One molecule of sulphuric acid or 98 parts is mixed with one molecule of alcohol or 46 parts, or with 1 molecule of alcohol of 90 per cent. which contains 85.75 per cent. of absolute alcohol, hence with 53.6 parts of alcohol, and distilled with 1 molecule or 82 parts of anhydrous sodium acetate. Since commercial sulphuric acid always contains 5 or 6 per cent. of water, this has to be taken into consideration, and 105 to 106 parts of it have to be used in order to decompose the entire quantity of sodium acetate. The crude sodium acetate found in commerce may be used. It is nearly white and at the utmost contaminated by traces of sulphuric acid and chlorine, which in this case are not injurious. The crystallized salt is heated in an iron kettle whereby it melts in its water of crystallization. With constant stirring the water is then completely evaporated until an entirely dry mass of salt remains behind. The latter may be quite strongly heated without fear of destroying the acetic acid. The dried salt is immediately powdered, passed through a medium fine sieve and kept for use in well-closed vessels.
On a large scale the distillation of the ether may be effected in an iron kettle, which is provided with a well-fitting lid and connected by a copper head with a cooling apparatus—a worm lying in cold water. Bring into the kettle the required quantity of concentrated sulphuric acid, add, with vigorous stirring, the alcohol and allow the mixture to rest for 24 hours. Then throw the dry sodium acetate into the mixture, mix it thoroughly, by stirring, with the ethyl sulphuric acid, and, after luting all the joints of the apparatus, heat at first moderately. Distillation proceeds quietly and uniformly, the fire being regulated according to how the ether runs off from the worm. Such uniform distillation is, however, only attained by the use of the sodium acetate in the form of powder, and thoroughly mixing it with the acid. If large pieces of the salt are present or the powdered salt balls together, the formation of ether sometimes takes place so suddenly that the vapors cannot condense in the cooling apparatus, but escape violently, or if they cannot escape rapidly from the condenser, may even burst the apparatus. The reason for this is that the larger pieces float in the superheated acid without being saturated by it, and, when they suddenly collapse, form a mass of ether-vapors.
Distillation is continued until that which at last passes over is not inflammable. With the above-mentioned proportions 88 parts of acetic ether are formed, but as some water always passes over, distillation need not be interrupted until the receiver contains at least 90 parts of crude ether.
The crude ether always contains more or less water, some alcohol, and a small quantity of free acetic acid. With the above-mentioned proportions, the content of alcohol can, however, be only very small. To neutralize the acetic acid, add some burnt magnesia or shake with carbonate of soda solution until the acid reaction disappears. For the absorption of the water and alcohol, add as much sharply dried (not fused) calcium chloride as the fluid will dissolve, and then let it stand with an excess of the salt for one day. The calcium chloride combines with the water and alcohol and separates as a heavy layer beneath the ether. The latter is decanted off and brought into a rectifying vessel—a copper still, heated by steam, and provided with a cooling pipe. The ether is distilled off at a moderate heat, the last portion, about 1/10, being caught in a special receiver, to be again rectified at the next operation.
According to Grossschopf, 40 lbs. of pulverized anhydrous sodium acetate, together with a cooled mixture of 46 lbs. of concentrated sulphuric acid and 37 lbs. of 95 per cent. alcohol, free from fusel oil, are distilled in a copper still heated by steam. Distillation is continued with constant stirring by means of an apparatus in the still, until no more fluid smelling and tasting of acetic ether passes over. The crude distillate, amounting to 55 or 56 lbs., is brought into bottles which are filled ⅔ full. The bottles are then filled up with water and potassium carbonate is added until the fluid, after shaking, shows no acid reaction. The aqueous fluid beneath the ether is then drawn off by means of a siphon, and the ether several times washed by shaking with water and allowing to settle. Since the wash-water absorbs a quite considerable quantity of ether, it is collected and subjected to rectification, whereby an alcoholic acetic ether is obtained. The ether, being freed from acetic acid and alcohol by neutralization and washing, is brought in contact with fused calcium chloride to free it from water, and finally rectified over magnesia. In this manner 36 to 37 lbs. of pure acetic ether are obtained.
Acetic ether is a clear, colorless fluid of a pleasant, etheral odor. It boils at 170.6° F., and at 59° F. its specific gravity is 0.9068. Pure acetic ether dissolves in 11 to 12 parts of water; a content of alcohol or the addition of water increases its solubility. Hence, its solubility in water is a criterion of its purity.
Benzoic ether or ethyl benzoate, C7H5O.OC2H5, is most readily prepared by mixing 4 parts of alcohol, 2 parts of crystallized benzoic acid, and 1 part fuming hydrochloric acid, and for some time heating the mixture in a flask. The benzoic acid is thereby gradually and completely converted into ether. The fluid is mixed with water, whereby the ether is completely separated. It is several times washed with carbonate of soda solution, and, for the purpose of withdrawing the last trace of free acid, distilled over lead oxide. It forms a colorless oil of an aromatic odor, specific gravity 1.0502, and boils at 412° F. In cold water it is insoluble. However, like all varieties of ether, it dissolves readily in alcohol and ether.
Butyric ethyl ether or ethyl butyrate, C4H7O.OC2H5. The preparation of this ether must be preceded by that of butyric acid. The latter is obtained, according to Bensch, by dissolving 6 lbs. of cane sugar and 8 drachms of tartaric acid in 13 quarts of hot water, allowing the liquid to stand a few days and then adding 7 ozs. of old rotten cheese, which has been stirred up in 4 quarts of skimmed sour milk and 3 lbs. of finely pulverized chalk. The mixture must be kept at a uniform temperature of from 86° to 95° F. for some weeks, from time to time mixing it by stirring, and replacing the water lost by evaporation.
By the action of a ferment the sugar is first converted into lactic acid. In 10 to 12 days the entire mass congeals to a paste of calcium lactate. By now allowing fermentation to proceed without interruption, it gradually enters another stage; gas bubbles consisting of carbonic acid and hydrogen rise up, until in the course of 5 or 6 weeks the process is finished. This is recognized by the fluid becoming quiet, no more gas being evolved. The fluid then contains a solution of calcium lactate, which is converted into the corresponding sodium salt by the addition of 8 lbs. of crystallized soda. It is then filtered and concentrated by evaporation to 5 quarts. By adding 5½ lbs. of sulphuric acid, diluted with an equal volume of water, butyric acid is separated as a dark-colored oily mass.
The crude butyric acid thus obtained and freed from water by shaking with calcium chloride, is a mixture of acetic, butyric, and capric acids, but does not contain propionic and valerianic acids. To obtain from it pure butyric acid, fractional distillation is required. For manufacturing on a large scale, a copper distilling apparatus with silver head and silver cooling pipe is used, the bulb of a thermometer being placed in the head. In the first rectification, the receiver is changed after the thermometer has risen to 311° F.; the portion passing over between 311° and 329° F. is caught up by itself, and the receiver being again changed, distillation is continued until finished. The first distillate contains mostly acetic acid, besides a small quantity of butyric acid, the second the greater portion of the butyric acid besides a little acetic and capric acids, while the third consists chiefly of capric acid. For preparing butyric ether for technical purposes, the fraction passing over between 311° and 329° F. is sufficiently pure. To obtain chemically pure butyric acid, the rectification of the portion passing over between 311° and 329° F. is in the same manner repeated, until finally a product with a constant boiling point at 324.2° F. is obtained.