647 



F'or H in eompoundy only the values 3,2 and chiefly 1,6 hold. 

 The value 1,1 calculated directly from Ti- and pk of H, is only 

 found for H.^ itself. 



3. However — what is self-evidently not found for h — it 

 should be taken into account that for (he fundamental values of 

 ya the indicated attractions can be entirely or partly destroyed by 

 an interception of the rays of attraction. Thus the value of V'a of 

 a cejitral atom suri-ounded on all sides by atoms or atom groups 

 — as e.g. in CH^, C,H„ etc., Si in SiCl,, Sn and Ge in SnCI^ 

 and GeCl^, N and P in NHg and PH.^ — is found = everywhere, 

 so that these enclosed atoms do not exert any attractive action, 

 tonmrds the outside ^). 



But as soon as the C-atom gets partly free again, by double 

 bindings e.g. as in CjH^ (only imagine the position of the C-atom 

 stereo-chemical), the value of ^au I'ises immediately from to 1,55, 

 hence half the fundamental value 3,1. And when the C-atom gets 

 entirely free, for triide bindings e.g. as in C,H,, the full value 3,1 

 is accordingly at once found. 



This rule holds everywhere. An interesting example is the iso- 

 amylene. Here thei-e are three singly bound and two doubly bound 

 C-atoms. Hence the value 3 > 0-^2 1,55 + 10 X J, 6 = 19,1 is 

 calculated for \'^ak. From 7'^ and />/,. 19,2 was found. Indeed, an 

 exceedingly remarkable confirmation of the rule. 



The same thing holds for benzene and naphtalene. But for the 

 singly bound C-atoms in the substitution groups the old value is 

 again valid. Thus for Toluoene = CgHj.CHj the value of y^ajc is = 

 = 6 1,55 + 1 X + 8 > 1,6 = 22,1, while 22,2 is found ; for 

 O-Xylene = C«H,(CH,), we calculate 6 X 1 ,55 + 2 X + 10 X 1,6 = 

 =: 25,3, quite identical with the value 25,3 found from Ti and pk. 

 We might add numerous others to these examples, but we refer for 

 this to the earlier princi|)al papers. 



We have now reached the )nain question: what happens when 

 the atoms no longer occur in compounds, as N in N,, CI in CI,, 

 etc. — but can occur entirely free, as for the metals, or for the 

 free atoms CU, Br aiul I in Cl^, Br.,, I,, which get decomposed at 



1) Accordingly in consequence of this (see the table) we were not able <o give 

 tlie values of t' «^. for Si, Ti, Ge and Sn in compounds, though compounds of 

 them are known, of which Tk and pL have been determined. But it is exactly in 

 these compounds (SiCl^., GeCI^ etc.) that the attraction of the central atom Si, Ti, 

 Ge, Sn is eUminaled. 



