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the string at e, furnished with a valve which acts in a similar manner to that of the copper ball. When not in use the brass case d is slid off, and the instrument then becomes a walking-stick. The head of the cane unscrews at a where the extremity of the piston-rod in the barrel is shown. An iron rod is placed in a ring at the end of this, and the air is condensed in the barrel in a manner similiar to that of the air-gun, but its foree is not so great as in that machine.

The first notice of the modern air-gun is in the "ELSmens d'Artillerie" of David Eivaut, who was preceptor to Louis XIII. of France. He ascribes the invention to Marin of Lisicux, who presented one to Henry IV. It appears, however, that Ctesibins, an Alexandrian Greek, who lived B. C. 150—120, applied the elasticity of the air to the construction of wind-guns; but in these machines the ball was not immediately exposed to the action of the air, but was impelled by the longer arm of a lever, while the air acted on the shorter. The air-gun is now seldom used, and indeed it must be regarded chiefly as a scientific toy, except in those cases, which we should hope are of rare occurrence, where it has been made the instrument of private revenge. ALABASTER. [See Gypsum.] ALBUMEN or ALBUMINE, (from the Latin albumen, the white of an egg,) an organic nutritive principle, the chief ingredient in the white of eggs (ovalbumine), and in the fluid portion of the blood (seralbumine). It also occurs in the sap or juices of many vegetables, as the potatoe, carrot, turnip, cabbage, asparagus, &c.; in the seeds of the cereal grasses; in almonds, filberts, oily nuts, the houseleek, &c. The most characteristic property of albumine is that of solidifying or coagulating when exposed to a moderate heat, in which state vegetable albumine, that from potatoes for example, is not to be distinguished from boiled white of egg.

Animal albumine is that which is chiefly employed in the useful arts, and we shall confine our attention to it. The albumine of eggs and of blood is associated with certain inorganic salts and a small portion of free soda, which gives it an alkaline reaction, and renders it soluble in the animal system. Albumine deprived of its alkali is no longer soluble. Ovalbumine is a thick glairy fluid, denser than water, without taste or smell, and dissolves readily in cold water. Exposed to atmospheric air it soon putrefies, but if a thin layer be spread out and exposed to evaporation in a warm place it dries up to a pale yellow, brilliant gum-like substance, in which state it may be preserved for any length of time, the presence of water being in all cases necessary to putrefactive fermentation.

"YVTien white of egg is exposed to heat it gives out a peculiar and characteristic odour. At about 134° white fibres of coagulum begin to appear; at 160° it becomes a solid mass. At 212° it dries, shrinks, and assumes the appearance of horn. In proportion as albumine is diluted with water it requires a higher temperature to coagulate it; but water with only one

thousandth part of its weight of albumine is rendered opaque by boiling. If the quantity of albumine be so great that the liquid appears slimy, a heat of 145° or 150° is sufficient to render the whole solid, white and opaque; but in a very dilute state the albumine separates in light flocks. After coagulation albumine is no longer soluble in water, but it dissolves in caustic alkali. The only chemical change that can be traced in coagulated albumine is the loss of alkali and soluble salts, which are removed by the hot water.

From its property of coagulating by heat, albumine is used to clarify syrups, and other liquids. The albumine is first mixed with the liquid to be clarified, and heat is gradually applied; the albumine coagulates in every part of the liquid, and entangles with it all the minute insoluble substances which render the liquid cloudy, and carries them to the surface in the form of a scum which can be removed. Albumine may also be employed as a clarifier at ordinary temperatures for wine, beer, &c., in which case it unites with the tannine, and forms an insoluble compound which acts in the same manner as coagulated albumine. But for this purpose isinglass acts much better.

Albumine is also coagulated by aleohol, which unites with the water which held the albumine in solution, and it is precipitated in white filaments. It is also coagulated by sulphurie, hydrochlorie, and nitric acids, but not by acetic acid, for this dissolves it. Metallic salts, such as muriate of tin and subacetate of lead, also coagulate it; bichloride of mereury, or corrosive sublimate, is on this account a delicate test of the presence of albumine, for if a single drop of the saturated solution of this salt be allowed to fall into water containing only the two-theusandth part of albumine, it will occasion a milkiness in the water, and a curdy precipitate. Albumine is an effective antidote in cases of poisoning by corrosive sublimate. It should be administered in the form of fluid white of egg, one white being required to neutralise the effect of 4 grains of the poison.

Albumine is also coagulated by voltaic electricity. If a fluid containing it be exposed to the action of a voltaic battery, soda will appear at the negative pole, and albumine will coagulate round the positive pole. Albumine contains in 100 parts:—

Carbon 54.84

Hydrogen 7.09

Nitrogen 15.83

Oxygen 21.23

Phosphorus ..'... 0.33
Sulphur 0.68

100.00 The presence of sulphur is shown by a boiled egg blackening a silver spoon; a trace of alkaline sulphuret being formed or separated during the coagulation.

Lime, baryta and strontia form insoluble compounds with albumine, which harden on drying. A lute formed by mixing slaked lime with white of egg, and spread on strips of paper or linen, is useful in making tight the joints of chemical apparatus.

ALCOHOL (an Arabic word) is the spirituous portion of fermented liquors, sometimes called ardent spirit. [See Fermentation, and, for its composition, Ether. See also Acetic Acid.] By carefully distilling fermented liquors the aleohol, mixed with a portion of water, can be separated, forming a product the properties of which differ according to the substances from which it is derived. Thus, the fermented and distilled juice of grape yields brandy; that of the sugar cane, rum; the wort of barley, which is generally malted for the purpose, yields whisky and spirits of wine. The rectified spirit of wine of the London Pharmacopoeia contains about 82 parts of absolute aleohol and 18 of water. Its specific gravity is directed to be 0.838. To obtain pure or absolute aleohol, the spirit of wine must be mixed with some substance which has a strong affmity for water and little or no affinity for aleohol. Thus, carbonate of potash is a deliquescent salt; that is, when exposed to the air it attracts moisture therefrom, and dissolves, or deliquesces: it therefore has a great attraction for water; but it is quite insoluble in aleohol. When, therefore, dry carbonate of potash is added to rectified spirit of wine, the water of the spirit dissolves the salt, and forms a dense solution upon which the aleohol floats. It is not, however, quite free from water, for, when poured off and distilled, it still contains about 5 per cent. of water. Aleohol of the specific gravity of 0.835 may by this treatment be reduced to 0.815. Powdered quicklime may be substituted for the carbonate of potash with greater advantage; but it must be left for three or lour days in contact with the spirit, in a well stoppered bottle, and be occasionally shaken. Chloride of caleinm, fused in order to get rid of its water, may also be- employed for separating water from aleohol. Equal weights of the spirit and the salt must be mixed in a well-stoppered bottle, and, when the salt is dissolved, the clear solution is poured into a distilling apparatus, and distilled at a moderate heat. About half the quantity of spirit employed must be sent over, and the process then be stopped. This will be absolute aleohol. Its specific gravity at 60° is 0.794.

There are other methods by which spirit may be deprived of a portion of its water. Thus, if a quantity of brandy or other strong spirit be put into a bladder, or into a wide-mouthed bottle and tied over with bladder, and be exposed to a temperature of from 105° to 120°,the aqueous portion will pass through the membrane in preference to the aleoholic, and in this way the spirit may be made stronger. Smugglers, who carry spirits about their persons in bladders, are aware of this fact; and this explains why their customers prefer the smuggled to the legitimate article, on account of its being stronger than ordinary spirit. Spirit of wine, of the specific gravity of 0.867, has in this way been reduced to 0.817. But by this process of exosmose absolute aleohol cannot be procured.

Alcohol is a limpid colourless liquid, of an agreeable

odour and a strong pungent taste. In its pure state it is poisonous, and when diluted produces intoxication. It is extremely inflammable, burning with a pale bluish flame, the heat of which is intense. When diluted with water the heat of the flame is less intense, and its colour more yellow. It produces no smoky deposit, and the products of combustion are carbonic acid and water. According to Saussure, jun., the combustion of 100 parts of aleohol produces 136 parts of water. The intense heat of the flame and the absence of any smoky deposit make aleohol so useful in the spirit-lamp of the chemist. The flame may be coloured by certain salts: boracic acid and salts of copper give it a green colour; salts of baryta yellow; and the salts of strontia an intense red. Aleohol has never been frozen. When exposed by Faraday to a temperature of 166° below the zero of Fahrenheit's scale, it thickened considerably, but did not congeal. Hence the great use of spirit thermometers for measuring low degrees of temperature. The low temperature thus obtained by Faraday was by a mixture of solid carbonic acid and ether; but it is stated by another authority that spirit of wine, of the specific gravity 0.820, entirely congeals under similar circumstances. The boiling point of aleohol, specific gravity 0.7947, is 173°, under an atmospheric pressure of 29.5. The boiling point varies with the specific gravity, that is, it becomes higher for each addition of water. Under the exhausted receiver of an air-pump, aleohol boils at common temperatures. The rate of expansion under the influence of heat is such that 1,000 measures of aleohol (specific gravity 0.817) at 50° become 1,079 measures at 170°.

Absolute aleohol has so great an affinity for water that it absorbs it rapidly from the atmosphere, and sensibly increases in specific gravity in a short time. It combines with water in all proportions; and the mixture gives rise to a diminution in bulk, and a considerable disengagement of heat in consequence of the increased density. Equal parts of aleohol (specific gravity 0.825) and water, each at 50°, when snddeuly mixed, give rise to a temperature of 70°; and equal measures of proof spirit and water, each at 50°, give a temperature of 60°.

The uses of aleohol in the arts are very numerous. It can be used as a solvent in cases where water altogether fails. It dissolves resins, and hence its use in varnish-making. It does not readily unite with the fixed oils, except castor oil; but it freely dissolves the essential oils and camphor, and hence its use in pharmacy and perfumery. It dissolves sugar, soap, and oxalic, tartaric, gallic, benzoic, and some other acids. It is extensively used in the preparation of ether. From its great attraction for moisture it is employed in preserving vegetable and animal substances, and anatomical preparations. It is valuable to the chemist as a fuel, and also for many purposes of ehemical analysis; but its high price in this country is an impediment in the way of science and the useful arts. •

Aleohol is an agreeable stimulant in fermented drinks; but the want, suffering, and disease occasioned by its abuse far outweigh any benefits likely to be derived from its use, as forming part of a beverage. The quantity of aleohol in wine, beer, &c., is very variable. According to Professor Brande, port and sherry, and some other strong wines, contain from 19 to 25 per cent. of aleohol; the lighter wines of France and Germany, about 12 per cent. Strong ale contains about 10 per cent.; ordinary spirits, as brandy, gin, and whiskey, 40 to 50 per cent., or occasionally more. The latter owe their peculiar flavours to certain essential oils which are present in very small quantity, and are generated during fermentation, or are purposely added. The strength of such spirituous liquors as consist of water and aleohol may be judged of by the taste, the size and appearance of the bubbles, when, shaken, the sinking or floating of olive oil in them, and the appearances they exhibit when burned; for, if the spirit burns away to dryness, and inflames gunpowder, or a piece of cotton immersed in it, it is considered as aleohol. "The different spirituous liquors leave variable proportions of water, when thus burned in a graduated vessel. But it must be recollected that in rum, brandy, and several other spirits, the specific gravity is often interfered with by extractive, colouring, and saccharine substances, often fraudulently added, with a view to increase the specific gravity, and therefore to diminish their apparent strength. In examining these liquors, they should be distilled, and the specific gravity of the distilled portion will then give an indication of the proportion of aleohol that may be relied on. In respect, however, to the excise, distillation is inconvenient, and is therefore only resorted to in extreme or suspicious cases."— Brande.

The only correct mode of ascertaining the specific gravity of liquids is by weighing them against an equal volume of pure water at the same temperature. [See Specific Gravity.] In practice, however, the hydrometer is used; and the form of the instrument, and the method of using it for the purposes of the excise, were given in the report of a Committee of the Royal Society to the Government. The following extract from this report will afford much useful information on this subject, especially as relates to the composition and density of proof spirit, which is defined by 58 George III. c. 28, to be such "as shall, at the temperature of 51° Fahr., weigh exactly twelve thirteenth parts of an equal measure of distilled water." The term proof spirit usually means a mixture of equal bulks of aleohol and water; but the specific gravity of such a mixture will depend upon that of the standard aleohol, which is not specified in the act referred to; but it appears, that equal weights of aleohol, specific gravity 0.796 at 60°, and water, have a specific gravity of 0.917, which is very nearly that of legal proof spirit.

The Beport says:—" With regard to the substance, aleohol, upon which the excise duty is to be levied, there appears to be no reason, either philosophical or practical, why it should be considered as absolute. A definite mixture of aleohol and water is as invariable in its value as absolute aleohol can be. It is also in

VOL. I.

variable in its nature, and can be more readily, and with equal accuracy, identified by that only quality or condition to which recourse can be had in practice— namely, specific gravity. A diluted aleohol is, therefore, that which is recommended by us as the only excisable substance; and as, on the one hand, it will make no difference in the identification, and, on the other, will be a great commereial advantage, it is further recommended, that the standard be very nearly that of the present proof spirit.

"The proposition of your Committee is, that standard spirit be that which, consisting of aleohol and water alone, shall have a specific gravity of 0.92 at the temperature of 62° Fahr., water being unity at that same temperature; or, in other words, that it shall, at 62°, weigh -JJ&ths, or fjths of an equal bulk of water at the same temperature. The temperature of 62° Fahr. is recommended as the standard, because it is that at which water was taken in the late national survey and adjustment of weights and measures. The specific gravity of 0.92 is taken rather than 0.918633, (the specific gravity of present proof spirit at 62°,) because the fraction expressing its relation to water is much more simple, and will facilitate the construction of the tables and the verification of the instruments proposed to be used.

"This definition of standard spirit appears to your Committee to be very simple, and yet as exact as it can be, or as any other standard spirit can be. This standard is rather weaker than the old proof spirit, in the proportion of nearly 1.1 gallon of the present proof spirit per cent. But this disadvantage your Committee consider as trifling, compared with the great convenience which will result if the specific gravity of 0.92 be taken rather than 0.918633.

'* It may be interesting hereafter to ascertain what proportion of absolute aleohol enters into the composition of the recommended standard spirit, should the latter be adopted by the Government; but the point possesses not the slightest practical importance in relation to the present question. The proposed standard is, in fact, more definite, more sure, and more ascertainable than that of the aleohol which it must contain. Philosophers are not yet agreed upon the density of absolute aleohol; and the differences of specific gravity assigned to it vary from 0.7910 to 0.7980. But, assuming the truth to be somewhere within these extremes, the proposed standard would contain nearly one-half, by weight, of absolute aleohol.

"In any mixture of aleohol and water, the specific gravity appears to be the only quality or condition to which recourse can be had for the practical purposes of the Excise, in order to indicate the proportion of standard spirit present. Your Committee are of opinion, that the hydrometer is the instrument best fitted, in the hands of the excise officer, to indicate that specific gravity; and they think it ought to be so graduated, as to give the indication of strength, not upon an arbitrary scale, but in terms of specific gravity at a fixed temperature, which, in the present case, should be 62°, or that of the standard spirit. The graduation, in terms of specific gravity, will not

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tilled, or the substance to be sublimated; a head or capital, H, furnished with a pipe, leading into a receiver It. Heat is applied to the body M, either by means of a lamp or a sand-bath. The rising vapour is condensed in the head, and, trickling down the sides, is received into its depressed channel C, from which it flows down the pipe into the receiver, which is loosely fitted to it by means of a ring of cork. The condensation is more rapid if the receiver be immersed in cold water. The alembic is now seldom used, it having been superseded by better forms of apparatus, which will be described under Distillation.

ALKALI. A term applied by the Arabians to the carbonate of soda found in the ashes of marine plants. The same term was afterwards extended to carbonate of ammonia, and also to the carbonate of potash found in the ashes of land plants, which was long considered as identical with carbonate of soda. It was discovered that these three alkaline carbonates arc rendered much more caustic by contact with lime; and hence the mild (or carbonated) alkalies were distinguished from the caustic (or pure) alkalies. Dr. Black, in 1756, showed that this change is due to the abstraction of carbonic acid from the mild alkalies by the action of lime. The older chemists distinguished ammonia as the volatile alkali from the two fixed alkalies, and of these potash received the name of vegetable alkali, soda that of mineral alkali,—the one being found chiefly in the ashes of plants, the other in rock-salt. It was afterwards found that potash exists in many widely diffused minerals; and, consequently, the term vegetable alkali could not properly be applied to it. Klaproth suggested that the word icali should be used to designate it; but the French chemists invented the word potassc to distinguish the pure alkali, deriving the term from the German word,

poltasche, which, probably, owes its origin to the use of iron pots in burning the materials from which the alkali is obtained. The alkalies and earths were long regarded as simple substances, although Lavoisier had suggested that they were metallic oxides. Sir Humphry Davy, in 1807, first succeeded, by means of a powerful voltaic battery, in separating the metals from potash, soda, baryta, strontia, and lime, and in obtaining traces of metallization from the earths. These results were extended and confirmed by GayLussac, and others. The discovery of these metals also led to that of pure potash and soda; for, up to that time, these substances were known only in the state of hydrates, and these hydrates were long regarded as anhydrous alkalies.1

Alkalies have a great affinity for acids, combining with them to form salts. Alkalies in solution convert vegetable blue colours into green, and vegetable yellows into reddish brown. The infusions of red cabbage, and of turmeric, or bibulous paper stained with these substances, are used as tests for the presence of an alkali. Unsized paper, tinged by a strong infusion of the petals of the red rose, is a very delicate test for the presence of an alkali: in a very strong alkaline solution, it is turned greenish brown; but when the solution is very dilute, its reaction is very delicate, and it becomes bright green; it will thus indicate the presence of an alkali when turmeric paper is not visibly discoloured. The alkalies restore the colour of vegetable blues which have been reddened by acids; and acids restore vegetable colours which have been altered by alkalies.

No metal yields two alkalies by different degrees of oxidation, nor does any one become, by this process, an alkali and an acid. All the fixed alkalies will bear a high temperature without decomposition. They arc of extensive use in various chemical arts; as in the manufacture of Soap and Glass.

There is a class of vegeto-alkalies, named alkaloids, which are produced in plants during vegetation, but always in combination with a peculiar acid. They arc, for the most part, sparingly soluble in water, but dissolve in hot aleohol, from which they often crystallize, in a very beautiful manner, in cooling. Two of them, however, are oily, volatile liquids. Their taste, in solution, is intensely bitter; and their action on the animal economy is very energetic. They all contain nitrogen, and are complicated in structure. None of the organic bases occurring in plants have hitherto been formed artificially. Morphia or morphine, the chief active principle of morphinc, and cinchonia and quina, to which the valuable medicinal qualities of the Peruvian barks are due, may be cited as examples of alkaloids.

ALKALIMETRY. A process for estimating the quantity of free alkali, or of carbonate, contained in any impure specimen. The process depends on the neutralization of the alkali by an acid, and the use of the test-papers, described in the last article. The dilute acid is usually placed in a graduated glass tube, called an alkalimeter, (Fig. 25,) which (1) Gmelin'a Hand-Book of Chemistry, vol iii.

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Potash Carl). Soda

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Fig. 25.

is prepared and used in the following manner, according to the directions given by Dr. Faraday in his work on "Chemical Manipulation." A tube, closed at one end, 9 j inches long, and f of an inch internal diameter, is selected, and 1,000 grains of water are weighed into it. The space thus occupied is graduated into 100 equal parts, and every ten divisions are numbered from above downwards. At 23.44 parts, 75 or 76.56 parts from the bot80 torn, an extra line is made on the opposite side, with the word soda written against it with a scratehing diamond. Lower down, at 48.96 parts, is another line, with the word potash. Still lower, at 54.63 parts, is a third line, with curb. soda marked; and at 65 parts, a fourth, marked carb. potash. It will be observed, that portions are measured off beneath these marks, in the inverse order of the equivalent numbers of these substances, and, consequently, directly proportionate to the quantities of any particular acid, which will neutralize equal weights of the alkalies or their carbonates. As these points arc of importance, they ought to be verified, by weighing in the tube first 350, then 453.7, then 510.4, and, lastly, 765.6 grains of water, which will correspond with the marks if they are correct. Or the graduation may be laid down from the surface of the four portions of fluid, when weighed in, without reference to where they fall upon the general scale. The aperture of the tube should be so formed as to be perfectly and securely covered by the thumb of the left hand.

The acid used with the tube is diluted sulphuric, of the specific gravity 1.1268, prepared by mixing 1 part by weight of oil of vitriol, of specific gravity 1.82, with 4 parts of water. A quantity of this acid measured into the tube up to any one of the four marks described will neutralize 100 grains of the dry alkali or carbonate set down at the mark; consequently, if water be added in the tube thus filled up to any one of the marks, until the 100 parts are full, and the whole uniformly mixed, 1 part of such diluted acid will neutralize 1 grain of the alkali or carbonate named at the mark up to which the tube was first filled with the acid of specific gravity 1.1268.

When a specimen of potash, barilla, or kelp is to be examined, 100 grains are to be weighed out, dissolved in warm water, filtered, the insoluble portion washed, and the solution added to the rest. By this process the alkali will be separated from carbonate of lime, or other insoluble matters, which might otherwise lead to error in the estimation. The alkaline solution is to be put into a basin in the sand-bath, and the tube and acid prepared. The acid is to be

poured into the tube up to the mark which indicates the substance to be tested for; potash or carbonate of potash for the potash or pearlash of commerce, and soda or carbonate of soda for barilla or kelp. Water is then added until the 100 parts are filled up, and, closing the tube with the thumb, its contents are to be perfectly agitated and mixed. Then inverting tnc tube, so that the thumb and mouth of the tube are downwards, the acid is to be let out gradually into the alkaline solution in the basin, by relaxing the thumb, and admitting a succession of small bubbles of air. The hot solution beneath is to be continually stirred, so as to mix the acid instantly with the whole, and increased caution must be used as the point of neutralization is approached. The acid must then be let out in portions less than a drop. This process is carried on until the alkali is found by test papers to be exactly neutralized. Then the tube must be inverted, the thumb removed by drawing its under surface over the edge of the tube, so as to leave as much as possible of the fluid that otherwise might adhere to it; and having allowed the sides to drain, it must be observed how many parts of acid have been used, the number of which will indicate the number of grains of the alkali or carbonate contained in the 100 grains of the impure alkali operated with.

The proper strength of the acid used in the above process may be ascertained in the following manner: crystals of bicarbonate of potassa are fused in a platinum crucible, and when cold a portion of the resulting solid, 70, 80, or 100 grains, is to be weighed in water, thus furnishing a known weight of pure carbonate of potash in solution. The solution is then to be diluted, heated, and neutralized by acid from the tube, diluted as before described from the mark of carbonate of potassa. If it be found that as many parts of the acid have been used as of grains of the carbonate weighed out, the acid is of proper strength; if more acid has been used, it is too weak; if less has been sufficient, it is too strong.

A process of neutralization, quite the same in principle, may be adopted for the purpose of estimating the strength of acids. This is called Acidimetry. Acetic Acid is frequently estimated in this way, both because its specific gravity varies very little with its strength, and because it is much used in the arts in an impure state. As there is a very near agreement between the equivalents of acetic acid and carbonate of lime, by allowing the acid to act on fragments of marble, the quantity dissolved will at once express the quantity of pure acid present. In like manner hydrochloric, nitric, and any other acid which forms a neutral soluble salt with lime, may be estimated, and its strength become known. Thus, let 500 grains of the acid be put into a basin or flask with 100 grains of marble, in fragments, and, after the first effervescence is over, warmed, and the neutrality ascertained by test papers; the solution is then to be poured off, and the remaining pieces of marble washed, dried, and weighed. The number of grains of carbonate of lime dissolved in hydrochloric acid, multiplied by 0.74, indicate the number of grains of dry acid by

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