134 
CONTRIBUTIONS TO CHEMISTRY AND MINERALOGY. [bull. 167. 
Although the oil is doubtless a mixture, the above figures show that 
the constituents are members of the series (PNCl 2 ) n . A determination 
of the mean molecular weight was made, with the following results : 
Grams solvent. 
Grams sub- 
stance. 
Elevation 
(degrees). 
Molecular weight. 
46.72 
46.72 
4.130 
7.853 
0.178 
348 
1, 326 
1,290 
Mean 1,308. This does not lie far from that required by the formula 
PiiNn01 2 2 (calculated, 1,276). This result is interesting in as far as it 
shows that a phosphonitrilic chloride of this molecular weight may 
exist; that it is stable and miscible with benzene, gasoline, and ether, 
and that the molecular weight of the solid polyrner described below, 
which is insoluble, is probably very much higher. The oil has a red- 
dish-brown color, due to dissolved impurities, which are destroyed by 
heating with strong nitric acid. It can not be distilled even at 13 mil- 
limeters, as it polymerizes almost instantly. In its behavior toward 
water it resembles the preceding members of the series. 
Poly phosphonitrilic chloride (PN01 2 ) X . — This remarkable body, fre- 
quently alluded to above, is formed when any of the lower members 
are heated, slowly at 250°, and very rapidly at 350°. As the change is 
reversible, complete transformation can not be effected, but reaches 
perhaps 90 per cent, the remainder consisting not only of the original 
phosphonitrilic chloride, but of others. These can be extracted by 
anhydrous benzene. The sample, the analysis of which is given, was 
prepared by heating pure triphosphonitrilic chloride in a sealed tube 
at 350°-4G0°. The transparent elastic product was repeatedly extracted 
with benzene dried over sodium and the absorbed benzene removed in a 
vacuum with constant exhaustion over paraffin, and finally by heating 
in vacuo at 110°. Analysis gave: 
Calculated for 
(PNCl 2 )x 
Found. 
p 
26.75 
12.11 
61.14 
26.78 
12.27 
60.45 
N 
CI 
P:N:C1 = 1:1.01:1.98. 
Polyphosphonitrilic chloride, when perfectly pure, is colorless and 
transparent, but is' generally somewhat discolored by traces of organic 
matter. Its most striking property is its elasticity. It may be drawn 
out like rubber, and shows even a greater tendency to rebound from 
hard surfaces. It is readily cut with the shears. It is insoluble in all 
