138 Miscellaneous Bibliography. 
of atomic saturation. In this stage bodies can neither combine with 
other bodies nor replace them ; and. they cannot take fe in any chemi- 
eal change without undergoing decomposition. Below this point, how- 
ever, there are in most cases certain points of dese stability, at 
one of which this stability may be at its maximum, the compound un- 
dergoing decomposition less readily than when atomically saturated. 
Thus nitrogen atomically saturated is a pentad; but it has a trivalent 
and a univalent stage, of which the former is the stage of maximum sta- 
bility. In this stage bodies may unite directly with or replace other 
bodies, thus acting like compound radicals. ‘his fact Dr. Frankland ex- 
plains by supposing that the units of attraction or bonds of an atom may 
a | 
saturate each other by pairs. Nitrogen as a pentad is —N—, as a triad 
—N>, and a monad <N>. The maximum number of bonds he ealls 
the “absolute atomicity,” the number of bonds united to each other 
“latent atomicity ;” and those free to unite “active atomicity.” The ab- 
solute atomicity equals of course the sum of the other two. The hexad 
iron forms ferrous chlorid ‘vFe’’Cl,, in which the active atomicity is two; 
ferric chlorid “’F e2/"Cl,, in which it is three; and ferric acid Fe¥i0,Ho., 
in which all the atomicity is active 
e book above mentioned is a synopsis of a course of lectures de- 
iesacad at the Royal College of Chemistry in the fall of 1865-6, and is 
devoted to a development of these views. In all the eae formule it 
contains, the determinant is written first, printed in heavy type, thus 
OH,, Sn0,, PtCl,, GOKo, ; indicating ‘that “it is anited with all the 
active bonds ‘of the. other radicals, following upon the same line.” Wi 
one atom of the determinant as above, formule are mon-adelphic ; with 
two of equal power di-adelphic, ete. In the latter case one symbol is _ 
written below the other, connected by a bracket, thus: CH, a 
cH, 
Frankland uses the reacts sete to ree that the atoms it connects 
exchange one bond united indirectly as im Me 
thylic ether, {O , * where the dyad oxygen atom links them together. 
Speaking of rational formule the author says, ta formula ought to 
show, first, whether the hydrogen is combined with the carbon or with 
the oxygen; or if combined with both, it should indicate how many 
ith rbon h 
atoms are united with the ca and how many with the oxygen 
ondly, the formula ought to show whether the oxygen be united with the 
or with. or partly with the one and partly with the 
hyd 
other; or, lastly, whether it be performing the function of linking hydro- 
gen to carbon.” p. 2 he representation in a formula of the mode 
in which the atoms are held together (and not of aes their relative 
Loma in space) so necessary to explain cases of isomeri ich 
cannot be given by the ordinary typical formula, is well obtained by 
those of Dr. Frankland. In aluminic oxyd, for example, 1 A10° each 
aluminum atom exchanges one bond with its fellow, two with the dyad 
