7()(i . 



set free from the less soliiV)le compounds with optically' active bases 

 or acids, in the case of trict/u/hmedi((nüne-dev\ya\\yes exhibit just the 

 opposite I'Otatory power, as is observed in. the case of the complex 

 trioxalates ; a fact, which sustains the view, according to which it 

 is the basic or acid natui-e of the radicles placed round the central 

 meiallic atom, rather than the special nature of the latter, which in 

 the first instance determines the direction of the rotation. 



Anffular Values-. 



c:R = (0001): (1011) = 



m:t = (10T0):(022l) = 



m.m = (10T0):(0ri0) = 



R.R = (10ll):(Tl01) = 



c:r = (0001):(0lTl) = 



r:s = (0111): (0221) = 



s:m^= (0221):(0fl0) = 



s:R = (0221): (lOTl) = 



R.t = (0r[l):(02"21) = 



R:m= (10Tl):(10T0) = 



x:R = (2241): (01 11) = 



No distinct cleavage was observed. 



The specific gravity of these crystals was at 15° C^ determined 

 at: ^/^„= 1,8893; the molecular volume is therefore : 242,57, and tiie 

 topical parameters become: •/:*'* ^ 7, 4(i7(i : 6,(^971 ; or y/ = 6,3789. 

 Tlie values of / of the Co-, Uho-, and /r-compounds appear to 

 decrease therefore continuously with increasing atomic weight of the 

 metallic atom, while *.o reaches a minimum in the case of the 

 Rho-B&\\. 



Groningen, November 1918. 



Ldboratory for Inon/anic and Physical 

 Chemistry of the University. 



