206 Washington — Kaersutite from Linosa and Greenland. 



enes which are under discussion, as well as by the fact that 

 these constituents generally show such a constant ratio, as 

 pointed out by Doelter.* The partial replacement of Ea 2 by 

 (Fe, Mg) /; , sometimes observed, would harmonize this idea 

 with that of Firsson. 



The chromophoric titaniferous radical would seem to be 

 more intensely active or color-producing than the alumo-ferric- 

 soda one, since amphiboles high in titanium, but otherwise 

 chemically like those low in this element, are red-brown 

 rather than blue, as is shown by the relations of aenigmatite 

 and arfvedsonite. But its nature is at present difficult to 

 suggest. The ability of titanium to assume some seven states 

 of oxidationf complicates the problem immensely, even though 

 this possible number is lessened by considering only the oxides 

 most commonly met with, Ti 2 3 , Ti0 2 , Ti0 3 . It may only be 

 mentioned here that the violet or blue colors of solutions of 

 Ti 2 3 , and the yellows and deep browns of those containing 

 Ti0 3 4 such as are produced from colorless Ti0 2 solutions on 

 the one hand by reduction with zinc or tin, and on the other 

 by the action of H 2 2 , may be possibly significant of the con- 

 dition of oxidation of the titanium. 



The constant, characteristic pleochroism of the colored, 

 common amphiboles, which do not contain the supposedly 

 chromophoric Na (Al, Fe)"'- radical, as contrasted with the 

 equally characteristic non-pleochroism of the colored, common 

 pyroxenes (free from the acmite molecule), leads also to the 

 speculative suggestion that the difference is possibly connected 

 with difference in the structure of the molecule. Accepting 

 provisionally the suggestion of Penfield and Stanley that the 

 amphibole acid has a closed chain or ring structure, it might 

 be advanced as possible or probable, in analogy with the car- 

 bon compounds, that the pyroxene acid is of the open chain 

 type. Or the relations might be the reverse. § 



In our present state of complete ignorance as to the consti- 

 tution and structure of the mineral molecules any such sug- 

 gestion as is here made can but be regarded as a hypothesis 

 of the most speculative character. But such a difference in 

 structure would be a fundamental one between the molecules 

 of the pyroxenes and the amphiboles, and it undoubtedly 

 exerts a profound influence on the physical properties of iso- 

 mers, as the pyroxenes and amphiboles are regarded with 

 reason as being. 



*C. Doelter, Zeitschr. Kryst., vol. iv, p. 40, 1880. 



f P. E. Browning, Introduction to the Earer Elements, p. 61, 1903. 



I A. Classen, Ausgew. Methoden Anal. Chem., vol. i, p. 765, 1901. 



§ It is, of course, understood that the terms " open chain" and "closed 

 chain " are used as they are in organic chemistry, without implying that 

 they actually thus represent the structure of the molecule, or the arrange- 

 ment of the atoms in space. , 



