420 Dr. Thomas Thomson and Dr. Steel's [June 



into a solution of sulphated protoxide, and a yellow insoluble 

 subsalt, which precipitates. The sulphated peroxide of 

 cerium reddens vegetable blues. When heated it melts 

 into an orange coloured liquid, which becomes yellow when 

 all the water is driven off. A red heat decomposes the salt 

 altogether. 



20 grs. of this salt were digested in a flask with a large 

 quantity of distilled water. The solution was perfectly 

 colourless, but a yellow powder remained at the bottom. 

 It was collected on a filter, well washed with boiling dis- 

 tilled water, and dried. It weighed 2*7 grs., but after expo- 

 sure to the highest temperature of the sand-bath, it was 

 reduced to 2*362. By analysis it was found a disulphated 

 peroxide of cerium composed of . 



Peroxide of cerium . . 1*742 

 Sulphuric acid .... 0*621 



2*363 

 The residual colourless solution was reduced by evapora- 

 tion to a convenient bulk, and boiled in a flask with a solu- 

 tion of carbonate of ammonia. The precipitated carbonate 

 of cerium, after being well washed and dried, weighed 8*9 

 grs., and after ignition the weight was 5*33 grs. 



The residual solution, after being mixed with nitric acid 

 in excess, was precipitated by chloride of barium. The 

 sulphate of barytes, after washing and ignition, weighed 

 19*95 grs. = 6*87 grs. of sulphuric acid. This analysis 

 gives us, 



Peroxide of cerium . . 5*33 or 7*072 - 1 atom. 

 Sulphuric acid . . . 6*87 ,, 7*491 - 1 J atoms 

 Disulph. peroxide . . 2*362,, 

 Water ...... 5*438,, 5*438 - 5 atoms. 



20* 

 Thus, it appears that the salt was a sesquisulphated 

 peroxide of cerium containing 5 atoms of water. 



3. Disulphated protoxide of Cerium. — A white insoluble 

 powder obtained when the sulphate of cerium is thrown 

 down by ammonia. It is composed of, 



Protoxide of cerium . . 13* or 2 atoms. 

 Sulphuric acid .... 5* ,, 1 atom. 

 Water 2*1 ,, 2 atoms. 



