242 Professor Mosander on Cerium^ La?ithanhim, 



The double salt was afterwards decomposed in the moist way 

 with carbonate of soda, and with the carbonate of protoxide 

 of cerium thus obtained, all the preparations have been made 

 which will be now mentioned. 



After a long examination of various salts of protoxide of 

 cerium, I did not succeed in detecting a salt principally con- 

 sisting of the supposed new oxide, the presence of which, how- 

 ever, appeared more and more probable in the course [of the 

 experiments. As it was known that cerium gives two oxides, 

 I considered it probable that if hydrate of protoxide of cerium 

 mixed with water was exposed to the effect of chlorine, per- 

 oxide of cerium would be formed while the more electro-posi- 

 tive metallic oxide would be dissolved in the fluid, and it was 

 in this manner that I succeeded to my satisfaction. When 

 the chlorine was introduced into the fluid, the appearance of 

 the hydrate of protoxide of cerium began soon to change, the 

 volume diminished, and a heavy, bright, yellow, or rather 

 orange-yellow coloured powder fell to the bottom. If, after 

 the chlorine no longer appears to cause any change, the fluid 

 is filtered, a colourless solution, with the strong odour of 

 hypochlorous acid, is obtained, from which, with hydrate of 

 potash in excess, a precipitate is deposited, which collected on 

 a filter, is white, or approaching violet. This precipitate 

 begins soon, however, to grow yellow in contact with the air. 

 If the precipitate be again mixed with water and chlorine in- 

 troduced, the greater part is dissolved, while a new portion 

 of the yellow-coloured oxide is formed, and remains undis- 

 solved. The filtered solution forms a precipitate again with 

 caustic potash, which is treated as before with chlorine, and 

 this is repeated five or six times, when, finally, hydrate of 

 potash precipitates from the solution an oxide which does not 

 become in the least yellow by exposure to the air, and which 

 suspended in water, is completely dissolved by the intro- 

 duction of chlorine without leaving a trace of undissolved 

 yellow oxide. It was to this oxide, not capable of being more 

 oxidized either by the air or chlorine, that I gave the name of 

 oxide of Lanthanium, after the production of which, and a 

 nearer acquaintance with its properties, another and simpler 

 method was employed to obtain it. The strong basic qualities 

 of the new oxide afforded an easy means of separating it from 

 oxide of cerium, by treating the red-brown oxide which is 

 obtained when the so-called nitrate of protoxide of cerium is 

 heated with nitric acid diluted with 75 to 100 parts of water. 

 An acid thus diluted leaves the greater part of the red-brown 

 oxide undissolved, and from the solution thus obtained the 

 oxide of lanthanium was derived which was employed by me in 

 the experiments that I made in the beginning of the year 1839. 



