( 141» ) 



To ascertain, if Te comes more near to Bn or to Ir and Os 

 experiments with several acirls were tried, with a somewhat startino^ 

 result. Tellurium dioxide is dissolved by K HCn O4, forming well 

 developed microscopical crystals of a double oxalate, resembling 

 crystals of potassium-zirconium-oxalato in form, dimensions and 

 manner of formation. 



Here the question arose: How far may the isomorphism of tha 

 compound K2 Sn Clo with analogous compounds of other tetrachlorides 

 extend ? In the first place the behaviour of Pb CI4 was examined. With 

 strong hydrochloric acid, cooled l)y ice, Pb O2 gives a yellow solu- 

 tion, from which Cs CI precipitates dark yellow octaliedrons, while 

 in a solution, mixed with Sn CI4., bigger crystals of light yellow 

 colour are foi'med. From mixed solutions of Sn Cli and Pt Cli, no 

 compound crystals could be produced, while mixed solutions of SnCl^ 

 and Ir C'U gave a complete series, varying in colour from dark red 

 to a faint reddish yellow. Crystallization of pure chloroiridate is 

 prevented by means of a strong dose of hydrochloric acid and 

 heating, before adding rubidium chloride. At ordinary temperature 

 only a few compound crystals are formed, and these are faint) j- 

 tinged. Fractionating by repeated additions of Rb CI is to be recom- 

 mended; it facilitates the preparation of a complete series. Mixed 

 solutions of Sn CI4. and Os 04. are not so eas} to manage, besidoB 

 the variation of colour (from colourless to light brown) is not so 

 striking. Finally experiments were made with Mn CI4, prepared by 

 dissolving Mn Oj in cooled hydrochloric acid. From this solution 

 Cs CI precipitated dark red octahedrons, resembling crystals of the 

 compound K^ Ir Clo , while from solutions, mixed with Sn Cl^, 

 compound crystals of all shades between a dai'k red and a faint 

 reddish yellow were obtained, perfectly imitating the series productxl 

 from mixed solutions of Sn CI4 and Ir CI4. 



These last experiments are particularly suggestive. The isomor- 

 phism of K Mu O4 and K CI O4 is the principal argument for placing 

 Mn near CI in the seventh group of Mendelejeff; on account of 

 the isomorphism between K2 Mn O4 and K3 SO4 it might be placed 

 in the sixth group; reasoning from the experiments with the tetra- 

 chlorides of Mn and Sn would bring it into the fourth group; from 

 this it must be removed to the third group if you start from the 

 isomorphism between common alum and manganum-alum ; finally, 

 if you fix your attention to the crystalline forms of manganous 

 oxalate and of the double phosphate of ammonium and manganuni, 

 Mn must have its place in the second group, next to Mg. The 

 compounds of chromium exhibit a ;-imilar protean behaviour. 



11 



Procccdiugs Uujal Ac;ul Amstcrdani. Vul. I. 



