§160 GLUCOSIDAL NATUBE OF TANNINS 153 



splitting up under the influence of dilute acids into glucose and 

 some second substance, but of a numboc it must be denied that 

 they, possess any such gjucosidal, characters. 



§ J 60. (r/Mcos«rfaZ Ma/M««.— In. enumerating the charactwe of a 

 newly idiscovered tannic apid, it is, therefore, important to state 

 whether it has been found to be a ghitoside or not.<§ 61), Th^ 

 esfaininatiqn may be made, by heating weighed quantities ef the 

 tannin with 1 to 2 percent, aqueous hydrochloric aeid in sealed 

 tubes toIOO" for several hours, allowing them to stand for'sDme 

 time after being opeined, in order to observe whether any spaij 

 ingly sohtble decomposition-produet separates Qutin the cold. Tf 

 this is the case, the substance m3,y be filtered, off, but at the same 

 Ane it is ■advisa;ble to ascertain whether any portion that may 

 remain in solution cannot be removed by shaking with ether, 

 acetic ether or chloroform. After warming to expej dissolved 

 traces of those liquids, the solution may be examined for glucosa 

 ^ 61^ 83, et seq. 200, et seq.). 



The decomposition-products that are thus obtained, together 

 with glucose, are sometimes aryUoili'n&, as, for instance, gallic 

 aeid, from the tanniii of galls, suiaach, myrohalans, divi<livi 

 (cf.- § 151), and the yellow ellagic acid from the tannic acid 

 of thp Jximegranate and ■ bablali fnuts. But they are genarally 

 amorphous, difficultly soluble in pure or aeidiiied water and in 

 pure ether.; soluble in water containing ammonia, a»d fmelj; 

 soluble in spirit; they are, as a rule, deep in colour, arid agree in 

 all essential properties with the ^phlobaphenes mentioned in ^ 48 

 and 108. Some are stt sparingly soTuble that they may be of Use 

 in the quantitative estimation of the. respective tannins. Thi.«i 

 is especially the case if, after the. action of the acid, the. liquid is 

 svapqrated to dryness and treated with water, when they often 

 remain behind almost entirely insolublie.- 



Substances of fhis'description are yielded by the decomposition 

 of the tannic acid of oak, willoiv, elm, fir, bii-ch, and acacia barki 

 as well as by that from rhubarb, male-fefli, l«dum,' wine, and by 

 Inany others., Chemically the pMobaphenes approach many resina, 

 with which they share the solnbility in alcohdl and sti^t solubility 

 in water, differing frdm them in.their solubility in dilute ammonia, 

 but resembling thean again in the siibstancas they yield when 

 fused with ari alkali.. (CI § 42.) Lignin and snberin ftlao appear 

 to be connected- with the phlobaphenes. 



