The dispensatory of the United States of America / by Geo. B. Wood and Franklin Bache.

Date:
1883
Catalogue details

Licence: Public Domain Mark

Credit: The dispensatory of the United States of America / by Geo. B. Wood and Franklin Bache. Source: Wellcome Collection.

Provider: This material has been provided by the Gerstein Science Information Centre at the University of Toronto, through the Medical Heritage Library. The original may be consulted at the Gerstein Science Information Centre, University of Toronto.

    28/1944 page 16
    Kiliani has recently shown (Ber. Chem. Ges., 1880, p. 2304, and 1882, p. 34) that arabinose, the sugar obtained from arable acid by the prolonged action of dilute sulphuric acid, is identical with lactose obtained from milk sugar. Like lactose, it yields mucic acid on oxidation, and reduces Fehling's solution even in the cold. The optical properties of arabinose and lactose are also identical. Kiliani also found that while considerable differences exist in the amount of mucic acid (and corre- spondingly of lactose) formed, yet all of a number of specimens of the gum yielded the same product, the percentage numbers ranging from fourteen to thirty-eight. Gum arable undergoes no change by age, when kept in a dry place. Its concen- trated aqueous solution remains for a considerable time unaltered, but ultimately becomes sour, from the production of acetic acid. The disposition to sour is in- creased by employing hot water in making the solution. The tendency of a weak solution to become mouldy is said to be obviated by adding a few drops of sul- phuric acid, and decanting from the sulphate of calcium deposited. (A. J. P., 1872, p. 353.) SoWtion of gum arable does not ferment upon the addition of yeast, saliva, or gastric juice ; the addition of chalk and cheese, however, starts a fermentation which gives rise to lactic acid and alcohol, but not to mannite or glycerin. The addition of a solution of gum to an acidified albumen solution causes a precipitate, which disappears on further addition of gum, but the solution will then curdle and become flocculent on application of heat. Gum may be distinguished from dextrin by the following tests: 1. Gum contains no dextro-glucose, which, how- ever, is present in dextrin, and may be recognized by the copper test.* 2. Gum contains a lime compound; hence its solution is rendered milky by oxalic acid, while a solution of dextrin remains almost clear. 3. Gum gives a shiny, yellow deposit when its solution is mixed with a neutral ferric salt. (Hager, Chem. Central., 1873, pp. 408 and 584.) The properties above enumerated belong to gum arable generally. There are, however, pharmaceutic varieties with differences which deserve notice. 1. Gum that is transparent and readily soluble. This constitutes by far the greater portion of the commercial varieties distinguished by the names of Turkey and Senegal gum. It is characterized by its transparency, ready solubility, and the comparatively slight degree of thickness and viscidity of its solution. Under this head may be included the gomme blanche fendi.llee of Guibourt. It is distinguished by the whiteness and deficient transparency of the pieces, attributable to the minute cracks or fissures with which they abound, and which render them very brittle and easily pulverizable. This peculiar structure is generally ascribed to the influence of solar heat and light; but is conjectured by Hayne to arise from the exudation of the juice in the frothy state noticed by Ehrenberg. Though the unbroken pieces are somewhat opaque, each minute fragment is perfectly transparent and homogeneous. This variety, in consequence of its prompt and entire solubility, is usually preferred for medical use, and for most purposes in pharmacy. 2. Gum less transparent and less soluble. Guibourt has proposed for portions of this gum the name o^ gomme pelliculee, from the circumstance that the masses are always apparently covered, on some part of their surface, by a yellowish opaque pellicle. Other portions of it have a mammil- lary appearance on the surface. It is less transparent than the former variety, is less free]y and completely dissolved by water, and forms a more viscid solution. It melts with difficulty in the mouth, and adheres tenaciously to the teeth. It is found in all the commercial varieties of gum, but least in that from Egypt. Its peculiari- ties have been ascribed to variable proportions of bassorin or cerasin associated with the soluble arabin. Between these two varieties of gum there are insensible grada- tions, so that it is not always easy to classify specimens.f Impurities and Adulterations. In parcels of gum arable there are sometimes pieces of a dark color, opaque, and incorporated with ligneous, earthy, or other im- * Fehling's Solution. 40 Gra. of crj'stallized cupriu sulph.ate dissolved in 200 C.c. of water; 160 Gm. of neutral potassium tartrate and 130 Gm. of fused sodium hydrate dissolved in 600 C.c. of water: mix the two solutions, dilute to 1 litre, and boil for some minutes. + A very handsome white gum was noticed in the market during 1876, which had the property of makin a glairy solution with water. On allowing the mixture to stand for some days at a temperature of 95° C. (203° F.) it resumed its ordinary condition.
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