AGRICULTURAL CHEMISTRY AGROTECHNY. 113 



hydroxid." From the results "it is clear that there is present in the asbestos, 

 as an impurity, some easily decomposable silicate which is gradually dis- 

 solved away by the strongly alkaline Fehliug solution." " Weighing the re- 

 duced copper as cuprous oxid is likely to give rise to large error [if used for sub- 

 stances like plant extracts], and a process of weighing as cupric oxid, with 

 certain precautions, is recommended." 



For heating the saccharin solution and Fehling's solution u special form of 

 bath was devised which is illustrated. 



The results of an extended study of the Ling-Rendle-Jones and Bertrand 

 methods show tliat the methods are at best approximate, but preference is to 

 be given to the former. For inverting cane sugar in the estimation of sugars 

 in plant substances it was found advisable to use either invertase or a weak 

 acid such as citric or oxalic. " In dealing with plant extracts [clarified with 

 basic lead acetate], owing to the accumulation of sodium acetate in tlie 

 solutions analyzed, inversion by citric acid of lower concentration than 10 per 

 cent is generally incomplete. Inversion by invertase is, however, not inter- 

 fered with by this salt. To estimate cane sugar inversion both by invertase 

 and 10 per cent citric acid is recommended. No loss of sugars occurs owing to 

 the use of basic lead acetate as has been sometimes stated; the supposed loss 

 is probably due to incomplete inversion caused by the presence of sodium acetate. 

 It is shown by a detailed study of the action of dilute hydrochloric acid on 

 different sugars that it is impossible to completely hydrolyze maltose at either 

 70 or 100° C. without simultaneously destroying large quantities of levulose 

 or dextrose." Minute details of the invertase method are given. 



While it has been frequently proposed to estimate maltose by hydrolysis 

 with dilute hydrochloric or sulphuric acid at 100°, noting the change of cupric 

 reduction power or specific rotation after allowing for the inversion of cane 

 sugar present, the method often, when carefully regulated, will give only 

 approximate results. It is inapplicable in all cases where cane sugar and 

 levulose, or pentoses, are present in solutions prepared from plant extracts. 

 Under the conditions recommended by Brown and Morris the levulose is de- 

 stroyed very early in the process. " With both cane sugar and levulose a con- 

 siderable decomposition was made evident by the production of much brown, 

 humus-like material." " The only available method for the accurate estimation 

 of maltose consists in the employment of special maltase-free yeasts, such as 

 Saccliaromyces cxiguus, S. marxianiis, or 8. anomalus, introducing a correc- 

 tion (for pentoses, etc.) obtained by a special fermentation with baker's or 

 brewer's yeast. 



"A scheme for the quantitative estimation of sugars in plant material is 

 given." 



An easily conductible procedure for the quantitative determination of 

 pentoses in the presence of other sugars with the aid of the spectroscope, 

 E. PiNOFF and K. Gude {Chem. Ztg.. 37 (1913). No. 61, p. 621).— The pentose 

 content of a sugar solution can be determined according to the following 

 method : 



Twenty-five ce. of the aqueous solution, containing not more than 3 per cent 

 of pentose, is placed in a 150 to 200 cc. Erlenmeyer flask holding a cork stopper 

 provided with a 1-meter glass tube, or instead, a small reflux condenser. Then 

 25 cc. of hydrochloric acid, specific gravity 1.19, 50 cc. of 90 per cent alcohol, 

 and 0.6 gm. of phloroglucin are added. The mixture is heated from the time 

 the alcohol begins to boil for exactly one-half hour and the flask with its 

 contents is then quickly cooled. Twenty cc. of the solution Is run into a 

 Hehner colorimeter with a pipette and alcohol is added until the tube when 



