452 PROCEEDINGS OF THE AMERICAN ACADEMY. 



the whole series of investigations, and during a single experiment no 

 appreciable variation in weight could be detected. 



The boat was now filled with caesic chloride, and placed within the 

 drying apparatus in the position indicated in the diagram, which illus- 

 trates the " bottling apparatus," but not the elaborate purifiers of air 

 and nitrogen. The weighing bottle belonging to the platinum boat is 

 placed in the extreme left of the tube A, while its stopper rests in the 

 crevice B, and pure nitrogen thoroughly dried by means of phosphoric 

 oxide was allowed to traverse the apparatus. After about three-quarters 

 of an hour the platinum boat was gradually warmed by means of a large 

 " fish-tail " spreader on the Bunsen burner, so that the whole of the 

 boat may be equally heated. The caesic chloride soon fused, and was 

 kept in a state of tranquil fusion until it was reasonably certain that 

 every trace of residual water must have been expelled. The tempera- 

 ture was now gradually lowered, and the boat was finally allowed to 

 cool to the temperature of the room. A current of air dried by phos- 

 phoric oxide was then turned on by opening the appropriate stop-cock, 

 and was allowed to flow for about an hour before the bottling, so as to 

 sweep out all the nitrogen. While the dry air was still flowing, a glass 

 rod was inserted at the right, and the boat was pushed back into its 

 weighing bottle. The stopper was now rolled out of its hiding-place, 

 and was pushed by means of the glass rod firmly into the neck of the 

 weighing bottle. After the tube A had been removed, the weighing 

 bottle was partly removed by means of a hooked wire, and transferred 

 by the aid of a pair of tongs to the desiccator. After suitable delay, 

 the tube, boat, and substance were weighed in the same manner as 

 before. 



Since argentic chloride is essentially insoluble in solutions containing 

 either silver or chloride, the chlorine in this pure, dry caesic chloride 

 was precipitated by means of an excess of argentic nitrate. Since, more- 

 over, it was desired to determine the weight of silver needed to effect 

 the precipitation, this argentic nitrate was prepared from a carefully 

 weighed portion of pure silver, and the excess in the filtrate also was 

 weighed as chloride. It is not necessary to describe again the many 

 precautions necessary to carry out, in a strictly quantitative fashion, the 

 solution, mixing, and filtration of these materials, because previous 

 communications from this Laboratory have discussed them in adequate 

 detail. Due care was taken concerning the use of nonactinic light, the 

 collection of the fragments of asbestos often lost from the Gooch cruci- 

 bles, the traces of water retained by argentic chloride even at 150°, 



