CONSTITUENTS OF COTTON-FIBRE. Ill 



was exceedingly small. It amounted to about i per cent, 

 of the weight of the brown precipitate thrown down by acid 

 from the alkaline extract. It is by no means certain,, how- 

 ever^ that this was the total quantity contained in the 

 cotton. 



Fatty Acid. 



This substance when prepared in the manner above de- 

 scribed has the appearance of a white mass consisting of 

 microscopic needles arranged in spheres. It fuses at 

 55°'5 C. and solidifies again at 50°*5 C. When heated on 

 platinum it melts and then burns with a highly luminous 

 flame. Heated in a tube it is volatilized, leaving hardly 

 any residue and furnishing an oily sublimate which soon 

 becomes solid. It dissolves readily in alcohol and ether. 

 The alcoholic solution reddens litmus-paper slightly. It 

 dissolves in warm caustic potash and soda-lye. as well as in 

 liquid ammonia; and the solutions froth on being boiled. 

 The solution in potash yields, on cooling and standing, a 

 quantity of crystalline needles, while the solution in soda 

 gives immediately a thick soap which fills the whole liquid. 

 The solution in ammonia deposits on cooling shining crys- 

 talline scales. The compound with soda is obtained in a 

 state of purity by adding carbonate of soda to the alcoholic 

 solution of the acid, evaporating to dryness, treating the 

 residue with boiling absolute alcohol, filtering and evapo- 

 rating. When this compound is dissolved in boiling water, 

 and the solution is allowed to cool, it is deposited again as 

 a gelatinous mass, which when examined under the micro- 

 scope is found to consist of small needles, arranged in star- 

 shaped or fan-shaped masses. The watery solution gives 

 with the chlorides of barium and calcium white flocculent 

 precipitates, with acetate of lead an abundant white pre- 

 cipitate, and with nitrate of silver a white flocculent pre- 

 cipitate which becomes only slightly discoloured on expo- 



