Chemistry. — “The Metastability of the Elements and Chemical 
compounds in consequence of Enantiotropy or Monotropy and 
its bearing on Chemistry, Physics and Teehnies”. 1. By Prof. 
Ernst COHEN. 
(Communicated in the meeting of June 26, 1915), 
1. On the basis of the researches on allotropy of the metals 
carried out by myself and my collaborators, I pointed out © that 
the strongly marked reluctance to undergo transformation shown by 
these elements is doubtless one of the reasons why these phenomena 
remained for so long undiscovered. 
However, by employing certain devices (using the metals in a 
very finely divided state, adding an electrolyte) we succeeded in 
increasing the transition velocity to such a degree, that the change 
of the metastable to the stable form ocenrs within a short time, so 
that these phenomena can now be studied in the laboratory. 
2. Having stated that the metals as we have known them 
hitherto are metastable systems, consisting of two (or more) allotropie 
forms, the question arose whether this might also be the case with 
the non-metals and with chemical compounds, i.e. whether we have 
to deal with a special’ property of the metals or with a special case 
of a phenomenon occurring quite generally in nature. 
We shall discuss in this and in some subsequent papers the 
materials which seem to prove that this is really the case. 
3. Considering in the first place the non-metals, sulphur at once 
attracts notice. Each page of the interesting investigation carried out 
by Rercner*) (The temperature of the allotropie change of sulphur 
and its correlation with pressure), which summarises also the observ- 
ations of others, shows that the same phenomena observed by us 
in the case of the metals, play a role here. 
4. I especially mention here the investigations carried out at the 
request of van ’r Horr by Ruys*), when he wintered in the Kara 
Sea. He determined the rate of stabilisation of monoclinic sulphur 
at low temperatures. If molten sulphur is quenched, only a small 
part undergoes immediate transformation into the rhombic modifi- 
1) These Proceedings 16, 632 (1914); 17, 200 (1914); 17, 926, 1238 (1915). 
*) Dissertation, Amsterdam 1883. Zeilschr. für Kristallographie 8, 593 (1884). 
5) Rec. des Trav. chim. des Pays-Bas 3, 1 (1884). 
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