

of Certain Elements whichform Insoluble Sulphates. 247 



was substituted for the sulphuric acid no precipitation took 

 place even in the presence of an abundant excess of that 

 reagent. To test the delicacy of the barium precipitation 

 under these conditions 1" ? of Ba was added to a clear solution 

 containing 01 grin, of Pb, 4 grm. of ammonium acetate, and 

 1 grm. of ammonium sulphate in 10 cm ' of water. The barium 

 sulphate was precipitated at once. It is evident from the>e 

 experiments that barium sulphate in small amounts may be 

 precipitated in the presence of lead salts by insuring the pres- 

 ence of a sufficient amount of ammonium acetate, and that 

 ammonium sulphate is to be preferred as the precipitant. 



In a previous paper from this laboratory* we have discussed 

 the application of fusion with carbon to the reduction of the 

 difficultly soluble double sulphates of the cerium earths with 

 the alkali sulphates, and mentioned the fact that this fusion 

 process had been used for the preparation of soluble barium 

 and strontium salts from barite and celestite. It is now our 

 purpose to show the application of this process to the detection 

 of the alkali earths when present as the sulphates. 



Several solutions containing m 5 me of Ea were treated with 

 sulphuric acid, the barium sulphate after filtration was treated 

 directly on the filter paper with a little pure sugar carbon, and 

 the paper containing the sulphate and carbon inserted in a 

 closed glass tube and heated to full redness for a few minute-. 

 After the ignition the mass was extracted by boiling with a little 

 hydrochloric acid, and after filtration the extract was treated 

 with sulphuric acid. In every case the precipitate was distinct. 

 although in a few instances faint. Comparative tests were 

 made by putting equal amounts of barium sulphate through 

 the treatment just described, and through the well-known 

 fusion process with sodium carbonate (fusing, washing with 

 water, and dissolving the carbonates in hydrochloric acid), with 

 possibly a little advantage in the carbonate process so far as 

 concerns the amount of barium shown, but scarcely enough 

 advantage to balance the saving of time in the employment of 

 the carbon ignition method. 



As the outcome of this work the following method is 

 suggested. 



About 10 cmS of a solution which may contain mercury in the 

 mercurons condition, silver, lead, barium, strontium, and cal- 

 cium, besides other elements, is treated with hydrochloric acid 

 in faint excess and the precipitated chlorides are filtered off. 

 To the filtrate are added about 5 grm. of ammonium acetate 

 and a 10 per cent solution of ammonium sulphate to complete 

 precipitation. After gentle warming, the alkali earth sulphates 

 are filtered off and washed with a saturated solution of ammo- 



* This Journal, xxxii. 164. 



