Chemistry and Physics. 61 



SCIENTIFIC INTELLIGENCE 



I. Chemistry and Physics. 



1. New Volumetric Method for Manganese.— Metzger and 

 Maers have devised a new volumetric method for the determina- 

 tion of manganese, which is particularly interesting as it is based 

 upon a novel reaction, and as it appears to be unusually import- 

 ant on account of its simplicity and accuracy in its application to 

 the analysis of iron and steel. It had been noticed previously, 

 particularly by Hillebrand, that considerable amounts of hydro- 

 fluoric acid interfere with the usual titration of ferrous iron by 

 permanganate on account of what appeared to be a partial reoxi- 

 dation of the resulting manganous fluoride by the permanganate 

 in such solutions. The present authors have found that with a 

 sufficient amount of hydrofluoric acid and fluorides present, the 

 reaction with manganous fluoride and permanganate proceeds to 

 a definite end-point with the formation of manganic fluoride, 

 MnF 3 . This remarkable reaction is represented by the equation 



KMn0 4 + 4MnF 2 + 8HF = KF + 5MnF 3 + 4H 2 0. 



Hence the iron value of the permanganate multiplied by the 

 factor *7868 gives its manganese value for the method under con- 

 sideration. The manganic fluoride when present in considerable 

 amounts imparts a brown color to the liquid, so that the method 

 appears to be more suitable for small than for large quantities of 

 manganese. The authors, thus far, have tested it only for rather 

 small quantities, and have obtained exceedingly good results. 

 Their method for steel and cast iron is as follows : Dissolve 

 about 1 g. in 10 cc of 1:1 nitric acid. Cool slightly, add 1 g. of 

 ammonium persulphate (to destroy carbon compounds), and let 

 stand until effervescence ceases ; boil briskly for a few seconds ; 

 remove cover and evaporate to dryness, but do not bake ; take 

 up in 20 cc of 1 : 2 sulphuric acid and 30°° of water and boil until the 

 solution is clear. Cool, transfer to a wax beaker, add 5 g. of ammo- 

 nium fluoride, and 25 co of hydrofluoric acid, dilute with water to 

 100-150 cc , and titrate the colorless liquid with permanganate solu- 

 tion until a pink end-point is reached. In the case of cast iron 

 containing much graphite it is advisable to filter off this substance 

 before adding the ammonium fluoride and hydrofluoric acid. 

 Since ferric iron does not interfere with this titration, and since 

 no filtration is usually necessary, the method is remarkable for 

 rapidity and simplicity. — Jour. Indust. and Eng. Chem., iii, 301. 



h. l. w. 



2. Sulphite Method for Separating and Identifying Strontium 

 and Calcium. — Since strontium sulphite is sparingly soluble 

 (0*033 g. to the liter) while calcium sulphite is quite soluble (l'2g. 

 to the liter - ), and since strontium sulphite is considerably less solu- 



