The sun., 1900-12-30

ILL ~ ~
light OF this theory. Take. for example.
the ordinary equation:
Az NO,. Aq = Ma Cl. hg X Ag Cl \ Ma Nos. AQ:
/. e., solutions Of silver nitrate and sodium
chloride give precipitate OF silver chloride.
leaving sodium nitrate In solution BY the
new views. such an equation must be written
Ag 40 : no.. Aa = Ma. Aa+CL 40 AgG
Ma. Az = NO, Az
Tho compound, silver chloride. being
insoluble in water. is formed by the union Of
the ions Ag and CT and their consequent dis
charge, forming an electrically neutral
compound, while the sodium ions. charged
positively together with the NO, ions.
negatively charged. remain In solution.
One more application of the principle
may be given. Many observers. Andrews.
Favre and Sibermann. but especially
julius Thomson OF Copenhagen and NJ.
Berthelot OF Paris. have devoted much labor
and time to the measurement OF the heat
evolved during chemical reactions. Now.
while very different amounts Of heat are
evolved when chlorine. bromine or iodine
combine respectively with sodium or potas-
stun, the number OF heat units evolved
on neutralizing sodium or potassium hydrox-
ide with hydrochlorio. hydrobromio. hydri-
odio or nitric acids Is always about 1880.
How can this fact be explained? 1t finds It's
explanation as follow: These acids and
bases are ionized In solution as shown
In the equation:
II. Ao + c. Aa INA Aa r OH. Aa K II. Oh
Ma Aa + ca 40.
Water Is the only compound formed; and 1t
Is produced by the union Of the hydrogen
Ion originally belonging to the acid and
the OH. or hydroxyl ion originally be-
longing to the base. No further change
has occurred: hence the uniform evolution
Of heat by the interaction OF equivalent
quantities of these acids and bases.
PERIODIC ARRANGEMENT OF THE RLEMENrs.
1t now remains 10 give a short account
Of the greatest generalization which has
as yet been made in chemistry; 1t has been
termed the Periodic arrangement Of the
clements.
In 1854 Newands OF London and Lotbar
Meyer. late OF T0bingen. found that by
arranging the elements In the order Of their
atomic weights certain regularities were
to be observed between each element, and
In general the eighth In succession from It.
In the order OF their numerical value. Such
similar elements formed groups or quanti-
ties, while the elements separating them
belong TO period. hence the name periodic
arrangement Commencing with lithiuIn,
a light, hlstrous metal found a. silioate in
certain minerals. We have the following
series:
Lithium B"Sllium Boron carbon
s,d.pm Z, Massssium ss Alnn,?am y sa:soH !.
Nitrogen Oxygen Fuor!ns Neon
pho;Shoru. + sa;sAar i cnis;,n' ,ss Atsoa s
and so on. II is only necessary 10 point out
in detail the resemblanoes between the
elements which stand In tho vertical columns.
but 1t may be stated that the resemblance
extends also TO the formula and properties
Of their compounds. Thus. the chlorides
Of lithium and sodium are each white.
. soluble salts IL the formula ICl and NaCl:
oxides Of magnesium and OF berylli uin
are both insoluble. white. earthly powders.
MgO and BeU GeOi. and so on. New
lands In his preliminary sketch termed this
order the Law OF Octaves." and predicted
the existence of certain undiscovered e!e-
ments which should occupy unified positions
! IN the table Mendeleef. professor at St.
Petersburg. In 1859 arnpuaed and extended
these relations. and he and Meyer pointed
out that the volume occupied by equal
numbers Of atoms OF such elements under
went a periodic variation when the ele-
ments are classified as above. The pre-
Giction OF undiscovered elements was made
by AlendeIeef In more assured manner;
and In several cases they have been real
tied. Thus, what Mendeeef called "eka-
boron" has since been discovered by LecoQ
de Boisbandron and named patriotically
-Galliun," Mendelects "eka-silloon" Is
now known as "germanium," discovered
by Winkler. and -eka-aluninum" is now
Cleve's "scandium." Moreover. the atomic
weights Of cesium. beryllium. molybdenum
and mercury have been altered so that they
II the periodic table. and further research
has justified the alteration.
The valency OF these elements increases
from right to left. as will be seen by in
spection Of the following series:
y.Go sMiS5 Ro,, &c, Sc, TF;a St.
Munad Dyad Triad. 1etrad. Triad and
Prntid.
or, FIJI Ne
SO, q l(OH o. 4
Dyld and Nouad and No vslency.
II xad Hegtad
The elements Of no valency are OF recent
discovery In 1894 Lord Rayleiph had
determined the density OF the nitrogen
Of the atmosphere. having separated from
1t the oxygen and carbon dioxide which
are mixed with nitrogen in air He found
1t 20 he OF somewhat higher density than
that obtainabe from ammonia and other
compounds u nitrogen. In conjunction
with Ramsay he Investigated atmospheric
nitrogen; it WA absorbed either by a
method devised by Cavendisb. or by max
Ing IL combine with MAGNESIUM at a red