( 232 ) 



namely both to a higher K NO3 proportioa so that these limits have 

 become at 108°.5 : 40 pCt. and 84 pCt. 



The homogeneous rhomboedrie «'-crystals only begin below 129°. 5 

 to be transformed in rhombic mixed crystals ft'. 



For crystals of 100 — 84 pCt. K NO3 the transformation tempe- 

 rature falls from 129°.5— 108°.5 {GJ). At 108°.5 the composition 

 is attained, also possessed by the «' mixed crystals, which were 

 already present in the conglomerate with /^-crystals from 133°. Below 

 108°. 5 all the «'-crystals in the conglomerates are now transformed 

 in rhombic ones. The transformation is completed at this tempe- 

 rature. 



In consequence of the discontinuity of the mixing-series there 

 remain however below 108°. 5 still 3 mixing-types of rhombic crystals 

 viz. homogeneous ft and ft' crystals and conglomerates of both 

 limit-crystals. 



The limits of mixing and consequently the composition of the 

 two component parts in the conglomerates, being at 108°.5 ± 40 

 pCt. and 84 pCt. K NO3, diverge still more with falling tempera- 

 ture, so that they have become at 10°: 15.5 pCt. and 96.5 pCt. 

 {Jr,K and J^K^). 



At the lower temperatures these limits are easily found, by deter- 

 mining the limits of the mixtures in the crystals that are deposited 

 from aqueous solution. 



Physics. — ^]^ariation of voliune and of pressure in mixing {ÏÏ):" 

 By Prof. J. D. van der Waals. 



For a simple substance we may calculate how much its volume 

 under a given pressure and at a given temperature differs from that 

 which it would have occupied, if it had perfectly followed the law 

 of Boyle. 



Let us call the real volume v, and that which it would occupy 

 according to the law of Boyle v\ then the quantity to be examined 

 is v' — V. Let the quantity of matter be equal to the molecular 

 weight. 



From 



MET MRT a 

 P — 



v—b 



follows 



1 + 



-b (1 +a)(l —b){l +«0 V 



