METALS AND METALLOIDS 69$ 



of sodium, the iodine and alkyl radicals became separately 

 attached to zinc : 



2C2H5I + 2Z11 = Znl 2 + Zn(C 2 H 5 ) 2 . 



Zinc ethyl is a liquid boiling at 1 18 and solidifying at — 28 ; 

 it is spontaneously inflammable in air, and is decomposed 

 violently by water. It is a remarkably energetic substance 

 and a most valuable reagent in research, as it reacts with a great 

 variety of inorganic or organic materials. 



The organo-mercury derivatives next discovered were pre- 

 pared either through the agency of zinc alkyls or directly by 

 the action of alkyl iodides on sodium amalgam : 

 Hg( 2 Na) + 2 C 2 H 5 I = 2 NaI + Hg(C 2 H 5 ) 2 . 



With zinc ethyl and mercuric chloride an intermediate 

 compound is formed : 



2 HgCl 2 + Zn(C 2 H 5 ) 2 - ZnCla + 2Hg(C 2 H 5 )Cl. 

 This mercury ethyl chloride gives rise to an iodide in which 

 moist silver oxide replaces iodine by hydroxyl. The product, 

 mercury ethyl hydroxide, is a strongly caustic base like potassium 

 hydroxide ; it liberates ammonia from ammonium salts, and 

 precipitates alumina and other metallic oxides from their 

 soluble salts. 



By the agency of the zinc and mercury alkyls it has been 

 found possible in many instances to combine the alkyl radicals 

 with other metals, but the reaction is by no means general, and 

 some metals have not as yet yielded organo-metallic derivatives. 

 It might therefore be profitable at this stage to consider in 

 which cases favourable results are obtained. 



2. The Position of Elements in the Periodic Scheme in 

 Relation to their Capacities for Forming Organic 

 Derivatives 



The periodic classification due to Newlands and Mendeleef 

 is now too well known to need detailed description. It is based 

 on the principle that the physical and chemical properties of 

 the elements are periodic functions of their atomic weights. 

 Starting with the elements of least atomic weight, excluding 

 hydrogen, it is found that during two periods recurrence occurs 

 at the ninth element, subsequently the periodicity becomes 

 doubled, but nevertheless all the elements can be arranged in 

 eight vertical series, each of these vertical series being divisible 



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