stokes.] HKJIIER CHLORONITRIDES. 127 
residue for some time with water, when the resulting oil is again in a 
condition to continue fractioning. The loss in this operation is small, 
but the tediousness of a fractional distillation is thereby extraordina- 
rily increased. 
It is noteworthy that no regular progression exists in the molting 
points of the phosphonitrilic chlorides, and the same is true of their 
solubility in the ordinary neutral solvents, but the solubility varies in 
the same sense as the fusibility. Of the members of known molecular 
weight, the second, tetraphosphonitrilic chloride, is the least soluble 
and has the highest melting point, while the corresponding tetrameta- 
phosplmuic acid is the least soluble and most stable of the derived 
acids. With respect to their stability toward water, the new mem- 
bers (polyphosphonitrilic chloride excepted) resemble those already 
described, being scarcely attacked by prolonged boiling. In ethereal 
solution, however, there is a perceptible decrease of stability toward 
water as we rise in the series, a fact already noted with regard to the 
first two members. 
Notwithstanding the high molecular weight of the bodies isolated, no 
indication of isomers has been observed, although the fractioning was 
carried out very thoroughly up to 300° at 13 millimeters. 
Experimental Part. 
A mixture (which need not be very intimate) of 4 parts perfectly dry 
phosphorus pentachloride and 1 part ammonium chloride, as required 
by the equation 
PCI, + NH,C1 = PNCL + 4HC1, 
is introduced into an ordinary "bomb " tube, which has previously been 
drawn out to a neck. It is practicable to fill the tube entirely to the 
neck, so that the charge for a tube of ordinary dimensions is about 125 
grains, yielding 50-55 grams of chlorouitrides. After sealing, the length 
of the neck, exclusive of the rather long capillary, should be about 10 
centimeters. As the mixture liberates i>5 per cent hydrochloric acid, it 
is necessary to regulate the heating with great care and to open the tube 
repeatedly. The temperature of the furnace is allowed to rise to 150°, 
at which the reaction begins, when the gas is at once shut off, and the 
tube opened at about 100° (in the furnace !). This operation is repeated 
several times, the temperature being allowed to rise l°-2° higher each 
lime. When the evolution of hydrochloric acid has slackened and the 
contents of the tube are mainly liquid while hot, the temperature may 
be carried to 200° or higher, until little or no gas is given off. The 
operation requires care and judgment, but with careful working it is 
possible to avoid explosions, and to obtain with a four-tube furnace 
about 200 grams of mixed chlorouitrides in sixteen hours. 
The contents of the tube, after cooling, generally consists of a buttery 
mass or of a thick, yellow liquid filled with fine prisms and plates 5 if 
