undergo any change by keeping. At the temperature of 62° it requires more than seven times its weight of water to dissolve it. Though allowed to remain in contact with water, or dissolved in it, no change takes place, but when left in contact with caustic potash, acetic acid is gradually evolved, which saturates the alkali. If it be distilled in this state, alcohol comes over very much diluted with water. No gaseous matter is disengaged. It was analyzed by Dumas and Boullay in the same way as nitrous and oxalic ethers. They obtained the following con stituents: Sect, IV. 7 atoms hydrogen, to leave no doubt that these atoms represent the true constitution of the ether. But I have shown formerly that acetic acid is a compound of 2 atoms hydrogen, 4 atoms carbon, 3 atoms oxygen. If we subtract these atoms from the numbers in the preceding table, there will remain 5 atoms hydrogen, 4 atoms carbon, 1 atom oxygen. Now, it has been already shown that these are the constituents of sulphuric ether. Thus it appears that acetic ether, like the two preceding, is a compound of an integrant particle of acetic acid and an integrant particle of sulphuric ether. Its atomic weight, therefore, is 10-875. * Ann. de Chim. et de Phys. xxxvii. 27. Chap. III. Let us see how well the specific gravity of its vapour will correspond with this constitution. This was determined by Dumas and Boullay to be 3.067. Now 1 volume sulphuric ether 1 volume acetic acid vapour 2.5694 3.4722 26.0416 History. Preparation, Properties. 3:0208 If we consider it as a compound of 1 volume of sulphuric ether and 1 volume of acetic acid vapour united together without any diminution of volume, the specific gravity will be 3:0208. This comes within one per cent. of the determination of Dumas and Boullay, and may therefore be considered as agreeing with it. There seems therefore no reasonable doubt that the constitution of this ether agrees with that of the two last, namely, that it is a compound of 1 atom acetic acid with 1 atom of sulphuric ether. 9. Benzoic Ether. This ether was discovered by Scheele.* It was afterwards slightly examined by Thenard, and more particularly by Dumas and Boullay.‡ The process of Scheele, as modified by Thenard, is the one which is usually followed. It consists in distilling a mixture of 4 parts of alcohol, 2 parts of benzoic acid, and 1 part of muriatic acid, till half the liquid has passed over. It is then poured back, and the process repeated. This distillation is renewed two or three times. The greatest part of the ether exists in the liquid remaining in the retort. It is separated by means of water, and two or three washings deprive it of the greatest part of its excess of acid. If we boil it on powdered litharge till the boiling point become fixed, and till all the excess of acid which it contains is saturated, and afterwards distil it over with caution, we obtain it in a state of purity. Thus prepared, it is a colourless oily-looking fluid. It has a weak smell, somewhat like that of benzoic acid. Its taste is pungent; its specific gravity at 51° is 1·0539, and its boiling point is 408 as determined by Dumas and Boullay. The specific gravity of its vapour, according to the same chemists, is 5.409. It was subjected to analysis by them in the same way as the three preceding ethers. They obtained the following as its constituents: Sect. IV. Composition. 20.46 atoms carbon, 4 atoms oxygen, But if we were to consider benzoic ether as a compound of 19 atoms carbon, 4 atoms oxygen, 11 atoms hydrogen, then the weight of each of these constituents in 100 parts of the ether would be Now, the deviation of these numbers from those found by experiment, is not greater than frequently occurs in such experiments. The analogy of the three preceding ethers gives so much probability to these numbers, that Dumas and Boullay have adopted them as more accurate than their own. Let us see what the constitution of benzoic ether will be, admitting its atomic constituents to be as above stated. It has been shown in a preceding part of this volume that benzoic acid is a compound of 6 atoms hydrogen, 15 atoms carbon, 3 atoms oxygen. If we subtract these atoms from the preceding table, there will remain 4 atoms carbon, 5 atoms hydrogen, 1 atom oxygen. But these are the constituents of sulphuric ether. It follows, therefore, that benzoic ether, like the three preceding, is a compound of 1 integrant particle of benzoic acid, and 1 integrant particle of sulphuric ether. Its atomic weight then is 19-625. Chap. III. Let us see how the specific gravity of its vapour accords with this view of its composition. It was found to be 5-409. Now 1 volume sulphuric ether 1 volume benzoic acid vapour 2.5694 8.3333 2 10.9027 History. Properties. 5.4513 If we consider it as a compound of 1 volume of sulphuric ether vapour, and 1 volume of benzoic acid vapour, united together without diminution of volume, the specific gravity will be 5.4513. Now this does not differ so much as one per cent. from the experimental result of Dumas and Boullay. This coincidence seems to leave no doubt that the constitution of benzoic ether is really as above determined. 10. Formic Ether. This ether was first formed by Arvidson in 1777, but only in an impure state. Bucholz examined it anew in 1782, and Gehlent prepared it in a state of greater purity, and determined its properties, in 1812. It was obtained by Gehlen by the following process: Equal weights of absolute alcohol and concentrated formic acid were distilled in a retort to dryness. The product was distilled a second time; and the liquid in the receiver being mixed with a weak solution of potash, the formic ether separated, amounting to about four-fifths of the alcohol employed. This ether is a colourless liquid, which has a strong smell of peach kernels, yet Gehlen and Rose could find no trace of hydrocyanic acid in it. Gehlen compares the taste also to that of peach kernels. Its specific gravity, as determined by Gehlen, is 0.9157. It boils when heated to 133°. At the temperature of 73° the elasticity of its vapour is capable of supporting a column of mercury 8.74 inches in height, according to the determination of Dobereiner. It burns with a bluish flame inclining to yellowish white. At the temperature of 55° it requires 9 times its weight of water to dissolve it. It dissolves readily in alcohol, and is separated again by the addition of water. According to Dobereiner, it contains 442 per cent. of formic ether. Though this ether has not yet been subjected to * Crell's Neueste Entdeck, vi. 55. Gilbert's Annalen, Ixxiv. 416. + Schweigger's Jour. iv. 14. analysis, there can be little doubt, from the analogy of the four preceding ethers, that it is a compound of 1 integrant particle of formic acid, and 1 integrant particle of sulphuric ether. 11. Tartaric Ether. Sect. IV. This ether was first prepared by Scheele ;* it was examined History. also by Thenard, but he did not succeed in procuring it in a state of purity.† It was prepared by distilling a mixture of 6 parts of tartaric acid, and 7 parts of absolute alcohol, and 2 parts of sulphuric acid, until ether began to be formed. The process was then stopped: on cooling it assumed the appearance of a thick syrup from which water did not separate any ether. It was then mixed with potash: much bitartrate of potash fell and was separated. The acid was then exactly saturated with potash, and the mixture digested in cold alcohol. The alcoholic liquid being evaporated, a liquid was obtained, which Thenard considered as tartaric ether. It has a brown colour and a syrupy consistence, is slightly Properties. bitter and disagreeable. It has no smell, and contains no excess of acid. It does not precipitate the solution of chloride of calcium, but it precipitates chloride of barium. It dissolves readily both in water and alcohol. 12. Citric Ether. This ether was also first made by Scheele,‡ and since his time has been examined by Thenards alone. It may be prepared by a process similar to that which succeeds with oxalic ether. Its colour is yellowish; it is rather heavier than water, not very volatile, destitute of smell, and has a bitter taste. It is but little soluble in water, but dissolves readily in alcohol. When digested with potash, citric acid is separated from it. 13. Malic Ether. This ether, so far as I know, has been examined only by Thenard. The process is the same as for oxalic ether. It has a yellow colour, is somewhat heavier than water, is not volatile, and is destitute of smell. It is but little soluble in water, but very soluble in alcohol, from which it may be separ * Opuscula, ii. 142. + Mem. d'Arcueil, ii. 13. |