210 VEGETABLE MUCILAGE. 



extraction has been complete, the amount of albumen, etc., in the 

 •washings must be the same as that in 35 cc. of the first filtrate 

 (which may be calculated from the first estimation) ; but should 

 the washings contain more than the corresponding quantity of 

 filtrate, the excess must be added to the total of the analysis. 



§ 195; Characters of SoluUe Mucilage. — Apart from their being 

 dissolved by' water and precipitated by alcohol from aqueous 

 solution, vegetable gum, arabin, arabic or gummic acid,, is also 

 charaeterlzed by -being converted into glucose when boiled Mdth ^ 

 dilute acid. It must, however, be observed, that the various 

 arabic acids, according to their origin, yield glucoses differing to a 

 certain extent from one another, some being more powerfidly 

 dextro-, others Isevo-rotatory ; some crystallizing with facility, 

 others again not at all, or only with difficulty, or passing first 

 through an intermediate stage as dextrin (according to Kirchner 

 with simultaneous production of cellulose). By means of these 

 properties, vegetable mucilages of particular origin can sometimes 

 be Accurately described. Some years ago it was shown by 

 Scheibleri that the arabic acid of beet-root yielded, on inversion, 

 a considerable quantity 'of dextro-rotatory arabinose, which 

 crystallizes with such facility that it was at first thought to be 

 mannite. 



Kiliani has recently asserted the identity of arabinose with 

 lactose. Many varieties of gum arabic also b^bave like arg^bic 

 add, whilst some which are not otherwise distinguishable from 

 good gum, differ in yielding isevo-rotatory non-crystallizable 

 glucose. In addition to these, B6champ^ has recently discovered 

 a ' gupimicose ' which appears to be allied to galactose (§ 205). I 

 am almost inclined to think that a minute investigation of these 

 properties might enable us to distinguish between the various 

 forms of vegetable mucilage soluble in water. ^ 



The examination of the oxidatiorirprodiiets obtained by the 



> Eer. d. d. ehem. Ges. yi. 6X2, 1873; Joum. f. pract. Chem. ciji. 458, 

 1868 (Joum. Oliem. Soo. Xxvi. 1124). See also Neubauer, Jahresb. f.Pharm, 

 6, 1854, and Graeger, ibid. 218, 1872. 



" Compare Bechamp, Joura. de Pharjn. et de Chim. xxvii. 51, 1878. 



3 In general it may be said that the action of dilute acids must be continued 

 for a longer time to convert vegetable mucilage (arabin) into glucose tha/a is 

 necessarj' for dextrin, triticin, etc. But it must be left for further experi- 

 ments to show to what extent tie amount of glucose produced may be taken 

 as an indioaiion of the quantity of arabin originally pissent. 



