinnamon water 7½ fluid ounces. The chalk is suspended, not dissolved. [ref]The Essentials of Materia Medica and Therapeutics by Alfred Baring Garrod (1865). Calcis Carbonas Praecipitata, Creta Praeparata, British mixture
- Mistura Ferri Composita: powdered myrrh 60 grains, potassium carbonate 25 grains, rose water 8 fluid ounces, ferrous sulfate 30 grains, Spiritus Myristicae 1 fluid drachm, sugar 60 grains. Triturate the myrrh with the spirit and potassium carbonate, then add the rose water with sugar, followed by ferrous sulfate; keep the resulting preparation stoppered. Formation of ferrous carbonate and its subsequent oxidation explain why the order and storage matter. [ref]
- Mistura Guaiaci: powdered guaiacum resin ½ avoirdupois ounce, sugar ½ avoirdupois ounce, powdered gum arabic ¼ avoirdupois ounce, cinnamon water 1 Imperial pint. The gum assists dispersion of the poorly water-soluble resin. [ref]The Essentials of Materia Medica and Therapeutics by Alfred Baring Garrod (1865). Zygophyllaceae, resin preparations
- Mistura Scammonii: scammony resin 4 grains with unskimmed milk 2 fluid ounces, triturated into a uniform dispersion. [ref]The Essentials of Materia Medica and Therapeutics by Alfred Baring Garrod (1865). Convolvulaceae, Scammonium, Mistura Scammonii
The category is an official preparation name, not every possible bedside combination of medicines. Camphor water and acacia mucilage are not additional entries under Mistura: the 1864 names are Aqua Camphorae and Mucilago Acaciae. [ref]
The Prescriber's Analysis of the British Pharmacopoeia by John Birkbeck Nevins (1864). pp. 30 and 52–53, mixture names and alterations
The compositions must be specified ingredient by ingredient; the two alkaloidal solutions contain 4 grains per nominal fluid ounce, but one contains a morphine salt and the other strychnine.
Pulvis Jalapae Compositus contains powdered jalap 5 avoirdupois ounces, potassium hydrogen tartrate 9 avoirdupois ounces, and powdered ginger 1 avoirdupois ounce. Thus the mass proportions are 5:9:1, and jalap supplies one third of the powder's mass. This is a compound purgative, not pure jalap resin. [ref]
The Essentials of Materia Medica and Therapeutics by Alfred Baring Garrod (1865). Convolvulaceae, Jalapa, compound powder
Pilula Scillae Composita contains powdered squill 1¼ avoirdupois ounces, powdered ginger, ammoniacum and hard soap 1 avoirdupois ounce each, with treacle 2 avoirdupois ounces, or sufficient to make a pill mass. Using the specified 2 avoirdupois ounces of treacle, the whole is 6¼ avoirdupois ounces and contains one fifth squill by mass. The allowance of sufficient treacle makes consistency a compounding requirement, not a claim that every moist pill batch has an analytically exact 20% squill content. [ref]
The Essentials of Materia Medica and Therapeutics by Alfred Baring Garrod (1865). Liliaceae, British compound squill pill, distinguished from bracketed American formula
Liquor Morphiae Hydrochloratis contains morphine hydrochloride 4 grains, dilute hydrochloric acid 8 minims, rectified spirit 2 fluid drachms and distilled water 6 fluid drachms. Its conventional strength is ½ grain of morphine hydrochloride per fluid drachm, not ½ grain of free morphine. The small quantity of hydrochloric acid maintains an acid solution. [ref]
Liquor Strychniae contains strychnine 4 grains, dilute hydrochloric acid 6 minims, rectified spirit 2 fluid drachms and distilled water 6 fluid drachms. Dissolve the strychnine in the acid mixed with part of the water, using the prescribed assistance of heat, then add the spirit and remaining water. Its conventional strength is ½ grain of strychnine per fluid drachm. Acid promotes solubility by forming a soluble salt of the alkaloid. [ref]
For the last two solutions, the stated historical strengths use the nominal 8 fluid drachms of spirit and water. The extra few minims of dilute acid must still appear in the actual recipe; treating all ingredient volumes as perfectly additive would not give an exact modern analytical concentration.