EXPERIMENT STATION RECORD. 



Vol. XXXI. Abstract Number. No. 6. 



RECENT WORK IN AGRICULTURAL SCIENCE. 



AGRICTJLTURAL CHEMISTRY— AGROTECHNY. 



Standardization of potassium permanganate solution by sodium oxalate, 

 R. S. McBride {U. S. Dept. Com. and Labor, Bur. Standards Bid., 8 (WIS), 

 No. If, pp. 611-642). — In view of the numerous metliods proposed for the 

 standardization of potassium permanganate solution, the Bureau of Standards 

 has sought a substance which would furnish reasonably correct results. " It 

 was desired, if possible, that the standard selected should serve a threefold 

 purpose, viz, first, as a primary standard of oxidimetry; second, as a working 

 standard for regular use in [our] own laboratories; and third, as a sub- 

 stance which could be distributed by the Bureau with a guaranty both as to 

 its purity and as to its reducing value when used under specified conditions." 



Sodium oxalate seemed best to fill the needs, and the results of the investi- 

 gation showed that the main source of error in the oxidimetric titration is the 

 loss of oxygen. " For this purpose the following detailed method of operation 

 is recommended : In a 400 cc. beaker dissolve 0.25 to 0.3 gm. of sodium oxalate 

 In 200 to 250 cc. of hot water (80 to 90° O.) and add 10 cc. of (1 : 1) sulphuric 

 acid. Titrate at once with tenth-normal KMn04 solution, stirring the liquid 

 vigorously and continuously. The permanganate must not be added more 

 rapidly than 10 to 15 cc. per minute, and the last J to 1 cc. must be added drop- 

 wise with particular care to allow each drop to be fully decolorized before the 

 next is introduced. The excess of permanganate used to cause an end-point 

 color must be estimated by matching the color in another beaker containing 

 the same bulk of acid and hot water. The solution should not be below 60° by 

 the time the end point is reached; more rapid cooling may be prevented by 

 allowing the beaker to stand on a small asbestos-covered hot plate during the 

 titration. The use of a small thermometer as a stirring rod is most convenient 

 in these titrations, as the variation of temperature is then easily observed." 



Benzoic acid as an acidimetric standard, G. W. Mokey (U. 8. Dept. Com. 

 and Labor, Bur. Standards Bui., 8 (1913), No. 4, pp. 643-650). — Benzoic acid is 

 considered a satisfactory reagent for standardizing acidimetric solutions. 

 See also a previous note by Phelps and Weed (E. S. R., 21, p. 610). 



A new apparatus for quantitative dialysis, A. Golodetz (Chem. Ztg., 37 

 (1913), No. 26, pp. 259, 260, fig. J).— The construction of the apparatus, which 

 is illustrated, is similar to that of the Soxhlet extractor. 



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