CAIN AND TUTTLE: DETERMINATION OF PHOSPHORUS 249 



CHEJVIISTRY. — The determination of phosphorus in steels con- 

 taining vanadium. J. R, Cain and F. H. Tuttle. To 

 appear as a Technologic Paper of the Bureau of Standards. 

 Communicated by W. F. Hillebrand. 



In order to precipitate phosphorus quantitatively as phospho- 

 molybdate from steels containing vanadium, it is necessary to 

 reduce the latter to the quadrivalent state, otherwise precipitation 

 is incomplete and there is contamination of the phosphomolybdate 

 by vanadium. In the present method ferrous sulphate in slight 

 excess is used as the reducing agent and the following conditions 

 should be observed : (1) The temperature of precipitation should 

 be held at a point (15° to 20°) where the nitric acid does not 

 oxidize the excess of ferrous salt or the reduced vanadium before 

 complete precipitation of phosphorus takes place; (2) the partial 

 neutralization with ammonia, frequently used when phosphorus 

 is precipitated as phosphomolybdate, must be made before reduc- 

 tion of the vanadic acid, otherwise the heat of neutralization 

 causes the oxidation of most of the ferrous iron and reduced 

 vanadium by the nitric acid: (3) care must be taken to prevent 

 the action of oxides of nitrogen, formed by interaction of ferrous 

 salt and nitric acid, on the reduced vanadium since these sub- 

 stances seem to catalyze the oxidation of the vanadyl salt and 

 may in some cases completely prevent precipitation of phosphorus, 

 owing to the large amount of vanadic acid produced ; (4) efficient 

 means for shaking or agitation of the solutions in which precipi- 

 tation is to take place must be provided. 



MINERALOGY. — The refractive indices of strengite. Waldb- 

 MAR T. ScHALLER, Geological Survey. 



The only published values for the refractive indices of strengite, 

 Fe2O3.P2O5.4H2O, which I have been able to find are those given 

 by Schroeder van der Kolk,^ namely 1.81 + 0.03; Lacroix- has 

 stated them in the form: a = 1.81, 7 = 1.84. Determination 

 of these values for a manganese strengite from California^ gave 



^Tabellen Mikrosk. Bestimmung d. Mineralien, p. 54, 1906. 

 ^Mineralogie de la France 4: 475, 1910. 

 »This Journal 2: 145, 1912. 



