Browning — Estimation of Ccesium and Rubidium, etc. 301 



Art. XXXII. — On the Estimation of Ccesiitm and Rubidium 

 as the Acid Sulphates, and of Potassium and Sodium as 

 the Pyrosulphates ; by Philip E. Browning. 



[Contributions from the Kent Chemical Laboratory of Yale University— CIL] 



Bunsen* is authority for the statement that the acid sul- 

 phate of rubidium does not lose sulphuric acid at a heat 

 approaching redness. It is statedf in the literature that the 

 acid sulphates of caesium and rubidium when subjected to a 

 low red heat pass into the form of the pyrosulphates. R. 

 Weber % found that by treating the dry sulphates of potassium, 

 caesium, rubidium and thallium with sulphuric anhydride in a 

 closed tube and heating on a water bath two layers separated. 

 In the lower layer he obtained crystalline bodies which proved 

 to have the constitution '_R 2 O8S0 3 . On strong heating he 

 obtained from these substances bodies of the form R 2 O2S0 3 

 and finally R a OS0 3 . Re also notes that in the case of the 

 caesium salt the removal of the excess of sulphuric anhydride 

 was attended with greater difficulty. 



Baum§ states that the pyrosulphates of the alkalies may be 

 obtained by heating the acid sulphates under atmospheric pres- 

 sure at low redness, or under diminished pressure at a tem- 

 perature between 260-820° C. 



In a recent paper] from this laboratory I have shown that 

 thallium may be estimated as the acid sulphate by evaporating 

 a thallous salt in solution with an excess of sulphuric acid and 

 bringing the residue to a constant weight at a temperature of 

 about 250° C. The similarity which thallium bears in some of 

 its combinations to the alkaline metals suggested the study of 

 the sulphates of these elements under the same general condi- 

 tions of procedure. 



My first experiments were made with a pure caesium salt 

 as follows : A weighed amount of the nitrate w r as placed in a 

 previously weighed platinum crucible and treated with an 

 excess of sulphuric acid. The crucible was then placed upon 

 a steam bath until the water and nitric acid were largely 

 expelled and then removed to a radiator, consisting of a porce- 

 lain crucible fitted with a pipe-stem triangle so arranged that 

 the bottom of the platinum crucible would be about midway 

 between the top and bottom of the porcelain crucible. This 

 improvised radiator was set in an iron ring and a thermometer 

 placed so that the mercury bulb would be on a level with the 



* Ann. Chem. (Liebig:), cxix, 110. 



f Graham. Otto Lehrbuchd. Chem., iii, 278, 269. 



% Ber. Dtsch. Chem. Ges., xvii, 2497. 



§ Ber. Dtsch. Chem Ges., xx, 752. || This Journal, ix, 137, 1900. 



