504 EXPERIMENT STATION RECORD. [Vol.41 



change adapted to the probable acidities of the solution are plaeetl in each tube 

 and shaken. The tubes are then collected in subgroups of similar colors, and 

 one specimen of each subgroup is tested with the hydrogen electrode to deter- 

 mine the H-ion concentration of the entire subgroup. 



A sensitive reaction of manganese salts, H. Caron and D. Raquet {Ann. 

 CJiim. Analyt., 2. ser., 1 {1919), No. 6, p. 174). — The authors state that man- 

 ganese salts in slightly acid solution react in the cold with an excess of an 

 alkaline oxalate and certain oxidizing agents (bichromates, hypochlorites, and 

 sodium peroxid) to form an alkaline manganic oxalate of a deep red color. 

 Potassium oxalate, acetic acid, and potassium hypochlorite are recommended 

 as furnishing the most sensitive reaction, it being possible to detect manganese 

 in a 1 : 200,000 solution. 



Iron in quantity is said to mask the color reaction, while zinc does not inter- 

 fere with the reaction provided sufficient oxalate is used to dissolve the pre- 

 cipitate of zinc oxalate formed and enough acetic acid is added subsequently 

 to acidify the solution. 



The reaction, while less sensitive than those based on the transformation 

 of manganese into permanganic acid by lead dioxid, persulphates, or bismuth 

 peroxid, has the advantage of not being interfered with by chlorids. 



Specific colored reaction of oxalates, H. Caeon and D. Raquet {Ann. Chim. 

 Analyt., 2. ser., 1 {1919), No. 7, p. 205). — The reaction noted above is said to be 

 equally applicable as a test for oxalic acid and oxalates in amounts as small 

 as 0.01 gm. In the case of free oxalic acid or a solution having quite a strong 

 mineral acidity, sodium acetate should be used in place of acetic acid. 

 Insoluble oxalates should be boiled for a few minutes with a solution of an 

 alkaline carbonate, and the test made with the cold filtered liquid acidified 

 with acetic acid. Phosphoric, hydrofluoric acid, etc., are said not to interfere 

 with the reaction. 



lodometric studies, I. M. Kolthoff {Pharm. Weekbl., 56 {1919), Nos. 12, pp. 

 391-404; 14, pp. 426-438; 15, pp. 460~465; 16, pp. 514-524; 18, pp. 572-585; 19, 

 pp. 621-634; 20, pp. 644-657, figs. 2; abs. in Clienn. Ahs., 13 {1919), Nos. 13, pp. 

 1434, 1435; 14, pp. 1569, 1570). — These numbers report, respectively, a series of 

 quantitative iodometric studies under the following headings : I, Introduction ; 

 II, the starch iodid reaction ; III, the iodometric bromate determination ; IV, the 

 iodometric determination of chloric acid; V, the iodometric determination of 

 chromic acid (with E. H. Vogelenzang) ; VI, the reaction of thiosulphate with 

 iodin ; VII, the reaction between arsenic trioxid and iodin ; and VIII, stand- 

 ardization of sodium thiosulphate solutions. 



The determination of nitrogen by the Kjeldahl process, A. Villiers and A. 

 Moreau-Talon {Ann. Chim. Analyt., 2. ser., 1 {1919), No. 6, pp. 183-185) .—The 

 authors recommend the use of both potassium sulphate and mercury in the 

 digestion process, the sulphate being added at the beginning and the mercury 

 (1 gm.) after the solution has become nearly colorless. The solution is heated 

 gently for 15 minutes or more after the addition of the mercury, and is then 

 distilled into dilute hydrochloric acid and the distillate evaporated to dryness. 

 The nitrogen is calculated by a gravimetric determination of the ammonium 

 chlorid formed, or by a volumetric determination with a standardized solution 

 of silver nitrate using potassium chromate as indicator. 



Notes on potash determination, L. G. L. Steuerwald {Arch. Suikerindus. 

 Nederland. Indie, 27 {1919), No. 9, pp. 435-438; abs. in Cliem. Abs., 13 {1919), 

 No. 13, p. 1436). — A modified method for determining potash by precipitation as 

 potassium platinic chlorid and reduction to metallic platinum is described in 

 which sodium formate is used as the reducing agent. 



