VY a 
nm al 
Lawrence Scientific School. 353 
the protoxyd of cerium in the nearly insoluble double sulphate 
of soda and cerium metals is only partially oxydized b 
heating with strong sulphuric acid and peroxyd of iad xleiosagie 
oxygen is freely evolved. 
A solution of hypermanganate of potash has no immediate 
action upon a solution of protoxyd of cerium either in nitric or 
in sulphuric acid, the violet color remaining unehanged even in 
ahot solution. On boiling for some time, however, the color 
changes slowly, the solution gradually becomes yellow and a 
rown flocky precipitate is thrown down, which consists of hy- 
‘drate of sesquioxyd of manganese. 
According to Stapff, a solution of hypermanganate of potash 
isimmediately decolorized by a solution of the sulphate of po- 
ium and protoxyd of cerium in chlorhydric acid, but after 
some time chlorine is evolved and the sesquioxyd of cerium 
found is reduced to protoxyd. It is clear that in this case the 
Bpizing agent is chlorine. The further investigation of this 
subject was committed to Dr. T. M. Drown, who has obtained 
the following results, 
en a solution of cerium, didymium, and lanthanum, is 
treated with nitric acid and peroxyd of lead in the manner 
pointed out above, the deep orange colored liquid evaporated 
to dryness, and heated for a short time to a temperature suffi- 
ciently high to expel a portion of the acid, it will be found that 
boiling water acidulated with nitric acid dissolves only the salts 
of lanthanum and did mium, leaving the whole of the cerium 
in the form of basic nitrate, insoluble in water. The insoluble 
matter is to be filtered off and thoroughly washed. A current 
of sulphydric acid gas passed into the filtrate removes the lead, 
after which the lanthanum and didymium may be precipita- 
together as oxalates, which if the process has been care- 
fully performed, are perfectly free from cerium. The mass on 
the filter is readily dissolved by fuming nitric acid. Sulphydrie 
acid is then to be passed through the solution sufficiently diluted 
With water until the lead is completely precipitated. The cerium 
May then be thrown down by oxalic acid, ignited and weighed 
a Ce, O,, or as sulphate. In this manner Dr. Drown obtained 
in four analyses of the same salt 
DiO and LnO = 24:84, 25°31, 25°54, 24°65 per cent. 
Nitrate of protoxyd of cerium obtained by this process gives, 
When tested by the spectroscope with transmitted light, even In 
Very thick layers, a scarcely perceptible indication of didymium. 
Tmay here mention that Gladstone’s lines farnish, with proper 
are, the most delicate test for the presence of didymium which 
We Possess, is only necessary to transmit the light through 
Very thick layers of liquid and to employ a condensing lens so 
Ax. Jour, Sct.—Szconp Srrres, Vou. XXXVII, No. 111.—Mar, 1864. 
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