ACICULA, the small pikes or prickles of the hedge-bog, echinus marinus, &c. ACIDALIA, an epithet given to Venus by Virgil, from ACIDALUS, which see.

ACIDALIUS, Valens, a critic of the sixteenth century, born at Witstock, in Brandenburgh. Having visited several academies in Germany, Italy, &c. he took up his residence at Breslaw, where he became a Roman catholic, and was chosen rector of a school at Niesse. Thuanus says that his sitting up at night, to compose his conjectures on Plautus brought upon him a disemper, which carried him off in three days, on the 25th of May, 1595, being just twenty-eight years of age. He wrote a commentary on Quin

ACID, n. & adj. ACID'ITY, ACID'ULATE, ACES'CENCY, ACES CENT.

tus Curtius; Notes on Tacitus; besides speeches, letters, and poems, which last are inserted in the Delicie of the German poets. A little piece, printed in 1595, under the title of Mulieres non esse Homines, was falsely ascribed to him. Mr. Baillethas given him a place among his Enfans Celebres; and says, that he wrote his comment upon Plautus when he was but seventeen or eighteen years old, and that he composed several Latin poems at the same age.

ACIDALUS, a fountain in Orchomenus, a city of Boeotia, in which the Graces are said to have bathed.

ACIDOTON, in botany, the trivial name of a species of ADELIA.

Acide, Fr. That which cuts or corrodes; having the quality of sourness.

The smoke of sulphur will not black a paper, and is commonly used by women to whiten tiffinies, which it performeth by an acide, vitriolis, and penetrating spirit ascending from it. Brown's Vulgar Errours.. The same persons (perhaps) had enjoyed their

health as well, with a mixture of animal diet, qua

lifed with a sufficient quantity of acescents; as bread, vinegar, and fermented liquors. Arbuthnot on Aliments. In spring-like youth it yields an acid taste; But summer doth, like age, the sourness waste; Then cloth'd with leaves from heat and cold secure, Like virgins, sweet and beauteous when mature.

Denham's Old Age, part iii. ACID, from acesco, to sharpen, a name given to a very extensive and important class of substances, from their prominent quality of sharpness or sourness. Sourness of taste, however, is merely one of the sensible properties of these substances, and they possess some others equally if not more characteristic. Of acids there is a large number and great variety, so that were we to devote the present article to the history of them individually, we should be under the necessity of amplifying it to an extent inconsistent with our plan of arrangement. It is merely then our design in the present instance to treat on the general principle of acidity, referring an account of the particular acids to the article CHEMISTRY, and to the alphabetical order into which they may fall. Thus for acetous or acetic acid, let the reader turn to the word acetous or acetic, and so on through the whole series of adjective designations.

The properties of acids are,

1. Sourness of taste, amounting in some of the species to a corrosive quality.

2. A general, though not invariable power of combining with water in any proportion, with a condensation of volume, and evolution of heat. (For the most part indeed, acids are found in a state of fluidity; but not so without exception, some being met with in a solid form.) 3. They are mostly susceptible of volatilization, or are decomposed by heat.

4. They change the purple or blue colour of vegetables to a bright red.

5. They combine in definite proportions with alkalis, (see alkali) earths, and salts; and by this combination is constituted that important class of bodies called salts.

"This last (says Dr. Ure) may be reckoned their characteristic and indispensable property. The powers of the different acids were originally estimated by their relative causticity and sourforce towards any particular base; and next by the ness; afterwards by the scale of their attractive quantity of the base that they could respectively neutralize. But Berthollet proposed the converse of this last criterion as the measure of their powers, The power by which they can exercise their acidity,' he estimates by the quantity of each of the acids which is required to produce the same effect, viz. to saturate a given quantity of the same alkali.' It is therefore the capacity of saturation of each acid which, in ascertaining its acidity according to him, gives the comparative force of the affinity to which it is owing. Hence he infers, that the affinity of the different acids for an alkaline base, is in the inverse ratio of the producible quantity of each of them, which is necessary to neutralize an equal quantity of the same alkaline base; an acid is therefore, in this view, the more powerful, when an equal weight can saturate a greater quantity of an alkali. Hence, all those substances which can saturate an alkali, and cause their properties to disappear, ought to be classed among the acids; in like manner among the alkalis, should be placed all those which, by their union can saturate acidity, and the capacity of saturation being the measure of this property, it should be employed to form a scale of the comparative power of alkalis as well as that of acids.'

"However plausible," continues Dr. Ure, “à priori, the opinion of this illustrious philosopher may be, that the smaller the quantity of an acid or alkali required to saturate a given quantity of its antagonist principle, the higher should it rank in the scale of power and affinity; it will not however accord with chemical phenomena: 100 parts of nitric acid are saturated by about 36 of magnesia, and 52 of lime."

"Hence by Berthollet's rule, the power of these earths ought to be as the inverse of their 524,

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quantities: viz. and yet the very opposite effect takes place, for lime separates magnesia from nitric acid, and in the present example the difference of effect cannot be imputed to the difference of force with which the substances tend 10 assume the solid state.

"We have, therefore, at present, no single acidifying principle, nor absolute criterion of the scale of powers among the different acids; nor is the want of this of great importance. Experiment furnishes us with the order of decomposition of one acido-alkaline compound, by another acid, whether alone or aided by temperature; and this is all that practical chemistry seems to require.”

The question respecting the principle of acidity will be found to involve a great deal of what is very important in its bearing upon the doctrines of chemistry generally, and it is a question, which perhaps may be regarded as open to still further investigation than that which it has received from the extraordinary ingenuity and industry of modern chemists. A disposition to generalize beyond the warrants of fact, has pervaded the speculations of individuals in reference to the rationale of acidity from very early times. Paracelsus conceived that there was only one acid principle in nature. Becher maintained the same doctrine, and modified it by the supposition, that this acid principle is a compound of earth and water, both of which, were regarded as two distinct elements. Stahl adopted the same theory, and imagined the sulphuric acid to constitute the general principle of acidification-a supposition, which upon the authority of Stahl, was for a long time held in the schools; but was at length openly combated by Bergmann and Scheele. Still, however, the hypothesis of acidity, being the result of some pervading principle, continued to obtain; and Wallirius, Megar, Sage, and others in their turns advanced several speculations on the essential nature and mode of this principle, when at length the French chemists, with Lavoisier at their head, propounded a doctrine entirely new, and of most extensive application: viz, "That acids result from the union of a peculiar combustible base, called the radical, with a common principle, technically called oxygen, or acidifier;" the radical or base giving the specific or peculiar property to the respective substances, and oxygen being the essence of acidity in the whole.

"I have already shewn," says Lavoisier, "that phosphorus is changed by combustion into an extremely light white flaky matter. Its properties are likewise entirely altered by this transformation: from being insoluble in water, it becomes not only soluble, but so greedy of moisture, as to attract the humidity of the air with astonishing rapidity. By this means it is converted into a liquid considerably more dense, and of more specific gravity than water. In the state of phosphorus, before combustion, it had scarcely any sensible taste; by its union with oxygen, it acquires an extremely sharp and

sour taste; in a word, from one of the class of combustible bodies, it is changed into an incombustible substance, and becomes one of those bodies called acids.

"Sulphur also, in burning, absorbs oxygen gas; the resulting acid is considerably heavier than the sulphur burnt; its weight is equal to the sum of the weight of the sulphur which has been burnt, and of the oxygen absorbed; and lastly, this acid is weighty, incombustible, and miscible with water in all proportions."

"The examples, above cited," continues Lavoisier, "may suffice for giving a clear and accurate conception of the manners in which acids are formed. By these it may be clearly seen that oxygen is an element common to them all, and which constitutes or produces their acidity; and that they differ from each other according to the several natures of the oxygenated or acidified substances." Although," he further adds, "we have not been able either to compose or to decompound the acid of sea-salt, we cannot have the smallest doubt that it, like all other acids, is composed by the union of oxygen with an acidifiable base." We have therefore called this unknown substance, the muriatic base, or muriatic radical."

The above communication of Lavoisier was generally received, and accepted as the foundation of a new system of chemical doctrineboth inflammability and acidity were thought to be fully explained by the oxygenous theory; and it was expected that every new development of fact would harmonize with the new theory of causation.

The nomenclature of acids was now altered to suit the new theory; the terminations ous, ic, and the prefix ory being employed to denote the different measures in which the acidifiable base was combined with oxygen.

In the first state, or that in which acid bodies were supposed to exist, with the least possible quantity of oxygen, their names terminated in ous, as sulphurous, nitrous, phosphorous, or acetous.

The second state, or that in which they contained a saturating quantity of oxygen was expressed by the termination ic, as sulphuric, or nitric: and when imagined to contain an excess of oxygen the term ory was prefixed, as oxymuriatic.

But it was soon suggested that Lavoisier in thus conceiving oxygen to be the universal principle of acidity, had run into a hasty generalization which was unwarrantable by nature. "It is carrying the limits of analogy too far (observed Berthollet) to infer that all acidity, even that of the muriatic, fluoric, and boracic acids arises from oxygen, because it gives acidity to a great number of substances. Sulphuretted hydrogen, which really possesses the property of an acid, proves directly that acidity is not in all cases owing to oxygen. There is no better foundation for concluding that hydrogen is the principle of alkalinity, not only in the alkali, properly so called, but also in magnesia, lime, strontian and barytes, because ammonia appears to owe its alkalinity to hydrogen. We must not, therefore, always infer from the acidity of a sub

stance that it contains oxygen, although this may be an inducement to suspect its existence in it." Sir H. Davy, was however, the first to shew in a systematic manner, that the French chemists had been in error when they assumed oxygen to be the absolute essence of acidity; and, he at length propounded those highly interesting principles concerning acidification, which have shaken the Lavoisierian system to its foundation. He demonstrated that oxy-muriatic acid is, as far as our knowledge extends, a simple substance, which may be classed in the same order of natural bodies as oxygen gas, being determined like oxygen, to the positive surface in voltaic combinations; and, like oxygen, combining with inflammable substances, producing light and heat. The combinations of oxymuriatic acid with inflammable bodies were shewn to be analogous to oxides and acids in their properties and powers of combination, but to differ from them in being, for the most part decomposable by water; and finally, that oxymuriatic acid has a stronger attraction for most inflammable bodies than oxygen. His preceding decomposition of the alkalis, (see ALKALI) and the earths, having evinced the absurdity of that nomenclature which gives to the general and essential constituent of acid nature, the term oxygen or acidifier; his new discovery of the simplicity of oxymuriatic acid shewed the theoretical system of chemical language to be equally vicious in another respect. Hence, this philosopher most judiciously discarded the appellation oxymuriatic acid, and introduced in its place the name chlorine, which merely indicates an obvious and permanent character of the substance, its greenish yellow colour. See CHLORINE and CHE

MISTRY.

Succeeding chemists have brought powerful analogies in support of the new theory of Davy, by shewing that hydrogen alone has the power of changing certain undecompounded bases into real acids; and that this is effected without the presence or assistance of oxygen. Dr. Murray has indeed argued with a good deal of ingenuity against the unqualified reception of Davy's principles, and has suggested that acidity may in most, if not in all cases, consist of a species, so to say, of oxy-hydrogenation.

When," says Dr. Murray, "a series of compounds exist, which have certain common characteristic properties, and when these compounds all contain a common element, we conclude with justice, that these properties are derived more peculiarly from the action of this element. On this ground, Lavoisier inferred, by an ample induction, that oxygen is a principle of acidity. Berthollet brought into view the conclusion, that it is not universally so, from the examples of prussic acid and sulphurated hydrogen. In the latter, acidity appeared to be produced by the action of hydrogen. The discovery of Gay Lussac of the compound radical cyanogen, and its conversion into prussic acid by the addition of hydrogen, confirmed this conclusion; and the discovery of the relations of iodine still further established it. And now the system must be still further modified. While each of these conclusions is just, to a certain extent, each of them VOL. I.

requires to be limited in some of the cases to which they are applied; and while acidity is sometimes exclusively connected with oxygen sometimes with hydrogen, the principle must also be admitted, that it is more frequently the result of their combined operations."

"There appears," continues Dr. Murray, even sufficient reason to infer, that from the united action of these elements, a higher degree of acidity is acquired, than from the action of either alone. Sulphur affords a striking example of this. With hydrogen it forms a weak acid: with oxygen it also forms an acid, which though of superior energy, still does not display much power: with hydrogen and oxygen, it seems to receive the acidifying influence of both, and its acidity is proportionably exalted."

These speculative objections of Dr. Murray to the simplicity of chloridic theory, go, it will be seen, partly upon the supposition, that the agency of media is not sufficiently appreciated in that theory; and that the elements, at least of water, are always at work in modifying the combinations of substances upon which the experiments are made. "He thinks it doubtful," says Dr. Ure, "whether nitrogen and oxygen can alone form an insulated acid. Hydrogen he conceives essential to its energetic action. What, may we ask then, exists in dry nitre, which contains no hydrogen? Is it nitric acid? or merely two of its elements in want of a little water to furnish the requisite hydrogen ? The same question may be asked relative to the sulphurate of potash. Since he conceives hydrogen necessary to communicate full force to the sulphuric and nitric acids, the moment they lose their water they should lose their saturating power, and become incapable of retaining caustic potash in a neutral state. Out of this dilemma he may indeed try to escape, by saying, that moisture or hydrogen is equally essential to alkaline strength, and that therefore the same desiccation or hydrogenation which impairs the acid power, impairs also that of its alkaline antagonist. The result must evidently be, that in a saline hydrate or solution, we have the reciprocal attractions of a strong acid and alkali; while in a dry salt, the attractive forces are those of relatively feeble bodies. On this hypothesis the difference ought to be great between dry and moistened sulphate of potash. Carbonic acid is admitted to be destitute of hydrogen, yet its saturating power is very conspicuous in neutralizing dry lime. Now, oxalic acid, by the last analysis of Berzelius, as well as my own, contains no hydrogen. It differs from the carbonic only in the proportion of its two constituents, and oxalic acid is appealed to by Dr. Murray, as a proof of the superior acidity bestowed by hydrogen."

"On what grounds," continues Dr. Ure, "he decides carbonic acid to be a feebler acid than oxalic, it is difficult to see. By Berthollet's test of acidity, the former is more energetic than the latter, in the proportion of 100 to about 58, for these numbers are inversely as the quantity of each requisite to saturate a given base. If he be inclined to reject this rule, and appeal to the decomposition of the carbonate by oxalic acid, as a criterion of relative power, let us adduce

his own commentary on the statical affinities of Berthollet, where he ascribes such changes not to a superior attraction in the decomposing substance, but to the elastic tendency of that which is evolved. Ammonia separates magnesia from its muriatic solution at common temperatures: at the boiling heat of water, magnesia separates ammonia. Carbonate of ammonia, at temperatures under 230°, precipitates carbonate of lime from the muriate: at higher temperatures, the inverse decomposition takes place with the same If the oxalic be a more energetic ingredients. acid than the carbonic, or rank higher in the scale of acidity, then, on adding to a given weight of liquid muriate of lime, a mixture of oxalate and carbonate of ammonia, each in equivalent quantity to the calcareous salt, oxalate of lime ought alone to be separated. It will be found, on the contrary, by the test of acetic acid, that as much carbonate of lime will precipitate as is sufficient to unsettle these speculations.

Finally, dry nitric acid and dry sulphate of potash, are placed, by this supposition, in as mysterious a predicament as dry muriate of soda in the chloridic theory. Deprived of hydrogen, their acids and alkali are enfeebled or totally changed. With a little water, both instantly recruit their powers. In a word, the solid sulphuric acid of Nordhausen, and the dry potash of potassium, are alone sufficient to subvert this whole hypothesis of hydrogenation."

The able chemist whom we have last quoted proposes the following distribution of acids "to give general views to beginners in the study." We treat them, as before stated, in their alphabetical order :

I. Division 1st, Acids from inorganic nature, or which are procurable without having recourse to animal or vegetable products.

II. Division 2d, Acids elaborated by means of organization.

The first group is subdivided into three families: 1st, Oxygen acids; 2d, Hydrogen acids; 3d, Acids destitute of both these supposed acidifiers. I. Division 1. Inorganic Acids. Family 1st.-Oxygen acids. Section 1st, Non-metallic.

The acids of the last division are all decomposable at a red heat, and afford generally carbon, hydrogen, oxygen, and in some few cases also nitrogen. The mellitic is found like amber in wood, coal, and, like it, is undoubtedly of organic origin.

ACIDIMETRY, in chemistry, the measurement of the power or strength of acids; generally effected by saturating a given weight of them with an alkaline base, when the quantity of alkaline is required in the measure of their power.

ACIDULE, in natural history, a species of mineral waters, distinguished by a latent acidity in their nature. When they are unaccompanied with heat, they are called acidula; but if heat be added to their brisk spirit, they are denominated therma. Acidula are native waters, impregnated with particles of some acid mineral, as vitriol, alum, nitre, or salt, and contain a considerable quantity of fixed air. For Dr. Priestley's method of making artificial waters of this kind, see the article PYRMONT. The physicians also frequently include chalybeate and aluminous or ferruginous waters, under the class of acidule. An analysis of mineral waters may be made, either by evapo ration, which will discover both the quantity of solid matter contained in the water, and by subsequent trials, the peculiar nature of it; or by distillation, whence it may be known, whether the water contain any volatile matter, saline or bituminous; or again, by the mixture of certain liquors. The most common for this purpose are the infusion of galls, syrup of violets, oil of tartar, volatile alkaline salts, tincture of sulphur and aqu

afortis. A small quantity of the infusion of galls will discover whether the water be impregnated with iron. If it contain a coarse oker, the colour struck by the galls is very dark; the finer iron produces an inky purple; but the finest, such as the pyrmont water contains, gives an azure blue. A dram of syrup of violets, mixed with a small wine glass of the mineral water, will produce a green colour, if there be any alkaline salt, or alum in it; though, it is said, that if the spirit be new, alum will turn it red. This green colour is also observed, when a solution of iron is met with; with an acid, the syrup produces a red. Volatile alkaline salt precipitates the contents of hard water, and discovers mercury, or any of its preparations, by turning the liquor whitish, and coagulating part of it. It discovers copper, by producing a blue colour. Volatile tincture of sulphur discovers lead in water, by turning it into a dusky brown colour. Aquafortis turns the water into a green colour, if it contains a solution of copper. ACIDULATED, an epithet applied to medicines that have an acid in their composition. ACIDULOUS, in chemistry, expresses either generally a slight degree of acid, or in particular an excess of acid in a compound salt; thus acidulous sulphate of potash is the sulphate of potash with an excess of acid.

ACIDULUM, in chemistry, a genus of native vegetable salts, consisting of potash saturated with an excess of acid, and comprising two species, tartareous acidulum, or the acidulous tartrite of potash, and the oxalic acidulum, or ac.dulous oxalat of potash.

ACIERNO. See ACERNO.

ACILIA LEX, in Roman antiquity, a celebrated law, enacted by Acilius the tribune, for the plantation of five colonies in Italy. 2. Ánother law, called also Calpurnia, enacted A. U. C. 684, against bribing elections. 3. A law against

extortion.

ACILIUS, (M. Balbus) a consul with Portius Cato, A. U. 640; during whose consulship, according to Pliny, milk and blood fell from heaven.

ACILIUS, (Glabrio) a tribune who put down an insurrection amongst the slaves of Etruria. He was consul with P. Corn. Scipio Nasica, and conquered Antiochus A. U. C. 563, for which he obtained the honour of a triumph. He was a candidate for the censorship in opposition to Cato. Also, a son of the preceding, who erected a temple to Piety, and the first golden statue that was ever seen in Italy, to the memory of his father. The temple was erected on the scite where a Roman female had fed her aged father with her milk. There was also a consul of this name in Domitian's time whose son was put to death by the tyrant for exhibiting more strength than himself in a contest with wild beasts.

ACILIUS, the surname of a Roman family, which produced several great men. See GLA

BRIO.

ACINACIFORMIS, in botany, from ȧkiváns, a scimitar, scimitar-shaped, an epithet for a leaf: Folium acinaciforme, a leaf which has one edge convex and sharp, the other straight and thick, as in the Mysembryanthemum. Linn. Phil. Bot.

ACINACES in antiquity, a kind of cutlass or scimetar, in use among the Persians. ACINARIA, in botany, a name given by some to the marsh wortle-berries, or vaccinia palustria.

ACINESIA, akivucia, from a, negative, and Rivεw, to move. In medicine, the immobility of the whole body or any part of it, as in a palsy, apoplexy, &c. Also, applied by Galen to the suspension of the pulse.

ACINI, in botany, small grains, or berries, growing in bunches, after the manner of grapes; also the stones or seeds of grapes. The berries of the elder, privet, ivy, &c are of this kind, and so called.

ACINI GRANDULOSI, in anatomy, some glands, so called from their formation.

ACINIFORMIS TUNICA, the same with the tunica uvea of the eye. It is also called acinosa tunica.

ACINODENDRON, in botany, the name given by Burman, to a species of plants, called melastoma, belonging, in the Linnæan system, to the genus thymus, and to the class and order didynamia gymnospermia.

ACINOS, in botany, stone, or wild basil. See THYMUS.

ACINUS, in botany, properly signifies the grape. See ACINI. It is also the name of the staphyloma.

ACIPENSER. See ACCIPENser.

ACIS, in fabulous history, the son of Faunus and Simetheis, was a beautiful shepherd of Sicily, who being beloved by Galatea, Polyphemus the giant was so enraged, that he dashed out his brains with a piece of rock; after which Galatea turned him into a river, which was called by his name: now the Aci or liaci.

ACITLI, in ornithology, the common Mexican name of the great crested diver, common to Europe and America, and more usually called by authors, the lepus aqueus, or water hare.

ACKEN, a small town in the duchy of Magdeburg, situate on the Elbe, five miles below Dessaw. It has a citadel.

ACKLAND'S ISLAND, Sometimes called South Crooked Island, one of the Bahamas, lying in N. lat. 23°, 20°. and E. long. 73°, 30'. It is about 50 miles in length; and seven in breadth, at its northern extremity, but very narrow southward. Atwood's narbour, to the north, has good anchorage for small vessels. The flamingo roosts here in great numbers.

ACKLIN'S KEYS is a name sometimes given to a groupe of islands, of which the above and Longkey or Fortune's Island are the principal. ACKNOW', Composed of the ACKNOWLEDGE, prefix a-subsequentACKNOWLEDGEMENT, ly ac, cnawan, to know, ACKNOWLEDGING. and lecgan, to lay, Ang. Sax. To lay open to, to make known to, to discover to; to confess, to make a concession.

So ech that denyeth the sone hath not the fadir, but he that knowlechith the sone hath the fadir.

Wiclif, 1 Jon. chap. ii.

That their hearts might be comforted, being knit together in love, and unto all riches of the full assur