SILICIC AND BORACIC ETHER.

227

Ethyl. Sp. gr. of liquid o'933; of vapour 7'32; Rel. wt. 104; Boiling pt. 330° (165°5 C.)—When absolute alcohol is gradually added to silicic tetrachloride, a powerful reaction occurs; hydrochloric acid is evolved in abundance, and a colourless liquid is obtained, which, when submitted to distillation, at first evolves hydrochloric acid, but the boiling point rises rapidly until it reaches 330°, at which temperature pure tetrethyl silicate distils over. It is a limpid liquid, of a pleasant ethereal odour, and a hot taste resembling that of pepper. It is combustible, and burns with a flame of dazzling whiteness, depositing pulverulent silica. The molecular volume of this body affords a good illustration of the tetrad character of silicon. This ether is not miscible with water, but is decomposed by it with the separation of gelatinous silicic hydrate. If this decomposition be allowed to take place slowly, by placing an imperfectly closed vessel containing the ether in a moist atmosphere, the silica is gradually deposited in the form of a hard transparent solid, resembling quartz in appearance.

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Silicic Ether or Diethyl Silicate [(Є2H,),SiÐ ̧]?—A second ether, containing only half the quantity of oxide of ethyl that is present in the foregoing compound, may be procured by acting upon alcohol of sp. gr. o'838 with silicic tetrachloride, and distilling; tetrethyl silicate is formed at the same time, and the first portions of the distillate consist entirely of this compound; but by degrees the boiling point becomes higher, and when it reaches 660° (349° C.) the diethyl silicate passes over. The tetrethyl silicate is in fact transformed into the diethyl silicate by the action of the water present in the dilute alcohol, whilst alcohol is set free:

Tetrethyl silicate.

Diethyl silicate.

Alcohol.

(CH,) ᎦᎥᎾ + H Ꮎ = (€ H.) ᎦᎥᎾ + 2 € Ꮋ ᎻᎾ.

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If more water be added, a viscous compound is obtained, which, according to Ebelmen, contains a third ether, with twice as much silica as the foregoing one.

(1155) Triethyl Borate [(E,H),B,], or Tribasic Boracic Ether. Sp. gr. of liquid 0·8849; of vapour 5'31; Rel. wt. 73; Boiling pt. 246° (119° C.).—This ether is obtained by the action of boric trichloride upon anhydrous alcohol; it is immediately decomposed by water. Boracic acid is readily soluble in anhydrous alcohol with evolution of heat. Ebelmen considers that under these circumstances a second ether is formed, which when pure is solid at ordinary temperatures. It softens at about 100° F., and can

228

FORMIC AND ACETIC ETHER.

be drawn out into long threads. Its composition is not certainly known, but it has been represented as [2(¤‚H.),0,2B,→] analogous to ordinary borax.

(1156) Ethyl Formiate or Formic Ether (¤‚Í ̧¤нÐ ̧). Sp. gr. of liquid 0915 at 64°; of vapour 2'573; Rel. wt. 37 ; Boiling pt. 127°3 (53° C.).—This ether is readily obtained by distilling 7 parts of dry sodic formiate with 10 of oil of vitriol, and 9 of alcohol of sp. gr. 0825. Wöhler prepares it from a mixture of 10 parts of starch, with 37 of finely powdered binoxide of manganese, and 15 parts of alcohol, 15 of water, and 30 of oil of vitriol the whole is distilled by a gentle heat in a capacious retort. The formic acid generated by the oxidation of the starch, reacts upon the alcohol at the moment of its formation. Formic ether does not mix with the water which accompanies it; and is purified by washing with water, and rectification from chloride of calcium. Formic ether is also a secondary product of the reaction of nitric acid upon alcohol. When pure it is colourless, and has an agreeable odour and taste, recalling that of peach kernels. If left in contact with water, it becomes readily resolved into formic acid and alcohol.

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(1157) Ethyl Acetate, (E,H,E,H ̧), or Acetic Ether (CH ̧O, CH2O). Sp. gr. of liquid 089; of vapour 3·067; Rel. wt. 44; Boiling pt. 165° (74° C.).—Acetic acid, if repeatedly distilled with alcohol, gives rise to the formation of acetic ether, but the effect is much hastened by the addition of sulphuric acid to the liquid. A mixture of 6 parts of alcohol, 4 of glacial acetic acid, and I part of oil of vitriol, yields the ether with facility. When a volume of liquid equal to that of the alcohol employed has come over, the process is stopped; the distillate is washed twice with its own bulk of water, and rectified from chloride of calcium. Sodic acetate or acetate of lead may be substituted for acetic acid in the foregoing process, but then a larger quantity of oil of vitriol is needed. If 6 parts of alcohol be employed, 100 of sodic acetate and 15 of oil of vitriol may be used; or 24 parts of acetate of lead (dried) and 9 of oil of vitriol.

Acetic ether has a burning taste and an agrecable odour, remotely resembling that of apples; a small quantity of it appears to be contained in several varieties of wine. Water dissolves about one-seventh of its bulk of it. Acetic ether is a good solvent for the essential oils, for the resins, and for pyroxylin. A mixture of this ether with an alcoholic solution of caustic potash, is immediately decomposed into potassic acetate and alcohol. Acetic ether dissolves calcic chloride readily, and forms

BUTYRIC, ENANTHIC, AND OXALIC ETHER.

229

with it a crystallizable compound, which yields the ether unchanged on the application of heat.

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(1158) Ethyl Butyrate, (Є,H,,H,0), or Butyric Ether. Sp. gr. of liquid 09041; of vapour 4'04; Rel. wt. 58; Boiling pt. 239° (115° C.).—This ether may be formed with great facility. If a mixture of 2 parts of alcohol and 2 of butyric acid be agitated with 1 part of oil of vitriol, which may even be diluted with an equal bulk of water, the liquid, on standing, separates into two layers, the upper of which is butyric ether. It is nearly insoluble in water, and when diluted with alcohol, has the odour of pine-apple, constituting, indeed, what is sold as pine-apple oil. It appears to be present in old rum, and is used for heightening the flavour of this spirit. The melon and strawberry are supposed to owe a portion of their flavour to the presence of this compound. In order to purify the ether, it must be agitated with water, and rectified after standing upon chloride of calcium.

(1159) Enanthic Ether (probably a mixture of rutic and caprylic ethers). Sp. gr. of liquid 0872; of vapour 7·042 (Delffs). -This ether is a fragrant liquid of a stupefying, extremely powerful odour, which is the cause of the peculiar smell that characterizes grape wine, and which adheres so tenaciously to vessels in which wine has been kept; hence its name, from owoc, wine. When large quantities of wine, or the lees of wine, are distilled, this ether passes over, mixed with free rutic and caprylic acids (Fischer, Lieb. Ann. cxviii. 307), in the form of an oily layer; the crude product is gently heated with a solution of sodic carbonate, which removes the free acid, whilst the ether floats as an oily layer upon the surface. It boils at from 435°2, to 446° and emits a very dense and highly inflammable vapour. The quantity of this ether appears to increase with the age of the wine. (1160) Diethyl Oxalate [(2H),,], or Oxalic Ether (2 CH ̧O,CO). Sp. gr. of liquid 10929; of vapour 5·087; Rel. wt. 73; Boiling pt. 363°2 (184° C.).-This is one of the most interesting of the numerous ethers which are formed with the organic acids. It is obtained by distilling rapidly a mixture of 4 parts of alcohol (sp. gr. o'825), 5 of oil of vitriol, and 4 of hydro-potassic oxalate (HKE,Ð ̧‚Í‚Ð). The distillate should be washed with water, and rectified from litharge to keep back any traces of free oxalic acid. Oxalic ether is heavier than water. It is colourless, and has an agreeable ethereal odour and taste. If pure it may be kept unchanged in contact with water, but if it retain any acid it is slowly decomposed into oxalic acid and alcohol; an excess of caustic potash

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230

OXALIC AND CARBONIC ETHER.

decomposes it with rapidity into normal potassic oxalate and alcohol; but if the quantity of potash be small, alcohol and potassic ethyloxalate (oxalovinate) are formed; the reaction in the first case being:

When an aqueous or an alcoholic solution of ammonia is added to oxalic ether, a somewhat analogous decomposition is effected, an excess of ammonia giving rise to the formation of oxamide and alcohol. Indeed, this reaction furnishes one of the best methods of procuring oxamide :—

:

If the ether be in excess, the decomposition is different; alcohol, and a substance soluble in alcohol but insoluble in water, crystallizing in beautiful pearly tables, is formed: this body was originally termed oxamethane, but it is now admitted to be oxamic ether, or the ether of amidated oxalic acid (1356) :

:

If equal parts of potassic ethyloxalate and potassic methylsulphate be thoroughly dried, then mixed, and submitted to distillation, a curious double ether (methyl-ethyl oxalate, EH, €,H,,,,) is obtained. It forms a yellowish oil, heavier than water, of sp. gr. 1127, boiling at about 329° (165° C.) and emitting a vapour of sp. gr. 4'67.

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(1161) Carbonic Ether, or Diethyl Carbonate [(Є2H;),¤¤ ̧]. Sp. gr. 0975; of vapour 409; Rel. wt. 59; Boiling pt. 257° (125° C.).—This ether cannot be obtained by the ordinary mode of preparing these compounds. It may be formed by heating carbonate of silver with ethyl iodide in a closed tube; but it is generally procured by heating sodium or potassium with oxalic ether, in which case carbonic oxide is disengaged abundantly, whilst carbonic ether distils over, and oxalate of the alkali remains in the retort. This reaction does not admit of a simple expression by an equation. Carbonic ether is a very mobile

URETHANE-CHLOROCARBONIC ETHER-CITRIC ETHER.

231

liquid, of a sweet aromatic odour; it is not very inflammable ; but it is readily decomposed by an alcoholic solution of potash. When heated in a sealed tube with an alcoholic solution of ammonia, alcohol, and carbamic ether (urethane) are formed; and if the temperature be raised to about 356° (180° C.), the excess of ammonia slowly converts the carbonic ether into alcohol and urea, or carbamide (Natanson); both decompositions being analogous to those which oxalic ether undergoes with greater facility by the same reagents:

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Urethane or Carbamic Ether (E,H,,H,NEO,). Sp. gr. of vapour 314; Rel. wt. 44'5; Boiling pt. 356° (180°C.).—This is a substance which resembles spermaceti in appearance; it evinces a remarkable disposition to crystallize, and forms large transparent leaflets, which are fusible below 212°, and very soluble in alcohol and ether. If distilled in a moist state it gives off large quantities of

ammonia.

(1162) Chlorocarbonic Ether (Є,H,,ЄCIO). Sp. gr. of liquid 1133; of vapour 3.823; Rel.wt. 542; Boiling pt. 201° ·2 (94°C.).This compound is obtained by absorbing phosgene gas (388) with absolute alcohol, and rectifying the product from powdered litharge and chloride of calcium. It is a colourless, very limpid liquid, which emits a suffocating odour, and irritates the eyes powerfully. Its vapour burns with a green flame. It is not soluble in cold water, but is decomposed by boiling water. Gerhardt represents this compound as an oxychloride, which bears the same relation to ethylcarbonic acid that benzoic oxychloride (chloride of benzoyl) does to benzoic acid :

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(1163) A tribasic Citric Ether [(¤‚μ¿)‚¤ ̧н¡Ð,], Triethyl Citrate, may be obtained by saturating an alcoholic solution of