This section is from the book "A Text-Book Of Pharmacology, Therapeutics And Materia Medica", by T. Lauder Brunton. Also available from Amazon: A text-book of pharmacology, therapeutics and materia medica.
Extracted from jalap by rectified spirit.
Characters and Solubility. - In dark-brown opaque fragments, translucent at the edges, brittle, breaking with a resinous fracture, readily reduced to a pale brown powder, sweetish in odour, acrid in the throat, easily soluble in rectified spirit, but only partially so in ether, and insoluble in oil of turpentine.
Composition. - The resin consists of convolvulin in combination with another resinous substance (gammaresin), which is the part dissolved by ether. The convolvulin of jalap differs from the jalapin of scammony in being insoluble in ether.
Pilula Seammonii Composita (vide p. 523).
Action and Uses. - Jalap is a 3hydragogue purgative, used for constipation, dropsy due to renal disease, and cerebral affections. It is best given with acid tartrate of potassium, as in Pulv. Jalapae Co. Like scammony, it is dissolved by the bile, and appears to require it in order to act. It has no action when injected subcutaneously, nor when injected into the veins. It has no irritant action when locally applied to the skin or mucous membranes of the eye or nose, nor has it any diuretic action, or any action on the nervous system.