104 MR. EDWARD SCHUNCK ON SOME 



substance belonging to the pectine series. I was unable 

 to procure pectine itself, though there can be little doubt 

 that it is pectine which exists originally in the fibre and 

 gives rise to the formation of the pectic and parapectic 

 acids which are contained in the alkaline extract. One 

 of the methods which I employed for preparing this acid, 

 founded on the insolubility of its alkaline compounds or 

 salts in an excess of caustic alkali, was as follows : — 



The precipitate from the alkaline extract of cotton, after 

 exhaustion with boiling alcohol, was, without being pre- 

 viously dried, dissolved in dilute caustic soda-lye. The 

 solution, after being filtered in order to separate the fila- 

 ments of cotton and other impurities which were present, 

 was mixed with alcohol, which produced an abundant 

 light-brown flocculent precipitate, consisting of impure 

 pectate and parapectate of soda. The liquid, which was 

 brown, contained a considerable quantity of colouring- 

 matter, and was filtered. The precipitate, after being 

 washed with alcohol, was again dissolved in water, and to 

 the solution there was added a quantity of strong caustic 

 soda-lye, which produced a precipitate of a much paler 

 colour than that with alcohol, while the liquid retained in 

 solution another portion of colouring-matter. The preci- 

 pitate having been allowed to settle, the liquid was decanted, 

 and the precipitate was stirred up with a fresh quantity of 

 caustic soda-lye, the process being repeated until the 

 supernatant liquid had become colourless. The precipitate 

 was now treated with warm dilute hydrochloric acid, which 

 took up the alkali, leaving a quantity of pale-brown flocks 

 undissolved. These were filtered off and washed for some 

 time with cold water, the latter being exchanged for 

 alcohol as soon as the principal part of the acid and 

 chloride of sodium had been removed, in order to prevent 

 a loss of parapectic acid, which is soluble in pure water, 

 though insoluble in water containing strong acids or salts. 



