313 
J By = 1312 tat S159. 
The value of p is obtained from this by multiplication by a, 7, : 
anp We shall directly find the value 11,72 .10-? for Vax, so 
that ap becomes = 137,4.10—-4. Further a, == 7.10, hence 
,: dp = 0,357. If we again take n, = 16, just as for red phosphorus 
at the transition liquid-solid, 7, == +4: 1,616 — 2,48 (see below), then 
n,: np becomes — 6,46. Hence a, n, : dr nj would become = 2,31. . 
But this renders g no more than 1,59 x 2,31 = 3,66 instead of 5 
or higher. Most probably, therefore, the value of aj; has been taken 
too high, or the degree of association of liquid Arsenicum at the 
triple point is still higher than 16. 
In connection with this we once more draw attention to what 
was found for red phosphorus, which modification is quite analogous 
to the ordinary arsenicum, whereas the yellow phosphorus seems to 
correspond with the drown-black Arsenicum. [density red P 2,20, 
yellow 1,83: only this latter value gave good results. Ordinary 
Arsenicum D=4,7, brown-black 3,7: again only the latter value 
gives correct results. Triple point red P is high (589°,5 C.) with a 
pressure of 43 atm. and near 7%, (695° C.); triple point ordinary As 
also very high (817° C.) with a pressure of 45 atm. and again 
near 77, (1050° ©.) |. It was namely found for the red P by ScHENCK 
(See inter alia HorremanN, Leerboek I, 2nd edition p. 223—224), that 
the polymerisation state must be considerably higher there than P,. 
Accordingly we may safely assume a degree of association both for 
red P and for ordinary As of at least 16 at the triple point. 
The above used value of az is calculated in the following way. 
We find the value a; = 340,i . 10-4: nz (for 0 = [28 : (8y —1)] x 
< lv: (vy +1)]? is found 0,970), hence, Vaz =18,44.10-?: yng with 
% = 1320, 6, =195.10-5 from the formula 7;,—= 780 nz X ag: br. 
Now at the critical temperature 77 is certainly < 4’), so that Vaz 
will be >9,2.10-2. And as the normal (theoretical) value for As 
amounts to 7.10~-2, there is necessarily already splitting up into 
isolated atoms As, at 7, which exhibit a so much greater attraction 
(Vaz = about 30.10—2). If we assume that the molecules As, split 
up directly into As,, without passing through tlie transition stage 
As,”), we may put n,—4:(1-+ 32), when « is the degree of 
1) According to PREUNER and BROCKMÖLLER (loc cit.) C° : c‚ would be = 0,066: p 
at 1100° C. for As, 2As), hence at a pressure of 125 atm. ¢?: cy = 0,00053, 
or C,=0,025, when -c, is near 1. Further ¢,?: c, = 0,013 : 125 = 0,00010, 1 e. 
c‚ =0,01, referring to c= 1, would hold for the reaction As, — 2As (also at 
1100° G.). 
*) Indeed, if we assumed a slight splitting up into Asg then of this almost every- 
