On the Equivalent and Spectrum of Ccesium. 197 



We concluded from these experiments that our chloride of 

 caesium was free from lithium, and as pure as it is well possible 

 to obtain any substance without the most extraordinary and for 

 most purposes unreasonable precautions.' 



As to the properties of the chloride of csesium, we observed that 

 not only is it not deliquescent, but it is hardly hygroscopic. The 

 unfused and porous salt may be weighed in moist air with as much 

 accuracy as chloride of sodium. After it has been fused it does 

 not alter in weight during twenty-four hours' exposure to the 

 air in cold dry weather. It may be fused in a platinum capsule 

 over the gas-tiame when the air is dry without acquiring an alka- 

 line reaction. In a damp atmosphere it is apt to lose chlorine 

 during fusion. The residue, after the reduction of platinochlo- 

 ride of csesium by hydrogen at a gentle heat, is alkaline. It is 

 hardly possible to fuse chloride of caesium without loss by vola- 

 tilization. Hence our first estimations of caesium in this form 

 were too low by 4- to 7-tenths of 1 per cent. 



For determining the equivalent of caesium we have made four 

 chlorine-estimations. Two of these (I. and II.) were made in 

 the chloride obtained as already described. Their details and 

 results are given below. The filtrates from these analyses, 

 contaiuing nitrates of caesium and silver, after the latter had 

 been removed, were added to a solution of several grammes of 

 the original chloride, and the whole was partially precipitated 

 with bichloride of platinum, and a second portion of chloride of 

 caesium procured, on which determination III. was made. Finally, 

 the nitrate of caesium from this analysis was mingled with repeat- 

 edly purified chloride obtained in the previous study of the spec- 

 trum ; about half the caesium was again thrown down as platino- 

 chloride, and with this product another estimation of chlorine 

 (IV.) was made. 



The determination of chlorine was conducted in the usual 

 manner, by precipitation with nitrate of silver and filtration. 

 Washed Swedish filters were employed, which gave each an ash 

 weighing four-tenths of a milligramme. The weighings were taken 

 on a balance by Becker and Sons, of Brooklyn, New York, which 

 with an ordinary load indicates one-twentieth of a milligramme 

 with great decision and perfect constancy. 



The data of our determinations are as follows : — 



I. 1-8371 grms.Cs CI gave V5634 Ag Cl=-386598 CI, and 1*4505 Cs. 



II. 2-1295 „ „ 1-8111 „ —447848 „ 1-68165 „ 



HI. 2-7018 „ „ 2-2992 „ =-56853 „ 2-13327 „ 



IV. 1-56165 „ „ 1-3302 „ =-32893 „ 1-23272 „ 



The percentage composition of chloride of caesium, and the 

 equivalents deduced from the above figures, are as follows, silver 

 being considered =107*94, and chlorine =35*46, Stas : — 



