A suitable material for the preparation of butyric ether is also the St. John's bread or carob, the pods of _Silequa dulcis_. Redtenbacher established in them the occurrence of about 2 per cent. butyric acid, which Gruenzweig later on proved to be isobutyric acid. Besides butyric acid and other volatile acids, St. John's bread contains about 40 per cent. of fermentable varieties of sugar, which can be utilized after their conversion to butyric acid. For this purpose Stinde has proposed the following process: Convert the pods together with the seeds to a coarse powder; bring 100 lbs. of this powder into a capacious barrel placed in a warm place, and pour sufficient water of 82.5° F. over it, to form a thin paste; after 4 to 5 days add 24 lbs. of whiting and await fermentation. The paste, which gradually becomes thicker, is from time to time stirred, and, if necessary, a small quantity of lukewarm water added. In summer fermentation is finished in six weeks, after which the preparation of the ether is proceeded with. For this purpose bring the paste into a still provided with a steam jacket; the evening before mix 36 lbs. of concentrated sulphuric acid with 60 lbs. of alcohol of 95 per cent., and add the mixture to the paste in the still; then lute the joints of the distilling apparatus, and quickly introduce steam. Distillation soon commences, and, when once introduced, is continued with a moderate admission of steam. The first pound of the distillate is caught by itself, and, after changing the receiver, distillation is continued until but little passes over, even with an increased admission of steam. Thus an abundant yield of alcoholic butyric ether is obtained. When distillation is finished 20 lbs. more of alcohol may be brought into the still; the distillate obtained thereby being still rich in butyric ether. The St. John's bread used should be of the best quality, free from worms and mould, as otherwise the ether would not possess the pure, agreeable odor characteristic of butyric ether. _Formic ethyl ether_, or _ethyl formate_, CHO.OC_{2}H_{5}.--This ether is also much manufactured for the preparation of the so-called essences which are employed for the purpose of imitating the odor of plants, fruits, etc. It is formed by the action of formic acid upon alcohol, or by bringing ethyl sulphuric acid, or a mixture of alcohol and sulphuric acid, in contact with formates, or finally by bringing formic acid at the moment of its formation in contact with alcohol. The most simple process is that recommended by Lorin:--