130 CONTRIBUTIONS TO CHEMISTRY AND MINERALOGY. [bull. 167. 
distilled to a much higher temperature. After eight to ten distilla 
tions three main fractions are obtained, which are then worked up 
separately. As P 5 N 5 Oli , though crystalline, is extremely soluble, it is 
necessary to carry out the distillations with the first main fraction until 
a practically sharp boiling point is obtained, in which connection it 
may be noted that at 17-20 millimeters a change of 1 millimeter pres 
sure causes a change of about 1° in the boiling point, and at 13 milli 
meters a change of about 2°. P 7 N 7 Cli 4 , being liquid, must also be iso- 
lated by distillation only, but at its boiling point polymerization is so 
rapid that great loss ensues during a series of distillations. 
P 6 N 6 Cli2 can not be separated by distillation from the P 6 N 7 C1 9 which 
accompanies it in small amount, the latter having nearly the same boil- 
ing point, nor is repeated recry stall ization effective. The separation is 
best effected by adding a crystal of pure P 6 N 6 Cli 2 to the supersaturated 
benzene solution, and filtering before the P (i N 7 Cl 9 begins to deposit. 
The latter thus concentrated is recrystalized from benzene. 
Owing to many modifications introduced in developing the above 
method, no accurate statement of the yield can be given ; the final 
product was about 225 grams P 5 N 5 Clio, HO grams P 6 K 6 C1 12 , 10 grams 
P 7 N 7 Cli 4 , and 5 grams P 6 N 7 C1 9 . 
Analytical methods. — With the exception of polyphosphonitrilic chlo- 
ride, the chloronitrides were analyzed by decomposing in the following 
manner: 
For phosphorus, by warming with alcohol and a little ammonia in a 
platinum crucible until completely dissolved, evaporating to dryness 
and heating to fuming for an hour with strong sulphuric acid, the 
crucible being kept covered. 
For nitrogen, by treating as above, omitting the ammonia. 
For chlorine, by heating with alcohol and ammonia. It is necessary 
to precipitate with silver nitrate in the presence of a large volume of 
10 per cent nitric acid and to filter hot, in order to avoid the forma- 
tion of silver metaphosphimates, which are difficultly soluble in dilute 
nitric acid. 
In decomposing polyphosphonitrilic chloride, which is attacked by 
water alone, the alcohol was omitted. The method of Carius was used 
for determining chlorine, as it was found that otherwise compounds 
insoluble in dilute nitric acid were formed. For the other chloronitrides 
this method offers no advantage. 
Molecular weight determinations were made by the boiling-point 
method with the apparatus of Hite, 1 using as solvent carefully purified 
and dried benzene. 
■Am. Chem. Jour., Vol. XVII, p. 512. The molecular weight of P 3 N 3 C1 6 has heen determined by 
the vapor-density method, Jour. Chem. Soc. London [2], Vol. II, p. 225. A series of determinations by 
the boiling-point method gave 346, 350, 353. Calculated 347.9. 
