Wells — Atoms in Inorganic Triple Salts. 417 



Art. XXXIX. — A Chromoplwre Grouping of Atoms in 

 Inorganic Triple Salts, and a General Theory for the 



' Cause of the Colors of Substances; by Horace L. 

 Wells. 



[Contribution from the Sheffield Chemical Laboratory of Yale University.] 



The intense black color and complete opacity of the 



two salts 



Cs,Ag 2 Au'" 2 Cl 12 and Cs,Au' 2 Au"' 2 Cl 12 

 together with the less intense blackness of 



Cs 4 CuAu"' 2 Cl 12 



which, although its minute crystals were very black, was 

 distinguished from the first two salts by yielding a pale 

 brown powder instead of a jet black one, while the salts 



Cs 4 ZnAu'" 2 Cl 12 and CaJBgAtTClu 1 



were comparatively pale in color and were transparent, 

 attracted much attention, and an explanation of these 

 very remarkable deep colors has been sought. 



In this connection attention was directed to Setter- 

 berg's very intensely colored salt 2 



Cs 4 Sb"'Sb T Cl 12 



which "Wells and Metzger 3 in this laboratory showed to 

 be octahedral and isomorphous with Cs 2 Pb iv Cl 6 , and which 

 has an exceedingly deep blue color, so that even very 

 small crystals of it appear absolutely black and opaque, 

 although the very fine powder, or the precipitate, shows 

 the deep color. 



Upon comparing the two salts 



Cs,Au' 2 Au'" 2 Cl 12 and Cs,Sb'"Sb v Cl 12 



it is to be observed that each of them contains atoms of 

 a metal in two states of valency. This is the main fea- 

 ture, requiring some modification on account of the colors 

 of the silver and cupric compounds already mentioned, 

 of the theory, now presented, of a chromophore grouping. 



*A11 of these triple chlorides were described by the writer in the May, 

 1922, number of this Journal. 



2 Ofversigt K. Vetensk. ATcad. FdrhandL, 1882, 23. 



3 Amer. Chem. Jour., 26, 268. 



