60 Royal Society : — 



Braconnot, of course, did not subject this substance to analysis, but 

 he described its appearance and properties in an exceedingly accu- 

 rate manner*. The observations of Braconnot had fallen into such 

 entire oblivion, however, that for many years past, we find in most 

 of the larger systems of chemistry the term datiscine used as syno- 

 nymous with inuline. 7'hus in Brande's ' Chemistry,* vol. ii. 

 p. 1168, we find it stated that a vanety of names had been given to 

 inuline, such as " dahline, datiscine," &c. 



The bruised roots were extracted in a Mohr's apparatus by long- 

 continued digestion with wood-spirit. The liquor obtained, which 

 had a dark brown colour, was concentrated by distilling off a por- 

 tion of the wood-spirit. The brown syrupy liquid remaining in the 

 retort, on being poured into open vessels and standing for some 

 time, deposited a resinous matter containing merely traces of a cry- 

 stalline substance. When this syrupy liquid, however, was treated 

 with about half its bulk of hot water, the greater portion of the 

 brown resin was rapidly deposited, and the mother-liquor having 

 been poured off and left to spontaneous evaporation, deposited a 

 considerable quantity of an imperfectly crystallizable substance 

 resembling grape-sugar. These crystals are datiscine containing a 

 considerable amount of resinous matter. The datiscine, however, 

 is rendered perfectly pure by treatment with a solution of gelatine, 

 to remove any trace of tannic acid, and repeated crystallizations out 

 of weak spirits of wine. 



Properties of Datiscine. — Datiscine, when pure, is perfectly 

 colourless. It is very soluble in alcohol, even in the cold, boiling 

 alcohol dissolving any amount of it. By slow spontaneous evapora- 

 tion, its alcoholic solutions yield small silky needles arranged in 

 groups. Cold water does not dissolve much of it, but it is tolerably 

 soluble in boiling water, the hot solutions on cooling depositing it 

 in shining scales. 



Datiscine is not very soluble in ether ; but an ethereal solution, 

 when evaporated, yielded larger crystals than were obtained by any 

 other method. On adding water to an alcoholic solution of datis- 

 cine, no precipitate is immediately obtained, unless the solution is 

 greatly concentrated ; but on standing, very pure, pale yellow- 

 coloured crystals of datiscine separate. 



When datiscine is heated to about 180° C, it melts, and if the 

 heat be increased, it burns, evolving an odour of caramel, and leaves 

 a voluminous charcoal. If datiscine be heated in a close vessel 

 while a stream of dry air is slowly passed over it, a small quantity 

 of a crystalline substance sublimes. Datiscine and its solutions have 

 a very bitter taste ; and though it does not produce any change on 

 test-paper, I think there is reason to regard it as a feebly acid body. 



It dissolves in solutions of the fixed alkalies and ammonia, also in 

 lime- and baryta-water. The addition of an acid to these solutions 

 causes the precipitation of the datiscine. 



The aqueous solution of datiscine is precipitated by neutral and 

 basic acetates of lead, and chloride of tin. These precipitates have 

 * Annales de Cliimie et de Physique, 1816, iii. 277. 



