208 CYANOGEN COMPOUNDS. 



and potassium salts of gummic acid. The latter is 

 obtained from this pure, by precipitating its solution, 

 containing hydrochloric acid, with alcohol. A white, 

 amorphous, easily soluble mass separates, which is 

 vitreous after being dried at 100 ; has the composition 

 Q6JJ10Q5 + JH 2 0, and does not lose its water under 120- 

 130. 



A solution of gum rotates the plane of polarization 

 to the left. When boiled for a long time with dilute sul- 

 phuric acid, it is converted into sugar (grape-sugar?). 

 Nitric acid oxidizes it, forming mucic, saccharic, tar- 

 taric, and oxalic acids. 



19. Vegetable Mucus (Bassoriri), C 6 H 10 5 . Is very 

 widely distributed in the vegetable kingdom, as a solid 

 mass deposited on the cell-walls, or in a condition simi- 

 lar to solution as a glairy mass. The following sub- 

 stances are richly supplied with vegetable mucus: 

 Tragacanth (the spontaneously exuded sap of Astragalus 

 varieties) ; gum of Bassora, cherry-tree gum, plum-tree 

 gum, salep (from different Orchis varieties), caragheen 

 moss ; further, linseed, Semen psyllii, quince seeds, the 

 root of Althcea officinalis, and Symphytum officinale, etc. 

 Colorless or yellowish, translucent thick mass, inodorous 

 and tasteless. Swells up with w T ater, forming an 

 exceedingly voluminous mucus, without dissolving. 

 Yields, with nitric acid, the same products as gum. 



NINTH GROUP. 



CYANOGEN COMPOUNDS. 



Cyanogen. 



C 2 N 2 



Formation. Cyanogen compounds are produced from 

 carbon and nitrogen, which unite at a high temperature 

 in the presence of metals ; by the distillation of a great 



