158 TANNINS. 



Kaabe found 33-4 per cent, of oxide of lead in the lead-salt, and 

 16-64 of oxide of copper in the copper-salt, i 



Morintannic acid, which occurs together with mmin and maclwrin 

 in fustic, also yields phloroglucin and protocatechuic acid by- 

 fusion with potash. Boiling water extracts morin from the. 

 wood in the form of a calcium-compound, which is sparingly 

 soluble in cold water, and is deposited, therefore, from the de- 

 coction on cooling. Alcohol acidified with sulphuric acid decom- 

 poses the compound, dissolving the morin ; the latter crystallizes 

 from alcoholic solution in yellow needles, , which are sparingly 

 soluble in cold, but more freely in boiling water. With acetate 

 of lead the boiling alcoholic solution gives an orange-red precipitate 

 containing 5 8 -4 per cent, of oxide of lead. 



According to Loewe, an aqueous solution yields both nrnin- 

 iannic acid and maclurm to acetic ether. By dissolving the 

 evaporation-residue in cold water and adding chloride of sodium 

 an amorphous precipitate of the former is obtained, whilst the 

 latter crystallizes out on standing. Maclurin is insoluble in a 

 mixture of equal volumes of water and saturated solution of salt/ 

 whereas morintannic acid is dissolved. Morintannate of lead 

 contains 64 '23 per cent, of oxide of lead. No accurate method, 

 of estimation is known. 



The doubt that has recently been thrown upon the glucosidal 

 nature of rhatania-tannic acid renders it very desirable that kino-, 

 tormentil- and bistort-tannic acids should be examined afresh.^ 

 These tannins yield similar products when fused with potash. > 

 Kino-tannic acid is characterized by the disposition its alcoholic' 

 solution shows to gelatinize. According to Giinther both kino- 

 and tormentil-tannic acids can be estimated by gelatine-solution 

 (see above, and also § 52, xii.), 1 cc. of which indicates O'OISO 

 gram kino, and 0'0168 gram tormentil-tannic acid. 



For ellago-tannic^cid see below. 



The tannin of the horse-chestnut,^ which is likewise non-glucosidal, 



^ Possibly there is another copper-salt conta.ining 22 to 23 per cent. CuO ; 

 that would, at least, appear probable from some experiments of Gttnther. 



^ For the tannin of kino see Eisfeldt, Annal. d. Chem. imd Pharm. xoii. 

 101, 1854 ; for its crystalline decompoaition-product, kinoin, see Etti, Ber. d. 

 d. chem. Gea. xi. 1879 (.lourn. Chem. Soc. xxxvi. 159). Tormentil-tannic 

 acid is discussed by Bembold, Annal. d. Chem. und Pharm. cxIt. 5, 1S68 

 (Amer. Journ. Pharra. xl. 311). 



' Compare Chem. Centralblatt, x. 318 ; xii. 513. 



