Cerium Earth Double Sulphates. 



165 



Four portions of 1 grm. each were thoroughly mixed with 2 

 grm. of charcoal and heated in a covered porcelain crucible 

 over a bunsen flame for from 30-45 minutes. After cooling, 

 the mass was treated with about 4 om3 of strong hydrochloric 

 acid and 10 cm3 of water when the solution of the cerium earths 

 took place with the abundant evolution of hydrogen sulphide. 

 The residue of the charcoal was filtered off and the cerium earths 

 in the filtrate were precipitated by oxalic acid in the usual 

 manner. The average of these results, agreeing within a few 

 milligrams, was 0*3908 grm. Three determinations each with 

 5 grams of the material and 5 grm. of charcoal heated 45 

 minutes gave an average result of 2*021 grm. ; and four 

 portions of 10 grm. heated with from 8-15 grm. of charcoal 

 from 15-35 minutes yielded an average of 4*37 grm. of the 

 oxides. Finally a portion of 100 grm. was mixed with 200 

 grm. of charcoal and heated in a battersea crucible in a furnace 

 for about one hour. The yield of this experiment was a little 

 over 40 grm. of the oxides. 



The conclusion from this work is that the double sulphates 

 of the cerium earths with alkali sulphates are readily decom- 

 posed by heating with charcoal into a form easily attacked by 

 hydrochloric acid with the formation of soluble chlorides. 



In course of this investigation it was found that the reduc- 

 tion of the double sulphates to sulphides by charcoal was not 

 complete although the product was readily attacked by hydro- 

 chloric acid. Accordingly several experiments were made to 

 determine the best conditions for forwarding the reducing 

 action. The results appear in the table and were obtained by 

 determining the amount of sulphate present in the hydro- 

 chloric acid extract after carbon fusion, by precipitation with 

 barium chloride. 





Amount of 











double 



Amount of 





Per cent 





sulphate 



charcoal 



Time of 



sulphate 





taken 



used 



fusion 



reduced 





. grm. 



grm. 



mins. 





(1) 



1 



2 



30 



60-5 



(2) 



1 



2 



60 



70*5 



(3) 



1 



2 



120 



91*0 



(*) 



1 



2 



140 



84*6 



(5) 



1 



2 



240 



80-6 



(6) 



1 



4 



30 



59*0 



(?) 



1 



4 



60 



75-4 



(8) 



1 



4 



30 



70*8 



(9) 



1 



4 



30 



64.0 



(10) 



1 



4 



60 



93*7 



Am. Jour. Sci.— Fourth Series, Vol. XXXII, No. 188.— August, 1911. 



1* 



