384 G. F. Barker on normal and derived Acids. 
Art. XLIL—On normal and derived Acids ; by Grorcz FF. 
BaRKER.* 
Tue law of saturation by equivalence, introduced into chem- 
istry by Kekulé, determines at once the formula of every pos- 
sible binary compound.+ Assuming that the simple radicals 
may be divided into four groups, it will be seen that the num- 
ber of binary compounds is limited to the following ten classes; 
monads with monads, as K’'Cl’; with dyads, as O’H’,; with tri- 
ads, as Au'’Cl’,; and with tetrads, as Pt*l’,; dyads with dyads, 
as Mg’0”; with triads, as As'’”,O”,; and with tetrads, as C0"; 
triads, with triads, as B’"N’”; and with tetrads, as Zr,N’”,; and 
finally tetrads with tetrads, as Pt‘’Si', The number of atoms 
therefore, which enter into such compounds, is determined by a 
very simple mathematical law. On this fact rests the possibility 
of graphic representation, Of the various methods in use, that 
of A, rown, in which the atom is represented by a cir- 
cle, and its equivalence by projecting lines called bonds or units 
ps the 
must be saturated, i.e, have all its bonds engaged, the ten — 
classes given above may be very clearly represented in this 
2 
® fl 
manner, thus: (@-() @-O-G) a L OO 
i) b 
©@=© @=8-0-@8=-9 @=0=0 @=0 
®=©-O=©=8-H=0 G=9 
Here it will be noticed, no bonds are exchanged by similar 
atoms; i.e., those of the same element, 
“ip Whee een? = o=16, S=32, C=24, Al—55, Si=56, ote 
unr 
t+ When two er, the number of vy 
Tai saturation, is obtained by dividing the least common multiple of the pes’ 
bers their equivalencies by the equivalence o ; 
number of atoms of each radical is inversely as i valence, four triad 
at equi +h each 
7 ng tetrads, for example. Atoms thus combined, alternate eg 
other, the two units of attraction in each exchange, belonging to r 
hiv back however, similar atoms unite directly, two units of attraction Two & 
rein pair of atoms, being occupied in holding these atoms together. 
a Atoms thus combined, h e therefore an equivalence o' six, three a 63), the 
rkan cour of ton, ete.’ Or, as Kelculé has shown (Lehrbuch, 1861, i, poo’ 
Cee is oot of attraction left free by the union of any number of Cai : 
poarch equal to twice the number of such atoms, acs two (=2n+2). cetnndets ‘ 
extended this law to all the uivalen atts i 
Minin formula ar ape fap which E indicates the group ede 
ration Guumber of poly-equivalent atoms, and 8 the sum f their unite © be. 
bon ay the highest number of hy: n atoms which can” 
hal atoms example, is 40 —2(10—1)=22, giving the b 
this a series of lower Gcocucka may be formed, each : 
next higher, by H,. ae 
= 
