508 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 54 



In liis later paper Eammelsberg gives these figures concerning cerium 

 oxalate. One hundred parts gave 10.43 of carbon and 21.73 of water. 

 Hence the dry salt should yield 48.862 per cent, of CO2, whence C'e = 

 138.18. 



In all of the foregoing experiments the eerie oxide was somewhat col- 

 ored^ the tint ranging from one shade to another of light brown, according 

 to the amount of didymium present. Still, at the best, a color remained, 

 which was supposed to be characteristic of the oxide itself. In 1868,. 

 however, some experiments of Dr. C. Wolf ^ were posthumously made 

 public, which went to show that pure ceroso-ceric oxide is white, and 

 that all samples previously studied were contaminated with some other 

 earth, not necessarily didymium but possibly a new substance, the re- 

 moval of whicli tended to lower the apparent atomic weight of cerium 

 very perceptibly. 



Cerium sulphate was recrystallized at least ten times. Even after 

 twenty recrystallizations it still showed spectroscopic traces of didyiuium. 

 The water contained in each sample of the salt was cautiously estimated, 

 and the cerium was thrown down by boiling concentrated solutions of 

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

 duce from the weighings the percentage of CeOo given by the ankydrons 

 sulphate : 



Sulphate. Water. CeO.. Per cent. CeO.. 



1.4542 .19419 .76305 60.559 



1.4104 .1898 .7377 60.437 



1.3502'J .1820 .70665 60.487 



Mean, 60.494 



After the foregoing experiments the sulphate was further purified 1)y 

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

 The precipitate was converted into sulphate and analyzed as before : 



Mean, 60.302 

 From another purification the following weights were obtained : 

 1.4684 grm. .1880 grm. .7717 grm. 60.270 per cent. 



A last purification gave a still lower percentage: 



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



' Anier. Journ. Science (2), 46, 53. 



