( 356 ) 



From this it appears that this photochemical transformation is qnite 

 analogous to that wiiich the acid itself, according to Boësekkn, under- 

 goes by heat. From what has been stated above, this reaction cannot 

 be put on a level with the photochemical decomposition of the tri- 

 chloroacetate, without further evidence. 



Labor, for Inorg. and Phi/.s. Cltem. 

 15 September 1911. of the Univ., Groningen. 



Clieinistry. — "xl remarkable case of isopohj mor plasm with sails 

 of the alkali-metals". By Prof. F. M. Jaeger. (Communicated 

 by Prof. P. VAN Romburgh.) 



(Communicated in tlie meeting of Sept. 30, 1911). 



§ 1. The numerous researches which have been made to explain 

 the morphotropic relation of the alkali-metals, may be said to have 

 led to no other view but the conviction, that the problem of the 

 mutual replacement of these metallic atoms is one of an almost 

 hopeless complexity. 



The most accurate researches in this dominion, — ^ those of Tutton, 

 — lead the author, with complete negation of all other well esta- 

 blished facts, to the conclusion that anyhow the metals K, lib and 

 Cs possess plainly an isomorphotropic relation, which numerically 

 runs parallel with the rise of their atomic weights, and that (-V/^4) 

 and Tl are, in many respects, to be placed outside the series; but 

 that with an eventual form relation the (A^//J-radical exerts an 

 influence which stands between that of lib and Cs. As to the optical 

 })roperties, no regularities seem to occur. As is well known, Tutton's 

 beautiful researches only relate to the alkali-sulphates, the alkali- 

 selenates and the monoclinic double sulphates and double selenates 

 of the formula: R\Jfe" {SO,),, 6//, O and A^', Jfe" {Se (),).„ QH, O. 



Even in these researches it seems here and there, that the con- 

 clusions drawn must be considered as being too general. For instance, 

 with the selenates, the 77-compound is very analogous to the lib- 

 salt ; the difference in molecular volume is here only 0,47o, as 

 against l,4"/„ between the lib- and (A^//J-salt. With the sulphates 

 this difference between the Rb- and Tl-^alt is about 0,8"/(,, between 

 Tl- and (X//J-salt only 0,087„, and a similar trifling difference 

 between (A^//J- and TAsalt is also observed with ammoninm-zinc- 

 sulphaie and thallous-zmc-sulphate (0,03"/(,), so that the place of 



