386 G. F. Barker on normal and derived Acids. 
The formulas in the upper row represent well known acids, and 
those in the lower, as well known bases. 
It has been thus far assumed that the equivalence of a rad- 
ical is invariable. But it seems evident that when one element 
combines with another in more than one proportion, its com- 
bining power must be different in the two cases. us in stan- 
nic oxyd SnO, and stannous oxyd SnOQ; tin is evidently a tetrad 
in the former case and a dyad in the latter. In all cases, however, 
the equivalence changes by two, either up or down; it therefore 
never alters from even to odd or the reverse. A dyad may act 
as a tetrad or hexad ; a monad as a triad, pentad or heptad. 
.pplying this principle now to the compounds of the radicals 
with hydryl, we notice that the negative radicals vary their 
equivalence by several stages, forming a series of acids; but 
at the positive radicals rarely form more than a single series 
of bases, their equivalence being fixed at a single stage. With 
negative radicals, we may have for example :— : 
Monad. Dyad. Triad. Tetrad. 
Cl'(HO) 8’(HO), P”(HO),  Sn*(HO), 
Cl’"(HO),  S'*(HO), E'(10) | eee 
(HO), : 
I sumamiaae : pdltuies “rebate elec 
But the only instance of such changes with the positive radi- 
Cals, is in the case of the perhydrates of the alkaline earths ; 
as Ba'*(HO),, Sr“(HO),, etc., the composition of which, how- 
ever, is not fully decided. ; 
I. It will be noticed in the formulas of the acids above give? 
Such acids, thus simply derived, I propose to call normal acids. 
A normal acid then, is on i 
ie the carbon gro 
in the above tables have consequently mS 
Cl'(HO) Ortho-hypochlorous acid, $’(HO),Ortho-hyposulphurous acid 
err " z 5 > § ypos P . 
Cl'""(HO), Ortho-chlorous acid, SHO) Ortho-sulphurons acid. 
se . svi = a 
: 38 HO 
Cl (HO), Ortho-jitieMoris’ acid. 
Pu(HO), Orth 7 ne ee 
oS (Ho) Ortho-phomphonie act” Sn'v(HO), Ortho-stannic ack 
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