116 



crystalline appearance under the microscope, easily friable, in- 

 odorous, of an acrid bitter taste. At 140° it turns gi'ey, at 150° 

 brown, at 194° it fuses, and becomes carbonised with more heat. 

 It dissolves slightly in water, at 17° in 1300 parts alcohol of 45%, 

 and in 12 pai-ts alcohol of 90%, in hot alcohol and in ether almost 

 in eveiy jjroportion. The solutions have an acid reaction. It is 

 also rather soluble in hydrated alkalies. Chloride of iron forms 

 in the aqueous as well as in the alcoholic solution a strong brown, 

 acetate of lead a grey-yellow precipitate. Concentrated sulphuric 

 acid dissolves Koussin with yellow-brown colour; the solution, at 

 first clear, becomes spontaneously turbid after a few minutes, and 

 throws down white flocks. 



Labdanum = Ladanum. 



Laburilill. Alkaloid of the unmatiired seeds of Cytisus La- 

 burnum. It is obtained from the aqueous extract, which has been 

 purified by subacetate of lead, by precipitating with phospho- 

 molybdic acid and boiling the deposit, after mixing with chalk and 

 diying, with alcohol. The base is afterwards purified by isolating 

 it from the platinum salt. It does not combine with acids, and 

 forms large concretions of crystals, consisting of klinorhombic 

 prisms containing water of crystallisation; dissolves most readily 

 in water, difficultly in absolute alcohol, scarcely in ether, and 

 evolves with caustic potash ammonia even when cold. 



Lactic Acid = Cc H5 O5 -f HO. As this acid is easily formed 

 during the spontaneous decomposition or fermentation of vegetable 

 extracts, its presmice in the living plants must be traced with great 

 caution; especially it must be ascertained, if no kind of fermenta- 

 tion takes place while the analysis is cari'ied on. However, 

 Lactic acid is no uncommon ingredient of plants, and I, for my 

 part, have encoimtered it not rarely in the examination of the 

 constituents of plants, though it may often have been overlooked 

 on account of its not being endowed with any striking properties, 

 and because it yields no preci[)itate with metallic salts. The 

 Lactates of the alkalies being very deliquescent, it is probable that 

 the hygi'oscopicity of vegetable extracts is not occasioned by 

 malates, as generally assumed, but by alkaline Lactates. The 

 presence of Lactic acid is ascertained by the following process : — 

 Free the aqueous liquid from all precipitable matters by means of 

 acetate and subacetate of lead, remove excess of lead by carbonate 

 of ammonia, evaporate to a liquid of syrup consist^Micy, add a 

 concentrated solution of acetate or chloride of zinc, and leave the 

 mixture to stand cold for several days. In the presence of Lactic 

 acid crystalline crusts will be formed of Lactate of zinc, slowly 

 soluble only in 50 parts cold water. This salt has the formula Zii 

 O + L + 3 HO (in 100: 27-13 Zn O, 54-69 l and 18-18 HO); 

 it loses at 100° all its water and contains then 66-83% acid. From 



