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D. S. (David Samuel) Margoliouth.

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corresponds to the sum of positive electricity going forward and nega-
tive electricity going backward.

This established, Faraday's law tells us that, through each section
of an electrolytic conductor, we have always equivalent electrical and
chemical motion. The same definite quantity of either positive or
negative electricity moves always with each univalent ion, or with
every unit of aftinity of a multivalent ion, and accompanies it during
all its motions through the interior of the electrolytic fluid. This we
may call the electric charge of the atom.

Now, the most startling result, perhaps, of Faraday's law is this :
If we accept the hypothesis that the elementary substances are com-
posed of atoms, we can not avoid concluding that electricity also, posi-
tive as well as negative, is divided into definite elementary portions,
which behave like atoms of electricity. As long as it moves about
on the electrolytic liquid, each atom remains united with its electric
equivalent or equivalents. At the surface of the electrodes decompo-
sition can take place if there is suflicient electro-motive power, and
then the atoms give off their electric charges and become electrically
neutral.

Now arises the question. Are all these relations between electricity
and chemical combination limited to that class of bodies which we
know as electrolytes '? In order to produce a current of suflicient
strength to collect enough of the products of decomposition without
producing too much heat in the electrolyte, the substance which we
try to decompose ought not to have too much resistance against the
current. But this resistance may be very great, and the motion of the
ions may be very slow — so slow indeed that we should need to allow
it to go on for hundreds of years before we should be able to collect
even traces of the products of decomposition ; nevertheless, all the
essential attributes of the process of electrolysis could subsist. If you
connect an electrified conductor with one of the electrodes of a cell
filled with oil of turpentine, the other with the earth, you will find
that the electricity of the conductor is discharged unmistakably more



FARADAi^S CONCEPTION OF ELECTRICITY. 247

rapidly through the oil of turpentine than if you take it away and fill
the cell only with air.

Also in this case we may observe polarization of the electrodes as a
symptom of previous electrolysis. Another sign of electrolytic con-
duction is, that liquids brought between two different metals produce
an electro-motive force. This is never done by metals of equal tem-
perature, or other conductors which, like metals, let electricity pass
without being decomposed.

The same effect is also observed even with a great many rigid
bodies, although we have very few solid bodies which allow us to
observe this electrolytic conduction with the galvanometer, and even
these only at temperatures near to their melting-point. It is nearly
impossible to shelter the quadrants of a delicate electrometer against
being charged by the insulating bodies by which they are supported.

In all the cases which I have quoted one might suspect that traces
of humidity absorbed by the substances or adhering to their surface
were the electrolytes. I show you, therefore, this little Daniell's cell,
in which the porous septum has been substituted by a thin stratum of
glass. Externally, all is symmetrical at both poles ; there is nothing
in contact with the air but a closed surface of glass, through which
two wires of platinum penetrate. The whole charges the electrometer
exactly like a Daniell's cell of very great resistance, and this it would
not do if the septum of glass did not behave like an electrolyte. All
these facts show that electrolytic conduction is not at all limited to
solutions of acids or salts.

Hitherto we have studied the motions of ponderable matter, as
well as of electricity, going on in an electrolyte. Let us study now
the forces which are able to produce these motions. It has always
appeared somewhat startling to everybody who knows the mighty
power of chemical forces, the enormous quantity of heat and of me-
chanical work which they are able to produce, and who compares with
it the exceedingly small electric attraction which the poles of a battery
of two Daniell's cells show. Nevertheless, this little apparatus is able
to decompose water.

The quantity of electricity which can be conveyed by a very small
quantity of hydrogen, when measured by its electrostatic forces, is ex-
ceedingly great. Faraday saw this, and has endeavored in various ways
to give at least an approximate determination. The most powerful
batteries of Leyden-jars, discharged through a voltameter, give scarcely
any visible traces of gases. At present we can give definite numbers.
The result is, that the electricity of one milligramme of water, sepa-
rated and communicated to two balls one kilometre distant, would
produce an attraction between them equal to the weight of twenty-
five thousand kilos.

The total force exerted by the attraction of an electrified body
upon another charged with opposite electricity is always proportional



248 THE POPULAR SCIENCE MONTHLY.

to the quantity of electricity contained in the attracting as on the at-
tracted body, and therefore even the feeble electric tension of two
Daniell's elements, acting through an electrolytic cell upon the enor-
mous quantities of electricity with which the constituent ions of water
are charged, is mighty enough to separate these elements and to keep
them separated.

We now turn to investigate what motions of the ponderable mole-
cules require the action of these forces. Let us begin with the case
where the conducting liquid is surrounded everywhere by insulating
bodies. Then no electricity can enter, none can go out through its
surface, but positive electricity can be driven to one side, negative to
the other, by the attracting and repelling forces of external electrified
bodies. This process, going on as well in every metallic conductor,
is called " electrostatic induction," Liquid conductors behave quite like
metals under these conditions. Professor Wiillner has proved that
even our best insulators, exposed to electric forces for a long time, are
charged at last quite in the same way as metals would be charged in
an instant. There can be no doubt that even electro-motive forces
going douTi to less than y^ Daniell produce perfect electrical equilib-
rium in the interior of an electrolytic liquid.

Another somewhat modified instance of the same effects is afforded
by a voltametric cell containing two electrodes of platinum, which are
connected with a Daniell's cell, the electro-motive force of which is
insufficient to decompose the electrolyte. Under this condition the
ions carried to the electrodes can not give off their electric charges.
The whole apparatus behaves, as was first accentuated by Sir W. Thom-
son, like a condenser of enormous capacity.

Observing the polarizing and depolarizing currents in a cell con-
taining two electrodes of platinum, hermetically sealed and freed of all
air, we can .observe these phenomena with the most feeble electro-mo-
tive forces of yoVo Daniell, and I found that down to this limit the
capacity of the platinum surfaces proved to be constant. By taking
greater surfaces of platinum I suppose it will be possible to reach a
limit much lower than that. If any chemical force existed besides
that of the electrical charges, which could bind all the pairs of oppo-
site ions together, and require any amount of work to be vanquished,
an inferior limit to the electro-motive forces ought to exist, which forces
are able to attract the atoms to the electrodes and to charge these as
condensers. No phenomenon indicating such a limit has as yet been
discovered, and we must conclude, therefore, that no other force re-
sists the motions of the ions through the interior of the liquid than the
mutual attractions of their electric charges.

On the contrary, as soon as an ion is to be separated from its elec-
trical charge we find that the electrical forces of the battery meet with
a powerful resistance, the overpowering of which requires a good deal
of work to be done. L^sually the ions, losing their electric charges,



FARADAY'S CONCEPTION OF ELECTRICITY. 249

are separated at the same time from the liquid ; some of them are
evolved as gases, others are deposited as rigid strata on the surface of
the electrodes, like galvanoplastic copper. But the union of two con-
stituents having powerful affinity to form a chemical compound, as
you know very well, produces always a great amount of heat, and heat
is equivalent to work. On the contrary, decomposition of the com-
pound substances requires work, because it restores the energy of the
chemical forces which has been spent by the act of combination.

Metals uniting with oxygen or halogens produce heat in the same
way, some of them, like potassium, sodium, zinc, even more heat than
an equivalent quantity of hydrogen ; less oxidizable metals, like copper,
silver, platinum, less. We find, therefore, that heat is generated when
zinc drives copper out of its combination with the compound halogen
of sulphuric acid, as is the case in a Daniell's cell.

If a galvanic current passes through any conductor, a metallic wire,
or an electrolytic fluid, it evolves heat. Mr. Prescott Joule was the
first who proved experimentally that, if no other work is done by the
current, the total amount of heat evolved in a galvanic circuit during
a certain time is exactly equal to that which ought to have been gen-
erated by the chemical actions which have been performed during that
time. But this heat is not evolved at the surface of the electrodes,
where these chemical actions take place, but is evolved in all the parts
of the circuit, proportionally to the galvanic resistance of every part.
From this it is evident that the heat evolved is an immediate effect,
not of the chemical action, but of the galvanic current, and that the
chemical work of the battery has been spent in producing only the
electric action.

If we apply Faraday's law, a definite amount of electricity passing
through the circuit corresponds to a definite amount of chemical de-
composition going on in every electrolytic cell of the same circuit.
According to the theory of electricity, the work done by such a defi-
nite quantity of electricity which passes, producing a current, is pro-
portionate to the electro-motive force acting between both ends of the
conductor. You see, therefore, that the electro-motive force of a gal-
vanic circuit must be, and is, indeed, proportionate to the heat gener-
ated by the sum of all the chemical actions going on in all the electro-
lytic cells during the passage of the same quantity of electricity. In
cells of the galvanic battery chemical forces are brought into action
able to produce work ; in cells in which decomposition is occurring
work must be done against opposing chemical forces ; the rest of the
work done appears as heat evolved by the current, as far as it is
not used up to produce motions of magnets or other equivalents of
work.

Hitherto we have supposed that the ion with its electric charge is
separated from the fluid. But the ponderable atoms can give off their
electricity to the electrode and remain in the liquid, being now elec-



250 THE POPULAR SCIENCE MONTHLY.

trically neutral. This makes almost no difference in the value of the
electro-motive force. For instance, if chlorine is sepai-ated at the anode
it will remain at first absorbed by the liquid ; if the solution becomes
saturated, or if we make a vacuum over the liquid, the gas will rise in
bubbles. The electro-motive force remains unaltered. The same may
be observed with all the other gases. You see in this case that the
change of electrically negative chlorine into neutral chlorine is the
process which requires so great an amount of work, even if the pon-
derable matter of the atoms remains where it was.

The more the surface of the positive electrode is covered with neg-
ative atoms of the anion and the negative with the positive ones of the
cation, the more the attracting force of the electrodes exerted upon
the ions of the liquid is diminished by this second stratum of opposite
electricity covering them. On the contrary, the force with which the
positive electricity of an atom of hydrogen is attracted toward the
negatively charged metal increases in proportion as more negative
electricity collects before it on the metal and the more negative elec-
tricity collects behind it in the fluid.

Such is the mechanism by which electric force is concentrated and
increased in its intensit}- to such a degree that it becomes able to over-
power the mightiest chemical affinities we know of. If this can be
done by a polarized surface, acting like a condenser, charged by a very
moderate electro-motive force, can the attractions between the enor-
mous electric charges of anions and cations play an unimportant and
indifferent part in chemical affinity ?

You see, therefore, if we use the language of the dualistic theory
and treat positive and negative electricities as two substances, the phe-
nomena are the same as if equivalents of positive and negative electric-
ity were attracted by different atoms, and perhaps also by the differ-
ent values of affinity belonging to the same atom, with different force.
Potassium, sodium, zinc, must have strong attraction to a positive
charge ; oxygen, chlorine, bromine, to a negative charge.

Faraday very often recurs to this to express his conviction that the
forces termed chemical affinity and electricity are one and the same.
I have endeavored to give you a survey of the facts in their mutual
connection, avoiding, as far as possible, introducing other hypotheses,
except the atomic theory of modern chemistry. I think the facts leave
no doubt that the very mightiest among the chemical forces are of
electric origin. The atoms cling to their electric charges and the op-
posite electric charges cling to the atoms. But I don't suppose that
other molecular forces are excluded, working directly from atom to
atom. Several of our leading chemists have begun lately to distinguish
two classes of compounds, molecular aggregates and typical compounds.
The latter are united by atomic affinities, the former not. Electrolytes
belong to the latter class.

If we conclude fi'om the facts that every unit of aflfiinity of every



GLUCOSE AND GRAPE-SUGAR. 251

atom is charged always with one equivalent, either of positive or of neg-
ative electricity, they can form compounds, being electrically neutral,
only if every unit charged positively unites under the influence of a
mighty electric attraction with another unit charged negatively. You
see that this ought to produce compounds in which every unit of affin-
ity of every atom is connected with one and only with one other unit
of another atom. This is, as you will see immediately, indeed, the
modern chemical theory of quantivalence, comprising all the saturated
compounds. The fact that even elementary substances, with few ex-
ceptions, have molecules composed of two atoms, makes it probable
that even in these cases electrfc neutralization is j^roduced by the com-
bination of two atoms, each charged with its electric equivalent, not
by neutralization of every single unit of affinity.

But I abstain from entering into mere specialties, as, for instance,
the question of unsaturated compounds ; perhaps I have gone already
too far. I would not have dared to do it if I did not feel myself shel-
tered by the authority of that great man who was guided by a never-
erring instinct of truth. I thought that the best I could do for his
memory was to recall to the minds of the men, by the energy and in-
telligence of whom chemistry has undergone its modern astonishing
development, what important treasures of knowledge lie still hidden
in the works of that wonderful genius. I am not sufficiently acquainted
with chemistry to be confident that I have given the right interpreta-
tion — that interpretation which Faraday himself would have given,
perhaps, if he had known the law of chemical quantivalence, if he had
had the experimental means of ascertaining how large the extent, how
unexceptional the accuracy of his law really is ; and if he had known
the precise formulation of the law of energy applied to chemical work,
and of the laws which determine the distribution of electric forces in
space as well as in ponderable bodies, transmitting electric current or
forming condensers. I shall consider my work of to-day well rewarded
if I have succeeded in kindling anew the interest of chemists for the
electro-chemical part of their science.



GLUCOSE ATs^D GRAPE-SUGAR.

By Professok HARVEY W. WILEY.

THE manufacture of sirup and sugar from corn-starch is an indus-
try which, in this country, is scarcely a dozen years old, and yet
it is one of no inconsiderable magnitude. On August 1, 1880, ten
glucose-factories were in operation in the United States, consuming
daily about twenty thousand bushels of corn. These, with their sev-
eral capacities, are as follows :



252 THE POPULAR SCIENCE MONTHLY.

Firmenich's, Buffalo 4,000 bushels.

Buffalo, Buffalo 5,000 "

American, Buffalo 3,000 "

Higher, St. Louis 1,000 "

Peoria Refinery, Peoria 2,500 "

Peoria Grape-sugar, Peoria. 850 "

Davenport, Davenport, Iowa 1,500 "

Freeport, Freeport, Illinois 1,500 ''

Duryea, Brooklyn 1,500 "

Sagetown, Sagetowu, Illinois 250 "

At that time, also, there were in process of construction nine fac-
tories, with a total capacity of twenty-two thousand bushels daily.

At the same time additional machinery was in process of erection
in the two Peoria factories, which increased their capacity two thou-
sand and twenty-five hundred bushels, respectively.

The new factories were building in —

Detroit capacity, 3,000 bushels.

Chicago " 10,000 "

Geneva, Illinois " 1,000 "

Iowa City " 1,500 "

Danville, Illinois " 1,500 "

Tippecanoe, Ohio " 500 "

Rockford, Illinois " 1,000

Pekin, Illinois " 500 "

Marshalltown, Iowa " 3,000 "

We may safely assume that at the present time one half of these
new factories are in running order. The total daily consumption of
com, therefore, for sugar- and sirup-making, is not far from thirty-five
thousand bushels.

Eleven million bushels of corn during the present year will be
used for this purpose, and every indication leads us to believe that the
amount will be doubled in 1882.

The capital invested in this sugar industry is likewise no incon-
siderable one. Taking the large and small establishments together,
each thousand bushels of daily capacity represents sixty thousand
dollars of capital. Over two million dollars are therefore actively
employed in the glucose-works. The number of men employed
amounts to about sixty for each thousand bushels capacity, making a
total of twenty-one hundred. On account of the nature of the process
of manufacture, the mills are run night and day, and work is not
entirely suspended on Sunday.

To avoid confusion of ideas, the following statements seem neces-
sary : The word glucose, in this country, is employed among dealers
to designate exclusively the thick sirup which is made from corn-
starch. On the other hand, grape-sugar is applied to the solid product
obtained from the same source. The glucose and grape-sugar of the



GLUCOSE AND GRAPE-SUGAR. 253

trade have optical and chemical properties quite different from many-
other substances bearing the same name. 1 shall use the words in the
signification explained above.

Properties of Glucose. — Glucose is a thick, tenacious sirup,
almost colorless, or of a yellowish tint. It has an average specific
gravity, at 20° C, of 1*412. That which is made for summer con-
sumption is a little denser than that manufactured for winter use.
This sirup is so thick that, in the winter, it is quite difficult to pour it
from one vessel to another.

The sweetness of glucose — i. e., the intensity of the impression it
makes on the nerves of taste — varies greatly with different specimens.
Some kinds approach in intensity the sweetness of cane-sugar, while
others seem to act slowly and feebly. It has been shown that the
degree of sweetness depends on the extent of the chemical changes
which go on in the conversion of starch into sugar. When the process
of conversion is stopped as soon as the starch has disappeared, the
resulting glucose has a maximum sweetness.* The color of glucose
depends on the thorough washing of the substance, during the process
of manufacture, through animal charcoal, and lowness of temperature
at which it is evaporated, and rapidity of evaporation. The methods
of securing these conditions will be described further on.

There is one variety of glucose which is made for confectioners'
use, which is much thicker and denser than that just described. Its
specific gravity may reach 1"440, but it has no tendency to become
hard and solid, like the so-called grape-sugar.

The grape-sugar made from corn-starch, when well made, is pure
white in color when first made, but has a tendency to assume a yellow-
ish tint when old. It is hard and brittle, does not usually take on a
visible crystalline structure, and is less soluble in water than cane-sugar.
Perhaps it would be more accurate to say that it dissolves more slowly,
since both cane- and grape-sugar dissolve in all proportions in hot water.
I have found its specific gravity to be as high as 1*6. It is much less
sweet to the taste than glucose, and a faint bitter after-taste is to be
perceived.

Uses of Glucose axd Grape-Sugar. — Glucose is used chiefly for
the manufacture of table-sirups, candies, as food for bees, for brewing,
and for artificial honej .

It is impossible at present to get any reliable statistics concerning
tlie amount of glucose used in beer-making. The brewers themselves
try to keep its use a secret, since it is quite common to proclaim that
beer is made from barley and hops alone, although this is rarely the
case. Dealers and manufacturers are likewise reticent when approached
on this subject, since it is but natural for them to wish to protect the
interests of their patrons. We shall not go far wrong, however, when

* See paper read by the author at the Boston meeting of the American Association
for the Advancement of Science.



254 THE POPULAR SCIENCE MONTHLY.

we say that the amount of ghicose used by brewers is by no means
small, and that the quantity is constantly increasing. I do not know
any reason why its moderate use should injure the quality of the beer.

Bees eat glucose with the greatest avidity, or, rather, they act as
funnels by which the glucose is poured into the comb. For it is quite
true that honey made by bees which have free access to glucose differs
scarcely at all from the glucose itself. But the quantity of honey
which a bee will store away when fed on glucose is truly wonderful.
This gluttony, however, rapidly undermines the apiarian constitution,
and the bee rarely lives to enjoy the fruits of its apparent good for-
tune. In commercial honey, which is entirely free from bee mediation,
the comb is made of paraffine, and filled with pure glucose by appro-
priate machinery. This honey, for whiteness and beauty, rivals the
celebrated real white-clover honey of Vermont, but can be sold at an
immense profit at one half the price.

All soft candies, waxes, and taffies, and a large proportion of stick-
candies and caramels, are made of glucose. Very often a little cane-
sugar is mixed with the glucose, in order to give a sweeter taste to the
candies, but the amount of this is made as small as possible. As
has been stated above, the glucose which is used in confections is
evaporated nearer to dryness than that which is used for sirups. In
such glucoses I have found the percentage of water to .be as low as
6'37. Such a product is almost thick enough for " taffy " without any
further concentration.

A very large percentage of all the glucose made is used for the
manufacture of table-sirups. The process of manufacture is a very
simple one :

The glucose is mixed with some kind of cane-sugar sirup until the
tint reaches a certain standard. The amount of cane-sugar sirup re-
quired varies from three to ten per cent., according to circumstances.
These sirups are graded A, B, C, etc., the tint growing deeper with
each succeeding letter.

When these sirups are sent into the shops, they are sold to con-
sumers under such altisonant names as " Maple Drip," " Bon Ton,"



Online LibraryD. S. (David Samuel) MargoliouthThe Popular science monthly (Volume 19) → online text (page 31 of 110)