

1884.] the Atomic Weight of Cerium. 151 



a smaller quantity of lanthanum, besides other metals. About 

 250 grins, of the crude material were taken at once, and the lumps 

 were broken down in a mortar, then it was transferred to a flask of 

 about 3 litres capacity and 100 cub. centims. of strong nitric acid were 

 added to it, afterwards gradually water until the bulk was about 

 3 litres. After shaking frequently for a day, it was allowed to settle 

 all night, and next morning the clear liquid was siphoned into 

 another flask. Any undissolved was left in the flask to go on with 

 the next lot, to be treated in the same way. The clear liquid which 

 had been siphoned off was saturated with sulphuretted hydrogen, then 

 filtered from the reddish-brown precipitate thrown down. To the 

 filtrate oxalic acid was added, until there was no further precipitate 

 formed ; the precipitated oxalate was allowed to settle down, and the 

 clear liquor was siphoned off and thrown away. The oxalate was 

 then well washed with water made slightly acid with nitric acid on a 

 filter, using a Bunsen pump, dried over a water-bath, and then ignited. 

 The oxides thus obtained were dissolved in nitric acid, the solution 

 was transferred to a dish and evaporated down on a water-bath to a 

 thick syrup, until it would scarcely pour from the basin. It was then 

 transferred to two large beakers, each containing 1500 cub. centims. 

 of boiling dilute sulphuric acid 20 cub. centims. of sulphuric acid, 

 sp. gr. 1'84 in 1000 cub. centims. of water well stirred and allowed 

 to settle. There was a considerable precipitate of basic cerium sul- 

 phate; after it had settled down well, the clear liquid was siphoned 

 off, precipitated with oxalic acid, and the above process was exactly 

 repeated to obtain more of the basic cerium sulphate. After siphon- 

 ing off as much as possible of the clear liquid from the second preci- 

 pitate, both precipitates were thoroughly drained together on a filter 

 at a Bunsen pump, and washed with dilute sulphuric acid. The 

 washings and the clear liquid from the second precipitate were pre- 

 cipitated with oxalic acid, and the oxalates obtained, principally of 

 didymium and lanthanum, were reserved for further treatment. 



Bunsen's process was now to dissolve the basic sulphate, and re- 

 precipitate as such, repeating the process until he obtained a small 

 quantity of the pure sulphate ; but I found it better from this stage 

 to adopt Gibbs's method of treatment with lead peroxide. Accord- 

 ingly I dissolved the washed and drained basic sulphate in strong 

 nitric acid, added to the solution some lead peroxide, and boiled the 

 whole until a small quantity of the solution diluted with water gave 

 no precipitate with barium nitrate. If properly done, the cerium 

 was now peroxidised and in solution as nitrate. I now allowed the 

 excess of lead peroxide and the lead sulphate formed during the pro- 

 cess to settle down, then decanted the clear liquid into an evaporating 

 basin, and heated it on a water-bath until it became a thick syrup. 

 This syrup was treated with boiling dilute nitric acid 25 cub. 



