stokes.] TRI- AND TETRAPHOSPHONITRILIC CHLORIDES. 81 
denser. Distillation is continued only as long as much substance 
passes over; during the later stages large needles — mainly the new 
chloride, P 4 N 4 Cl y — slowly collect in the condenser. There remain in the 
flask, besides a strongly acid liquid, a little solid material, consisting 
partly of phospham, partly of the crystalline acid ammonium tetra- 
metaphosphimate, P 4 N 4 8 H 6 (NH 4 ) 2 , and a considerable amount of oil, 
which solidities, on cooling, to a crystalline cake of the compound 
P 4 N 4 01 8 , impregnated with an oil of the same empirical composition. 
The distillate, consisting of triphosphonitrilic chloride, mixed with 
about 5 per cent of tetraphosphonitrilic chloride, is dried, and an 
approximate separation effected by systematic recrystallization from 
benzene. This solvent has proved the most satisfactory, because the 
chlorides, in benzene solution, are scarcely affected by water, and no 
care need be taken to exclude it completely; aqueous ether, on the con- 
trary, acts with considerable ease. The triphosphonitrilic chloride is 
pure after three or four recrystallizations, the tetraphosphonitrilic 
chloride accumulating in the mother liquors, the residues from which 
are again subjected to distillation with steam, the substance remaining 
in the flask being added to the first residue. 
Apart from its influence on the melting point, the presence of very 
small quantities of the new body in the triphosphonitrilic chloride is 
readily detected by dissolving in alcohol free ether and agitating for 
several hours with a little water, the tetraphosphonitrilic chloride being 
indicated by the formation in the water of microscopic needles of the 
difficultly soluble tetrametaphosphimic acid. 
The residue from the distillation with steam is sucked out, whereby 
most of the oily chloride runs through with the water, and may be col- 
lected. The substance is then dried, the tetraphosphonitrilic chloride 
extracted with benzene and purified by several recrystallizations from 
this solvent. The residue left by the benzene, treated with dilute 
ammonia, leaves amorphous substances, and gives up tetrametaphos- 
phimic acid, which is thrown down, on acidifying, as its acid ammonium 
salt. It may be mentioned here that the affinity of this acid for ammo- 
nia is such that its acid salt remains uiidecom posed even in large excess 
of hot 10 per cent nitric acid. 
The yield of pure chlorides (from 9 kilograms of phosphorus pentachlo- 
ride) was P 3 N 3 C1 () , G.9 per cent of the pentachloride, P 4 N 4 G1 8 , 0.76* per 
cent of the pentachloride, of which 0.42 per cent was obtained from the 
residue and 0.34 per cent from the crude steam distillate; these are 
respectively 12.4 and 1.4 per cent of the theoretical. A further small 
amount of tetraphosphonitrilic chloride was decomposed during distil- 
lation and, in part, recovered as tetrametaphosphimic acid. The yield 
of oily chloride was not determined, but it was approximately 1 per 
cent of the pentachloride. 
It is not easy to give a reason (or the relatively much higher yield of 
the triple phosphonitrilic chloride. Doubtless more of the quadruple 
Bull. 1H7 G 
