p. E. Browning — Reduction of Ycmadic Acid, 185 



The foregoing table shows that satisfactory results in the 

 determination of phosphorus in iron can be obtained by pre- 

 cipitating the ammonium phospho-molybdate according to the 

 usual methods of iron analysis; then reducing the phospho- 

 molybdate thus obtained with potassium iodide and hydro- 

 chloric acid ; neutralizing the residue with acid sodium carbon- 

 ate, and reoxidizing with standard iodine. 



In conclusion, I wish to express my thanks to Professor 

 Gooch for his help and friendly interest. 



Art. XXIII. — On the Reduction of Yanadic Acid hy Hydri- 

 odic and Hydrohromic Acids, and the Volumetric Estima- 

 mation of the same hy titration in alkaline solution with 

 Iodine; by Philip E. Browning. 



[Contributions from the Kent Chemical Laboratory of Yale University — LY.] 



The reduction of vanadic acid from the condition of the 

 pentoxide to that of the tetroxide by the action of hydriodic 

 and hydrobromic acids has been applied to the volumetric de- 

 termination of vanadium. Holverscheit* has shown that 

 when a vanadate is treated with potassium bromide and strong 

 hydrochloric acid, and the bromine liberated on boiling is 

 passed into a solution of potassium iodide, the iodine set free 

 and estimated shows the reduction to have gone to the condi- 

 tion of the tetroxide. This method is said to yield most satis- 

 factory results. 



Friedheim in a recent paperf gives the method favorable 

 comment, and shows also by a carefully made series of experi- 

 ments that the pentoxide may be reduced to the tetroxide 

 by boiling with potassium iodide and sulphuric acid, and, fur- 

 ther, that the reduction may be carried even to the condition 

 of the trioxide by substituting for the sulphuric acid strong 

 hydrochloric acid. 



In both of the above mentioned methods the iodine liberated 

 is conducted into a solution of potassium iodide and estimated 

 in the usual manner. 



In a former paper;}: I have shown that vanadic acid may be 

 determined conveniently and rapidly by reducing it to the 

 tetroxide by the action of tartaric acid and estimating it in the 

 residue by direct oxidation with standard iodine after having 

 cooled the solution and having made it alkaline with a bicar- 

 bonate. The possibility of applying this method of oxidation 



* Dissertation, Berlin, 1890. 



f Berichte d. d. chem. G-esell., xxviii, 206*7 (1895). 



X Zeitschr. f. anorgan. Chem., vii, 158 (1894). 



