412 EXPERIMENT STATION RECOED. [Vol. 37 



Preliminary experiments are noted which indicate that " nicotinic acid may 

 exist in a betaiu form and that the curative properties of Funk's vitamin frac- 

 tions of i'east and rice polishings may have been due in part to this isomeric 

 form of nicotinic acid or a polymer or simple derivative of it." 



Titration of magnesium, F. W. Beuckmilleb {Jour. Amer. Chem. Soc, 39 

 (1917), No. 4, pp. 610-615). — From experimental results obtained in the titra- 

 tion of magnesium as applied to water analysis the author indicates that mag- 

 nesium can be determined volumetrically, provided great care is exercised in 

 the formation of the phosphate precipitate in the one procedure, and special 

 precautions taken in the titration of the iodin liberated by the arsenate pre- 

 cipitate from potassium iodid or the arsenious acid remaining after all the 

 iodin has been expelled in the other procedure. 



The modified methods are described in detail. Experimental data submitte<l 

 indicate the accuracy of the methods as compared to the gravimetric procedure. 



A study of the volumetric or Pemberton method for determining phos- 

 phoric acid, with some experiments showing the influence of temperature 

 and the sulphuric acid radical on results, 1'. McG. Shuey {Jour. Indus, and 

 Engin. Chem., 9 {1917), No. J,, pp. S67-S70).—The author discu.sses the method 

 and points out certain precautions* neces.sary in the u.se of the procedure. Some 

 experimental data relative to. the temperature of titration are also submitted 

 and discussed. 



It is concluded in general that, " with a knowledge of the method and with 

 strict attention to detail, very accurate and reliable results may be obtained. 

 The fact that it is extremely delicate is a point in its favor." 



The iodometric determination of ammonium sulphate, W. S. J. Schouten- 

 Ilcken and 11. W. Tuinzing {Verslaij. Lamlhouick. Oiulcrzuek. Rijkshindboutc- 

 pioefstat. [Netherlands], No. 20 {1917), pp. 12-20).— The authors briefly re- 

 view the distillation and other procedures used for the determination of 

 ammonia in ammonium sulphate and other fertilizers. A procedure which de- 

 pends on the following reactions is described : 



(1) 2NH,-f3NaOBr=3NaBr-f3tLO+N, 



(2) (NH4)2S04+3NaOBr+2NaOH=Na,S04 4-3NaBr4-5H.O-HN, 



(3) NaOBr+2HI=^'aBr^-^20+I, 



(4) 2Na2S=Oa+I,=NasS.O,+2NaI 



The alkaline-bromin solution is prepared by adding, with constant stirring, 

 15.5 gm. of bromin to 5 liters of sodium hydroxid solution (containing 15.5 gm. 

 of NaOH). This solution is allowetl to stand for several days and its titer 

 then determined with a standard thiosulphate solution. Since the titer does 

 not remain constant it should be determined every few days. 



The ammonia determination is made by treating 10 cc. of a solution of am- 

 monium sulphate (0.5 gm. In 100 cc. water) or a solution of ammonium super- 

 phosphate (1 gm. in 100 cc. of water) in a 700-cc. flask with 75 cc. of the alka- 

 line-bromin solution. After having been set aside for several minutes 5 cc. of 

 a 10 per cent solution of potassium iodid, 20 cc. of a 10 per cent hydrochloric 

 acid solution, 5 cc. of a saturated solution of sodium carbonate, drop by drop, 

 and 200 cc. of water are added to the mixture, in the order named. The liber- 

 ated iodin is titrated with standard thiosulphate solution, u.'?iug methylene 

 blue as an indicator. From the amount of alkaline-bromin solution used the 

 amount of nitrogen and ammonium sulphate present in the sample is calculated. 



Analytical data submitted Indicate the accuracy of the procedure. The 

 method is reconnnendod as being more economical than the usual distillation 

 procedure in point of time and materials. 



