§ 213. QUEBCITE, ETC. 225 



Dulcite, or melainpyrite, is isomeric with mannite, and shares 

 most of its important properties. The crystals of the former 

 belong to the monoclinic system, those of the latter to the rhombic. 

 Dulcite dissolves in three parts of cold water, is optically inactive, 

 does not ferment, and melts at 182°. 



Isodulcite (rhamnodulcite) is also isomeric with the foregoing. 

 Crystals of isodulcite melt at 93° to 94°, dissolve in 2*09 parts of 

 water at 18°, and also in aljsolute alcohol. It is not fermentable, 

 but reduces Fehling's solution, and is dextro-rotatory, (a)y=:8-4°. 



Hesperidin-stigar and sorbite are also said to be isomeric with 

 mannite. The former crystallizes in the monoclinic system, is 

 dextro-rotatory, sparingly soluble in hot absolute alcohol, but 

 more easily in hot 70 per cent, spirit. It melts at 70"5° to 76°, 

 and slowly reduces Fehling. Anhydrous sorbite melts at about 

 110°, and does not reduce Fehling. ^ 



§ 213. Quercite, etc. — Quercite and pinite are isomeric Avith 

 mannitan and dulcitan and are sweet to the taste. 



Quercite crystallizes in the monoclinic system, dissolves in 8 to 

 10 parts of cold water, is dextro-rotatory ( + 33 '5°), and melts 

 at 235°. 



Pinite is indistinctly crystalline, freely soluble in cold water, 

 and somewhat soluble in dilute spirit ; it melts at 150°, and has 

 a dextro-rotatory power of 58-6°. 



Ahietite differs from the foregoing in containing the elements 

 of a molecule of water less ; it has been the subject of commu- 

 nications by Eochleder. - 



ACIDS. 



§214. Detection of Acids. — In addition to the reaction of malic 

 acid mentioned in § 81, Barfoed^ describes another depending upon 

 the conversion of the acid, at a temperature of 160° to 170°, into 

 maleic and fumaric acids, with production of a crystalline sublimate. 

 A third is the lime-reaction ; malate of lime requires the addition 

 of at least 1 to 2 volumes of spirit for precipitation ; and when thus 



^ Compare Boussingault, Journ. de Pharm, et de Chim. xvi. 36, 1872 

 (Pharm. Journ. Trans. [3], iii. 28). 



-Journ. f. pract. Cham. cv. 63, and Apoth.-Ver. viii. 363, 1868. For 

 catharto-mannite, see Kubli and Dragendorff, Pharm. Zeitschr. f. Russland, 

 iv. 467, 1865, and Keussler, ibid. xvii. 363, 1878. For bergenite, see Morelle, 

 Chem. Centralblatt, 758, 1881 (Comptes rendus, xciii. 646). 



ä Zeitschr. f. anal. Chem. vii. 403, 1868. 



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