TRANSACTIONS OF THE SECTIONS. 63 



On Vanadium, illustrated by Preparations of its Compounds. 

 By Prof. H. E. Roscoe, F.B.S. 



On the Chemical Composition of Cotton. By E, Schtinck, Ph.D., F.R.S. 



It is generally supposed that cotton, wlien quite pure, consists entirely of woody 

 fibre or cellulose, and that its composition is conseq[uently represented by the for- 

 mula 0(2, Hjo, OxQ. It is certain, howerer, that in the raw state, as furnished by 

 commerce, it contains a number of other ingredients, some of which occur so coni 

 stantly that they must be considered essential constituents of cotton, viewed as a 

 vegetable product. The object of the bleaching process, to which most cotton 

 fabrics are subjected, is to deprive the fibre of these other ingredients, and leave the 

 cellulose behind in a state of pmity. Notwithstanding the importance of an accu- 

 rate knowledge of every thing relating to cotton from an industrial point of view, 

 the substances contained in it along with cellulose have never been subjected to a 



?)ecial chemical examination, and, consequently, very little is known about them, 

 he object which the author had in view in undertaking his investigation was to 

 endeavour to throw a little more light on the nature of these substances. All 

 foreign and extraneous matter inti'oduced during the process of manufacture was 

 left entirely out of consideration. The author fm-ther confined his attention to those 

 constituents of the fibre which are insoluble iu water, but soluble in alkaline lye, 

 and are consequently precipitated by acid from the alkaline solution. 



The material employed by the author was cotton yarn, which he preferred to 

 unspun cotton for several reasons, the principal being that yarn is comparatively 

 free from mechanical impurities (such as fragments of seed-vessels, &c.), while, oil 

 the other hand, if proper care be taken, no impurity is added dm-ing the process of 

 spinning to those previously existing. The yarn was boiled in an ordinary bleacher's 

 keii- for several hours, with a dilute solution of soda-ash. The resulting dark- 

 brown liquor, after the yam had been taken out, drained, and slightly washed, was 

 removed from the. keir into appropriate vessels, and mixed with an excess of suU 

 phuric acid, which produced a copious light-brown flocculent precipitate, while the 

 liquid became colourless. This precipitate was allowed to settle, the liquid was 

 poured off; and after being washed with cold water to remove the sulphate of soda 

 and excess of acid, it was put on calico strainers and allowed to drain. A thick 

 pulp was thus obtained, which, when dried, assumed the appearance of a brown, 

 brittle, horn-like substance translucent at the edges. In one experiment 450 lbs. of 

 yam, made from East-Indian cotton, of the variety called "DhoUerah," yielded 

 0-33 per cent, of the dried precipitate. In another experiment, made with 500 lbs. 

 of yarn spun from American cotton, of the kind called in commerce " middling 

 Orleans," 0-48 per cent, was obtained. The total loss sustained by yam during the 

 bleaching process amounts to about 5 per cent, of its weight. Only'a small portion, 

 therefore, of the matter lost is recovered by precipitation of the alkaline extract with 

 acid. This precipitate formed more especially the subject of the author's investi- 

 gation. It was found to consist almost entirely of organic substances ; and of these 

 the following were distinctly recognized : — 



1. A species of vegetable wax, to which the name of "cotton wax" may be 



given, 



2. A fatty acid, identical with margaric acid. 

 3 and 4. Brown resinous colouring-matters. 



5. Pectic acid. 



6. A trace of albuminous matter. 



The author described the method employed by him for separating these sub- 

 stances from one another, and obtaining them in a state of purity ; and he then gave 

 an account of their properties and composition. 



On the Phenomena of the Crystallization of a Double Salt. 

 By J, Bekgeb Spence. 



