76 HISTORY OF GEINE. 



apply the name ulmin, it is to the mucilage of elm. 

 As this has been the source of no small confusion, 

 an account of it may be here introduced. Elm 

 bark is treated with alcohol. The tincture is evap- 

 orated dry, and the extract treated with water, which 

 dissolves a brown extractive matter, leaves an insol- 

 uble residue, which, being treated with ether, leaves 

 a small quantity of a brownish matter, analogous to 

 the extractive of chemists, or the brown apotheme of 

 Berzelius. The sap of elm contains acetate and- 

 carbonate of potash. Here, then, are all the ele- 

 ments of elm gum, as examined by Vauquelin, 

 Klaproth, Smithson, Thomson. Not only the elm, but 

 other trees, under diseased action, exude these matters, 

 and under the influence of air, and the potash, the 

 diseased exudation from the elm bark, is changed to 

 true ulmic acid, which unites with the potash, and 

 both with the mucilage. The mucilage, may, by 

 processes, not here necessary to be detailed, be pro- 

 cured pure, as a hard, opaque, colorless, insipid, and 

 inodorous gum. It moistens easily, swells in water, 

 becoming a semi-transparent mucilage. It is insol- 

 uble in alkali, affords no ammonia by dry distillation. 

 Boiled with alkaline ley, it affords a clear mucilagi- 

 nous liquor, which browns by being exposed to air. 

 If this ley or solution is exactly neutralized by acetic 



