ON THE PHOSPHOEUS- BASES. 
599 
This cannot surprise us, when we consider the close analogies which phosphorus and 
arsenic present in many other directions. Both phosphorus and arsenic form weU-cha- 
racterized polybasic acids; the acids of antimony are not yet sufficiently investigated, 
but the acids of nitrogen, which are better examined, are all found to be essentially 
monobasic. The equivalent numbers, too, of phosphorus, arsenic, and antimony, present 
a remarkable connexion, the difference between those of phosphorus and arsenic, and 
those of arsenic and antimony being virtually the same — 
Phosphorus ... 31 J difference 
Arsenic ; . . . 75i 
[ difference 
Antimony .... 120 J 
44 
45, 
whilst the equivalent of nitrogen stands altogether apart from the rest. 
The same relative position of the elements nitrogen, phosphorus, arsenic and antimony, 
may also be traced in their hydrides, 
H3N H3P H3AS H3Sb. 
Ammonia is a powerful alkali ; — phosphoretted hydrogen only unites with hydro- 
bromic and hydriodic acids, whilst in arsenietted and antimonietted hydrogen, the power 
of combining with acids has altogether disappeared. In these hydrogen-compounds the 
gradation of properties is indeed much more marked than in their trimethylated and 
triethylated derivatives. On comparing the terminal points of the series, ammonia and 
antimonietted hydrogen, we cannot fail to be struck by the dissimilarity of properties 
which at the first glance appears to limit the analogy of the two compounds to a mere 
parallelism of composition. 
In the methylated and ethylated derivatives of these compounds, the intensity of the 
chemical tendencies in general is so much raised, that the gradation is no longer per- 
ceptible to the same extent. 
We cannot conclude this memoir without thankfully acknowledging the able and 
untiring assistance we have received, during this lengthened inquiry, from Dr. A. Leibius 
in the analyses, and from Messrs. W. H. Peekin and C. Hoffmann in the preparation of 
the numerous compounds which had to be investigated. 
4i2 
