stokes.] HIGHER METAPHOSPHIMIC ACIDS. 141 
General Summary. 
The principal results of the preceding investigations may be summed 
up as follows : 
1. There exists a series of bodies of the general formula (PNCL)„, 
beginning with Liebig's chloronitride of phosphorus, and extending 
indefinitely upward. 
2. Each of these bodies yields, on saponification, an acid with the 
same number of phosphorus and nitrogen atoms. 
3. The first four of these acids exist in two forms — the lactam form, 
(PM) 2 H 2 ) U (metaphosphimic acids), where n is either 3, 4, 5, or (>, which 
is formed only in neutral or acid solution, and the open-chain form 
(PJTO 2 H 2 ) + H 2 0, formed under the influence of alkalies. 
4. The acid derived from the fifth chloronitride, P 7 N 7 C1| 4 , and possi- 
bly those from the higher members, do not form lactams, but persist in 
the open form under all circumstances. 
5. The properties of these acids with respect to stability, power of 
forming lactams, and nature of decomposition products may be 
explained by stereochemical considerations, analogous to those of von 
Baeyer on the methylene hydrocarbons and of Joh. Wislicenus on the 
lactones. 
Experimental Part. 
Saponification of the phosphonitrilic chlorides. — As pointed out in the 
preceding papers, triphosphonitrilic chloride is conveniently saponified 
by shaking its ethereal solution with an aqueous solution of sodium 
acetate, and tetraphosphonitrilic chloride in a similar manner with 
water, the trifling quantities of secondary decomposition products being 
easily removed. These methods can not be applied to the higher chlo- 
rides, for the secondary products formed by the liberated acetic or 
hydrochloric acid can not be separated from the main product owing to 
the uncrystallizable nature of the latter. A smooth saponification 
without secondary products maybe effected by using sodium hydroxide 
in sufficient amount to keep the solution always strongly alkaline. 
Four parts chloride are dissolved in about 20 parts alcohol-free 
ether and shaken with a solution of 5 parts pure sodium hydroxide in 
20 parts water. A bottle with a carefully paraffined glass stopper must 
be used, corks being inadmissible, as they give rise to colored prod- 
ucts which can not be removed. The shaking is conveniently effected 
by a rotator, moved by a small electric motor, and about fifty hours are 
sufficient for complete saponification. As soon as the ether is found to 
be practically free from chloronitrides, the alkaline solution is drawn off 
and precipitated by 2 or 3 volumes of alcohol. This throws down the 
sodium salt as a thick sirup, which is repeatedly washed by stirring 
with GO per cent alcohol, dissolved in water, reprecipitated by alcohol, 
and again washed in the same way until it is free from sodium chloride. 
It is then dehydrated by stirring, kneading, and finally pulverizing 
