Chapter VIII: Hydrogen

This substance is one of the most interesting with which the chemist has to deal. On account of its chemical and physical properties, by reason of the many important compound substances into which it enters, by reason of the part it has played in the history of chemical progress, it is entitled to a large share of the student’s attention.

Meaning of the Word Hydrogen.

The name hydrogen was applied to it some time later than the first recognition of the substance. The word is derived from two Greek words (ὕδωρ, _hydor_, water, and γεννάω, _gennao_, I form or produce), the word as a whole meaning _water former_. In fact hydrogen is in all water wherever that substance exists. That this is a very comprehensive expression appears when it is remembered that the atmosphere always contains water diffused through it in the form of invisible vapor even before that vapor is precipitated as the gentle dew, or the crystalline snow, or the streaming rain. Again, water in seas and oceans, lakes and rivers, is the mantle of nearly three-fourths of the earth’s surface. Every living being on the dry land, whether animal or vegetable, contains large quantities of water in its structure: the blood of the higher animals is nearly nine-tenths water.

While water is the principal substance containing hydrogen, this gas exists also as a constituent part of a great many other solid and liquid matters found in the earth.

Why Free Hydrogen is not Found in the Earth.

Hydrogen scarcely ever exists on our globe alone, that is in the free or uncombined condition. Indeed there are certain definite reasons why it should not. These are based mainly upon the very strong chemical affinity that hydrogen has for oxygen. Now, as has been declared already, the latter substance is the most abundant element in nature, and it exists in very large quantities in our atmosphere. Spread all over the surface of the earth then, the free oxygen of the air stands prepared to combine with hydrogen wherever the latter may be liberated. Such combination might not occur, it is true, unless initiated by influence of heat or some flame of fire; but owing to the constant agitation of the air by reason of uniform currents like trade winds, as well as those produced when the atmosphere is agitated by violent storms, any mixture of hydrogen and oxygen would be likely soon to come into contact with some flame or fire, and so these components would enter into combination. Thus hydrogen would not be likely to remain long uncombined even were it produced in considerable quantity by natural terrestrial operations.

The Discoverer of Hydrogen.

Hydrogen was first distinctly described and its properties as a special kind of gaseous matter clearly pointed out in the year 1766, by an English chemist, the Honorable Henry Cavendish. This philosopher, the son of Lord Charles Cavendish, and the grandson at once of the Duke of Devonshire and the Duke of Kent, is one of the most curious characters in the history of the natural sciences. He was of an exceptionally careful, thorough and painstaking temper, which well fitted him for the scientific pursuits which were the prime objects of his thoughts. Sir Humphry Davy said of him: “The accuracy and beauty of his earlier labors have remained unimpaired amidst the progress of discovery, and their merits have been illustrated by discussion and exalted by time.”

In addition to his possession of many special aptitudes for the exact studies to which he devoted his entire existence, it should be recognized that he lived at a period that was remarkably favorable to the pursuit of the natural sciences. The times, the state of knowledge, the condition of society all over Europe seemed to be ripe for this kind of progress, for in Scotland, in England, in France, in Germany, in Sweden there appeared experimenters of unsurpassed skill, and chemistry as a science had then its birth under most fortunate auspices.

Cavendish was very peculiar in his manners and habits, living in great seclusion and retirement and in the most simple and methodical manner; indeed his oddities attained for him the unenviable distinction of a place in a book devoted to the lives of English eccentrics. In that work, as well as in Dr. Wilson’s life of him, are many amusing anecdotes of his way of life. One most remarkable episode was his inheritance of wealth. Though poor in his youth he was suddenly made rich in middle life by a bequest whose origin is scarcely known. M. Biot neatly described him as “le plus riche de tous les savants, et probablement aussi, le plus savant de tous les riches.” He lived on however in as great seclusion as before, his chosen associates being his flasks and his thermometers. His millions made no observable impression upon his habits, notwithstanding at his death they made him the largest holder of the stock of the Bank of England.

Lord Brougham says that Cavendish probably uttered fewer words in the course of his life than any other man who ever lived to fourscore years, not at all excepting the monks of La Trappe—who were bound to perpetual silence except in cases of absolute necessity.

Born in Bordeaux, in 1728; died in Edinburgh, Nov. 26, 1799.]

Why Hydrogen was not Discovered Earlier.

Doubtless those prehistoric men who in earliest days looked about upon the face of the earth, curiously examining their heritage from the Creator, were familiar with water in its various forms. They must have prized its bland and refreshing powers and have learned many of its most important uses. But the idea that it is made up of more than one kind of substance or matter was not suspected until very recent times, and not proved until the masterly investigations of Cavendish clearly set forth the facts. Indeed the very idea of a chemical compound, that is of a substance as made up of inconceivably small portions of matter in a union of almost inconceivable intimacy, an idea very familiar to students of the present day, probably did not enter the minds even of those profound thinkers who suggested the earlier atomic philosophies. In fact the notion of chemical union is scarcely more than a century old.

Moreover, hydrogen is a gas, and _the notion of gas_ is itself decidedly a modern one. It was first stated in well-defined form in the year 1752, by Dr. Joseph Black, professor in Glasgow and Edinburgh. Black clearly and conclusively demonstrated the existence of _airs_ of a different kind from that familiar to us in our atmosphere. It is true Van Helmont and even others, fully one hundred years before Black’s time, had known and stated more or less distinctly the existence of a gas or air different from that we breathe, but owing to a variety of circumstances these wonderful discoveries were allowed to relapse into forgetfulness. Thus the human race lost for a century much advantageous knowledge; but probably the general social advancement of those times had not then prepared mankind for the benefits which the development of modern chemistry has conferred upon the present citizens of the world. Again, _experimenting_ with gases was not well understood until about the year 1770, when Joseph Priestley invented that contrivance for manipulating them known as the pneumatic trough, for which no better substitute has yet been devised.

Further, in water—which has already been referred to as the most abundant and widely diffused compound of hydrogen—the partner elements are bound together by a chemical affinity that cannot be readily overcome. This intensity of attractive force between the constituent elements is therefore another reason why the true composition of water was so long an unsolved riddle and why hydrogen was not earlier recognized as a thing or kind of matter by itself, although in its principal compound—one of the most admirable gifts of the Creator to man—it was well-known from the first days of the human race.

How Hydrogen is Prepared.

Hydrogen may be obtained by the chemist in several ways:

_First._—There is a method of directly tearing the elements composing water apart from each other. Considered theoretically this process is a most direct and simple one. In order to realize its results, however, advantage must be taken of the galvanic current. This force may be obtained readily it is true: thus in most cases where two metals, dipped in a liquid, are connected by a wire it is generated. But no one knows fully what the current is. The words galvanic current and voltaic current suggest the two investigators, Galvani and Volta, who were the pioneers in this field, but they give nothing that can be called an _explanation_ of the wondrous, invisible, imponderable form of energy referred to. It is a force of an exceedingly interesting character and about which a certain considerable body of knowledge has been collected.

Among the variety of facts known about it is that one which relates to water; namely, when the poles or electrodes of a suitable galvanic battery are dipped into a vessel of water, bubbles of gas may be seen to flow freely from each of them. The gases may be collected in a vessel placed over the electrodes, but the experimenter may well beware of incautiously treating what has now been produced; he has obtained a mixture of oxygen and hydrogen from the original water, and these elements which he has rended apart from their more intimate union, are ready upon the approach of the smallest flame to rush into union again, with extraordinary violence, and in such a way as to produce a tremendous explosion. In the act of this explosion, therefore, water is again produced, first as expansive vapor, then condensible back to the liquid drops whence it came.

FIG. 6.—Apparatus for decomposition of water, (by action of two cells of the Bunsen galvanic battery,) and for collection of hydrogen and oxygen gases in separate receivers over the two electrodes of the battery.]

If however the product from each electrode is collected _by itself in a separate tube_, the one gas is found to be very different from the other. The one is found to be hydrogen, the other oxygen. In accordance with the formula H₂O—which it has before been stated represents the composition of water—the hydrogen is found to be given off in a bulk or volume that is twice as great as that of the oxygen obtained at the same time from the same amount of water.

_Second._—Hydrogen may be obtained by bringing into contact with water under proper conditions certain substances that have a very strong affinity for its oxygen and at the same time but little affinity for its hydrogen. Now every one is familiar with the fact that iron rusts readily in the air. The chemist can demonstrate that this rust is a compound of iron and oxygen. The union of these elements under ordinary conditions suggests at once that that union arises from an affinity between the iron and the oxygen. This affinity is much greater at high temperatures, for it is well known that iron rusts more violently when subjected to heat. These facts then are made use of for the purpose of withdrawing oxygen from water and thus forcing the hydrogen out in the free or uncombined condition so that it may be obtained and experimented upon.

FIG. 7.—Apparatus for preparation of hydrogen gas. Steam, generated in the small retort, is conveyed through the tube placed in the gas furnace; iron turnings within the tube being highly heated, decompose the water-vapor, which thereby evolves hydrogen. The liberated gas is collected in the little bell-glass.]

To produce hydrogen by this method, there must be provided a long iron pipe which passes through a hot furnace; the pipe should contain fragments of iron such as iron turnings, or iron filings, or pieces of iron wire. Then a current of steam must be passed through the pipe. The iron becomes red hot, and under these circumstances manifests more affinity for the oxygen of the steam than the hydrogen does. The iron then grasps the oxygen and holds it fast. As a result a peculiar kind of oxide of iron of a black color is produced. Its chemical formula is Fe₃O₄ and it is called by chemists ferroso-ferric oxide. The iron has now taken the place as a partner of the oxygen that the hydrogen formerly had. The hydrogen is thus cast out from its combination and is set free as an uncombined gas, in which liberated condition it is expelled at the end of the tube. The chemical action between the iron and the steam may be represented by the following equation:

=Fe₃= + =4H₂O=

Three atoms of Four molecules of
Iron, Water,
168 72
parts by weight. parts by weight.
\____________________________________/
|
240

= =Fe₃O₄= + =4H₂=

One molecule of Four molecules of
Ferroso-ferric oxide, Hydrogen,
232 8
parts by weight. parts by weight.
\_________________________________________/
|
240

The gas produced as just described may be collected by adjusting a suitable tube in connection with the pipe containing the iron. When the gas is examined it is found to be in fact hydrogen. It will burn with a blue flame and perform all the various actions that acknowledged hydrogen will.

_Third._—There are other metals, not known to the common every-day uses of life but still familiar to the chemist, which have far greater affinity for oxygen than iron has. One such metal is that called sodium. Its affinity for oxygen is so great that it cannot be long preserved if exposed to the air: a block or lump of it would, in a day or two in the open air, turn entirely to a mass of rust of sodium, that is oxide of sodium. This metal therefore is preserved by the chemist in bottles containing petroleum oil. The oil keeps the air away from the metal; moreover the oil contains no oxygen in its composition as many other liquids do. This metal sodium though heavier than the oil is lighter than water. If thrown upon water it floats. But by virtue of its intense affinity for oxygen, it at the same time decomposes the water. It draws the oxygen to itself and it liberates the hydrogen. Some chemical skill is requisite in the performance of this apparently simple experiment, for occasionally the violent affinities involved set the sodium and the hydrogen on fire and give rise to dangerous explosions. When properly conducted, however, the hydrogen from this process may be collected in a vessel and its various characteristics displayed.[2]

[2] Appleton’s “Young Chemist,” Philadelphia, Cowperthwait & Co. pp. 26, 27, 28.

_Fourth._—The most common way of producing hydrogen is by bringing together sulphuric acid and zinc. The formula for sulphuric acid is H₂SO₄. Now the zinc has affinity for the compound radicle SO₄, known as the sulphuric acid radicle. The chemical change is represented by the following equation:

=Zn= + =H₂SO₄=

One atom of One molecule of
Zinc, Sulphuric acid,
65 98
parts by weight parts by weight
\___________________________________/
|
163

= =ZnSO₄= + =H₂=

One molecule of One molecule of
Zinc sulphate, Hydrogen,
161 2
parts by weight parts by weight
\_________________________________/
|
163

Here it is plain that by reason of its affinities the zinc has taken the place of the hydrogen—or the place which the hydrogen formerly held as related to the sulphuric acid radicle, SO₄—and that the hydrogen thereby left without anything to combine with, appears as a free and uncombined substance. The hydrogen produced by this method can be readily collected and examined.

FIG. 8.—Apparatus for production of hydrogen, by action of sulphuric acid on zinc, and for collection of the gas in a receiver.]

Perhaps it ought to be stated that neither of the processes thus far explained is likely to yield hydrogen in an absolutely pure condition. The various substances used are likely themselves to contain associated with them small amounts of other substances which give some impurity to the gas evolved.

The Powers and Properties Manifested by Hydrogen.

Hydrogen has been seen, from the explanation already given, to be a gas. Down to within a few years it resisted all attempts to liquify it. Chemists submitted it to intense cold and enormous pressure and to both these influences at the same time but without avail. Within a few years, however, by use of ampler resources and contrivances for the application of these condensing agencies, it has been brought down to the liquid and perhaps even to the solid state.

As a gas it is colorless, odorless, tasteless.

Bulk for bulk it is the lightest substance known in nature. Thus a quart of atmospheric air, light as it is, weighs over fourteen times as much as a quart of hydrogen. A cubic inch of gold weighs more than two hundred thousand times as much as a cubic inch of hydrogen. This lightness is properly illustrated by inflating a soap bubble with hydrogen rather than with air. When soap bubbles are filled with air they fall, unless indeed carried upward by a temporary current; but when filled with hydrogen they invariably rise with great rapidity. By reason of this great lightness hydrogen was formerly used for the inflating of balloons, but at the present day illuminating gas is so much cheaper, that the latter is generally used, although it is much heavier than hydrogen.

Diffusive Power of Hydrogen Gas.

It is not inappropriate to call attention here to certain interesting relations that hydrogen manifests towards gases and solids. Thus hydrogen possesses to a marked degree that curious facility of passing into and permeating other gases which is spoken of as its _diffusive power_. True, this power is possessed by all gases to a certain extent; but in rapidity of action none approach hydrogen. As early as 1825 a German chemist named Döbereiner announced his observations of this power. He noticed that upon collecting some hydrogen in a cracked jar, placed in a pneumatic trough, the hydrogen leaked out into the air more rapidly than the air went in. So that in fact the water of the trough rose on the inside of the jar. It has been since discovered that when almost any two gases whatsoever, if only of different densities, are separated by a partition having fine cracks or holes in it, the lighter gas always moves out into the heavier one more rapidly than the heavier gas moves in. As hydrogen is the lightest of all, of course it diffuses into other gases with the greatest rapidity.

In liquids, hydrogen does not ordinarily dissolve in any considerable quantity.

With solids however it displays some properties that are well nigh incredible. Thus it has a very curious aptitude for passing into the very interior of certain solid metals. The white, compact, solid metal palladium, although it has no visible pores, has the power of swallowing up into itself in some mysterious way nearly a thousand times its bulk of this gas; and again a thin sheet of this same solid metal, air-tight to all appearances, allows hydrogen to pass through it as easily as a sieve does water.

The Most Interesting Chemical Property of Hydrogen.

By all means the most interesting chemical property of hydrogen is its power to unite with oxygen. When it does so unite all the phenomena of combustion appear. These phenomena are generally the production of heat, light, flame, and the formation of some new chemical compound. So then when hydrogen unites with oxygen, it burns, it gives out light (although that light is of but feeble intensity), it gives out an enormous quantity of heat, it forms an oxidized product. This product is water, but water that—owing to the great heat of the combustion—is raised to the form of invisible vapor. When however a jet of hydrogen gas is burned under a bright but cool bell-glass, the deposit of mist quickly formed on the inside of the glass shows that the vapor produced by combustion has now condensed on the bell to minute liquid drops.

FIG. 9.—A glass tube held over a hydrogen flame, for the purpose of developing a musical note.]

In the matter of the heat involved, hydrogen has the distinction of being above every other substance. One pound of hydrogen when burned under favorable conditions evolves heat enough to raise over _thirty-four thousand pounds_ of water from zero centigrade to one degree centigrade, or nearly the same as from 32 degrees Fahrenheit to 34 degrees Fahrenheit. This expression of the calorific power of hydrogen has the same meaning as the following more technical one, namely: burning hydrogen affords over thirty-four thousand thermal units. Now carbon, a fuel which nature has provided, and which is certainly admirably fitted to be man’s chief combustible, yields but eight thousand thermal units of the kind just referred to, and for purposes of comparison it maybe added that sulphur yields but two thousand thermal units.

Hydrogen Cannot Supply the Uses of Atmospheric Air.

Notwithstanding the remarkable evidences of chemical affinity suggested by what has just been said, hydrogen can in no sense act as a substitute for the atmospheric air. Thus it does not support animal life nor will it sustain the combustion of a candle. A living animal immersed in a room full of hydrogen would be drowned in it; a burning candle carried into such a chamber would be extinguished as if dipped in water. In fact the comparison with drowning is very proper, for in drowning a living animal the water does not chemically injure the organism; the hydrogen and the water, in the cases supposed, have similar action _in depriving both the animal and the taper of their requisite oxygen_.

The Uses to Which Hydrogen May be Put.

Hydrogen as the elementary gas finds but few applications in the arts. It is true that from what has been said, it appears as if its wonderful calorific power might be utilized in some of the arts where high temperatures are requisite. But the cost and difficulties attending its preparation, the liability to loss during its storage, and the danger from explosion while in actual use, these and other circumstances have led even the skilled artisan to content himself in most cases with other though inferior materials. But if the reader has attentively followed the introductory chapters of this work he must have perceived that hydrogen is made of great service in many of the measurements employed by the chemist. It has been noted that it is used as the standard of _equivalence or atom-fixing power_. It has been spoken of as the standard of _atomic weight_, and from what has appeared in the remarks upon its lightness it will seem that it has been properly adopted as the _standard of density for gases_.

READING REFERENCES.

Cavendish, Henry
=Brougham=, H.—Lives of Men of Letters and Science, etc.
p. 429.
=Timbs=, J.—English Eccentrics, etc. p. 132.
=Wilson=, George.—Life of Cavendish. London. 1851.

Black, Joseph
=Brougham=, H.—Lives of Men of Letters and Science, etc.
London. 1845 p. 324.

Diffusion of Gases.
=Graham=, T.—Elements of Chemistry. 2 v. London. 1850. i, 84.
———— Jour. of Chem. Soc. of London. xvii, 334.

Occlusion of Hydrogen by Palladium.
=Graham=, T.—Jour. of Chem. Soc. of London. xxii, 419.