( 410 ) 



Tlie lower the sul)limati()n temperature of the added substance, 

 the further (h)u-nward tlie course of the sulilimatiou li]ie of a solid 

 substance will extend. If, therefore, gases are used as admixtures 

 and in sufticient excess, any solid substance ought, theoretically, to 

 volatilise at a very low temperature. 



Of this circumstance advantage has often been taken in the artiti- 

 cial preparation of minerals by sublimation-methods in which gases 

 or \apours (.V/f, (7) have been used as second substance. 



If, however, they exercise a chemical action on tiie others, the 

 subUuiatiou phenomena belong to systems of tlu-ee or more components. 



The sublimation pheiKuuena may also be accompanied by plieno» 

 mena of fusion, as may be decbiced from an exaiuiuatiou of other 

 sections through mv three (buiensional tigure. 



Chemistry. — "A qmnitifatlri' research concerniiH/ Baeyer's Ti'nsani 

 Thi'nni'' By Prof. A. F. Holleman and Dr. G. I.. Voerman. 



(Commuüicaled in llie meeting of November iX, 1903'. 



Pjaeyer's tension theory gives an explanation of numerous pheno- 

 mena in organic chemistry, but it is, however, almost exclusively 

 of a qualitative nature. The preference for die formation of cyclic 

 compounds with 5 and the instability of cycle systems with a larger 

 or smaller number of atoms required by the theory are con- 

 firmed in many instances. Meanwhile as far as I am aware, that 

 "preference" and that "instability" has never been expressed in 

 figures. And so long as this is not the case such expressions remain 

 vague, as we do not possess any measure with which we can gauge 

 the ''preference" for the cycle formation w ith 5 over one with a 

 different number of atoms, and also are not in a position to compare 

 the stability of one compound with that of another. 



I, therefore, suggested to Dr. Voerman to investigate quantitatively 

 the relative stability of the members of a special class of cyclic sys- 

 tems, namely the anhydrides of the dibasic acids of the normal satu- 

 rated series. They are again converted by the action of water into 

 the dibasic acids. The ease with which they re-absorb Avater must 

 depend on the degree of tension in the ring contained in these 

 anhydrides, as the ring opens and the l»onds then can retake their 

 normal position. The velocity with which these anhydrides are 

 converted into the corresponding acids may therefore, be taken as 

 the measure of the tension in the ring. 



