880 



The following preparations are then analogous to i; the qnantity 

 of the metasilicate diminishes gradually, compared witii the closely 

 intermixed orthosilicate, which presents itself in round or polygonal 

 corns, often twinned in a particular way. The preparations, which 

 are in gross composition very close to Li^SiO^, show the crystals of 

 the orthosilicate often in a highly altered condition ; the immersion- 

 liquids also seem to he attacked by the expelled alkali, and measure- 

 ment is often impeded by it. 



The fact, that the crystals of the orthosilicate appear often more 

 or less attacked under the microscope, could make more probable 

 the view, according to whii;h the temperature of 1256° C. were rather a 

 "transfbrmation"-temperature than an ordinary melting-point; the 

 compound would be converted thus into a liquid, with partial dissociation. 



In the principal outlines we may say, that the binary diagram 

 Qf SiO., — LLJJ is known now. It will doubtlessly prove for the 

 present impossible, to investigate the behaviour of the components 

 at concentrations between orthosilicate and lithiunioxide in their 

 complete details, because of the enormous volatility of this oxide 

 at these extreme temperatures. 



Laboratory of Inoryanic and 

 Groningen, February 1914. /'/u/sical Ch>'niistri/ of the University. 



Physics. — -'The ro/ume of molecules ami the volume of the com- 

 ponent atoms." By Prof. J. D. van der Waals. 

 (Communicated in the meeting of January 31, 1914). 

 1 think 1 may assume as known that for normal substances the 

 \olume of the molecules expressed in parts of the gas volume at 

 0° and 1 atmosphere pressure may be calculated in a simple way 

 bv means of the critical quantities. When it is not yet taken into 

 account that the quantity b of the equation of state decreases with 

 V we find : 



J\_ 8 X 273 ^ 

 ''%,.~(l+a)(l-è) ' 

 in which b represents 4 times the volume of the molecules. If we do 

 take into account that this factor 4 diminishes when the volume, as 

 is the case for the critical state, has decreased to almost 2b, we find 

 by approximation: 



pj, — {l-Ya){l-h) '^ 



