Art. 10. — K. Matsnno: 



NH, 



H,0' 



NH3 



Cl + 



COOH 

 COOH 



NHj 



coo. 



KH, 



COO 



(Indigo blue) 



If we assume that the two water molecules are placed in the 

 cis-position in tlie indigo blue [Co C1(H,0), (NHg)«] SO^. they must 

 necessarily be situated in tlie trans-position in tlie other isomer, 

 i.e. in tlie violet [Co Cl (H^Oj^ fNH3)3] SO,. This presumption was 

 clearly vei-itied by tlie study of the absoi-ption spectra (cf. the part 

 on the absorption spectra). Therefore in the dichro-salt the two 

 chlorine atoms must coordinate in the trans-position. These 

 relations are shown as folloAVs : 



SH, 



HjO^ 



NHj 



SOiH -^ 

 H...0 

 in cold 



(IndiiJfo blue) 



SO, -- ^ 



warmed 



SO4 



NH. 



(Violet) 



If the indigo blue compound [Co Cl (H.,0)« (NH,)J SO, is ground 

 up with concentrated hydrochloric acid, a grey coloured powder is 

 obtained, analysis of which gives the formula [CoCl.HsO (NH3)3]C1"\; 

 this substance must be considered as the isomer of the greenish 

 dic'iro-salt of the following configuration : 



NH, 



1 1.0 



ML 



SO4 ^ 



HCl 



NH, 



Cl 



NH3 



(Indigo b]\ii') 



Having come lo this conclusion, we have 110 nci'd for fuither 



(li N\ «lutr : Ztit. auorg. Cht-u:., 15, 144, 1897, 



