432 PROCEEDINGS OP THE AMERICAN ACADEMY. 



crucible protected from the flame by a very large crucible. While the 

 silver iodide was fused, a small quantity of the purest iodine was placed 

 upon the lower side of a second crucible cover, and this cover was sub- 

 stituted for the one which had been weighed with the crucible. The 

 iodine immediately vaporized and the silver iodide was thus fused in an 

 atmosphere containing iodine vapor. Finally, the cover was removed, 

 so that the uncombiued iodine escaped from the crucible, and the salt 

 was kept fused, covered with the original crucible cover, until it was 

 certain that all excess of iodine had been eliminated. That no excess 

 of iodine was retained by the silver iodide was readily shown in one 

 experiment with eighteen grams of salt by reheating the salt to its fusing 

 point and reweighing. A loss in weight of only 0.00003 gram resulted. 

 After the silver iodide had been weighed it was heated in a current of 

 chlorine. This gas was generated by dropping concentrated liydrochloric 

 acid upon manganese dioxide, and it was purified and dried by bubbling 

 through water and passing through a three-foot tube filled with beads 

 moistened with concentrated sulphuric acid. Traces of bromine or iodine 

 in the chlorine would have been no disadvantage, and it is inconceivable 

 that it should have contained fluorine. In order to prevent spattering of 

 the fused salt from the crucible, a perforated porcelain disk, which fitted 

 the crucible half-way between the bottom and the top, was placed in the 

 crucible. This disk was always weighed with the crucible. The chlorine 

 was conducted into the crucible by means of a small hard glass tube, 

 which glassed just through the perforated cover of a Rose crucible. The 

 apparatus for generating chlorine was constructed wholly of^lass with the 

 exception of the joint between this hard glass tube and the drying tube. 

 The chlorine did not come in contact with the rubber tube used in making 

 the connection tight, however, for the hard glass tube telescoped into the 

 drying tube for some distance and the joint was sealed with concentrated 

 sulphuric acid. In order to avoid volatilization of the silver salts, the heat 

 applied was very gentle and only suflicient to fuse the silver chloride. 

 Even at this temperature the iodine was rapidly replaced. Heating in 

 chlorine was continued some time after the color of the iodine vapor had 

 ceased to be visible. Then the Rose cover was replaced by the ordinary 

 cover and the silver chloride was kept fused for several minutes, with 

 occasional lifting of the cover, so as to drive off" any chlorine which might 

 have been dissolved by the fused salt. Although fused silver chloride, 

 when cooled in chlorine, dissolves this gas very appreciably, no evidence 

 was found that any remained in the solidified salt when it was heated for 

 a short time in air. In one experiment eighteen grams of the chloride 



