83 



Cellulose, thus purijSecl, is white, of loose texture, without 

 taste, becomes carbonised by heat without fusing, and burns 

 •completely away (leaving nothing or only traces of ash), is not 

 affected by ether, alcohol, water, diluted acids, alkalies or solution 

 of chloride of lime ; but dissolves even at ordinary temperature in 

 the blue ammoniacal solution of sulphate of copper, and acquires, 

 Avhen kept in a cold concentrated solution of chloride of zinc, the 

 property of turning blue -with iodine, also to dissolve in it, when 

 warmed, under conversion into sugar, which latter, however, is 

 destroyed by the continued application of heat. 



Filicic Aci(l=C26 Hu Os+HO. Found in the rhizoma of 

 Aspidium Filix mas. Exhaust with ether (free from alcohol), 

 evaporate to an oily consistence, leave to stand cold for a few days, 

 collect on a filter the acid, which will have separated in yellow 

 crusts, wash with small quantities of a mixture of equal volumes of 

 absolute alcohol and ether, afterwai-ds with a mixture of two 

 volumes of alcohol and one volume of ether, until the remnant 

 becomes of a pale lemon-yellow, and recrystallise in hot ether. — 

 Small, green-yellow, rhombic laminae or loose, light-yellow, crys- 

 talline powder of faint odour, and slightly nauseous taste ; liecomes 

 electric by rubbing; fuses at 161°, and decomposes afterwards; 

 has an acid reaction when dissolved in ether; is insoluble in 

 water, slightly soluble in aqueous, better in boiling absolute 

 alcohol, little in cold, better in hot ether, readily in sulj^hide of 

 carbon, fixed and volatile oils. Yields with alkalies salts, which 

 dissolve in water, with other bases insoluble compounds. 



Filixoleic Acid. In the rhizoma of Aspidium Filix mas; is 

 ■scarcely different from oleic acid. 



Fla vequisetill. Yellow pigment, found in Equisetum fluviatile, 

 is only known in the impure state. 



Formic Acid = Co HO3 + HO. As yet it has been found 

 only in a few plants, viz., in the leaves, bark and wood of the 

 Coniferse, in the fiiiits of Sapindus Saponaria, Tamarindus Indica, 

 the leaves of Urtica urens, Sempervivum tectorum ; but exists, in 

 all likelihood, in many other plants. As it is a volatile acid (it has 

 an acrid, pungent odour, similar to acetic acid), it must be first and 

 best looked for in the water which has been distilled fi-oni the 

 respective plants. Saturate this distillate Avith a little excess of 

 carbonate of soda, evaporate to a small bulk, neutralise carefully 

 with nitric acid, add nitrate of silver and heat; if the liquid 

 becomes grey from reduced silver Formic acid was present. 



The whole of the Formic acid is obtained by distilling the 

 respective substance with water containing phosphoric acid. (See 

 No. IX., Division III., Part II.) 



g2 



