302 Browning — Estimation of Caesium and Rubidium 



bottom and close to the side of the platinum crucible. An 

 ordinary Bunsen burner served as the source of heat and the 

 temperature was kept so far as possible between 250° C. and 

 270° C. After the fuming attending the removal of the large 

 excess of sulphuric acid ceased, the crucible and contents were 

 removed to a desiccator, and after being allowed to cool, 

 weighed. This process of heating was continued for half- 

 hour periods until the weights were constant. The results 

 shown in Table I were obtained by this method of treatment. 

 In experiments (1), (4) and (9) it will be noticed that the 

 weights were constant somewhat above the conditions of the 

 acid sulphate, a fact which would go to show a tendency on the 

 part of the caesium salt to hold an excess of sulphuric acid over 

 the amount necessary to form the ordinary acid sulphate. The 

 results show that by regulating the heat at a temperature 



Table I. 



1 



2 

 3 

 4 

 5 

 6 

 7 

 8 

 9 

 10 



CsN0 3 

 taken, 

 grm. 



0-1706 

 0-1706 

 0-1032 

 0-1032 

 0-1218 

 0-1214 

 0T214 

 0-1150 

 0-1056 

 0-1056 



CsHS0 4 

 calcu- 

 lated, 

 grm. 



0-2013 

 0-2013 

 0-1217 

 0-1217 

 0-1437 

 0-1435 

 0-1435 

 0-1356 

 0-1245 

 0-1245 



1st 

 constant 

 weight. 



grm. 



0-2054 

 0-2010 

 0-1201 

 0-1252 

 0-1458 

 0-1430 

 0-1422 

 0-1330 

 0-1272 

 0-1252 



2d 



constant 



weight. 



grm. 



0-2020 



0-1222 



0-1248 



Error 



on 

 CsHS0 4 . 

 grm. 



0-0007 + 

 0-0003 — 

 0-0016 — 

 0-0005 + 

 0-0021 + 

 0-0005 — 

 0-0013 — 

 0-0026- 

 0-0003 + 

 0-0007 + 



Cs 2 S0 4 

 calcu- 

 lated, 

 grm. 



0-0961 

 0-1130 



Cs 2 S0 4 

 found, 

 grm. 



0-0948 

 0-111S 



Error 



on 



Cs. 2 S0 4 . 



scrm. 



0-0013 



o-oo 



between 250° O. and 270° C. caesium may be brought with a fair 

 degree of certainty to the condition of the acid sulphate. As 

 a check upon the results the acid sulphate was, in a few cases, 

 treated with a little ammonium hydroxide, the excess of this 

 was removed upon a steam bath and the neutral sulphate was 

 obtained by ignition at a red heat to a constant weight. These 

 determinations agreed fairly well with the theory. 



The same procedure was followed with rubidium, a 

 pure rubidium chloride having been chosen as the starting 

 point. The results are given in Table II. No tendency was 

 observed on the part of this element to hold sulphuric acid in 

 excess of the amount necessary for the formation of the acid 

 sulphate. When the same method of treatment was applied to 

 the sodium and potassium salts, pure chlorides being used as 

 the starting point, a somewhat different result w T as obtained, 

 in that the weight of the final product appeared to indicate the 

 formation of the pyrosulphate. 



