Chapter II: Deposition of the Precious Metals (6)

2. The strongest oil of vitriol, 3 parts, are mixed with alcohol, q. s. (about 2 parts at ·830) to reduce its sp. gr. to 1·780; an object which may be easily obtained by distilling off some of the ether if required. The still or retort is then connected with a vessel full of alcohol, of at least 90%, by means of a small syphon tube, furnished with a stop-cock; the longer limb of which should be of glass, and so arranged that it just dips into the mixture of acid and alcohol. Heat is next applied, and the contents of the still raised to the boiling-point as rapidly as possible, and as soon as full ebullition commences the stop-cock of the syphon is cautiously turned, so as to allow the alcohol to flow down in such a manner as to keep the boiling liquid exactly at the same level; or, in other words, to supply a quantity of alcohol exactly equal to that of the liquid which distils over. By careful manipulation the whole of the alcohol which enters the retort passes over as ether and water, and this decomposition proceeds for some time, and would continue for an unlimited period did not the sulphuric acid ultimately become too weak to form ether, from the gradual absorption of the superfluous water contained in the alcohol. Were it convenient or practicable to use absolute alcohol, a given weight of sulphuric acid of the proper strength, would maintain the power of producing ether for an indefinite period. In practice, the quantity of alcohol that may thus be etherified is twice or thrice as much as by the common process, while neither sulphurous acid, sulphovinic acid, nor sweet oil of wine is generated, and the residual liquid of the distillation continues limpid, and has only a pale-brown colour. This is termed the 'continuous,' or 'Boullay's' method. (This process is similar to that given in the B. P.)

3. Alcohol of 90%, five parts are mixed with oil of vitriol, 9 parts, in a vessel of copper or iron immersed in cold water; the mixture is next introduced into a still or retort, and raised to a state of ebullition as rapidly as possible, as before. A fresh quantity of alcohol, equal in bulk to the liquid distilled over, is then added to the liquid in the still, and distillation again had recourse to. As much concentrated alcoholic solution of potassa as will give it a perceptible alkaline reaction is next added to distilled liquor, which is then rectified by the heat of a water bath, as long as the ether which distils over has the sp. gr. ·720 to ·725 at 80° Fahr. Instead of the potassa, a little milk of lime may be used, along with its own bulk of water. By allowing the product to stand for some days over chloride of calcium or quicklime, and again rectifying it along with one of these substances, perfectly pure ether may be obtained.

_Obs._ The mixture of alcohol with sulphuric acid requires some caution. It is best done by introducing the alcohol into a suitable vessel, and imparting to it a rapid whirling motion, by which a considerable conical cavity is formed in the centre, and into which the acid may be gradually poured with perfect safety. The mixed fluids should be brought to a state of rapid ebullition, as quickly as possible, as without this precaution much of the alcohol distils over before the liquor acquires the proper temperature for etherification. On the small scale, a tubulated retort, connected with a Liebig's condensing tube, and two globular receivers surrounded with a freezing mixture, or ice-cold water, may be employed as the distillatory apparatus. The second receiver should be connected with the first one by means of a bent glass tube, reaching nearly to the bottom of the former; and the whole of the joints should be securely luted, as soon as the expanded air has been allowed to escape. We have employed the following convenient little apparatus for the preparation of small quantities of ether, and it will be found very suitable for the distillation of most other highly volatile liquids, and particularly for boiling mixtures of alcohol and organic acids. By connecting the neck of a flask or digester containing volatile fluids with the lower instead of the upper end of the refrigerator, ebullition may be carried on without loss, as the vapour will be condensed, and run back into the vessel from which it has distilled.

_a._ Condenser tube.
_b, c_ Glass tube.
_d._ Funnel by which cold water runs in from the water bottle _h_.
_e._ Pipe by which water escapes through _f_ into the bottle _g_.
_i._ Retort.
_k._ Adapter, connecting the retort with the condenser.
_l._ Adapter, connecting the condenser with the bottles _t, t_.
_A._ Wooden tressel, with movable arms _n, o_, for supporting and
adjusting the heights of the condenser.
_B._ Wooden stool for supporting the water bottle.
_q._ Furnace.
_r._ Support for the furnace.
_p._ Gutter for carrying off water that overflows the funnel _d_,
and preventing its escape along the pipe _c_.
_s._ Leg of syphon connected with bottle containing alcohol.
_t, t._ Glass globes, placed in the basins _v, v_, and surrounded
with pounded ice or ice-cold water.
_w._ Safety tube, containing a little mercury at _x_.]

For the rectification of ether, a water bath is employed along with the above simple refrigerator, and the receivers surrounded by ice or a freezing mixture.

_Chem. comp., &c._ Ether is generally regarded as the oxide of ethyl, and alcohol as the hydrate of this base. This view is borne out by analysis, which proves that ether differs from alcohol by the elements of water. Recent experiments have also shown that the relation existing between the two compounds is--if alcohol be expressed by the formula C_{2}H_{6}O, the true formula of ether will be (C_{2}H_{5})_{2}O. We cannot describe these experiments here, but we may remark that ether cannot be made to combine with water directly, nor can alcohol be converted into ether by the abstraction of water, pure and simple, without the aid of other substances.

The compound ethers may be compared to ordinary salts in which the metal is replaced by a radical termed ethyl, having the formula C_{2}H_{5}. This view is, of course, in accordance with the theory which regards ether as the oxide of ethyl.

According to theory, 1 equivalent, or 46 parts of absolute alcohol, should produce 1 eq., or 37 parts, of pure ether; but in practice, the greatest product obtained by operating according to Boullay's method, which produces more ether than any other, does not exceed 33-1/2 parts for the preceding quantity of alcohol, or 71·5%. A mixture of 9 parts of oil of vitriol, and 5 parts of alcohol of 90%, ceases to produce ether after 31 parts of such alcohol have been added.

The most economical method of etherification is that known as the continuous ether process, or the process of Boullay. When this is adopted, the retort or flask should be fitted with a sound cork, perforated by an aperture to receive a thermometer, and the application of the heat, and the flow of alcohol, should be so managed, that a temperature of 300° Fahr. and a state of rapid and violent ebullition (points of essential importance) are maintained.

_Prop., Uses, &c._ Pure ether is a colourless, transparent, and very limpid fluid, having a penetrating and agreeable smell, and a burning, sweetish taste; its evaporation produces the sensation of extreme cold; when prevented, a sensation of heat is experienced. Its specific gravity varies between ·712 and ·724. If it contains water it begins to crystallise in brilliant white plates when cooled to -24° Fahr., and become a white crystalline mass at -46° or -47° Fahr.; but if absolutely pure, ether cannot be solidified by any degree of cold that can be produced, it remaining fluid when placed in contact with solid carbonic acid, at a temperature of about -148° Fahr. Boils at 96° or 97° Fahr.; is very combustible; is soluble in about 10 parts of distilled water, and mixes with alcohol in all proportions. It abstracts corrosive sublimate, terchloride of gold, sesquichloride of iron, and many of the alkaloids, from their watery solutions, and is hence invaluable in analysis and pharmacy. It readily dissolves the volatile and fixed oils, and most fatty matters, as well as sulphur and phosphorus in small quantities. By exposure to light and air it absorbs oxygen, and water and acetic acid are gradually formed. It is decomposed by exposure to a high temperature. Its evaporation occasions intense cold. The greatest degree of cold yet produced (-166° Fahr.) has resulted from the admixture of ether with solid carbonic acid. Ether is powerfully stimulant, narcotic, and antispasmodic, and externally refrigerant, if allowed to evaporate, or stimulant and counter-irritant if its evaporation is prevented, and is used in various diseases. Applied to the forehead by means of the fingers or a strip of linen, it generally relieves simple cases of nervous headache. In _pharmacy_ it is largely employed in the preparations of tinctures alkaloids, spirits, &c.; and in _chemistry_ is invaluable in organic analyses. Its principal commercial application is as a solvent for pyroxyline, in the manufacture of collodion. It is also employed as a solvent of resins, india rubber, &c., in the preparation of varnishes, and for several other useful purposes.--_Dose_, 20 drops to 2 fl. dr.; in water or wine. Excessive doses of ether produce intoxication resembling that from alcohol, and require similar antidotes. Sulphuric ether is said to be taken largely in the north of Ireland as a stimulant, particularly in Antrim. Shortly before the discovery of chloroform, it was found that when the vapour of ether was inhaled it gradually produced insensibility to pain. It was therefore employed as an anæsthetic in surgical operations. Having been found less efficient than chloroform, and more troublesome to administer, its use for this purpose has been abandoned.

_Tests._ Ether may be recognised by its volatility, odour, taste, sparing solubility in water, admixture with alcohol in all proportions, great inflammability (burning with a yellowish-white flame), and its power of dissolving fats and resins. Its further identification can only be effected by ultimate analysis.

_Pur._ The ether of the shops generally contains alcohol, water, or acetic acid, and sometimes all of them. Its usual specific gravity fluctuates between ·733 and ·765. Exposed to the air, it volatises entirely. It turns litmus paper red; sometimes very slightly, and occasionally even not at all. 1/2 fl. oz. mixes completely with 1/2 pint of water. Pure ether should, however, be neutral to test-paper, although seldom so. When shaken in a minim measure with half its volume of concentrated solution of chloride of calcium, its volume should not lessen. 10 fluid ounces of water should only dissolve 1 fluid ounce of ether, and remain transparent.

_Preserv._ Ether rapidly evaporates at common temperatures when kept in corked bottles, and even in bottles secured with ground-glass stoppers and tightly tied over with bladder and leather; it also becomes sour by age. To prevent this waste, the stoppers should fit accurately, and the bottles should be placed in as cool a situation as possible. Bottles furnished with ground-glass caps, as well as stoppers, are frequently employed. (See _engr._) Dewar's 'ether phial' is formed on a similar principle. We have seen bottles of ether accurately stoppered, tied over with bladder, and thickly coated with wax, which have yet become quite empty by a voyage to the tropics, though they still appeared to be as closely secured as when they were first filled.

_Caution._ The vapour of ether is very inflammable, and when mixed with atmospheric air, it forms a violently explosive mixture. The density of this vapour is 2·586, that of air being 1; hence it rapidly sinks, and frequently accumulates in the lower parts of buildings, especially cellars which are badly ventilated, in the same way as water does. The only remedy is thorough ventilation. Many serious accidents have arisen from this cause, for no sooner is a light carried into an apartment where such vapour is present than an explosion takes place.

=Ethyl, Acetate of.= C_{2}H_{5}C_{2}H_{3}O_{2} _Syn._ ACETATE OF OXIDE OF ETHYL, ACETIC ETHER, PYROLIGNEOUS ETHER; ÆTHER ACETICUS, L. A compound discovered by the Count de Lauraguais in 1759.

_Prep._ 1. Acetate of potassa, 3 parts (or an equiv. quant. of acetate of soda), alcohol (85%), 3 parts, oil of vitriol (strongest), 2 parts, are mixed together and distilled, by the heat of a sand bath, from a glass or earthenware retort into a well-cooled receiver; the distillate is agitated with a little water to remove undecomposed alcohol, and then digested first with a little chalk to remove acidity, and afterwards with fused chloride of calcium, to absorb water; it is, lastly, rectified by a gentle heat.

2. Rectified spirit (sp. gr. ·84), 50 parts, acetic acid (sp. gr. 1·075), 33 parts, are mixed together, and oil of vitriol (strongest), 10 parts, added; the distillation is continued until 65 parts have passed over, and the distillate, after digestion for some hours on a little dry carbonate of potassium, is rectified as before, the first 50 parts only being kept for use.

_Prop., &c._ Acetic ether is colourless, and bears a considerable resemblance to ordinary ether, but it has a much more agreeable and refreshing odour. It boils at 165° Fahr.; has a sp. gr. of ·89 at 60° Fahr., dissolves in about 7 parts of water; and mixes in all proportions with alcohol and ether. It is decomposed by alkalies and the strong acids.

Acetic ether is diaphoretic, stimulant, antispasmodic, and narcotic.--_Dose_, 1/2 to 2 fl. dr.; in similar cases to those in which sulphuric ether is employed, and especially in nervous and putrid fevers, spasmodic vomitings, and diseases of the bowels and stomach, arising from debility, and not of an inflammatory character. Its principal consumption is in the manufacture of British brandy.

=Ethyl, Benzoate of.= C_{2}H_{5}C_{7}H_{5}O_{2}. _Syn._ BENZOIC ETHER, BENZOATE OF ETHER, B. OF OXIDE OF ETHYL; ÆTHER BENZOICUS, L. _Prep._ Alcohol (sp. gr. ·830), 4 parts; benzoic acid (cryst.), 2 parts; concentrated hydrochloric acid, 1 part, are distilled together; as soon as the product turns milky when mixed with water, the receiver is changed, and the liquid that distills over collected; to this liquid water is added, and the supernatant ether is decanted, and boiled with water, and a little oxide of lead (to separate benzoic acid); it is, lastly, freed from water by allowing it to stand over chloride of calcium.

_Prop., &c._ A colourless oily liquid, slightly heavier than water, and possessing an aromatic odour and taste. It boils at 410° Fahr., and is miscible with alcohol and ether.

=Ethyl, Bromide of.= C_{2}H_{5}Br. _Syn._ ÆTHER HYDROBROMICUS, L. A volatile, ethereal liquid, discovered by Serullas.

_Prep._ Bromine, 8 parts; alcohol, 32 parts; dissolve, place the mixture in a retort, add of phosphorus, 1 part, and distil by a gentle heat as soon as the liquid becomes cold. The ether is separated from the distillate by the addition of water.

_Prop., &c._ A very volatile liquid, with a penetrating taste and smell; boiling at 105° Fahr., and heavier than water.

=Ethyl, Bu'tyrate of.= C_{2}H_{5}C_{4}H_{7}O_{2}. _Syn._ BUTYRIC ETHER, PINE-APPLE OIL; ÆTHER BUTYRICUS, L. _Prep._ By passing hydrochloric acid gas into an alcoholic solution of butyric acid, and purifying the product from free acid.

Commercially, from crude butyric acid saponified with caustic potassa or baryta, and the resulting soap distilled along with alcohol and oil of vitriol.

_Uses._ Crude butyric ether forms the 'pine-apple oil' of commerce, and when largely diluted with rectified spirit, the 'pine-apple essence' so much employed as a flavouring substance by confectioners, liqueuristes, &c. It imparts a delicious flavour to sweetmeats, rum, arrack, punch, &c. The Germans add it to common rum, to form the flavouring for their 'pine-apple ale.'

=Ethyl, Carbonate of.= (C_{2}H_{5})_{2}CO_{3}. _Syn._ CARBONIC ETHER, CARBONATE OF OXIDE OF ETHYL; ÆTHER CARBONICUS, L. _Prep._ Fragments of potassium are added to oxalic ether, gently warmed, as long as bubbles of gas are formed; the excess of metal is removed from the semi-solid mass, some water added, and the whole distilled. The carbonic ether floats on the surface of the liquid in the receiver, and is collected, dried by contact with chloride of calcium, and rectified along with some potassium or sodium, till it ceases to yield acetate of potassa when acted on by caustic potassa.

_Prop., &c._ Colourless, limpid, and aromatic; tastes pungent and burning; boils at 259° to 260° Fahr. It greatly resembles oxalic ether. It is decomposed by alkalies.

=Ethyl, Chlo'ride of.= C_{2}H_{5}Cl. _Syn._ LIGHT HYDROCHLORIC E., CHLORIDE OF ETHYL; ÆTHER HYDROCHLORICUS, L. A highly volatile compound, formed of ethyl and chlorine.

_Prep._ Rectified spirit of wine is saturated with dry hydrochloric acid gas in the cold, and the product is distilled in a retort connected with a Wolfe's apparatus, the first bottle of which should be two thirds filled with tepid water (70° to 75° Fahr.), and the remainder surrounded with a mixture of ice and salt. To render it perfectly anhydrous, it must be digested on a few fragments of fused chloride of calcium.

A mixture of oil of vitriol, 3 parts, and alcohol, 2 parts, is poured upon common salt (dried), 4 parts; and the whole distilled as before.

_Prop., &c._ This ether has a sweetish taste; is soluble in about 15 parts of water, and miscible in all proportions with alcohol; boils at 54° Fahr.; burns with a flame edged with green; is neutral to test paper; and does not affect a solution of nitrate of silver. Sp. gr. ·921, at 32° Fahr.--_Dose_, 10 to 30 drops, as an antispasmodic and a powerful diffusible stimulant. Owing to its extreme volatility it can only be taken dissolved in spirit.

=Ethyl, Cy'anide of.= C_{2}H_{5}CN. _Syn._ ÆTHER HYDROCYANICUS. L. _Prep._ Cyanide of potassium and sulphovinate of baryta, equal parts, are mixed and distilled in a glass retort by a moderate heat. The product separates into two strata; the lighter one is impure hydrocyanic ether; this is decanted and agitated with 4 or 5 times its bulk of water at 120° to 140° Fahr., and the operation is repeated with about 2 parts of water; the ether is again decanted, and placed in contact with chloride of calcium for 24 hours, and then rectified.

_Prop., &c._ It boils at 190° Fahr. Sp. gr. ·788. In its therapeutical effects it resembles hydrocyanic acid, but is less active. Its odour is, however, more penetrating and offensive.--_Dose_, 2 to 6 drops, in mucilage or emulsion; in obstinate or convulsive coughs, gastrodynia, hysterical affections, &c.

=Ethyl, Cy'anate of.= C_{2}H_{5}CNO _Syn._ CYANIC ETHER, CYANATE OF OXIDE OF ETHYL. _Prep._ By distilling a dry mixture of cyanate of potassa and sulphovinate of potassa in nearly equivalent proportions. A mixture of cyanic and cyanuric ethers passes over into the receiver. By distilling this mixture the two are readily separated; that which passes over by the heat of a water bath being the first, and the residuum in the retort the second.

_Prop., &c._ An ethereal, very mobile liquid, boiling at 140° Fahr.

=Ethyl, Cyan'urate of.= (C_{2}H_{5})_{3}C_{3}N_{3}O_{3}. _Syn._ CYANURATE OF OXIDE OF ETHYL. _Prep._ See CYANIC ETHER.

_Prop., &c._ Tasteless, inodorous, colourless, transparent, needles and prisms; fusing at 185° Fahr.

=Ethyl, I'odide of.= C_{2}H_{5}I. _Syn._ ÆTHER HYDRIODICUS, L. _Prep._ Phosphorous, 4 parts, alcohol (sp. gr. ·84), 70 parts, and iodine, 100 parts, are gradually and cautiously mixed together, and distilled.

_Prop., &c._ A colourless liquid, possessing a strong ethereal odour, and boiling at 158° Fahr.; sp. gr. 1·92. It is reddened and decomposed by exposure to air and light.

=Ether, Methy'lic.= _Syn._ OXIDE OF METHYL, WOOD-ETHER, METHYL-ETHYL. See METHYL.

=Ether, Muriatic (Heavy).= _Syn._ ÆTHER MURIATICUS PONDEROSUS, L. _Prep._ Alcohol, of 80 to 85%, is saturated, in the cold, with chlorine gas, water is next added, and the oily fluid that separates collected and washed with water, as long as any of it is dissolved.

_Prop., &c._ Heavy muriatic ether is a volatile, oily, colourless liquid, boiling at about 245° Fahr., and heavier than water. Its precise constitution is undetermined. This ether enters into the composition of the SPIRITUS MURIATICO-ETHEREUS, a remedy occasionally used on the Continent.

=Ethyl, Nitrate of.= C_{2}H_{5}NO_{3}. _Syn._ NITRIC ETHER, NITRATE OF OXIDE OF ETHYL; ÆTHER NITRICUS, L.

_Prep._ Nitric acid (sp. gr. about 1·375), 50 parts; nitrate of urea, a little (say 2 or 3 parts); dissolve, add alcohol, 50 parts, and distil with the usual precautions, until 7-8ths of the whole (of the liquid portion) have passed over; agitate the distillate with a little water to separate the ether, and preserve the heavier portion.

_Prop., &c._ Nitric ether possesses an agreeable sweetish taste and odour; it is insoluble in water; the alcoholic (but not the aqueous) solution of potassa decomposes it rapidly; sp. gr. 1·112. Its vapour is very apt to explode when strongly heated, and therefore a small quantity only should be prepared at a time.

=Ethyl, Nitrite.= C_{2}H_{5}NO_{2}. _Syn._ NITRIC ETHER, HYPONITROUS ETHER, NITRITE OF ETHER, NITRITE OF OXIDE OF ETHYL, HYPONITRITE OF E.; ÆTHER NITROSUS, Æ. HYPONITROSUS, L. This is a compound, of which 'sweet spirit of nitre' is an impure alcoholic solution.

_Prep._ 1. Starch (potato farina), 1 part; nitric acid (sp. gr. 1·30), 10 parts; mix in a capacious retort, connected with a wide tube, 2 or 3 feet long, bent at right angles, and terminating near the bottom of a two-necked bottle, containing a mixture of alcohol (of 85%), 2 parts, and water, 1 part, and surrounded with a freezing mixture, pounded ice, or very cold water; the other neck of the bottle being connected by a long glass tube with a good refrigerator or condenser. All elevation of temperature must be avoided. The heat of a water bath only must be cautiously applied to the retort. The gas liberated passes into the alcohol, causing the ether to distil in a gentle stream. The tube connecting the retort and bottle must be cooled by means of rag or moist paper, kept wetted with ice-cold water; as, if the temperature of the tube and the alcohol rises only a little, the latter becomes spontaneously hot, and boils violently, by which the product is vitiated. This process is very productive and economical, and yields pure nitrous ether.

2. A mixture of oil of vitriol, 8 parts, and alcohol, 9 parts, is poured upon crystallised nitrate of ammonia, 11 parts, contained in any suitable distillatory vessel connected with a well-cooled receiver. Nitrous ether gradually distils over on the application of a gentle heat. An admirable process, but more expensive than the preceding. Even a common fire may be employed without danger, as the liberation of the ether proceeds gradually, and not almost instantaneously, as in operating in the usual way. Sulphate of ammonia is left in the retort. The product is scarcely inferior to that of the last formula.

3. Rectified spirit, 46 fl. oz.; pure nitric acid (sp. gr. 1·500), 7 fl. oz.; put 15 fl. oz. of the spirit, with a little clean sand, into a quart matrass, fitted with a cork, and a safety tube reaching to within an inch of the spirit, and a second tube leading to a refrigeratory. Fill the safety tube with pure nitric acid, then add through it, gradually and cautiously, 3-1/2 fl. oz. of the acid. When the violent action that ensues is nearly over, gradually add the remaining portion of the acid, 1/2 fl. oz. at a time, and at intervals. Agitate the ether that distils over, first with a little milk of lime, till it ceases to redden litmus paper, and then with half its volume of concentrated solution of chloride of calcium. The pure hyponitrous ether thus obtained should have a density of ·899.

4. (Mr John Williams.) Nitrite of ethyl is best made by passing nitrous acid gas into alcohol.

The nitrous acid gas is prepared by acting upon such bodies as starch, copper, mercury, or arsenious acid with nitric acid. The alcohol is generally recommended in the text-books to be diluted with half its bulk of water; this, however, I consider a decided mistake. The alcohol should be as concentrated as possible, even absolute alcohol is preferable. The main points to be attended to are that the current of nitrous acid gas should be slow and steady, so as to give time for the reaction to proceed properly, and that the vessel containing the alcohol should be kept as cool as possible; in this way much of the production of bye-products will be avoided, and the gas can be passed through the alcohol, as long as it continues to be absorbed.

The resulting liquid is anything but pure; it contains much nitrite of ethyl, some aldehyde, acid--it is even stated to contain malic acid. In fact it is well known that the reaction between the nitrous acid, and such products as alcohol, however pure, is not sharp, but is always accompanied by secondary products.

From the crude alcoholic solution obtained by the method I have described, the pure nitrite of ethyl can be obtained without difficulty. Nitrite of ethyl is an extremely volatile liquid; it boils at about 61° F., whereas aldehyde boils at 90° F., and alcohol at 180° F. Taking advantage of this fact, we are enabled to separate it from the crude liquid by distillation. Some precautions are, however, necessary, to ensure the purity of the product. The flask containing the crude product is placed in a water bath, and connected by bent tubes with several other flasks and bottles. The first tube should be passed into a small empty flask, this will condense most of the alcohol which may pass over during the operation. Then a second bent tube passes into a second flask containing a little water; this condenses any alcohol which may not have been stopped in the first flask, together with free acid, and nearly all the aldehyde.

From this wash bottle a third tube proceeds into a somewhat shallow flask, containing a strong solution of caustic potash; the gas, however, is not allowed to pass through this alkaline liquid, but simply over the surface. In this way the last portion of the aldehyde is absorbed, and the potash solution gradually assumes an amber colour. From this vessel, the gas (for such at the ordinary temperature of the laboratory, the nitrite of ethyl is--in very cold weather it would be necessary to gently warm the different flasks) is passed through a tube charged with anhydrous chloride of calcium to absorb moisture, and the pure and dry nitrite of ethyl thus produced, finally passes into alcohol, which readily absorbs it.

It is only necessary to note the weight of the alcohol used for absorbing the gas, and its weight at the end of the operation, to know the strength or per-centage of nitrite of ethyl which must be in solution. Thus, if 9 oz. of alcohol becomes 10 oz., it is evident we have a solution of 10 per cent.; if it becomes 12 oz., then the strength must be 25 per cent., and so on. Ordinary spirits will answer for condensing the nitrite of ethyl, but it is better to use absolute alcohol, as it is very desirable to avoid the presence of water in any form. The solutions made with weaker spirit soon turn acid; those made with absolute alcohol, on the other hand, keep a long time. It is very true the very strong solutions of 50 and 25 per cent. show traces of acidity when tested with moistened litmus paper, but the 10 per cent. solution is quite neutral.[283]

[Footnote 283: The object of Mr Williams' paper, which is published in the 'Pharmaceutical Journal' for Dec. 8th, 1877, is to give instructions for the preparation of a pure nitrite of ethyl, which when mixed with alcohol in definite proportions, shall supersede the variable compound sold under the name of "Sweet Spirits of Nitre."]

One point I have not mentioned; it is that the distillation must be conducted at the very lowest possible temperature; in fact, the water in the water-bath should only be kept gently warm, and the process should be continued only so long as the conducting tubes feel cool to the touch; when they become warm the distillation should be discontinued. By passing the gas into a tube in a freezing mixture, instead of into alcohol, the pure nitrite of ethyl is readily obtained in a liquid form; it is, however, necessary to seal the tube, otherwise the very volatile liquid would soon be lost.

_Prop., &c._ Pure nitrous ether has a pale-yellow colour, an agreeable odour of apples, and boils at 62° Fahr.; sp. gr. ·947 at 60° Fahr. Commercial nitrous ether contains aldehyde, boils at 70° Fahr., has a more or less suffocating odour combined with that of the pure ether, has a sp. gr. of ·886 at 40° Fahr., and turns brown when mixed with alcoholic solution of potassa, while the latter remains unaltered. It also acidifies by age, whilst pure nitrous ether remains neutral. They are both very inflammable, and burn with a white flame. Ordinary nitrous ether dissolves in about 48 parts of water, and mixes in all proportions with alcohol and sulphuric ether.

Nitrous ether is refrigerant, diaphoretic, and diuretic, but is seldom employed alone, though, when largely diluted with alcohol (sweet spirits of nitric, spirit of nitric ether), it is a common remedy in several diseases. It is also used to flavour malt spirit, in imitation of brandy (British brandy), although for this purpose it is vastly inferior to acetic ether. See SPIRITS (Medicinal).

=Ethyl, [OE]nanthate of.= _Syn._ [OE]NANTHIC ETHER, PELARGONIC ETHER, [OE]NANTHATE OF OXIDE OF ETHYL. _Prep._ 1. The oil obtained towards the end of the distillation of fermented liquors, especially wines, consists, in a great measure, of the crude ether. It is purified by agitation with a weak solution of carbonate of potassa, freed from water by a few fragments of chloride of calcium, and then re-distilled.

_Prop., &c._ [OE]nanthic ether is colourless; lighter than water; boils at about 500° Fahr.; and has a powerful, intoxicating vinous odour, resembling that of an empty wine cask or bottle that has been exposed to the air for some time. It is very sparingly soluble in water, but freely soluble in alcohol. Its sp. gr. is ·862. As obtained by distillation, it is united with a little [OE]NANTHIC ACID. 2200 imperial gallons of wine (about 35 hogsheads) only yielded 2-1/5 lbs. of the mixed oil.

=Ethyl, Oxalate of.= (C_{2}H_{5})_{2}C_{2}O_{4}. _Syn._ OXALIC ETHER, OXALATE OF OXIDE OF ETHYL; ÆTHER OXALICUS, L. _Prep._ Alcohol and dry oxalic acid, equal parts, are digested together in a glass flask furnished with a very long glass tube of small bore, so that the spirit, volatilised by the heat, may be condensed, and flow back into the flask. After 6 or 8 hours the process is generally complete, and the liquid contains merely a trace of free acid, from which it may be separated.

_Prop., &c._ A colourless, oily liquid, slightly heavier than water, boiling at 363° Fahr., only slightly soluble in water, and having an aromatic smell. Alkalies decompose it. Sp. gr. 1·09.

=Ethyl, Sulphate of.= (C_{2}H_{5})_{2}SO_{4}.

_Prep._ The vapour of pure anhydrous sulphuric acid is passed (with the usual precautions) into perfectly anhydrous ether; the resulting syrupy liquid is agitated with a mixture of 4 volumes of water, and 1 volume of ether, and after repose the upper stratum, which is an ethereal solution of the sulphate of ethyl, is decanted, and the oxide of ethyl volatilised by a very gentle heat. The colourless liquid forming the residuum is the true sulphuric ether or sulphate of ethyl just referred to. It is a very unstable compound, and cannot be distilled without suffering decomposition.

=Ethyl, Valerianate of.= C_{2}H_{5}C_{5}H_{9}O_{2}. _Syn._ VALERIANIC ETHER, VALERATE OF OXIDE OF ETHYL; ÆTHER VALERIANICUS, L. _Prep._ By passing dry hydrochloric acid gas into an alcoholic solution of valeric acid. It is a fragrant, volatile liquid, lighter than water, having a high boiling-point, and a rich fruity odour, said to closely resemble that of butyric ether or pine-apple oil. It is used to flavour liqueurs, &c.

=ETHYL'AMINE.= NH_{2}(C_{2}H_{5}). _Syn._ ETHYL-AMMONIA. One of the bases of the ethyl-series, obtained by substituting one atom of hydrogen in ammonia NH_{3} by ethyl C_{2}H_{5}.

=EUCALYP'TIN.= A peculiar substance existing in Botany Bay kino. A substance exuded by several species of the _Eucalyptus_. It has been employed medicinally in diarrh[oe]a.

=EUCALYPTOL.= See EUCALYPTUS.

=EUCALYPTUS.= The _Eucalypti_, of which there are many species, belong to the natural order _Myrtaceæ_, and are natives of Australia, where they are known under the names of "gum-trees," or as "stringy-bark trees." The most interesting and important characteristic of these plants is the power they undoubtedly possess of correcting, if not of removing, the pestilential exhalations which are regarded as the origin of the fevers that occur in marshy localities. This discovery is due to M. Ramel, and was made by him in 1856.

M. Gimbert, amongst other cases, cites one of a farm, twenty miles from Algiers, the atmosphere surrounding which was of a very pestilential character. In the spring of 1867 13,000 eucalyptus trees were planted on the farm, and M. Gimbert states that since then not a single case of fever has taken place, the freedom from disease occurring the same year the plants were placed in the ground, and the good effects commencing whilst the trees were only two or three mètres in height.

The following is extracted from 'Les Mondes' (1876):--"Between Nice and Monaco there is a locality so unhealthy that the Paris, Lyons, and Mediterranean Railway Company have been obliged to change every two or three months the watchman at a crossing there.

"Plantations of the eucalyptus have been formed there, and at present the same watchman has resided there for several months with his family without experiencing the least inconvenience."

Again:--"In the Campagna, about three miles from Rome, there stand some deserted church buildings and a monastery, the latter having been abandoned because of the mortality amongst the monks caused by the noxious exhalations. Some six years since a company of French trappists, having obtained permission from the Italian Government, planted the grounds in and around the monastery with eucalyptus trees, and the result is stated to have been so total an immunity of the building from fever, although situated in the worst part of the Campagna, that the monastery is now tenanted, the health of the occupants being, it is said, unimpaired."

The writer in the 'Pharmaceutical Journal,' who contributes this statement, adds:--"Whether this grand result has been obtained through the efficacy of the extract of the eucalyptus taken each morning with their cup of black coffee, or whether it is to be attributed to the effects of the plantations, I leave to scientific men to determine."[284]

[Footnote 284: Bentley.]

It seems very probable that the effects above described are due to the eucalyptus having such extensive and far-spreading roots, which suck up and appropriate the moisture of the surrounding soil, the presence of which, aided by heat, giving rise to vegetable decomposition, is believed to be the cause of malarial poisoning.

The avidity of the plant for water is very great; it has been computed that one tree will absorb ten times its weight of moisture from the soil.[285] It is most likely owing, at any rate in very large measure, to this cause, rather than to the supposed antiseptic and disinfecting odours exhaled by its leaves, that the salubrious effects of the eucalyptus are due. The blue gum tree, or _Eucalyptus globulus_ (so distinguished because of the rounded form of the lid which covers its unexpanded flower bud), has been successfully introduced into Asia, Africa, and Southern Europe. If, as asserted, it can only exist in a climate where the temperature is never lower than the freezing point, its domestication (save in hot-houses) is impossible in our own country.

[Footnote 285: 'Pharm. Journal,' February 5th, 1876.]

The _Eucalyptus globulus_ is a very rapidly-growing tree, and attains to great proportions. "In some cases it has been known to attain the colossal dimensions of 350 feet in height and a 100 in circumference."[286]

[Footnote 286: Bentley.]

This magnitude is entirely out of proportion to the size of the seed, which is very minute; so minute that it has been computed one pound weight of the seed could produce 162,000 trees. Various preparations of the leaves and bark of the eucalypti have been introduced into medicine, which will be found under the respective pharmaceutical preparations. They were asserted to be specially serviceable in intermittent fevers and bronchitis. The idea that their efficacy in the former class of disease was due to the presence in the barks of the eucalypti of an alkaloid similar to, if not the same as, quinine, has been shown to be an erroneous one, from the experiments of the Government chemist of Ootacamund (Mr Broughton), who, after a most careful chemical analysis, failed to discover either quinine, quinidine, cinchonine, cinchonidine, or the least trace of any one of the cinchona alkaloids.

When the leaves of the _Eucalyptus globulus_ are held to the light they reveal the presence of little semi-transparent dots, which are found to be receptacles for a volatile oil, that may be obtained in large quantity by submitting the plant to aqueous distillation.

This volatile oil has been examined by Cloez, who found it to consist chiefly of a substance allied in chemical characters to camphor, which substance he named _eucalyptol_.[287] Any therapeutic power possessed by the eucalyptus may be referred to this substance, since, as just stated, it cannot be due to a bark alkaloid.

[Footnote 287: Messrs Faust and Homeyer state that Cloez's "Eucalyptol" is a mixture of terpen and cymol.]

Before finishing our notice of the reputed curative effects of the eucalyptus we may mention that Dr Gimbert employs the leaves instead of lint for dressing wounds and fetid ulcers, and says he has found them, when thus used, excellent deodorisers; that another method of employing the leaves of the eucalyptus consists in having them made into cigarettes, which are reported to be useful in asthma and bronchial complaints. Lastly, let us state that another species of eucalyptus exudes a very astringent substance, which, from its appearance and properties, being so analogous to kino, has been denominated _Botany Bay kino_. (See EUCALYPTIN.)

The essential oil of eucalyptus, which, according to the species of the plant from which it is obtained, varies in colour from light yellow to light blue, is now largely employed as a diluent for the more delicate volatile oils used in perfumery.

Many species of the eucalyptus yield excellent timber, possessed of great hardness and durability, and little affected by moisture. This timber has the power of resisting the attacks of insects. The wood of the eucalyptus is also very rich in potash. The maple and the elm, which are regarded as yielding a large per-centage of this substance, afford only about half as much as can be obtained from the eucalyptus, this latter tree yielding 21 per cent. of potash.

The barks of different species have also been advantageously utilised for paper making, as well as for tanning.

In this country eucalyptus seeds are reared in a greenhouse. They may be sown in a mixture of loam, peat, and ordinary soil, with a sprinkling of sand on the surface.

The following directions for the cultivation of the eucalyptus in England were communicated to the 'Medical Times and Gazette' of 1873 by Mr Bennett Stanford, of Pyt House, Tisbury:--"I have successfully reared from seed two dozen of these trees, and they are now growing well out of doors. I obtained the seed five years ago from South Australia, and forced it in a hothouse; in one year it was four feet high, and now, in its fifth year, it is growing rapidly in a sheltered position in the park, having attained a height of thirty feet. The first three years the tree must be taken under cover in the winter, and the fourth and fifth years should be protected for several feet up with wisps of hay or straw. When the trees are kept indoors in winter it should be in an orangery or very high greenhouse, with plenty of light and a little water."

=EUCHLO''RINE.= A bright-yellow gas, prepared by gently heating chlorate of potassa with hydrochloric acid. It is probably a mixture of chlorous acid and free chlorine. Prof. Stone, of Manchester, has found Euchlorine of a great service as an aerial disinfectant.

=EUGLENÆ.= These are ciliated infusorial animalcules inhabiting ponds and water-tanks. Sometimes they abound in water in quantities so enormous as to impart to that fluid a blood-red appearance. The principal species are the _Euglena viridis_ and the _Euglena pyrum_. Their presence is supposed to indicate the existence in the water in which they are found, of decaying animal and vegetable matter upon which they are believed to feed.

=EUPHOR'BIUM.= _Syn._ GUM EUPHORBIUM; EUPHORBIUM (Ph. E.), L. The concrete resinous juice of the _Euphorbia canariensis_, and other species of the same genus. It is a powerful acrid, purgative, rubefacient, sternutatory, and vesicant, and the violence of its action has led to its disuse.

=EU'PIONE.= An ethereal liquid forming the chief portion of the light oil of wood-tar, and which also exists in the tar obtained during the destructive distillation of animal substances, and in the fluid product of the distillation of rape oil. It is separated from these substances by agitating them with oil of vitriol, or a mixture of oil of vitriol and nitre, and subsequent cautious distillation. Pure eupione is tasteless, exceedingly thin, limpid, and aromatic; boils at 116° Fahr.; and is the lightest fluid known; sp. gr. ·655. It is very inflammable, burns with a very bright flame, and gives a transient greasy stain to paper. It is isomeric with hydride of amyl. Other volatile hydrocarbons of like origin are often confounded with eupione by chemical writers.

=EUPYR'ION.= Any contrivance for obtaining instantaneous light; as a lucifer match, &c.

=EVAC'UANTS.= _Syn._ EVACUANTIA, L. Medicines which augment the secretions or excretions. CATHARTICS, DIAPHORETICS, DIURETICS, EMETICS, ERRHINES, EXPECTORANTS, and SIALOGOGUES, belong to this class.

=EVAPORA'TION.= The conversion of a fluid into vapour by means of heat, diminished atmospheric pressure, or exposure to a dry atmosphere. Evaporation is had recourse to--1. For the vapour as a source of heat or power, as in the case of steam-boilers, &c.;--2. To separate volatile fluids from impurities or other bodies, which are either fixed or less volatile;--3. To recover solid bodies from their solutions, as in the preparation of extracts, chemical salts, &c.;--4. To concentrate or strengthen a solution by the expulsion of some of the fluid matter that forms the menstruum;--5. To purify liquids by the dissipation of the volatile matters which may contaminate them.

It is found that, under ordinary circumstances, evaporation is confined to the surface of the heated liquid, and is therefore slower or quicker, in proportion to the extension of that surface. Hence has arisen the adoption of wide, shallow vessels for containing fluids during their exposure to heat for this purpose. Evaporation proceeds most rapidly when a current of air (especially hot and dry air) is made to pass over the surface of the fluid; as, in this ease, the vapour is prevented from resting upon the surface, and impeding the process by its pressure. For a similar reason, liquids evaporate more rapidly in vessels partially covered than in open ones. In the former case the cool incumbent air condenses and throws back a portion of the vapour, which thereupon, besides its cooling action, offers mechanical resistance to the diffusion of the vaporous particles as they arrive at the surface of the liquid. In the latter case these obstacles are avoided, and the impetus of the vapour pouring forth from a contracted orifice (or pipe), not only readily overcomes the pressure of the atmosphere, but offers less surface for its cooling action, until it has passed much beyond the points at which it can exert any influence on the fluid from which it has escaped. In this way the chemical action of the atmosphere on the liquid operated on is also considerably lessened. On the small scale, shallow capsules of glass, wedgwood-ware, porcelain, or metal, are commonly employed as evaporating vessels, and these are exposed to heat by placing them over a lamp, or naked fire, or in a water bath, or sand bath, according to the temperature at which it is proper to conduct the process. On the large scale, high-pressure steam is usually employed as the source of heat. The term 'spontaneous evaporation' is applied to the dissipation of a fluid by mere exposure in open vessels, at the common temperature of the atmosphere, and without the application of artificial heat. The celerity of this species of evaporation wholly depends on the degree of humidity of the surrounding air, and differs from the former, in which the rate of evaporation is proportionate to the degree of heat at which the process is conducted, and the amount of pressure upon the surface of the liquid. Evaporation '_in vacuo_' (as it is called) is conducted under the receiver of an air-pump, or in an attenuated atmosphere, produced by filling a vessel with steam, by which means the air is expelled, when all communication with the external atmosphere is cut off, and the vapour condensed by the application of cold. Fluids are also evaporated in air-tight receivers over sulphuric acid, by which they are continually exposed to the action of a very dry atmosphere. When such a receiver is connected with an air-pump in action, evaporation proceeds with increased rapidity, and intense cold is produced. It appears, from the experiments of Dr Ure, that "if the bottom of a pan, and the portion of the sides immersed in a hot fluid medium (solution of chloride of calcium, for example), be corrugated, so as to contain a double expanse of metallic surface, that pan will evaporate exactly double the quantity of water, in a given time, which a like pan, with smooth bottom and sides, will do, immersed equally deep in the same bath. If the corrugation contain three times the quantity of metallic surface, the evaporation will be threefold in the above circumstances. But if the pan, with the same corrugated bottom and sides, be set over a fire, or in an oblong flue, so that the current of flame may sweep along the corrugations, it will evaporate no more water from its interior than a smooth pan of like shape and dimensions placed alongside it in the same flue, or over the same fire."

In the laboratory, steam heat is now almost exclusively employed. Copper, or tinned, glazed, or silvered coppered pans, boilers, and stills, are surrounded by a 'jacket' of cast iron, and high-pressure steam admitted between the two. By due management of the supply-cock, a range of temperature may be thus obtained extending from about 90° to 325° Fahr.

It is found that, under ordinary circumstances, 10 square feet of heated surface will evaporate fully 1 lb. of water per minute; and that a thin copper tube exposing 10 feet surface will condense about 3 lbs. of steam per minute, with a difference of temperature of about 90° Fahr. This is equal to 30° Fahr. per lb.; and, consequently, the heat of the steam employed to produce the evaporation should be 212° + 30° = 242° Fahr.

An attention to the facts and principles thus briefly explained above will be found of great value in the laboratory.

=EXCIP'IENT.= See PRESCRIPTION.

=EXCI'TANTS.= See STIMULANTS.

=EXCORIA'TIONS.= _Syn._ _Sprays_, CHAFINGS.

In _surgery_ and _pathology_, superficial injuries or affections of the skin, consisting of the removal of the scarf-skin or cuticle, accompanied with more or less irritation and slight inflammations. When arising from rough friction or attrition, they are more commonly called abrasions. Young children are very apt to be chafed under the arms, behind the ears, between the thighs, and in the wrinkles and folds of the skin generally, unless great attention is paid to cleanliness, and wiping the skin perfectly dry after washing them. Whenever there is a tendency to excoriations of this kind, either in adults or children, a little finely powdered starch, or violet powder, applied by means of a puff, or a small bag of muslin, once or twice a day, will generally remove them, and prevent their occurrence in future. Mild unguents, as cold cream, or spermaceti cerate or ointment, may also be used with advantage. The preference should, however, be given to the remedies first named, from their not soiling the linen. See ABRASION.

=EXCRETA.= The excrementitious matter evacuated from the bowels varies of course in composition and quantity according to the food from which it is derived.

Berzelius found a sample analysed by himself to yield about seventy-five per cent. of water, the remainder being made up of alimentary waste, and biliary matter. A large amount of phosphates of calcium and magnesium was found in the ash remaining after the incineration of the solid matter. A specimen of fæcal matter examined by Playfair yielded 15 per cent. of nitrogen and 45 per cent. of carbon. Marcet states that he has obtained from excrement a crystallisable body possessing an alkaline reaction; to which he gives the name _excretin_; also a fatty substance, which he terms _excretolic acid_. To excretin he assigns the formula C_{7}_{8}H_{1}_{5}_{6}SO_{2}; the composition of the acid has not been determined.

Hinterberger has succeeded in getting excretine (excretin), free from sulphur, and gives as its simplest formula C_{2}_{0}H_{3}_{6}O; which shows a close resemblance to cholesterin, C_{2}_{6}H_{4}_{4}O.

But cholesterin is less easily dissolved in vinegar than excretin, and the solution deposits crystals which, when viewed by the microscope, are found to be beautiful silky six-sided prisms, while the excretin solution yields round masses.

Treated with bromine, excretin gave a crystalline body having the formula C_{2}_{0}H_{3}_{4}Br_{2}O; but the author did not succeed in preparing a chlorinated compound of excretin.

In the excreta of carnivorous animals no excretin has been discovered, although a substance resembling it has been found. Cholesterin has been obtained from the fæces of the crocodile, but no urates; whilst the excreta of the boa contain urates, but are destitute of cholesterin.

The fæces of animals that live on vegetables contain neither excretin, butyric acid, nor cholesterin.

The excreta of birds and serpents, which mixed with the secretion from the kidneys, are discharged from the animals by the cavities, are very similar to urine, and consist chiefly of alkaline urates and earthy phosphates.

The excrements of insects consist mainly of the remnants of the tissues, animal or vegetable which they have swallowed as food, mixed with constituents of the urine, provided the insect has no special urinary organs.

Briéger examined the fæces of healthy persons, and of convalescents, and found in addition to acetic, butyric, and isobutyric acids, small quantities of phenol and indol, and a new crystallisable body, which he terms _skatol_ (_skatos_, fæces). It crystallises in irregular-dentate shining plates, resembling indol, which by frequent recrystallisation from hot water, can be obtained snow white. Skatol forms the chief constituent of the volatile aromatic components of human fæces. Fæces of dogs (whether fed on meat or bread diet) contained no skatol, but indol, and in addition a yellow oil, with a revolting and peculiarly irritating smell.

Briéger has not yet been able to analyse this yellow oil, although it forms the chief volatile constituent of dogs' fæces. He has repeatedly obtained it from distillation from human pathological fluids. In the pancreas after putrefaction, and in the fæces of typhus patients, no skatol was found. The author considers skatol identical with the substance which Secretan obtained by the decomposition of egg albumen under water for six months.

Skatol injected under the skin of rabbits, passes out in the urine as a substance yielding colouring matter. Skatol is believed by the author to be the substance in human urine which, according to Jaffé, yields a red or violet colour on the addition of hydrochloric acid and chloride of lime.

Phenol, the author finds, is a constant component of human fæces. The above results show that specific products of decomposition are normal components of intestinal digestion.[288]

[Footnote 288: 'Deut. Chem. Ges. Berg.,' x, 1027-1031.]

Liebig calculated that the daily average amount of fæcal matter passed by a man is 5-1/2 oz; Lawes says that it averages in healthy male adults, 4·2 oz; Parkes estimates it (in Europe) at 4 oz. on the average; Letheby at 2·784, and Frankland at 3 oz. In India, a native on the average excretes as much as 12 oz., this increase over the above quantities being due to the large proportion of rice and farinaceous food of which the Hindoos' diet consists.

The daily average amount of urine excreted by a human being has been given by Lawes at 46 oz.; Parkes places it at 50 oz. by measure for each male adult; Letheby at 31·851, and Frankland at nearly 40 oz. by measure. According to Parkes' figures a population of a thousand persons, would thus void daily 156 lbs. of solids, and 260 gallons of urine; or 25 tons of fæces, and 91,250 gallons of urine per annum; whilst according to Letheby, from the same number of people, the daily discharge would be 2266 lbs. avoirdupois of urine and 177·5 lbs. of fæces.