Preparation.—Balsam of tolu, ten grammes (10 Gm.) [154 grs.]; precipitated calcium phosphate, fifty grammes (50 Gm.) [1 oz. av., 334 grs.]; sugar, eight hundred and fifty grammes (850 Gm.) [1 lb. av., 13 ozs., 430 grs.]; alcohol, fifty cubic centimeters (50 Cc.) [1 fl℥, 332♏]; water, a sufficient quantity to make one thousand cubic centimeters (1000 Cc.) [33 fl℥, 391♏]. Dissolve the balsam of tolu in the alcohol, in a small flask or bottle, with the aid of a gentle heat. Mix the precipitated calcium phosphate with one hundred and fifty grammes (150 Gm.) [5 ozs. av., 127 grs.] of the sugar, in a mortar, thoroughly incorporate with it the solution of the balsam, and set the mortar aside, in a moderately warm place, until the alcohol has evaporated. Then triturate the residue well with five hundred cubic centimeters (500 Cc.) [16 fl℥, 435♏] of water, gradually added, and filter the mixture through a wetted filter, returning the first portions of the filtrate until it runs through clear. To the filtrate, heated to a temperature of about 60° C. (140° F.), add the remainder of the sugar, and dissolve it by agitation. Then allow the syrup to cool, strain it, and pass enough water through the filter and strainer to make the product measure one thousand cubic centimeters (1000 Cc.) [33 fl℥, 391♏]. Mix thoroughly. Syrup of tolu may also be made in the following manner: Prepare a percolator or funnel in the manner described under syrup (see Syrupus). Pour the filtrate obtained as directed in the preceding formula upon the sugar, return the first portions of the percolate, until it runs through clear, and, when all the liquid has passed, follow it by water, until the product measures one thousand cubic centimeters (1000 Cc.) [33 fl℥, 391♏]. Mix thoroughly"—(U. S. P.).
Or, take of balsam of tolu, carbonate of magnesium, each, 1/2 ounce; alcohol, 1 fluid ounce; refined sugar, 2 1/2 pounds; water, a sufficient quantity. Triturate the balsam of tolu and carbonate of magnesium together, with 1 ounce of the sugar, gradually adding the alcohol, and then water enough to make the whole measure 12 fluid ounces. Filter, add water enough to make 1 pint of filtrate, to which add the rest of the sugar, and dissolve by a very gentle heat. If required, strain the syrup, while hot, through a damp cotton-flannel bag (Prof. Procter). This forms a beautiful, clear syrup, free from turbidity, possessing a decided taste of the balsam, with most of its medicinal virtues.
A more decided flavor and fragrance would be insured if the alcohol were not driven off as directed in the official process. In that case the amount of sugar should be correspondingly decreased. The alcohol would better impart the properties of tolu to the syrup than water, which takes up but very little of the resin, oils, etc., upon which the drug depends for its aroma and flavor.
Action, Medical Uses, and Dosage.—This syrup is used in coughs, and to give a pleasant taste to medicines. The dose is from 1/2 fluid drachm to 2, or even 4 fluid drachms.
King's American Dispensatory, 1898, was written by Harvey Wickes Felter, M.D., and John Uri Lloyd, Phr. M., Ph. D.