( 153 ) 
grey modification is enormous. One of our tin blocks is entirely 
fissured and eaten away on the lower side whilst on the upper 
surface a number of grey protuberances are visible which gradually 
become greater finally developing into large cracks. 
We shall shortly report on some physical constants of grey tin 
and on its crystalline form. 
We shall be pleased to send a sample of grey tin to any one 
interested in the matter. 
Amsterdam, Chemical Laboratory of the University, 
September 1899. 
Chemistry. — “On a new kind of Transition Elements (sixth 
kina)” By Dr. Ernst Conen. (Communicated by Prof. TH. W. 
BAKHUIS ROOZEBOOM). 
(Read in the next meeting of September 30th 1899.) 
1. The name, sixth kind of transition element, will be applied 
to elements built up in accordance with the formula : 
Electrode of a metal M| Solution of a salt of | Electrode of the metal 
in the modification « the metal df. M in the modification 7 
(stable modification). (metastable modi- 
fication). 
Since, up to the present, no metal 
was known which, at suitable tempe- 
ratures, occurs in two modifications, 
it was impossible to realise an element 
of this kind. As Dr. van Eyk and [ 
have shown!), the metal tin has a 
transition point at 20° C. Below this 
temperature the socalled grey tin is 
the stable form, above it the white. 
Since the white modification may 
be considerably supercooled we may 
put together, below 20° C., an ele- 
ment (see Fig.) of the form 
1) Report of the session of June 24th, 1899, p. 36, and of this session, p. 149, 
