PECTINE. 129 



and M. Pelouze has even maintained that themannite thus prepared 

 is a product of fermentation.* 



Mai nite crystallizes in very white semi-transparent needles ; it 

 has a slightly sweet taste, and is soluble in water. According to 

 Liebig and Opperman it contains : 



Carbon 39.6 



Hydrogen 7.7 



Oxygen ■ ■•52.7 



100.0 



Liquorice. This substance, which is obtained from the root of 

 the Glycirrhiza glabra., is too well known to require particular con- 

 sideration ; it is soluble both in water and in alcohol. 



GUM. 



Gum is a substance very extensively diffused in the vegetable 

 kingdom ; there is, perhaps, no plant which does not contain some. 

 Gum is divided into two kinds ; gum, properly so called, the type 

 of which we have in gum-arabic, and vegetable mucilage, such as 

 we meet in gum-tragacanth. 



Gum in dissolving in water produces a thick and adhesive fluid. 

 It is insoluble in alcohol. Some plants contain such a quantity that 

 upon infusion they seem to give, as it were, nothing else : such are 

 the althea, the jnalva officinalis, &c. 



Gum does not crystallize, it is met with in concrete masses which 

 result from the solidification of the drops which flow spontaneously 

 from the trees that yield it : by long boiling with dilute sulphuric 

 acid it is changed into glucose. Nitric acid alters it, and several 

 new products are the result, among the number of which is mucic 

 acid. Gum-arabic, according to the analysis of M. Gay-Lussac and 

 Thenard, consists of : 



Carbon 42.3 



Hydrogen 6.9 



Oxygen • 50.8 



100.0 



To obtain vegetable mucilage, a quantity of linseed is treated with 

 water and expressed. It is also obtained by steeping gum traga- 

 canth in about 1000 parts of water and pouring off the solution which 

 covers the mucilaginous mass. The mucilage then forms a jelly 

 more or less consistent, which diluted with a large quantity of water 

 forms a ropy viscid fluid. Dried again, this mucilage becomes hard 

 and translucid ; in water it regains its former state. f 



VEGETABLE JELLY — PECTINE AND PECTIC ACID. 



It is well known that the juice of all fruits contains a gelatinous 

 substance to which many of them owe the property of forming jellies. 



* Annales de Chimie, voL xlvii. p. 419, 2d series.— The refuse wash of the distiller, 

 appreciated by the taste, appears to contain a considerable quantity cf saccharine 

 matter, which is probably mannite. — Eng. Ed. 



tBerzelins. Cheniistry, vol. v. 



