( 253 ) 



proportion bad fallen to 4,04 IL. 0, and for the next three months 

 this proportion varied according to the vapour-tension of the air, 

 between 4,64 and 4,55 IlaO. unaltered weight, rising or falling 

 were found to agree with the indications of the hygrometer (of 

 Klikkerfues). Meanwhile a little decline was observable. If the 

 vapour-tension of the air, which in that time varied between 10 

 and 8 m.m. had fallen to 7 ni.ni. and had remained stationary 

 for some time, the composition ± 4 HjO would have been 

 attained. For this amount has been obtained in the Gel I after 

 some months at that vapour-tension. That composition would have 

 risen but little if the vapour-tension of the air had become again 

 greater. 



That the composition depends on the temperature, that the power 

 of absorption is weakened by heating to higher temperatures, and 

 is destroyed at incandescence, all this I have already communicated 

 before ^). 



Dr. Klobbie and I have only succeeded in observing the transition 

 of colloidal ferric oxide to a crystalloidal chemical hydrate in case of 

 monohydrate-), by the influence of water at 15° on the hexagonal 

 crystals of the chemical compound FeoO;;. Na^O, in which Na^O is 

 gradually replaced by ITo without the crystalline structure (form, 

 tiansparency, power of polarisation) being modified. Nature provides 

 us with the crystalline Monohydrate: Göthit, that can bear heating 

 to ± 280° without losing v/ator and without passing into the amor- 

 ])hous state ^). 



Chemistry. — Mr. van Bkmmklen presents in the name of 

 Mr. B, de Bruijn a paper on an investigation held in the 

 Inorganic Chemical Laboratory of the University of Leydon, 

 concerning : „ T1t,e equilihrhim of sijstenis of Ihn'o siibsfnnrcsj 

 in irltich two liquids occur". 



In systems of three components, in which two licpiid phases 

 occur, the following cases may be distinguished : 



PK the components A and B form together two liquid phases; 

 equally so the components A and C and B and C. 



2'«i. the components A and B and A and C form two liquid 

 phases, but the components B and C do not, at least in stable 

 conditions. 



') Eecueil ?. 111—113. Zeitsclu-. ;ni(irii-. Cli. 18. 24.. 

 -') J. f. pr. Ch. ■»«. 523— 52'J. 

 ') J. f. pi'. Ch. 4e. 521. 



