•24-S Browning and Bhimenthal—Insolubh Sulphates. 



niiim acetate until the washings give no test l'i>r lead by hydro- 

 gen sulphide. The filtrate and washings are reserved for 

 treatment by the ordinary course of analysis. To the precipi- 

 tated sulphates on the paper a small amount of pure sugar 

 carbon is added, the paper is roiled up, and the mass placed 

 either in a porcelain crucible with a cover or in a closed glass 

 tube, and heated to full redness for a few minutes. The fused 

 mass is treated with about 5 cm3 of 50 per cent acetic acid and 

 warmed, when, if the alkali earth elements are present, an odor 

 of hydrogen sulphide will generally be evident. The extract 

 is thrown upon a filter and the residue washed with about 5'"' 3 

 of water. The filtrate containing acid and water is treated with 

 a few drops of a solution of potassium chromate to test for 

 barium. The barium chromate is removed by filtration, and 

 the filtrate boiled with sodium carbonate to precipitate stron- 

 tium and calcium as the carbonates. If the precipitate of the 

 carbonates is very small, it may be dissolved in hydrochloric 

 acid and tested spectroscopically. If, however, it is not too 

 minute in quantity, it should be dissolved in nitric acid after 

 careful washing, and the strontium and calcium separated by 

 dehydration with amyl alcohol. 



The results follow in the table. A.11 tests for strontium and 

 calcium were confirmed by the spectroscope, and in (4) and (5) 

 strontium was found by the spectroscopic test. 



Pb present Ba p resent Sr present Ca present 

 gi'm. grm, grm. grin. 



(1) 0-0500 0-0500 0-0500 0-0500 Good tests for all. 



(2) 



00250 



0-0250 



00250 



0-0250 



Good tests for Pb, Ba, 

 and Sr. Ca faint. 



(3) 



00100 



o-oioo 



o-oioo 



o-oioo 



Pb and Ba good. Sr fair. 

 Ca doubtful. 



(4) 



0-0050 



0-0050 



0-0050 



0-0050 



Pb and Ba good . Sr fair. 



(5) 



o-ooio 



o-ooio 



o-ooio 



o-ooio 



Pb good. Ba fair. Sr 

 faint. 



(6) 0-1000 0-0050 Pb and Ba good. 



(7) 0-1000 0-0010 Pb good. Ba faint. 



From these results it would appear that these tests proposed 

 for barium and strontium, effective to at least a milligram of 

 each element, may with advantage precede the group precipi- 

 tation by hydrogen sulphide in the ordinary course of quali- 

 tative analysis. 



June, 1911 



