CHEMISTRY. 23 



steadily. The change in the maltose content can be expressed accu- 

 rately only by a complicated equation, and the authors have therefore 

 chosen an approximate formula, which is derived from the exact differ- 

 ential equation: 



at 

 M represents the average maltose content during the period of obser- 

 vation. When Mi and M 2 are the amounts of maltose during the times 

 t\ and U and 1)[ and D 2 the corresponding dextrose contents, c, the 

 reaction constant we obtain: 



M, + M, 

 D 2 — Di = c 2 ^ — Ok— <i) 



or — 



D,— I), ^ 



c 2 . 



(^)( m!+m! ) 



Experiments with hydrochloric acid, sulphuric acid, oxalic acid, and 

 acetic acid, in varying concentration, showed that the constants are sat- 

 isfactory and that, therefore, the reaction follows the law of reactions 

 of the tirst class. — W. n. KRtXx. 



Constitution of the carbohydrates of the straw of cereals, 

 C. F. Cross and C. Smith (Chcm. Xeics, 74 (1896), p. 177). — The furfuroids 

 of the ripe straw have the formula OioH 10 5 . With phenylhydrazin they 

 give the osazones of pentoses, and on heating with hydrogen peroxid 

 generate much carbonic acid. The authors conclude from this that they 



have the structural formula C 5 H 8 3 <( ;>CH 2 . The sugar obtained by 



hydrolysis with acid is partially fermented by yeast in neutral solution, 

 when about 50 per cent of the furfuroid disappears. The stalks of the 

 growing plant contain a different class of furfuroids. The osazones 

 have a high melting point and are probably hexosazones. The furfu- 

 roids obtained by hydrolysis with acids are completely fermented by 

 yeast and give no carbonic acid on heating with hydrogen peroxid. 

 The amount of furfuroids present in the plant changes very little during 

 its life, and the authors conclude from this that the furfuroids are the 

 primary products of assimilation. — w. H. KRUGt. 



Investigations on phosphoric acid, M. Bertiielot and G.Andre 

 (Compt. Bend. Acad. Set. Paris,123 (1896),pp. 773-781; 121 (1897), Wo. 6', 

 pp. 261-269). — The principal feature of the work here reported was the 

 study of methods of distinguishing between the different forms of phos- 

 phoric acid. A colornnetric method for this purpose has been suggested 

 by Sabatier, 1 but it fails to distinguish between orthophosphoric acid 

 and pyrophosphoric acid. The method which the authors used for 

 determining pyrophosphoric acid is based upon the same principle as 

 that described in the American Pharmacopoeia and is briefly as 



•Ann. Chiin. et Phys., ser. 6, 1889, p. 409. 



