G. F. Barker on normal and derived Acids. 395 
Tetrad. Pentad. Tetrad. Pentad. 
Ortho, H,Si,0,* Hy P20,9* H,25i,0,.* H,,F,0..* 
Mono-meta, H,S8i,0, HF, H,,Si,O,, Hi yP,04, 
Ditmeta, Hj Si,0;* HP yO7t H,Si,0,, H,,P,0,, 
Tri-meta, H,Si,0, H,P,0, H,Si,O . H,P,0,,* 
Tetra-meta,  Si,0,° H,P,0,* H,Si,0,° -H,P,0., 
Penta-meta, PSO; H,5i,0, HP 0%, 
Hexa-meta, Si,;0, H,P,0,* 
Hepta-meta, fa Be ah 5 
A few examples of well known paebases) formed in this way, 
will make the preceding remarks clea 
Cupric mono-meta-di-arsenite, Cu, eee (Scheele’s Breen) 
Plumbic tri-meta-di-arsenate, Pb, As,O, 
Ferric tri-meta-di-sulphate, Fe "1S 6, 
Potassic penta-nreta-di-chromate, K 2Cr,0; 
Penta-meta-di. periodic aci H.T,0,° 
Di-hydro-plumbie mono-meta-tri-car- 
bonate, ie fm C,0,, (white lead), 
Hepta-meta- tri-iodic acid, HI,0 
Plumbic tri-meta- tetra-sulphantimonite Pb, Sb, S, (Jamesonite). 
dic penta-meta-tetra-bora a,B, rax). 
otassic ennea-meta-tetra- se K,[,0,, 
sinea-meta-tetra- periodic aci 164" O, 9 
_- penta-meta-hexa-sulphanti- 
ite OU a ns (plagionite). 
5 (boracite). 
PH 
Micnedie ennea-meta-octo-borate, Me, B, 0. 
IV. In the formulas of these and similar substances the atoms 
(Of the negative radical are united to each other by oxygen, as 
Frankland has already shown for many of them.7 It is evi- 
dent, Sasa that these atoms may unite directly together, 
in which case two units of attraction in each pair o atoms 
7 be occupied in uniting them. The equivalence of the group 
will then be represented bythe law of saturation E=S—2(n—1), 
already given. Certain artiads have a particular tendency to 
Combine in this manner; as mercury in Hg,Cl, and copper in 
~~ vu.H,; and particularly the iron group of ‘metals, which were 
long sup pposed to be triads for this reason. Two atoms of a 
P 
E 
] 
* The comp 
imple ortho or meta forms. See Wartz’ Che mical rPhocophy, piraie 1861, 158, 
‘ote. It may here be biyoe ss that Lepr phosphoric acid is ble of 
_ forming a series of polymeric compoun sponding to the rapgone given 
: bove. With silver; for example, A gaPaOs, as Asus a and AgeE oO: : “ 
; bec phosp’ ios geen second. as ioe 
ites, 
