Qualities. Form, dense striated concavo-convex cakes which are persistent in the air, or crystallized conical masses; in this latter form it generally contains other salts, especially muriate of lime, which render it deliquescent. Taste, bitter, acrid, and cool. Chemical Composition. In consequence of the present unsettled opinions respecting the nature of muriatic acid and ammonia, and the changes which they undergo by combination with each other, the composition of this salt is involved in some obscurity. According to Dr. Thomson, it consists of equal volumes of muriatic acid gas and ammoniacal gas, although he has subsequently observed that from the peculiar properties of the substance, it may be a compound of Chlorine and Ammonium (the hypothetical base of ammonia.) Unlike all the other ammoniacal salts, it does not undergo decomposition by heat. Solubility, f℥j of water at 66° dissolves about two drachms and a half; at 212° it dissolves its own weight; it is also soluble in 4½ parts of alcohol; its solution in water is accompanied by considerable reduction of temperature. Incompatible Substances. The sulphuric and nitric acids unite with the ammonia, and disengage the muriatic acid, whilst ammonia is disengaged by the action of potass and its carbonate, carbonate of soda, lime, magnesia, &c. which combine with its muriatic acid; with oxy-muriate of mercury it combines and increases its solubility, see Hydrarg: Oxy-murias. When united with acetate of lead, it decomposes it, and a muriate of lead is precipitated. It is obvious also that nitrate of silver, and all the metallic salts whose bases form insoluble compounds with muriatic acid, are incompatible with it. Uses. Rarely employed as an internal remedy, externally it is employed in lotions, either for the cold produced during its solution, in which case it should be applied as soon as the salt is dissolved, or for the stimulus of the salt, on which principle it acts as a powerful discutient in indolent tumours (Form. 146.) It is also an ingredient in a very useful plaster, in which it undergoes chemical decomposition; this plaster consists of Soap ℥j, lead plaster, ʒij, liquified together, to which, when nearly cold, are added of muriate of ammonia finely powdered ʒss. The alkali of the soap enters into combination with the muriatic acid of the muriate of ammonia, and forms thereby muriate of potass, or soda, and ammoniacal gas (on which the virtue of the plaster depends) is slowly but abundantly liberated, acting as a powerful stimulant and rubefacient: it should be applied immediately after it is formed, and be renewed every twenty-four hours, otherwise the intention is lost; (Pharmacopœia Chirurgica.) I have often applied this plaster with evident advantage to the chest in pulmonary affections, and I wish to recommend it to the attention of practitioners. It is very useful also in that rheumatic affection of the muscles of the chest, which is so frequently met with in persons in advanced life; during the last winter I was consulted in two cases where the distress after exercise was so considerable as to resemble angina pectoris. Officinal Preparations. Ammoniæ Sub-carbonas (I). L.E.D. Liquor: Ammoniæ (K). L. Aqua Ammoniæ. E.D. Hydrarg: præcip: alb: (I). L. Alcohol Ammoniatum, (I). E.D. Ferrum Ammoniat: (G). L.E.D. Adulterations. This salt, if pure, may be entirely volatilized by a low heat; the sulphate of ammonia however, as it is also volatile, cannot be discovered except by the muriate of baryta, which will indicate its presence by a copious precipitate.

Qualities. The sweet almond is inodorous, and has a sweet, bland taste; the bitter almond,^[368] when triturated with water, has the odour of the peach, and a pleasant bitter flavour. Chemical Composition. Boullay has lately confirmed the analogy which Proust had stated to exist between the emulsion of sweet almonds and human milk, viz. the former consists of sweet oil 54, albumen 24, sugar 6, gum 3, with traces of acetic acid; the indigestible property of the almond depends upon its albuminous matter. The bitter almond, in addition to those constituents, contains hydro-cyanic acid, (Prussic acid,) in union with a peculiar volatile oil, upon which its narcotic properties depend; but this deleterious element is so modified by the natural state of combination in which it exists with sweet oil and albumen, that they may be eaten without inconvenience. The bitter almond has long been regarded as an antidote to drunkenness; Plutarch states it as a fact on the authority of his physician Claudius. Other bitters were however supposed to possess similar powers in this respect, hence the Poculum Absinthiatum to which we have before alluded. See page 79. Both sorts of almonds yield by expression a large quantity of fixed oil, which is perfectly mild. See Oleum Amygdal. The water distilled from the bitter almond, when strongly impregnated, has been found to exert a deleterious action on the human body, and to prove fatal to many animals. Solubility. By trituration with water a milky mixture is produced, (an emulsion), for which purpose the sweet almonds should be previously freed from their cuticle, (blanched), and this ought to be performed by infusing them in tepid water; for when hot it separates a portion of their oil, as is evident from their being thus rendered yellow, and the emulsion is therefore more liable to ferment, and be decomposed. ℥ij of almonds saturate about f℥vj of water; since however this extemporaneous preparation is tedious and inconvenient, the London Pharmacopœia very judiciously directs a confection to be ready prepared, ʒj of which, when triturated with f℥j of water, immediately forms an elegant emulsion. See Mistura Amygdal. Almonds form a useful intermedium for suspending in water many substances which are of themselves not miscible with it, as camphor, and several of the gum-resins; they also assist in the pulverization of refractory substances, as Ipecacuan, &c. Officinal Preparations. Confectio Amygdalarum. L. Emulsio Camphoræ (M.) E. Emulsio Acaciæ Arab: E. D.

Amygdalæ Placenta. Almond Cake is the substance left after the expression of the oil, which when ground forms Almond Powder, so generally used for washing the hands.^[369]

Oil of Bitter Almonds. For obtaining this oil, the expressed cake is submitted to distillation, when a highly volatile, pungent, oil passes over. See Oleum Amygdalæ Amaræ.

Qualities. Form, white columnar masses; Odour and Taste, none. Chemical Composition. Fecula is one of the proximate principles of vegetable matter, and Starch is the fecula of wheat.^[371] Solubility. It is soluble in boiling water, forming with it a semi-transparent, insipid, inodorous, and gelatinous paste, very susceptible of mouldiness, but which is retarded by the addition of alum; it is insoluble, but falls to powder in cold water; nor is it dissolved by alcohol or ether; although potass dissolves starch, yet the solution of it is not disturbed by potass, carbonate of potass, nor ammonia, but an alcoholic solution of potass produces a precipitate; acetate of lead, and infusion of galls occasion also precipitates. Starch is susceptible of several interesting and important changes; thus, if it be exposed to heat until its colour becomes yellow, its properties are so far altered that it is no longer insoluble in cold water; and according to the experiments of Saussure, if it be mixed with water, a spontaneous decomposition takes place, and a quantity of sugar is formed, amounting in weight to one half of the starch employed, in addition to which a peculiar gummy matter results, and a substance intermediate between gum and starch, to which the name of Amidine has been given. Starch moreover is convertible into saccharine matter by the agency of sulphuric acid. Uses. Being demulcent it is generally employed as a vehicle for the exhibition of opium in the form of enema. The ordinary blue starch is coloured by a solution of smalt and alum, and is unfit for medicinal use; formerly it was tinged yellow with saffron or turmeric, but this went out of fashion on the execution of the famous midwife Mrs. Collier, who was hanged in a ruff starched with that colour. Officinal Preparations. Mucilago Amyli. L.E.D. Pulvis Tragacanth: comp: (B) L. Pil: Hydrargyri (M) E. Troschisi Gummos: E.

It has been lately observed that Iodine is a delicate test of the presence of starch; if a drop or two of a solution of this substance in alcohol be added to an aqueous solution of starch, a blue compound is formed which eventually precipitates. Iodine may therefore be employed for ascertaining the goodness of starch, a test which is very important, for much of what is sold under the name of starch, does not possess its peculiar characters; it ought however to be stated, that the blue indication is prevented from taking place by a variety of different bodies, as Arsenious acid, corrosive sublimate of mercury, &c. &c.

These seeds when dry have an aromatic sweetish odour, and a warm pungent taste, qualities residing in an essential oil, which is extracted by distillation with water and by digestion with alcohol; the bruised seeds yield their flavour to boiling water by simple infusion. The seeds are but rarely used. The distilled water is a valuable carminative for children.

Like the dill seeds, warm and carminative; water extracts very little of their flavour; rectified spirit the whole. It may be remarked in this place that the value of aniseed, as well as all those seeds which yield essential oil by distillation, may be estimated by their specific gravity, the heaviest yielding the largest proportion of oil; a chrondrometer employed by corn-chandlers might be very conveniently applied to such a purpose.^[372] The seeds imported from Spain, which are smaller than the others, contain most oil, and are to be preferred.

Qualities. The Odour of the flowers is strong and fragrant; Taste, bitter and aromatic, with a slight degree of warmth. Chemical Composition. The active principles are essential oil, resin, and bitter extractive. Solubility. Both water and alcohol take up the active parts of the flowers; hot water, by infusion, dissolves nearly one-fourth of their weight, but boiling dissipates the essential oil, on which account they should never form an ingredient in a decoction. Uses. The flowers given in substance are said to have cured intermittents; they are however but rarely used; externally they are applied in fomentations. See Infusum Anthemidis. Officinal Preparations. Decoctum Anthemidis nobilis. E.D. Infusum Anthemidis. L.^[373] There is a great variety in the quality and price of chamomile flowers; those which are large and whitish are to be preferred as the freshest; by keeping they become invalid, and are deprived of their aromatic principle and essential oil. They are always inferior in wet seasons. The double flowered varieties are also less powerful than the single kind, since the qualities reside in the disc florets.

Qualities. This article appears in the market in conical loaves, which are dark grey externally, but internally possess a bladed structure and considerable brilliancy; the Edinburgh and Dublin colleges direct this substance to be levigated with water, and kept in the state of powder; it should however never be purchased in that form, as it is not unfrequently adulterated with sulphuret of lead, whereas it cannot contain such admixture when its form is characteristically crystalline and bladed. Chemical Composition. Antimony 100, Sulphur 35·572. From the time of Basil Valentine to the present, this preparation has been known in the market by the name of Antimony, a name which it is evident can only with propriety be applied to the pure metal. Solubility. It is insoluble in water and alcohol; since however it is slightly acted upon by vegetable acids, cups were formerly made of it, which imparted to wine that stood in them for some time, an emetic quality.^[374] Uses. It is principally employed for the preparation of the other antimonial combinations, for which purpose it is more eligible than the metal itself, as being less contaminated with metallic impurities. Its medicinal energies depend altogether upon the state of the stomach, and must therefore be extremely uncertain; when it meets with any acid in the stomach, it acts with extreme violence, a circumstance which requires precaution. It was formerly much more employed as an Alterative than at present. Stoll recommends its use in chronic rheumatism, and advises its union with Myrrh. In the treatment of affections of the skin it has been long used, both singly, and in union with other substances, such as Conium, Dulcamara, Guaiacum, &c. In Scrophulous diseases, connected with cutaneous eruptions, or ulcerations, it has been a favourite remedy with many practitioners, and it forms the basis of several foreign Nostrums. In times of remote antiquity it was used by females as a black pigment for staining the eye-lashes, a custom which continues to this day in the east.^[375] It is at present given to horses mixed with their food, to make their coats smooth, and very large doses may be given to these animals without producing any deleterious effects. Officinal Preparations. Dr. Black constructed a table representing a view of all the preparations whose basis was antimony; many of these however have fallen into disuse, and the nomenclature of all is changed. The following arrangement of the medicines prepared from the sulphuret of antimony,^[376] is presented to us by Mr. Thomson, in his London Dispensatory. 1. By trituration, Sulphuretum Antimonii Præparatum. E.D. 2. By the Action of Heat with Phosphate of Lime, (oxidized) Pulvis Antimonialis, L.D. Oxidum Antimonii cum Phosphate Calcis. E. 3. By the Action of Alkalies, (oxidized), Antimonii Sulphuretum Præcipitatum. L.E. Sulphur Antimoniatum Fuscum. D. 4. By the Action of Acids, (oxidized,) Antimonii Oxydum. L. Oxydum Antimonii Nitromuriaticum. D. Antimonium Tartarizatum. L. Tartris Antimonii, olim Tartarus Emeticus. E. Tartarum Antimoniatum, sive Emeticum, D. Vinum Antimonii Tartarizati. L. Vinum Tartaritis Antimonii. E.

Adulterations. The importance of employing this article in a state of great purity, for the preparation of so many active and valuable medicines, is obvious. It ought to be entirely volatilized by a read heat; Lead is discovered by its imparting to the antimony a foliated instead of a bladed texture, and from not being vaporizable; Arsenic, by the garlic odour emitted when thrown upon live coals; or by the numerous tests mentioned under the history of that article; Manganese and Iron, from not being vaporizable, and from other tests: the most usual adulteration is black oxide of iron, or the scoriæ of that metal, “Smithy dust.”

Qualities. Form, a brilliant orange coloured powder; Taste, slightly styptic, but inodorous. Chemical Composition. Very complicated attractions are exerted during the preparation of this substance; the result of which is an hydro-sulphuret of Oxide of Antimony, with excess of sulphur. Solubility. It is quite insoluble in water. Uses. According to the dose, it is diaphoretic, cathartic, or emetic; it is, however, less certain than many other preparations, and, unless in combination with mercury, for cutaneous affections, is not very often employed. Incompatible Substances. All acids and acidulous salts increase its emetic properties; when therefore acid is suspected to prevail in the primæ viæ, it should be combined with soap, magnesia, (Form: 128,) or aromatic confection; on the contrary, the confection of roses, and vehicles containing acids, should be carefully avoided. Form of Exhibition. Pills. Dose, grs. 1 to v. Officinal Preparations. Pilulæ Hydrargyri Sub-Muriatis (H) L. Adulterations. It is often sophisticated with chalk and other extraneous matter; it ought not to effervesce with acids; it should be entirely vaporizable by heat, and its colour should be that of bright orange. A spurious article is vended, which consists of sulphur and sulphuret of antimony coloured with Venetian red.

Qualities. Form, crystals whose primitive form is the regular tetrahedron, although it assumes a variety of secondary forms. Colour, white. Odour, none. Taste, slightly styptic and metallic; on exposure to the air, the crystals slightly effloresce and become opaque; thrown upon burning coals, they become black and afford metallic antimony. Chemical Composition. This is involved in much doubt and obscurity; it is stated in the various dispensatories to be a triple salt, consisting of tartaric acid, oxide of antimony,^[378] and potass, and which therefore, says Mr. Thomson, on the principles of the reformed nomenclature, ought to be termed a tartrate of antimony and potass. The truth of these views, however, is extremely questionable. I am inclined to believe with Gay Lussac, that in the various metalline compounds, of which super-tartrate of potass is an ingredient, this latter substance acts the part of a simple acid; an opinion which receives much support from the great solvent property of cream of tartar, and from the striking fact that it is even capable of dissolving various oxides which are insoluble in tartaric acid, of which the protoxide of antimony is an example. According then to this view, tartar emetic is a salt composed of bi-tartrate (super-tartrate) of potass, which acts the part of an acid, and protoxide of antimony: from the experiments of Mr. Phillips, it would appear that 100 parts of the bi-tartrate will dissolve 70 of the protoxide. In this state of doubt it must be admitted that no name can be more appropriate than Antimonium Tartarizatum, and the London College have therefore properly disregarded the suggestions which have been offered for changing its name. Solubility. Much discrepancy of opinion exists upon this subject, owing probably to the variations and incidental impurities to which the salt is liable. Dr. Duncan, who selected very pure specimens for examination, states that it is soluble in three times its weight of water at 212°, and in fifteen at 60°. This solution, when the salt is pure, is perfectly clear and transparent, but if long kept, unless a portion of spirit be added, it undergoes decomposition; a precipitate indeed sometimes takes place very rapidly, but this is generally tartrate of lime, an incidental impurity, derived from the super-tartrate of potass. Incompatible Substances. Mineral Acids, Alkalies, and their Carbonates, most of the Metals, Soaps, Hydro-Sulphurets, and many infusions and decoctions of bitter and astringent Vegetables, e. g. f℥j. of the decoction of yellow bark is capable of completely decomposing ℈j of this salt, and of rendering it inert.^[379] Berthollet has accordingly recommended the immediate exhibition of this decoction when an overdose of the salt has been taken; and Orfila has given a very satisfactory case in which this antidote succeeded. Infusion and tincture of galls throw down curdled and inert precipitates of a dirty white colour, inclining to yellow. Rhubarb is equally incompatible: the extract of this substance therefore never ought to be employed in forming pills of tartar emetic: but it deserves notice that this salt is not decomposed by the infusions of gentian or wormwood. The Alkaline Sulphates, provided they be perfectly neutral, produce no disturbance in solutions of tartar emetic, and therefore cannot be considered incompatible with them; if there be any excess of acid, as in alum, bi-sulphate of potass, &c. then its decomposition is effected, and a white insoluble sulphate of antimony is precipitated. It appears therefore that the famous “Emeto-purgative” of the French school, consisting of sulphate of soda, and tartarized antimony in solution, is by no means the unchemical mixture which some have considered it to be, and that it really produces its effects from the operation of its original ingredients, and not from that of the compounds (Sulphate of Antimony, Tartrate of Soda, and Sulphate of Potass) which have been erroneously supposed to result. Forms of Exhibition. Solution is its best form, see Liquor Antimonii Tartarizati. Dose. It either vomits, purges, or sweats, according to the quantity exhibited; thus gr. 1/4 will, if the skin be kept warm, promote a diaphoresis; gr. ½ will procure some stools first, and sweating afterwards; and gr. j will generally vomit and then purge, and lastly sweat the patient; in very minute doses, as gr. 1/10 or 1/12 combined with squill and ammoniacum, it acts as an expectorant, see Formulæ 1, 2, 3, 8, 60. It is decidedly the most manageable, and the least uncertain of all the antimonial preparations, and the practitioner would probably have but little to regret, were all the other combinations of this metal discarded from our pharmacopœias. Some authors have considered this substance as possessing sedative powers, independent of its nauseating and diaphoretic effects. It undoubtedly acts upon the heart, and controls the force of the circulation in fevers, without occasioning any other sensible effect. Mr. Brodie, after having given large doses of this salt to animals, found that the heart beat very feebly, and although artificial respiration was kept up, it soon ceased to act altogether. Lenthois of Montpellier advises small doses of it in incipient phthisis, and it would on some occasions appear to diminish the febrile excitement. The following is the form in which Dr. Lenthois recommends it to be exhibited upon such occasions. He directs a grain of Tartarized Antimony to be dissolved in eight table spoonsful of distilled water, which are to be added to six or eight pints of water, and to be taken as common drink. Tartar emetic, when triturated with lard, in the proportion of ʒiss or ʒij to ℥j of the latter, forms a very powerful rubefacient, occasioning a pustular eruption on the skin, and proving very serviceable in deep-seated inflammation; or the application may be made by dusting a piece of adhesive plaster with tartarized antimony, taking care to leave a margin untouched that it may more firmly adhere. Dr. Jenner, in a late Essay on the influence of artificial eruptions on certain diseases, recommends the following formula for such a purpose.—℞. Antimonii Tartarizati (in pulverem subtilem trit.) ʒij—Unguenti Cetacei ʒix;—Sacchari albi^[380] ʒj;—Hydrargyri Sulphureti Rubri gr. v. M. ut fiat Unguentum. The Pustules which are produced by the inunction have been generally compared to variolous pustules, they are, however, in general much smaller, not so red at the base, nor so tense and white when fully suppurated. They are very painful. In Hooping cough, frictions with this ointment upon the region of the stomach have been greatly extolled. By this application, says Dr. Jenner, we can not only create vesicles, but we can do more,—we have at our command an application which will at the same time both vesicate and produce diseased action on the skin itself, by deeply deranging its structure beneath the surface. This is probably one cause why the sympathetic affection excited by the use of Cantharides, and those changes produced by Tartar Emetic are very different. The eruption should be kept up for some time, either by the re-application of small portions of the diluted tartaremetic ointment, to the affected part, or by other gently stimulating ointments. Should they become much irritated and very painful, a soft bread and milk poultice will in general afford relief, without interfering with the progress of the eruption. Officinal Preparations. gr. j. is contained in f℥ss of Liquor Antimonii Tart: L. and Vinum Tartratis Antimonii. E.^[381] Adulterations. It should be always purchased in its crystalline form; and a solution of it in distilled water ought to furnish a copious gold coloured precipitate with sulphuret of ammonia; a precipitate soluble in nitric acid, with acetate of lead; and a white and extremely thick precipitate, dissolving with facility in pure nitric acid, with lime water. If the crystals deliquesce, the presence of other salts may be inferred. M. Sexullas, in a memoir of which there is a copious extract in the Journal de Pharmacie for 1821, has shewn that all the antimonial preparations used in medicine, except carefully crystallized Tartar Emetic, contain more or less arsenic, which metal was originally combined with the antimony in the ore, and has continued pertinaciously associated with it through all its modifications.

Water, from its extensive powers as a solvent, never occurs in a state of absolute purity, although the nature and degree of its contamination must necessarily vary according to circumstances and situation. It is generally found holding earthy matter in a state of mechanical suspension, or saline and other bodies in chemical solution. The usual varieties of common water are classed and defined by Celsus; and modern chemists have not found any reason to reject the arrangement. “Aqua levissima pluvialis est; deinde fontana, tum ex flumine, tum ex puteo; posthæc ex nive, aut glacie; gravior his ex lacu; gravissima ex palude.”

1. Rain Water. Aqua Pluvialis, when collected in the open fields, is certainly the purest natural water, and consequently of the least specific gravity; the bodies which it holds in solution are, carbonic acid, a minute portion of carbonate of lime, with traces of muriate of lime. Dew is said to be water saturated with air. Rain water ought, however, to be boiled and strained whenever it is collected near large towns; Hippocrates gives this advice, and M. Margraaf of Berlin has shewn the wisdom of the precaution by a satisfactory series of experiments.

2. Spring Water. Aqua Fontana, in addition to the substances detected in rain water, generally contains a small portion of muriate of soda, and frequently other salts; but the larger springs are purer than smaller ones, and those which occur in primitive countries, and in siliceous rocks, or beds of gravel, necessarily contain the least impregnation. An important practical distinction has been founded upon the fact, that the water of some springs dissolves soap, whilst that of others decomposes, and curdles it; the former has been termed soft, the latter hard water; soft water is a more powerful solvent of all vegetable matters, and is consequently to be preferred for domestic as well as medicinal purposes; the brewer knows well from experience how much more readily and copiously soft water will dissolve the extractive matter of his malt. Horses by an instinctive sagacity always prefer soft water, and when by necessity or inattention they are confined to that which is hard, their coats become rough and ill-conditioned, and they are frequently attacked with the gripes. Pigeons also refuse hard water when they have been accustomed to that which is soft.^[382]

3. River Water. Aqua ex Flumine, being derived from the conflux of numerous springs and rain water, generally possesses considerable purity; that the proportion of its saline ingredients should be small, is easily explained by the precipitation which must necessarily take place from the union of different solutions; it is, however, liable to hold in suspension particles of earthy matter, which impair its transparency, and sometimes its salubrity; this is particularly observed of the Seine, the Ganges, and the Nile.^[383]

4. Well Water. Aqua ex Puteo, is essentially the same as spring water, being derived from the same source; it is, however, more liable to impurity from its stagnation, or slow infiltration;^[384] hence our old wells furnish much purer water than those which are more recent, as the soluble particles are gradually washed away. Mr. Dalton observes that the more any spring is drawn from, the softer the water becomes.

5. Snow Water. Aqua ex Nive, has been supposed^[385] to be unwholesome, and in particular to produce bronchocele, from the prevalence of that disease in the Alps, but it does not appear upon what principle its insalubrity can depend; the prejudice however is a very ancient one, for Hippocrates observes that snow or ice water is unwholesome, in consequence of its finer particles being evaporated and lost during its solution: it appears to differ only from rain water in being destitute of air, to which water is certainly indebted for its briskness, and perhaps for many of its good effects upon animals and vegetables. The same observations apply to Ice Water.

6. Lake Water. Aqua ex Lacu, is a collection of rain, spring, and river waters, contaminated with various animal and vegetable bodies, which from its stagnant nature have undergone putrefaction in it.

7. Marsh Water. Aqua ex Palude being the most stagnant is the most impure of all water, and is generally loaded with decomposing vegetable matter.

To what extent the impurities of water are capable of influencing its salubrity, has been a subject of interesting inquiry from the age of Hippocrates to the present day. To many of these natural contaminations, too much importance has been certainly attached; it is an affected refinement to suppose that the presence of minute portions of such earthy and calcareous salts, as generally occur in solution, can impart any noxious quality to water;^[386] whilst on the contrary, animal and vegetable impurities, or earthy bodies in a state of mechanical suspension, cannot fail to prove injurious, and must be regarded as the true “SCELERA AQUARUM.” Guided by false analogies many have supposed that they recognised the origin of all calcareous diseases in the earthy impurities of water; the researches however of chemistry have removed this delusion, by demonstrating that the substances found in water never enter into the composition of urinary calculi.^[387] Metallic and other accidental contaminations are necessarily highly injurious, and the water in which their presence is suspected, should be submitted to the most careful examination.

For the purification and preservation of water numerous methods have been adopted; the mechanical impurities may be removed by filtration, which is performed through porous stones, or alternate layers of sand or charcoal; muddy water may be also cleared by adding a few grains of alum to each pint,^[388] and in that proportion, the water is not rendered in the least disagreeable: when water has contracted a putrid smell, it may be rendered sweet by agitating it with a small portion of magnesia, or with black oxide of manganese, in the proportion of 1½ parts to 250 parts of water. Dr. Black observes that nitrate of silver, which is one of the most antiseptic substances known, will preserve water from putrefaction for ever, and that it may at any time be separated therefrom in a few minutes by adding a small lump of common salt; this fact in itself is curious, but the experiment is too hazardous to be recommended. Dr. Alston prefers lime, as a preservative of the water, and proposes to remove it by the addition of a carbonate of magnesia; Dr. Henry has however found that it is more economically precipitated by the introduction of a current of carbonic acid into the cask. As that peculiar property of water which is termed hardness, generally depends upon the presence of sulphate of lime, the addition of an alkaline carbonate twenty-four hours previous to its being used, will be found to restore it, or if it should depend upon supercarbonate of lime, long ebullition without any addition will be found sufficient for its cure.

Water when kept for a long time in casks, especially on long voyages, is partially decomposed, and a volume of carburetted hydrogen is evolved,^[389] imparting to such water the peculiar smell and taste which characterise it; this decomposition may in a great degree be obviated by charring the interior of the water casks; it is, however, prevented in the Navy by substituting iron tanks for wooden vessels. In Pharmacy it ought to be remembered that whenever common water is employed it should not be hard; filtered rainwater maybe recommended as the most eligible on such occasions.

Qualities. Taste, vapid from the absence of air, and slightly empyreumatic in consequence probably of the presence of a small quantity of extractive matter which has undergone partial decomposition; a fluid-ounce weighs 454½ grains. Medicinal Use. In extemporaneous prescriptions, distilled water should be always ordered whenever the formula contains any of the following substances:—Acidum Sulphuricum; Acidum Citricum; Antimonium Tartarizatum; Argenti Nitras; Cuprum Ammoniatum; Ferrum Tartarizatum; Hydrargyri Oxy-murias; Liquor Ammoniæ; Liquor Plumbi Sub-Acetatis; Liquor Potassæ; Plumbi Acetas; Solutio Muriatis Barytæ; Vinum Ferri; Zinci Sulphas; Ferri Sulphas. Distilled water ought also to be employed in preparations where much water is evaporated, as in the formation of extracts, since the residual matter of common water will remain mixed with the product of the process, and uselessly add to its bulk, or even in some cases produce in it chemical changes; unless however under such circumstances, common water purified by filtration should be ordered, as the air which it contains imparts to it a pleasant and sprightly flavour. In making infusions or decoctions, it is very important that the water should be free from those impurities which impart to it hardness, and which render it a far less powerful solvent of vegetable matter, nor indeed can resinous substances be mixed with such water, even when assisted by a mucilaginous medium. On which account, in prescribing emulsions, it may perhaps be prudent to direct the employment of distilled water. Tests of its Purity. Its transparency ought not to be disturbed by the addition of nitrate of silver, or muriate of baryta.

Until the late able researches of Dr. Murray, we possessed but an imperfect knowledge of the composition of sea water; it is not therefore surprising that the analysis performed by different chemists should be found to be so materially at variance; the true cause of such discordance is now easily understood, for it appears, that in the examination of a mineral water or any compound saline solution, the substances obtained from it are not necessarily the original ingredients, but frequently the products of new combinations established by the operation of analysis, and that consequently the nature of the result obtained may vary according to the modes in which such analysis has been conducted, or even according to the degree of dilution in which the saline substances exist.^[390] The elements of the salts contained in a pint of sea water are Lime 2·9, Magnesia 14·8, Soda 96·3, Sulphuric Acid 14·4, Muriatic Acid 97·7, total 226·1 grains, and supposing these elements to be combined in the modes which Dr. Murray’s views appear to establish, the saline contents of a pint of sea water may be expressed as follows, Muriate of Soda 159·3, Muriate of Magnesia 35·5, Muriate of Lime 5·7, Sulphate of Soda 25·6 grains, total 226·1 grains; besides such saline contents, it is contaminated with various animal and vegetable bodies, in consequence of which it becomes, when long kept, highly offensive; it ought also to be stated that Dr. Wollaston has discovered the presence of a minute proportion of potass in sea water; and Dr. Marcet has more lately detected ammonia in combination with muriatic acid. Medicinal Use. As a cathartic, a pint is the ordinary quantity, which should be taken in the morning, at two doses, with an interval of half an hour between each; this quantity contains half an ounce of purgative salt, of which about three-fourths are muriate of soda, but it is much more active than a similar portion of any artificial combination. In procuring sea water for medicinal purposes, there is a precaution, the importance of which experience has suggested to me, that it be not hastily drank on the beach, before the particles of sand, with which under such circumstances it is generally mixed, are allowed to subside; from the neglect of this precaution I have witnessed serious consequences. The most important advantages of sea water are derived from its external use as a bath.

These are waters impregnated with the essential oils of vegetables, and are principally designed as grateful vehicles for the exhibition of more active remedies; ample directions for preparing them are given in the several Pharmacopœias, and if they be rectified by redistillation they may be kept for several years; the usual mode of preserving them is by adding spirit, which has also the incidental advantage of preventing them from being frozen during the winter season. Some recommend a film of the essential oil to be diffused over the water’s surface. They may be extemporaneously prepared by adding to water what have been called Essences, which consist of essential oil and alcohol, or by rubbing any essential oil with ten times its weight of sugar, or, what answers still better, of magnesia: when however they are so prepared they never retain their transparency. The college, in the present Pharmacopœia, have directed the distillation off the essential oil, as well as off the recent herb; this alteration is one of practical convenience. The properties of each water may be learnt by referring to the vegetable from which it is distilled.

Although all waters that flow from the earth, are, as they contain mineral bodies in solution, strictly speaking, mineral waters, yet this term is conventionally applied to such only as are distinguished from spring, lake, river, or other water, by a peculiarity in colour, taste, smell, or any obvious properties, or by the medicinal effects which they produce, or are known to be capable of producing.

To the medical practitioner the history of these waters is most interesting and instructive, involving highly important subjects of chemical and physiological inquiry. These waters are without doubt indebted for their medicinal virtues to the operation of the substances which they hold dissolved, but this is so materially aided by the peculiar state of dilution in which they exist, as well as by the mere bulk and temperature of the water itself, as to render extremely doubtful the success of every attempt to concentrate their powers by evaporation. To what extent dilution may modify the chemical condition of saline solutions has been satisfactorily demonstrated by the researches of Dr. Murray (see Aqua Marina), and to what degree an increase in the solubility of any remedy may influence its medicinal properties has been considered at some length in the first part of this work, (page 172.) It is certain that, in general, soluble salts are capable of exerting a much more powerful effect upon the animal economy, than those which are insoluble; on which account, the earthy muriates, especially that of lime, are amongst the most active ingredients of mineral waters. Although chemical analysis has frequently from its own imperfection failed in ascertaining their presence, it seems probable that muriate of lime and sulphate of soda exist in all those springs that furnish, by the usual methods of examination, sulphate of lime and muriate of soda; for the same reasons it is equally probable that iron, which in certain waters has been supposed from the analysis to exist as a carbonate, is in its native solution a true muriate; this is undoubtedly the fact with respect to the Bath waters. Is it then surprising, that medical practitioners should hitherto have failed in their attempts to emulate, by artificial arrangements, the medical efficacy of active and mineral springs? For the investigation of the true composition of mineral waters the researches of Dr. Murray furnish a simple and elegant formula. Determine by precipitants the weight of the acids and bases, suppose them united in such a manner that they shall form the most soluble salts, and these salts will constitute the true saline constituents of the water under examination.

Mineral Waters admit of being divided into four classes, viz.

1. Acidulous; owing their properties chiefly to carbonic acid; they are tonic and diuretic, and in large doses produce a transient exhilaration; the most celebrated are Pyrmont, Seltzer, Spa, Carlsbad, and Scarborough.

2. Chalybeate; containing iron in the form of sulphate, carbonate, or muriate;^[391] they have a styptic, inky taste: Hartfell near Moffat, Peterhead, Tunbridge, Brighton, Cheltenham, Bath, Lemington Priors, Castle Horneck, near Penzance, &c.

3. Sulphureous Waters derive their character from sulphuretted hydrogen, either uncombined, or united with lime, or an alkali: Engien, Aix la Chapelle, Harrowgate, Moffat.

4. Saline; mostly purgative, and are advantageously employed in those hypochondriacal and visceral diseases that require continued, and moderate relaxation of the bowels; Cheltenham, Leamington, Seidlitz, and all brackish waters.

Some springs, as those of Bath, Matlock, and Buxton, owe their virtues rather to temperature than to any other cause, and others, as Malvern, to the diluent power of the water.

In the Codex Medicamentarius of Paris, formulæ are introduced for the preparation of several of the more distinguished mineral waters, under the head “Aquæ Minerales Arte Factæ.”^[392]