270 H. L. Wheeler— Double Halides of 



not appear possible to obtain the salt in pure condition." It 

 will be noticed that most of the analyses of the 3 : 2 chloride, 

 made in the present investigation, show a composition inter- 

 mediate between what is required for the formulas of the 3 : 2 

 and the 5 : 3 salts, but the bromide and the iodide were readily 

 obtained in pure condition and gave analytical results closely 

 corresponding to the 3 : 2 formula. Moreover the chloride, 

 bromide and iodide just mentioned are all hexagonal and may 

 be referred to axes which correspond closely to those of the 

 3 : 2 arsenic compounds. The chloride and bromide with a 

 complex composition (23 : 10 ?) confirm the results of Remsen 

 and Saunders on the chloride. The formula suggested by 

 them has been retained, subject to uncertainty. It will be 

 seen beyond that, as Remsen and Saunders have noticed, 

 the ratio 16:7 corresponds very closely to the analyses, and 

 it may be added that the ratios 9 : 4 and 7 : 3 differ so little 

 from the other two that it would be very difficult to dis- 

 tinguish between any of these ratios by analysis. 



For the preparation of the double halides the constituents 

 were mixed in the presence of the corresponding dilute acids. 

 In the case of the chlorides a 10 per cent acid was used. 

 The mixtures were then evaporated until crystals separated 

 on cooling. Further details will be given with the descrip- 

 tions of the salts. In the case of each salt several crops 

 were prepared and analyzed, and an attempt has been made 

 to determine approximately the limits of the conditions under 

 which these double halides are formed. It may be added that 

 the analytical results are not selected, for with the exception 

 of two antimony determinations, where an error had been 

 detected, every determination that was made has been given. 



Method of Analysis. 



. The salts were removed from the mother liquor, and, after 

 pressing on smooth filter paper, were dried in the air for a 

 short time. Portions of a little less than one-half a gram 

 were taken for analysis. In order to determine the halogens, 

 silver nitrate was added to a solution of the substance in 

 water containing a little tartaric and nitric acids, the mixture 

 was then warmed on the water bath for a couple of hours and 

 finally, after standing twelve hours, the silver halide was col- 

 lected, ignited and weighed in a Gooch crucible in the usual 

 manner. The determination of the antimony and rubidium 

 was effected in a separate sample. In order to do this, the 

 salts were dissolved in a little dilute hydrochloric acid and the 

 solutions were diluted with boiling water. Hydrogen sulphide 



