Drushel — Volumetric Estimation of Lanthanum. 197 



Art. XXI. — On the Yolumetric Estimation of Lanthanum 

 as the Oxalate ; by W. A. Drushel. 



[Contributions from the Kent Chemical Laboratory of Yale Univ. — clxiii.] 



Nearly thirty years ago Stolba* stated that cerium, lantha- 

 num and didymium may be estimated by treating their oxalates 

 with potassium permanganate in the presence of sulphuric acid, 

 but gave no experimental evidence in the form of analytical 

 results. Later this statement of Stolba was confirmed by a 

 paper from this laboratoryf in which it was shown that cerium 

 may be estimated by precipitating cerium oxalate with a defi- 

 nite amount of a standard solution of ammonium oxalate used 

 in excess. The precipitated cerium oxalate was decomposed 

 by dilute sulphuric acid and the oxalate estimated by perman- 

 ganate, and the ammonium oxalate in excess of the amount 

 recjuired for the precipitation was also estimated by permanga- 

 nate. By this process the results were checked. 



The work to be described was undertaken to determine 

 the best conditions for the estimation of lanthanum as the 

 oxalate and also to furnish the desirable experimental data in 

 support of Stolba's original statement. 



For this work about ten grams of pure ammonium lanthanum 

 nitrate were prepared by separating the lanthanum and didym- 

 ium from the cerium in a kilogram of the mixed sulphates 

 by Mosander's chlorine method. The mixture of lanthanum 

 and didymium chlorides thus obtained, having been shown to 

 be free from cerium by the hydrogen peroxide test, was con- 

 verted into a mixture of ammonium lanthanum nitrate and 

 ammonium didymium nitrate. By fifty recrystallizations about 

 forty grams of pure ammonium lanthanum nitrate were ob- 

 tained. This salt was dissolved in eighty cubic centimeters of 

 water, and the solution through a depth of nineteen centime- 

 ters showed no trace of absorption bands. A few cubic centi- 

 meters of the solution evaporated to dryness and ignited gave 

 a pure white oxide. Out of this solution of the double nitrate 

 about ten grams were recrystallized for the experimental work 

 of this paper. 



The procedure is as follows : 



From a neutral lanthanum solution (a 1 per cent ammonium 

 lanthanum nitrate solution being used in this work) the oxalate 



is precipitated by a measured amount of standard oxalic 



acid, or ammonium oxalate after the addition of a few drops of 



*Sitzber. d. Bohm. Gesellsch. d. "Wissenschaften, iv, July, 1879. 

 Zeitschr. fur Anal. Chem. xix, 194. 



f Browning, this Journal, viii, p. 451, 1899. 



