J. I. PMnney — Barium Sulphate in Analysis. 469 



more the recent work done in this laboratory by Drs. Mar and 

 Browning* on barium sulphate depends for its validity upon 

 the practical utility of this means of gathering and weighing 

 barium sulphate. Accordingly the following preliminary series 

 of experiments were undertaken with a view of discovering 

 under what conditions and how far the asbestos crucible could 

 be depended upon in quantitative methods as applied to the 

 estimation of barium as sulphate. In Series 1 the crucible with 

 a felt was ignited to bright redness for different periods of 

 time and weighed, then washed with hydrochloric acid, both 

 cold and hot, ignited, and re-weighed with results as shown 

 below. The crucible used was finely perforated and furnished 

 with a cover and cap, and the asbestos was prepared as directed 

 by F. A. Gooch,t in his original paper. A felt weighing 

 0*0258 grm. was thrown upon the crucible, washed thoroughly 

 with distilled water, dried, ignited, and weighed in less than 

 twenty minutes. The formation of blisters due to rapid 

 generation of steam was easily avoided by gradually increasing 

 the temperature from a gentle heat. A second crucible with 

 a felt weighing twice as much (0'0441 grm.) was ignited at low 

 redness for equal periods with similar results. 



Time of 



Seri 

 Weight 



ES T. 



Time of 



Weight 



ignition. 



in grams. 



ignition. 



in grams, 



2 min. 



00258 



10 min 



0-0258 



2 " 



0-0258 



10 ■' 



0-0258 



2 " 



0-0258 



20 " 



0-0258 



5 " 



0-0258 



20 " 



0-0258 



5 " 



0-0258 



30 " 



00258 



The same felt was washed with 20 cm 3 of a twenty-five per- 

 cent solution of hydrochloric acid, then treated with 5 cm 3 , 

 25 cm 3 cold, and 25 cm 3 hot concentrated acid respectively, and 

 suffered in no case the slightest diminution in weight, constant 

 weights being secured after an ignition of two minutes. 

 Finally as a matter of curiosity rather than because of its prac- 

 tical bearing the felt was digested in the crucible for fifteen 

 hours in concentrated acid, washed with 100 cm 3 distilled water, 

 and even then lost but 0'0001 grm. The stability of the asbes- 

 tos under the foregoing treatment is remarkable. An exces- 

 sive ignition for nearly two hours at bright redness gave no 

 appreciable change, while in the last experiment the trifling- 

 loss may perhaps be accounted for by mechanical disintegration. 



In Series II, barium sulphate brought to a constant weight 

 was treated with acid on the felt without difficulty — in the first 

 two cases with a few drops of dilute hydrochloric acid followed 



*This Journal, xli, 288; xliii, 314; xliv, 450. 

 f Amer. Chern. Jour., i, 317. 



