338 THE ATOMIC WEIGHTS. 



oxalic acid. The resulting oxalate was ignited with great care. I de- 

 duce from the weighings the percentage of CeO^ given by the anhydrous 

 suljihate : 



After the foregoing experiments the sulj^hate was further purified by- 

 solution in nitric acid and pouring into a large quantity of boiling water. 

 The precipitate was converted into sulphate and analyzed as before : 



From another purification the following weights were obtained : 

 1.4684 grm. .i8Sogrm. -7717 g'm. 60 270 per cent. 



A last purification gave a still lower percentage : 



1.3756 grm. .1832 gnn. .7186 grm. 60.265 per cent. 



The last oxide was perfectly white, and was spectroscopicallv free from 

 didymium. In each case the CeO^ was titrated iodometrically for its 

 excess of oxygen. It will be noticed that in the successive series of de- 

 terminations the percentage of CeO.^ steadily and strikingly diminishes 

 to an extent for which no ordinary impurity of didymium can account. 

 The death of Dr. Wolf interrupted the investigation, the results of which 

 were edited and published by Professor F. A. Genth. 



In the light of more recent evidence, little weight can be given to these 

 observations. All the experiments, taken equally, give a mean percent- 

 age of CeO^ from Ce,(S0,)3 of 60.866, ±: .0308. This mean has obviously 

 little or no real significance. 



The experiments of Wolf attracted little attention, except from Wing,* 

 who partially verified certain aspects of them. This chemist, ir.cidentall}'- 

 to other researches, purified some cerium sulphate after the method of 

 Wolf, and made two similar analyses of it, as follows : 



Sulphate. Water. CeO.,. Percent. CeO,. 



1.2885 grm. .1707 grm. .6732 grm. 60.225 



1.4090 " .1857 " .7372 " 60.263 



Mean, 60 244 

 * Am. Journ. Sci. (2), 49, 35S. 1870. 



