La gomma ammoniaco è il succo che scola dal Dorema ammoniacum e da varie specie di ferule. Dorema – forse dal greco δώρημα = dono – è un genere di piante della famiglia Ombrellifere, con 4 specie: sono grandi erbe perenni simili alle ferule, che vivono nelle regioni subdesertiche della Persia. Esse forniscono - soprattutto il Dorema ammoniacum - la gommoresina detta appunto gomma ammoniaco.
Ammoniacum, or gum ammoniac, is a gum-resin exuded from the stem of a perennial herb (Dorema ammoniacum), natural order Umbelliferae. The plant grows to the height of 8 or 9 ft., and its whole stem is pervaded with a milky juice, which oozes out on an incision being made at any part. This juice quickly hardens into round tears, forming the "tear ammoniacum" of commerce.
"Lump ammoniacum," the other form in which the substance is met with, consists of aggregations of tears, frequently incorporating fragments of the plant itself, as well as other foreign bodies.
Ammoniacum has a faintly fetid, unpleasant odor, which becomes more distinct on heating; externally it possesses a reddish-yellow appearance, and when the tears or lumps are freshly fractured they exhibit a waxy luster.
It is chiefly collected in central Persia, and comes to the European market by way of Bombay. Ammoniacum is closely related to asafoetida and galbanum (from which, however, it differs in yielding no umbelliferone) both in regard to the plant which yields it and its therapeutical effects. Internally it is used in conjunction with squills (Urginea maritima) in bronchial affections; and in asthma and chronic colds it is found useful, but it has no advantages over a number of other substances of more constant and active properties (Sir Thomas Fraser). Only the "tear ammoniacum" is official. African ammoniacum is the product of a plant said to be Ferula tingitana, which grows in North Africa; it is a dark colored gum-resin, possessed of a very weak odor and a persistent acrid taste.
Description: Natural Order, Umbelliferae. A native of Persia, India, and other Oriental countries. It is a biennial, attaining the height of six or seven feet, and abounding in a somewhat milky juice. This juice is gathered in the spring time, from incisions made in the roots, after the manner of asafoetida. It is a gum resin, and comes to market in the form of tears consolidated into rough masses; yellowish without, whitish within, compact and brittle. At a moderate heat, it softens without melting; and will burn with a white flame and much smoke. It is partly soluble in water, with which it forms a milky emulsion; and acts as other resins with alcohol.
Properties and Uses: Stimulant, with moderate relaxing powers, rather diffusive in its action, chiefly influencing the mucous membranes. It should not be used in any case where inflammation is present, but is suited to relaxed and atonic conditions. It is employed in old coughs with pulmonic debility and excessive mucous secretion; and sometimes in leucorrhea, and amenorrhea under similar circumstances. It has been found of use in asthmatic and catarrhal affections under the same conditions. It gently promotes the flow of urine; and a warm preparation will act moderately upon the skin. It is not an agent to be relied upon largely; but makes an excellent adjunct to stronger and less diffusive articles. From ten to twenty grains may be given at a dose, three times a day; and though it may be used as a pill, the form of emulsion is better. The emulsion is formed by triturating two drachms of the gum with half a pint of water; and one to two tablespoonfuls of this may be given as a dose.