_ these acids contain phosphorus as a pentad. I ne 
above stated be aaieick: it is igncee od the prgririo 
t basi | ose of the 
of basic hydrogen can never — Se uote 
G. F. Barker on normal and derived Acids. 391 
H,SO*. No true permanganic acid is known ; since the acid 
so-called does not contain the metal as an octad. If its form- 
ula be written HMnO,, monobasic, as the isomorphism of its 
salts with the perchlorates would seem to require, then manga- 
nese must be a heptad like chlorine; nor do we escape from this 
conclusion by writing it H,Mn,O,, as will be seen farther on. 
The acids of triad radicals may be divided into two groups; 
those of boron and gold, which have no higher equivalence: and. 
those of nitrogen, phosphorus, arsenic, antimony, and bismuth, 
which have a quinquivalent stage. Of the former, boron forms 
an ortho-acid H, BO, and a mono-meta-acid HBO, ; gold only 
@ mono-meta-auric acid, HAuO,. The acids of the nitrogen 
. group may be represented as follows : 
Triad. Pentad. 
Ortho-nitrous H,NO, nitric H,NO, 
Mono-meta H NO, H,NO, 
Drmets ..... ciaseews H NO, 
nitrogen; as plumbic ortho-nitrite Pb” ,(NO,),, and potassic 
dihydro-bismuthie ortho-nitrate 
MeP 
phate. tics salts of iron and manganese have been ob- 
tained. The mono-meta-phosphoric acid H,PO, is the ordi- 
nary tribasic form (Odling’s ortho-acid), and the di-meta acid 
is the common monobasic or. meta acid of Graham. It may 
here be remarked that the acids, called hypophosphorous and 
| 3 phosphorous, are misnamed, since the radical phosphorus is not 
trivalent in the latter and univalent in the former as analogy 
