232 REPORTS ON THE STATE OF SCIENCE. 



indications that the rotatory power varied fairly regularly in a series, 



thus : — 



Series I. [o]d 



Mon-arabinan-tri-galactan-geddic acid + 37° 



Ui- ,, ,1 t, J, ,, 1 • t . . + 4o 



Iri' )} >> }, )} ,, t , - . . . + 4y 



ietra- „ ,, ,, ,, ,,.,...+ 59 



Series II. 



Tri-arabinan-tetragalactan-geddic acid + 80° 



Pent- „ „ „ „ + 90° 



Hept- „ „ „ , +100° 



Non- „ „ „ , +110° 



Series III, 



Tri-galactan-geddic acid + 20° 



Tetra- „ „ +22° 



Penta- „ „ -, +30° 



The principal constants in identifying a gum acid are its ultimate 

 composition, its neutralising power for bases, and its rotatory power for 

 polarised light. As such acids do not crystallise, fractional precipitation 

 must be resorted to iu order to prove their individuality. Determinations 

 of the amount of mucic acid they yield, and also of the amount of furfural, 

 are helpful. In separating the nucleus acid, and in preparing inter- 

 mediate acicis lying between the natural gum acid and the nucleus, 

 hydrolyses of varying intensity must be used, followed by precipitation 

 with alcohol and purification by means of dialysis. Sometimes it is more 

 convenient to precipitate as barium salts instead of as the free acids. 



There is no doubt that in future work on the gums the methods 

 adopted by O'Sullivan should be followed, and that a determination not 

 only of the sugars they yield should be made, but also of the nature 

 of the nucleus acid. In fact, a great deal of investigation is required 

 to bring our knowledge of other gums up to the level of O'Sullivan's 

 discoveries in the case of gum arable, Geddah gum, and tragacanth. 



References. 

 Chevreul . , . . ' Nouvelles Annales du Mnseam d'Histoire Naturelle,' 



18H3, 2, 126. 

 Fr6my .... ' Comptes Rendus,' 1860, 50, 124. 

 Gay-Lussac and Th^nard . ' Annales de Chimie,' 1810, 74, 47. 

 Guurin .... ' Annales de Cbimie et de Physique,' 1832, 49, 248. 

 John ' Schweigger's ' Journal fiir Chemie und Physik,' 1812, 



6, 374. 

 Neubauer .... 'Journal fur Praktische Chemie,' 1854, 62, 193; 



Liebig's ' Annalen der Chemie,' 1857, 102, 105. 

 O'Sullivan .... 'Journal Chemical Society,' 1884,45, 41 ; 1890. 57, 59 ; 



1891, 69, 1029; 1901, 79, 1164. 'Proceedings 



Chemical Society,' 1889, 6, 166; 1891, 7, 131; 



1901. 17, 156. 

 Pelletier .... 'Bulletin de Pharmacia,' 1811, 3, 556. 

 Reichardt . . . . ' Liehig's Annalen der Chemie und Pliarmacie,' 1863, 



127, 297. 

 Scheibler .... ' Berichted. Deutschen ChemischenGesellschaft,' 1868, 



1, 58 and 108 ; 1873, 6, 614. 

 Vauquelin .... 'Bulletin de Pharmacie,' 181J, 3, 49. 



Fiirmation of Oum in the Plant. — Lutz, ' fitude des Gommea. Th^se presentee 

 A, rficole Superieure de Pharmacie de Paris,' 1894-95 ; Greig Smith, ' Journal Society 

 pf Chemical Industry,' 1904, 23, 105 and 972. 



