ERYTHORE′TIN. Syn. Red resin of rhubarb. A yellow or reddish-yellow substance, forming one of the three resins found by Schlösberger and Dœpping in rhubarb. It is very soluble in alcohol; less so in ether; with ammonia and potassa it forms soluble compounds of a rich purple colour. See Rhubarb.
ERYTH′RIC ACID. Prep. The lichen Roccella tinctoria (Canary or herb-archil) is boiled with milk of lime, and the filtered solution precipitated with hydrochloric acid; the dried precipitate is dissolved in warm alcohol, and filtered; as the solution cools, crystals of erythric acid are deposited.
Prep., &c. Feebly acid; colourless; inodorous; scarcely soluble in water; soluble in alcohol and ether; chloride of lime turns its solutions of a blood-red colour.
ERYTH′RINE, Amarythrine, Erythriline, Pseudo-erythrine, and Telerythrine. Substances obtained by Kane and Heeren from Roccella tinctoria, Parmelia roccella, Leconara Tartarea, &c. They are of little practical importance.
ESCHAROT′ICS. Syn. Escharotica, L. Substances that destroy the texture of living organic bodies, with the production of an ‘eschar’ or ‘scab.’ Escharotics have been divided into two classes—mechanical and chemical. Among the former are actual cauteries, as a heated iron, moxas, &c.; among the latter are all those substances commonly known as caustics. Some writers have subdivided chemical escharotics into ERODING ESCHAROTICS, as blue vitriol, red precipitate, burnt alum, &c.; and into CAUSTIC ESCHAROTICS, as lunar caustic, pure potassa, strong sulphuric acid, nitric acid, &c.; but these distinctions possess little practical value. “In cauterising with a heated iron, this should be at a white heat, as, at this temperature, it occasions less pain to the patient, from its causing an immediate death of the parts to which it is applied.” “The surrounding surface should be protected by some non-conductor of heat, but not by wet paper or cloth, as the sudden extrication of steam will produce a blistered surface around the burn, and will much increase the pain.” (Dr R. E. Griffith.) See Caustic, Solution, &c.
ES′CULENTS. Substances used for food. The more important esculents are noticed under their respective heads.
ESCU′LIC ACID. A peculiar acid found by M. Bussy in the bark of the horse-chestnut. It is but little known, and has not been applied to any use.
ESERINE. Powder of Calabar bean, 100 parts; tartaric acid, 1 part; potassium bicarbonate in powder, q. s.; alcohol (90°) q. s.; rectified and washed ether q. s. Exhaust the bean mixed with tartaric acid by several digestions in alcohol at the heat of a water-bath, alcohol equal to about three times the weight of the powder being used for each maceration. Distil the combined liquors and filter; heat the residue in a water-bath exposed to the air until it contains no more alcohol. After cooling suspend the extract in a small quantity of distilled water, and filter through paper to separate the insoluble resin.
Agitate the filtrate with rectified and washed ether, until the ether is no longer sensibly coloured; two or three treatments are usually sufficient. Treat the aqueous liquor which contains the eserine in the state of acid tartrate, with a slight excess of potassium bicarbonate, until the reaction is alkaline. Shake this liquor several times with ether, which removes the liberated eserine, and deposits it upon evaporation. The product is purified by fresh crystallisations from ether.
Pure eserine is colourless or slightly rose coloured; it crystallises in thin laminæ having a rhomboid form. Most frequently it occurs in commerce under the form of yellowish spangles, or amorphous masses more or less coloured by the action of the air.