•_'}''■ Browning and Blumenthal—Qualitativi Detection 



Aim. SLXVIIL— On tht Qualitative Detection of Certain Ele- 

 ments which form InsoluliU Sulphates: Barium, Stron- 

 tium, [Calcium,) <n,<l I..<t<l; by Philip E. Browning and 

 Philip L. Blumenth \i . 



[Contribution- from the Kent Chemical Laboratory of Vale Univ.— ocxxiv.] 



In the ordinary processes of qualitative analysis the alkali 

 earth elements are usually separated by ammonium carbonate, 

 after hydrogen sulphide and ammonium hydroxide have been 

 used to remove the greater number of the bases. It has long 

 been observed by those employing these processes that a con- 

 siderable part of the alkali earth, especially barium and stron- 

 tiuni. tail? to appear when the ammonium carbonate i> added. 

 The reasons given for this loss have been the oxidation >of 

 hydrogen sulphide or other sulphides to sulphates and the con- 

 sequent precipitation of the alkali earth sulphates, the forma- 

 tion in alkaline solution of carbonate^ and the consequent 

 precipitation of the carbonates, and the tendency of the large 

 amounts of ammonium salts which collect during the analysis 

 to interfere with the precipitation of the alkali earth carbonates 

 by ammonium carbonate. Various precautions have been sug- 

 1 to avoid these sources of error, such as the prompt 

 removal of the excess of hydrogen sulphide by boiling, the 

 use of freshly prepared hydroxides free from carbonate, and 

 the removal of the ammonium salts by ignition before attempt- 

 ing to precipitate the alkali earth carbonates. 



The work to be described in this paper was undertaken to 

 study, first, the effect of a direct precipitation of the insoluble 

 alkali earth sulphates, after the removal of the mercury in the 

 mercurous condition, silver, and the proportion of lead which 

 may be precipitated by hydrochloric acid : and. second, the 

 action of ignition with carl ion upon these sulphates. For the 

 work solutions were prepared containing to each cubic centi- 

 meter one milligram reckoned as the element. 



Preliminary experiments showed that in a volume of 1" . 

 l m " of Sr, 0-5 ms of Pb, and (M"' 6 of Ba wave distinct precipi- 

 tates when treated with a few drops of dilute sulphuric acid 

 and allowed to stand a few minutes, and 10" 16 of Ca gave a 

 precipitate on standing over night. 



The action of ammonium acetate upon the sidphates of 

 barium and lead was tried as follows : Two solution- contain- 

 ing 0*1 gnn. of Pb and 4 grin, of ammonium acetate in 1" 

 of water gave no precipitate when a slight excess of sulphuric- 

 acid was added. On addition of more sulphuric acid the lead 

 sulphate tended to precipitate. When ammonium sulphate 



