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(i) Chemical Sedtion of the American Association for
the Advancement of Science. (2) American Chemical
Society. (3) Chemical Sedion of the Franklin Institute,
Philadelphia. (4) Chemical Sedlion of the Brooklyn
Institute. (5) Association of Official Agricultural
Chemists. (6) Chemical Society of Washington, D.C.
(7) ManufaAuring Chemists* Association of the United
States. The newly formed Chemical Society of Cincin-
nati was not represented.

Professor Albert B. Prescott, of Ann Arbor, Michigan,
President-Elea of the American Association for the
Advancement of Science, was called to the chair, and
Dr. H. Carrington Bolton, of New York, was appointed
Secretary.

After a prolonged and interesting discussion the
following resolutions were adopted.

Resolution i.—It is desirable that an American Asso-
ciation of Chemists be formed to embrace all existing
American Chemical organisations.

Resolution 2.— Resolved, That this conference recom-
mend to all existing American Chemical organisations
that they call a meeting of their bodies to be held in
Washington, D.C, in connexion with the meeting of the
American Association for the Advancement of Science
for i8gi, and that each of these organisations be requested
to appoint a committee, or to continue theii" present
committee for the further discussion of the subjedt sub-
mitted to the conference now in session.

/?«io/M//off 3.— Resolved, That this general conference
committee, composed of the present sub* committees,. or
such others as may be appointed by the several organisa-
tions, be called together at as early a time as pradlicable
before the joint meeting recommended in Resolution 2.

Resolution 4. — Resolved, That meanwhile, each sub-
committee through its chairman, by correspondence or
otherwise, shall formulate such modifications of the
Constitution of the American Chemical Society as it
shall deem necessary to adapt it to the requirements of
the Association proposed.

Resolution 5. — Resolved, That the chairmen of these
sub* committees shall then, so far as possible, harmonise
the views embodied in these reports of their several
organisations, and bhall have printed, for presentation at
the joint meeting, a report, or minority and majority
reports, on a constitution for the proposed Association of
American Chemists.

The secretary of the conference was desired to com-
municate the above resolutions to Scientific Journals
with a view to obtain a wide publication of the same.
^Adjourned to meet at the call of the chairman. — 1|.
Carrimotom BoltoNi i>€crctar^ o/thi Couferencft



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CKbmical New*, 1
Ian. 30, 1891. I



Electricity in transitu : from Plenum to Vacuum.



5i



FROM



ELECTRICITY

IN TRANSITU:
PLENUM TO VACUUM.*



By WILLIAM CROOKES. F.R.S..
President of the Institation of Blearical Bngineeri.

Introduction.
Whilst steadily bearing in mind that I have the honour
to address a Society, not only o/ physicists, but of Eledtri-
cal Engineers, I shall not, I hope, be out of order in
venturing to call your attention to a purely abstra^ phase
of Ele^ical Science. Nurobetless instances show that
pure research is the abundant source from which spring
endless streams of practical applications. We all know how
speculative inquiry into the influence of eledricity on the
nervous system of animals led to knowledge of current
eledricity, and ultimately to the priceless possession of
the telegraph and the telephone. The abstrad study of
certain microscopic forms of parasitic vegetable life has
enabled us to give to fermented solutions of sugar the
exad flavour and aroma of the most highly prized wines,
and probably, ere long, will put us in a position to increase
at will the fertility of the soil. In a diilerent diredion the
same class of abstrad researches applied to medical
science has brought us within measurable distance of the
final conquest over a large class of diseases hitherto in-
curable ; and without egotism I may, perhaps, be allowed
to say that my own researches into hish vacua to some
extent have contributed to the present degree of perfedlion
of the incandescence lamp. Surely, therefore, whilst
eagerly reaping and storing the harvest of practical
benefits, we must not negled to scatter more seed for future
results, perchance not less wonderful and valuable.

In another resped I deviate to some extent from the
course taken by many of my predecessors. I am about
to treat eledricity, not so much as an end in itself, but
rather as a tool, by whose judicious use we may gain
some addition to our scanty knowledge of the atoms and
molecules of matter and of the forms of energy which by
their mutual readions constitute the universe as it is
manifest to our five senses.

I will endeavour to explain what I mean bycharadetising
eledricity as a tool. When working as a chemist in the
laboratory, I find the indudion spark often of great
service in discriminating one element from another, also
in indicating the presence of hitherto unknown elements
in other bodies in quantity far too minute to be recog-
nisable by any other means. In this way, chemists have
discovered thallium, gallium, germanium, and numerous
other elements. On the other hand, when examining
eledrical readions in high vacua, various rare chemical
elements become in turn tests for recognising the intensity
and charader of eledric energy. Eledricity, positive and
negative, effed respedivelv different movements and
luminosities. Hence the behaviour of the substances
upon which eledricity ads may indicate with which of
these two kinds we have to deal. In other physical re-
searches both eledricity and chemistry come into play
simply as means of exploration.

In submitting to you certain researches in which elec-
tricity is used as a tool, or as a means of bringing within
scope of our senses phenomena that otherwise would be
nnrevealed, I most for a moment recal to your minds the
now generally accepted theory of the constitution of
matter.

Kimtic Theory of Gases.

Matter, at its ultimate degree of extension, is conjec-
tured to be not continuous, but granular. Maxwell illus-
trates this view as follows: — To a railway contrador
driving a tunnel through a gravel-hill the gravel may be
viewed as a continuous substance. To a worm wriggling
through gravel, it makes all the difference whether the

* losugural Addreii delivered January X5tb, 1891.



creature pushes against a piece of gravel or direds ita
course between the interstices. To the worm, therefore,
gravel seems by no means homogeneous and continuous.

With speculations as to the constitution of liquid and
solid matter I need not trouble you, but will proceed at
once to the third or gaseous state of matter.

The kinetic theory of gases teaches that the constituent '
molecules dart in every possible diredion with great but
continually varying velocities, coming almost ceaselessly
in mutual collision with each other. The distance each
molecule traverses without hitting another molecule is
known as its free path ; the average distance traversed
without collision by the whole number of molecules of a
gas at any given pressure and temperature is called the
mean fne path. The molecules exert pressure in all
diredions, and are only restrained by gravitation from dis-
sipating themselves into space. In ordinary gases, the
length of the mean free path of the molecules is exceed-
ingly small compared with the dimensions of the vessel,
and the properties we then observe are such as constitute
th:^ ordinary gaseous state of matter, which depend upon
constant collisions. But if we greatly reduce the number
of molecules in a given extent of space the free path of
the molecules under eledric impulse is so long that the
number of their mutual collisions in any given time in
comparsion with the number of times they fail to collide
may be disregarded. Hence, the average molecule can
carry out its own motions without interference. When
the mean free path becomes comparable to the dimensions
of the containing vessel, the attributes which constitute
gaseity shrink to a minimum, the matter attains the
ultra-gaseous or *' radiant " state, and we arrive at a con-
dition where molecular motions under eledrical impulse
can easily be studied.

The mean free path of the molecules of a gas increases
so rapidly with progressive exhaustion, that whilst that of
the molecules of air at the ordinary pressure is only
i-io,oooth of a millimetre, at an exhaustion of a hundred-
millionth of an atmosphere—a point (which, with present
appliances, is easy to attain) corresponding to the rarefac-
tion of the air go miles above the eatth's surface — the
mean free path will be about 30 feet ; whilst at 200 miles
above the earth it will be 10,000,000 miles, and millions
of miles out in the depth uf space it will become pradically
infinite. I could go on speculating in spite of Aristotle,
who said :— *' Beyond the universe there are neither space,
nor vacuum, nor time.**

In discussing the motions of molecules we have to dis*
tinguish ihtfne path from the mean fne path. Nothing
is yet known of the absolute length of the free path nor of
the absolute velocity of a molecule. For anything we can
prove to the contrary, these values may vary almost from
zero to infinity. We can deal only with the mean free
path and the mean velocity.

The Vacuum Pump,

As most of the experiments I put before you to-night
are conneded with high vacua, it is not out of place to
refer to the pump by means of which these tubes are ex-
hausted. Much has been said lately in recommendation
of the Geissler pump and its many improvements, but I
am still strongly in favour of the Sprengel, as with it I
have obtained greater exhaustion than with any other. I
should like to point out that the adion does not stop when
we cease to see air specks passing down the tubes but
continues long after this point has been passed. Neither
is the non-conduding vacuum, so easily obtained by the
Sprengel pump, due in anyway to the presence of mercury
vapour, since non-condudion can be obtained just as
rapidly when special precautions have been taken to keep
mercury vapour out of the tubes.

One of the great advantages of the Sprengel pump over
all others lies in the fad that its internal capacity need
not exceed a few cubic centimetres, and there is, there^
fore much less wall surface for gases to condense upon.
I have brought the very latest modification of this form

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54



Electricity in Transitu : from Plenum to Vacuum.



i CatmcAi. Nt«i«
I Jao. 30*1891.



of pump here to-night, and you will have an opportunity
of seeing it in adion and of meaBuring with the McLeod
gauge the rarefadion it produces.*



* My meAtaremenU of high vacua have ail been taken with the
betutiral little gauge devised by Professor McLeod. Unmerited dis-
credit has recently been cast on this gauge, the principal fault alleged
being its inability to distinguish between the tension of the per-
manent gaa and that of the mercury vapour present. Now it is evi-
dent that, under ordinary circumstances, the tension of mercury
▼apoor may be disregarded, as it will be the same on both sides of the
gauge: and it will be only in cases where no mercury is present on
one aide of the gauge that a slight error is introduced. It is, how-
ever, very difficult to devise and successfully experiment with appara-
tus in which a trace of mercury vapour shall not enter, and it is not



The Passage of Electricity Through Reefed Gat,

The various phenomena presented when an iiidadioa
spark is made to pass through a gas at different degfoee
of exhaustion point to a modified coniition of the mattor
at the highest exhaustions. Here are three eaadly
similar bulbs, the ele&rodes being aluminium balls, and
the internal pressures being respectively 75 m.m., 2 m.m.,
and O'z m.m. If I pass the indu&ion current in succession
through the bulbs, you will perceive in each case a very
different luminous phenomena. Here is a slightly ex-
hausted tube (Fig. i), like the first in the series just e<-
hibited (75 m.m.), the indudion spark passes from oae



Fig. 1.— p. = 75 m.m.



Fio. 2.— P. = 0*1 m.m.



likely that an experimentalist who would be working with such mer-
curv-free apparatus would attempt to use the gauge without remem-
bering that in this special rase the indications would be incorredl.
To use the McLeod gauge requires much patience and some amount
of experience, but I have always found it trustworthy to register ex-
banstiont far beyond the millionth of an atmosphere. I can adduce
circumstantial evidence of the accuracy of its readings at these high
Vacua. In tbe year 1881 I read a paper before the Roval Society on
** The Vtsooeity of Gases at High Exhaustions " (Phu. Tram,, i88x,

r. 387), and illustrated my reauita in three large diagrams, 00 which
plotted the experimental results obtained at rarefadtiooa vp to 0*02
tmllionth of an atmosphere, giving curves comparing the decrease in
vitcoaity with that of tbe repulsion resulting from radlatioo, m the
different pressnrei. Now these curves, in the case of air for instance,
are perfcaly regular and uniform in their falling off, and it i« avi*
ilent that this could not have been the case unlets the ordinates



end to the other, a, b, and the luminous discharge is seen
as a line of light, ading as a flexible condudior. Under
the tube I have an elediro-magnet, c, and on makii^g con-
representing viscosity and the abscissa representing pressure were
equally accurate. I am satisfied that, within narrow limhs, the or*
dinates of viscosity are correA to the highest point, and tbe con*
formity of experiment to theory in the shape of these curvet is a con*
elusive proof that, at as high an exhaustion at o'oa M., the McLeod

Suge is to be trusted to give accurate retultt within 1 p«r vaal off
e truth. To give some idea what these high exhsastiont UMsa I
may mention that the hiehest measured exhaostion^o'oa M,— bean
the same proportion to the ordinary pressure of the atmosphere that
a millimetre does to 30 miles, or in point of time, that one tecond
bears to ao months.



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55



imCt the line of light dips in the centre down to the poles
of the magnet, and then rising again proceeds in a straight
line. On reversing ihe current the line of light curves
upwards. Notice that the adion of the magnet in this
case ia only local.

la a highly exhausted tube the adion is quite other-
wise. Such a tube is before you (Pig. 2), and in it I have
carried the exhaustion to a high point (ox). I pass the
indodioa current and you perceive the eledrified mole-
cules, like the line of light in the first tube, also move in
straight lines, and make their path apparent by impinging
on a pboephocescent screen, d e. If, however, I submit
them to tlie adion of a magnet, c, their behaviour is dif-
ieteut. The line dips down to f, but does tiot recover
itaeftf. It seems that in the tube first shown we have to
&o with the average behaviour of the molecules of gas in
its totality. In the second case, where the gas has been
greatly attenuated, we are merely concerned with the be-



strudion is created. The passengers behind catch up to
the block and increase it, and those in front, passing on
unchecked at their former rate, leave a comparatively
vacant space. If a crowd is moving all in the same direc-
tion the formation of these groups becomes more distind.
With vehicles in crowded streets, the result, as everyone
may have remarked, will be the same.

Hence mere differences in speed suffice to resolve a
multitude of passengers into alternating gaps and knots.

Instead of observing moving men and women, supposie
we experiment on little particles of some substance, such
as sand, approximately equal in size. If we mix the
particles with water in a horizontal tube and set them in
rhythmical agitation, we shall see very similar results, the
powder sorting itself with regularity into alternate heaps
and blank spaces.

If we pass to yet more minute substances we observe
the behaviour of the molecules of a rarefied gas, when



Fig. 3.— p. = 2 m.m.



Fio. 4. — P. =3 2 m.m.



haviour of the individual molecules of which it was
originally composed.

Thi Straiifitd Dischargi.

When the gas is rarer than is necessary to give the
flexible line of light, as shown in the first experiment, the
luminosity is plainly discontinuous, or, as it is termed,
stratified.

A very good illustration of this fad may be taken from
the moving crowd in any much freouented street— say
Fleet Street. If at some time when the stream of traffic
runs almost equally in both diredions, we take our stand at
a window from which we can overlook the passing crowd,
we shaH notice that the throng on the foot-way is not
Qniformly distributed, but is made up of knots — we might
alnoat say blocks — interrupted by spaces which are com-
paratively open. We may easily conceive in what manner
theee knots and groups are formed. Some few persons
walking rather more slowly than the average rate slightly
retard the movements of others whether travelling in the
tame or in an opposite direAion. Thus a temporary ob*



submitted to an indudion current. The molecules here
are free, of course, from any caprice, and simply follow
the law I seek to illustrate, and though originally in a
state of rampant disorder yet under the influence of the
eledlric rhythm they arrange themselves into well-defined
groups or stratifications; the luminosities show where
arrested motion with concomitant friAion occurs, and the
dark intervals indicate where the molecules travel with
comparatively few collisions.

Party -colound Stratifications,
As another illustration of stratifications in a moderately
exhausted tube (P b 2 m.m.), I will take the case of hydrogen
prepared from zinc and sulphuric acid after being passed
through various purifying agents, dried in the usual
manner, and exhausted with a mercury pump (Fig. 3). 'I
pass the indudion current, and we see that the stratifica-
tions are tri-coloured, blue, pink, and grey. Next the
negative pole a is a luminous layer, then comes a dark
interval or Faraday's dark space (see below), and after
this are the stratificationst the front component (b) of each
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56



Filtration of Natural Waters.



I CHBMIC4L RtHty

I Jan. 30, 1891.



group blae, the next (c) pink, and the third {d) gccy. The
blue disks are somewhat erratic. At a certain stage of
exhaustion all the blue components of the stratifications
suddenly migrate to the front, forming one bright blue
disk, and leaving the piok and grey components by them-
selves. The tube before you (Fig. 4) is at this particular
stage of exhaustion, and on passing the current you ob-
aerve the blue disk only (b) is in front. When the tube
contains a compound gaseous residue of this kind, the
form of stratifications can be very considerably altered by
varying the potential of the discharge. This alteration
in the forms of stratification was first pointed out by
Gassiot (1865, ** B.A. Abstrads," p. 15), who gave very
full descriptions and drawings of the alterations produced
by putting in resistances of various lengths of distilled
water. That the alteration depends simply upon the dif-
ference of potential the following experiment pretty clearly
shows I—Here is a tube giving on my coil the coloured
stratification usually attributed to the presence of residual
hydrogen, but which I find is due to a mixture of hydro-
gen, mercury, and hydrocarbon vapours. Now by altering
the brake so as to produce frequent discharges of lower
potential, you see the stratifications gradually change in
shape and become all pink ; again altering the brake so
as to send less rapid discharges at a much higher poten-
tial, once more we get the coloured stratifications. When
in this state, if we introduce a water resistance into the
circuit so as to damp down the potential, exadly the same
thing happens. The blue disk is caused by mercury ; its
speArum is that of mercury only, without even a trace of
the bright red line of hydrogen. Experiments not vet
finished make it very probable that the pink disks are due
to hydrogen, and that the grey disks indicate carbon. The
tube you have just seen contains nothing but hydrogen,
mercury, and a minute trace of carbon ; but with ail the
resources at my command I have not been able to get
hydrogen quite free from impurity. Indeed I do not think
absolutely pure hydrogen has ever yet been obtained in a
vacuum tube. I have so far succeeded as to completely
eliminate the mercury, and almost completely to remove
the trace of carbon. On the table is such a tube giving
uniformly pink stratifications and showing no blue or grey
disks with any potential of current.
(To be continued).



COMPOSITION OF BUTTER FAT.
By WILLIAM JOHNSTONE, Ph.D., D.Sc., F.I.C., F.C.S.

For tome considerable time now the insoluble fatty acids
of butter fat have been taken as varying from 87*5 to 89*5

rer cent, and in some extreme cases even to 90 per cent,
n the month of June, 1890, two samples of butter came
into my hands, and in course of analysis, my attention
was particularly directed to them on account of the low
results obtained for insoluble fatty acids with correspond-
ing highness in the soluble fatty acids, so I was induced
to furtner examine them in the hope that I should be able
to account for the apparent abnormal figures I had ob-
tained, namely, 85*68 and 86*25 per cent, as they were
undoubtedly genuine, the addition of cocoa-nut oil being
ont of the question. That investigation has resulted in
establishing the fadt that a butter fat yielding 85*81 per
•ent of insoluble fatt^ acids is a definite chemical com-
poand, a compotiod tri-glycerinof the following formula :~

C,6H3,Oa [ C3H5.

the iso-oleo-palmito capriate of glycerin.

Up to the present tiine it was by no means certain that
butter fat did really contain normal oleic acid or stearine,
and my results now confirm the accuracy of that suspicion.
A butter fat, therefore, yielding 85*81 per cent of insoluble
fatty acids it entirely devoid of stearine, and what was '



previously considered to be oleic acid now proves to bo
Iso-oleic acid —



cikTl^"'



or bntro-methene, tridacotic acid.

Furthermore, genuine butter fats yielding insoluble fat^
acids above 85*81 per cent do not contain stearic acid(r)
as is generallv supposed, but nondecatoic acid, the next
higher acid of the series, as a glyceride. Butter fat thea
becomes a mixture of iso-oleo-palmito capriate of gly-
cerin and tri* nondecatoic of glycerin in varying propor-
tions, a compound complicated tri-glyceride.

The following represent a butter fat o! that descrip-
tion :—

Fatty I

CieHjiOa^ C3H5 62-47 - 53'6i
C,oF -^



6H3,Oa[
oHxgOaj



c,u



3"S



37*53

lOO'OO



^ 36'oo
" 89*6x



Fatty acids adually found • • 89*95

From the above, it becomes evident that another acid
radicle might replace one of nondecatoic acid, and that
occurs in the following butter : —

Fatty acids.
CisHjaOa)
Ci6H3xOa[ C3H3 53*21 - 45-66



C3H5 4679 . 4£50
100*00 90-16



Fatty acids adually found . . 90*00

The radicle of oenanthylic acid replacing one of tho
nondecatoic acids in the tri-glyceride, and forming the di-
nondecatoic-oenanthylic of glycerin.

I append the following formula in support of my
theory. Thus :—



la^v,



Ci3Ha
CH.
C4H,0 ..
Cx3H3xOa
CioHxgOa
C3H3 .•



Theory.

26*34

«7



V



9-45

34*09 L
22-86 r

5'47
99*98



o .£

-^

m a
o

§-

D



Cx«Ha«Ot

Cli.? ..

C4H80a

CxeHaaOa

CxoHaoOa

C3U8O3



Theory.
a8*6o

2*13

xi-76
34-22

22-99

22*30

IX2'0O



FOOSd*



ii-yo



ia*23



The ultimate separation of the fatty acids is atill in
hand, and I refrain from giving results until I am able to
give a corre<5t process for the separation of the same ; but
results have been obtained near enough to prove the cor-
re^ness of the theory. Butter analysis is, therefore, now
placed on a satisfa^ry basis, and if the analyst be fbrtv-
nate enough to detect stearic acid in a sample of butter,
he need have no hesitation in certifying the addition of
animal fat other than butter, or at least to a fat contain-
ing stearic acid.



THE FILTRATION OF NATURAL WATERS.^

By THOMAS M. DROWN.
Member Boaton Society Civil Bogtoeers.



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