MANNA. 287 



copper and fermentation- tests of sugar, but is not sugar. 

 Haemoglobinuria after large doses has been already referred to. 



Oleic Acid, HC^H^O., (Not Officinal) One of 

 the constituent acids of oil obtained by the action of 

 superheated steam. 



Characters. A yellowish oily liquid, odourless, tasteless, 

 neutral in reaction. Sp. gr., -800 to -810. Insoluble in water ; 

 soluble in alcohol, chloroform, benzol, benzin, turpentine, and 

 fixed oils. It dissolves most metallic oxides, forming inde- 

 finite solutions of oleates in excess of oleic acid. 



Non-officinal Preparations of Oleic Acid. 

 Oleate of Mercury ; Oleate of Lead ; Oleate of Zinc ; and 

 various ointments and plasters. 



ACTION AND USES. 



Oleic acid is much more readily absorbed by the skin than 

 the fixed oils from which it is derived, and preparations made 

 with it as the solvent or basis have a high penetrating power. 

 The oleate of mercury is now extensively employed. 



Manna- MANNA. A concrete saccharine exu- 

 dation from the stem of Fraxinus Ornus. and F. 

 rotimdifolia. Obtained by making incisions in the 

 stems of the trees, which are cultivated for the pur- 

 pose, chiefly in Calabria and Sicily. 



Characters. In stalactiform pieces from one to six inches 

 in length, and one or two inches in width, uneven, porous, and 

 friable, curved on one side, of a yellowish- white colour, with a 

 faintly nauseous odour, and a sweetish taste. 



Composition. Manna consists principally of about 70 per 

 cent, of mannite, C 3 H 7 O 3 , common sugar, and extractive matter. 

 Mannite does not undergo vinous fermentation. 



Dose. 60 gr. to 1 oz. 



ACTION AND USES. 



Manna is a mild laxative, commonly given to children for 

 constipation, because not unpleasant and easily dissolved in 

 milk. 



