The Seattle post-intelligencer. [volume] (Seattle, Wash. Terr. [Wash.]) 1888-1914, 1900-12-30

element through ! degree c. is approxi-
mateiy s2; It varies between 81 and s.s
In actual part This affords means OF
determining the true value of the atomic
weight OF an element. as the foiiowing
example will show: The analysis or the
shows thai 1t contains 81 80 per cent. OF
zinc and So rs per cent. OF chlorine NOW.
one grain Of hydrogen combines with 81
grains OF chloride TO form $50 grains OF
hydrogen chloride, and. as already re-
marked, one volume Of hydrogen and one
volume OF chlorine combine, forming Two
Avoga aSd hypothesis, one moiecuie OF
hydrogen and one molecuie Of chlorine
react to Yield two molecules or hydrogen
chloride and as each moleeale rs s aidyos
hydrogen-chloride consists OF one atom no, 81
each Of It's. constituent elements inc
amount Of that element, therefore. wn men
combines with 35.5 grains OF chlorine may
give the numerical value Of the atomic
weight Of the element, II the COMPOUND
contains one atom of each element IN
that case the formula Of the above COM
pound would be zine and the atomic
weight of zinc 227; but the
formula IS Zucia, the atomic weight o.
zinc would be 32 7x2; IL ZuCis. 81. 7>lS. ana
so on. The specific heat of metallic zinc
enables this question to be solved. Tor y
has been found experimentally 70 DC
about COS; and 6.2-ao. oss=s5. 2 4 close APP
proximation 10 327<2-e5.4 The conclu-
sion is therefore drawn that zinc chiorioe
IL composed Of one atom Of zinc IN com.
bnation with two atoms o. chlorine; , ha.
the molecular weight OF zinc chloride y
65 ~ t35 .5x2)-l3G.i. Inasmuch as the rel
alive weight OF molecuie OF hydrogen ~
2 that OF an atom being ID, zinc chloride
IN the gaseous state should be l36.4.2.
$50 times that Of hydrogen. measured ~
the same temperature and pressure. Inis
has been found experimcntaliy 10 De tne
case.
The methods OF determining the vapor
densitfes, or relative weights Of vapors
are three In number: the first method, que
TO Dumas QszD consists In vaporizing the
substance In question In bulb OF glass
or of porcelain. at q known temperature,
closing the bulb while still hot, and weigh
pacity OF the bulb. the weight OF hydro
gen necessary TO fill 1t at the desired tenn
perature can be calculated, and the dens-
or,d method VAS devised by Gay-Lussac
and perfected by A. w, Hermann usosl,
and third preferable for its simplicity
and ease Of execution is due to Victor
Meyer liSsi).
Ia 1858. as already remarked. .Canniz-
sarro showed the connection between
these known facts, and for the hrst time
attention was called to the true atomic
weights, which were, up to that time;
confused with equivalents, or weights Of
elements required 10 replace one unit
weight Of hydrogen These were genel-
ally regarded as atomic weights by Dalton
and his contemporaries.
Some exceptions had. been observed TO
the law Of Dulong and Petit, VIZ: beryi-
itum or glucinium, an element occurring IN
emeralds; boron. OF which borax Is com
pound; silicon. the component OF quartz
and flint, and carbon. It was found by
Msssr that q h hsh 'epra sra nrher
and the atomic heats approximate 70 the
number OF SO; but this behavior Is not
peculiar to these elements. for II appears
that the specific heat of all elements in
creases with rise of temperature.
A certain number of exceptions have
also been noticed to the law OF Gay-lsus-
molecular weight OF compound in a
gaseous state Is twice It's density referred
TO hydrogen. Thus, equal volumes OF
ammonia and hydrogen chloride unite to
form ammonium chloride. II was to be
expected that the density should be half
the molecular weight. thus:
N Hs+H Ci=NH.ci: and bs.5a2=2s.7 5==
density. d44-s) n+35.8 $50
But the density actually found Is only
half that number, viz. 1887; and for long
this and similar cases were supposed to
be exceptions TO the law OF Gay-Lussac.
viz, that equal volumes OF gases at tne
Same pressure expand equally Tor equal
the gradual decrease in density with rise
Of temperature can be followed, as with
choral hydratc the products OF which
Il was recognized by st. Claire Deville
tiSb) that the decrease In density OF such
mixtures OF gases was due not TO their be-
the gradual decomposition OF the com
pound body with the rise OF temperatures
To this gradual decomposition he gave the
name dissertation. This conception has
proved of the utmost Importance to the
science as will be seen In the sequel. To
take the above instance OF ammonium
chloride. Its abnormal density Is duo to
Its dissertation into ammonia and hydro
gen chloride. and the gas which Is OBJ
tanned on raising its temperature con-
sists not OF gaseous ammonium chloride,
t.x44 49,.
gen chloride. which. as Is easily seen, &C.
chpy, when separate twfce tho volume
tina, would be occupied by the gaseous
compound. OF recent years II has been
shown by Brereton Baker that II per-
feotly free from moisture ammonium
chloride CASTLES ms such, and that It's dem
sity ia the state OF vapor is IN fact 1915
The molecular eomplexity OF gases has
thus gradually become comprehended, and
the truth OF Avogadro's law has gained
acceptance, And as a means OF pictnr-
the kinetic theory o. gases has been de-
yised 10y Joule. ClAusius, Maxwell Thom-
son d~ord Kelvin and others. on the
assumption that the pressure OF n gas ON
the walls Of the vessel which contains II
IL due 20 the continued Impacts OF its
molecules, and that the temperature of
sas Is represented by the product OF the
mass OF the molecules, or the square OF
their velocity Il has been possible 60 Of
fer mechanical explanation OF Boyle's
law that at constant Temperature tho
a. the pressure increases OF Gay-Lussac's
law. that oli gases expand equally for riso
OF temperature. provided pressure Is kept
constant, the condition being that equal
volumes OF gases contain equal numbers
or molecules. striking support Is lent
to this chain % reasoning hy the facts
discovered nv Thomas Graham QNsl- 1851
professor az University college. London,
and subsequently master OF the royal
mint, Graham discovered that the rates
OF diffusion ~ gases into each other Is
inversely as the sqgars roots 81 their
donsltias For instance. the density OF
hydrogen being taken as unity. that OF
oxygen ts sixteen times as great; II a
vessel containing hydrogen he made 10
communicate with one containing oxygen
the hydrogen VIII pass into the oxygen,
and mix with a; and conversely. the oxy-
gen viii pass into the hydrogen vessel
THIS Il due 70 the Intrinsic motion OF the
molecules ~ each gas Aud Graham
found Fundamentally that for each Vol-
utne OF oxygen which enters the hydro
sen vessel four volumes OF hydrogen will
enter the oxygen vessel Now A--N Is
ana as these masses are relatively I and
lS. and their temperatures arc equal the
square % their yslocities are respective
w and is
The question - the molecular coznplsx.
IT'S % gases being thus disposed Of II re-
mains 10 b eSpusttFrsa what ara IN.