510 EXPERIMENT STATION KECOKD. 



A contribution to nitrogen determination, K. A. Mit.sciikui.icii (CIkiii. ZI;;., 

 SJ (l!)0!)). At*. IJ'J, I). 1058). — This is a poloniifiil article in rol)ly to Sclioneke 

 ( E. S. !{., 21, p. (511), and compares tlio results obtained with the Mitscherlicb, 

 Scheiicke. and Deusch methods. For nitrates the Mitscherlich method yielded 

 the highest results of the three methods. The same was the case in determining 

 nitrites, and for these Scheuclie's method gave results ol.2 per cent lower than 

 that of tlie autlior. 



Determination of nitrogen in nitrites and nitrates, V. Schencke (Chcm. 

 Ztg., J3 (I'JO'J), ^'o. 136, p. I,i03). — A reply to Mitscherlich's criticism, noted 

 above. The author states that his metliod was only reconunended for nitrate 

 determinations, and further, that in order to secure accurate results witli the 

 reduction of nitrates according to Ulsch's method a certain concentration of the 

 solution must be present. 



On the determination of potassium, by the cobalti-nitrite method, L. T. 

 Bowser {Jour. Indus, ami Engin. Chcm., 1 {1909), No. 12, pp. 791-798, fig. 1). — 

 Owing to the advantages of the cobalti-nitrate metliod over the platinum 

 method, the author investigated Adie and Wood's all^ali method and tlie acid 

 method, but found that neither of these methods as now employed furnishes 

 results sutliciently correct for quantitative purposes. The author's method, 

 which is a modification of that of Adie and Wood, is more accurate. 



The method is carried on as follows: A 0.75 per cent potassium oxid solu- 

 tion is made, the potash being brought into solution by the usual methods, and 

 any excess of acid removed by evaporation. The residue after evaporation 

 is taken up with water, and any metal i)resent which may interfere is removed 

 by boiling with sodium carbonate. The solution is then filtered and the pre- 

 cipitate obtained is washed with hot water. The washings and the filtrate 

 are combined, acidified with acetic acid and the potassium precipitated as 

 follows: Five cc. of the 0.75 per cent solution (equivalent to 0.0375 gm. potas- 

 sium oxid). 10 cc. of the cobalti-nitrite reagent, and 1 cc. of strong acetic acid 

 are placed' in a porcelain evaporating dish. The mixture is then evaporated 

 to a paste on the steam bath and after cooling the residue is stirred up with 

 25 to 50 cc. of water and filtered through asbestos and the precii)itate washed 

 with sufficient water to remove the excess of reagent. The precipitate and 

 asl)estos are then transferred quantitatively to a 250 cc. beaker. To the beaker 

 there is then added an excess of decinormal potassium permanganate solution, 

 and the mixture brought to the boiling point. When the solution begins to 

 darken 5 cc. of a 1:1 sulphuric acid solution is added, and then titrated back 

 with decinormal oxalic acid solution and potassium permanganate solution to 

 the end point. Each cubic centimeter of potassium permanganate used is equiv- 

 alent to 0.0008573 potassium oxid. 



The cobalti-nitrite reagent is prepared by dissolving 220 gm. of sodium nitrite 

 in 400 cc. of water, and 113 gm. of cobalt acetate in 300 cc. of water and 100 cc. 

 glacial acetic acid. The solutions are then poured together, gently warmed, 

 and the nitrogen peroxid which is evolved removed from the bottle by means of 

 a filter pump which is allowed to run overnight. After this the solution is 

 filtered and made up to 1 liter. 



Determination of phosphoric acid in acid solution with alkaline molybdate 

 solution and glue, A. Grete (Ber. Dent. Chem. GeselL, Ji2 {1909), No. IS, pp. 

 3106-3115; ahs. in Chem. Netcs, 100 {1909), No. 2605, p. 220).— To the solution 

 containing phosphoric acid are added a glue solution, ammonium nitrate, and 

 nitric acid. After boiling, molybdic acid is added drop by drop from a burette 

 until a definite precii)itate remains. The solution is then again l)oiled and 

 well shakeu until a compact yellow precipitate is obtained, when more molybdic 



