Chapter 7

General Morin believes this alloy to be a perfect chemical combination, as it exhibits, unlike the gun metal, a most complete homogeneousness, its preparation being also attended by a great development of heat, not seen in the manufacture of most other alloys. The specific gravity of this alloy is 7.7. It is malleable and ductile, may be forged cold as well as hot, but is not susceptible of rolling; it may, however, be drawn into tubes. It is extremely tough and fibrous.

Aluminum bronze, when exposed to the air, tarnishes less quickly than either silver, brass, or common bronze, and less, of course, than iron or steel. The contact of fatty matters or the juice of fruits does not result in the production of any soluble metallic salt, an immunity which highly recommends it for various articles for table use.

The uses to which aluminum bronze is applicable are various. Spoons, forks, knives, candle-sticks, locks, knobs, door-handles, window fastenings, harness trimmings, and pistols are made from it; also objects of art, such as busts, statuettes, vases, and groups. In France, aluminum bronze is used for the eagles or military standards, for armor, for the works of watches, as also watch chains and ornaments. For certain parts, such as journals of engines, lathe-head boxes, pinions, and running gear, it has proved itself superior to all other metals.

Hulot, director of the Imperial postage stamp manufactory in Paris, uses it in the construction of a punching machine. It is well known that the best edges of tempered steel become very generally blunted by paper. This is even more the case when the paper is coated with a solution of gum arabic and then dried, as in the instance of postage stamp sheets. The sheets are punched by a machine the upper part of which moves vertically and is armed with 300 needles of tempered steel, sharpened in a right angle. At every blow of the machine they pass through the holes in the lower fixed piece, which correspond with the needles, and perforate five sheets at every blow. Hulot now substitutes this piece by aluminum bronze. Each machine makes daily 120,000 blows, or 180,000,000 perforations, and it has been found that a cushion of the aluminum alloy was unaffected after some months' use, while one of brass is useless after one day.

Various formulæ are given for the production of alloys of aluminum, but they are too numerous and intricate to enter into here.

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DETERMINATION OF POTASSA IN MANURES.

By M.E. DREYFUS.

The method generally adopted for the determination of potassa in manures, i. e., the direct incineration of the sample, may in certain cases occasion considerable errors in consequence of the volatilization of a portion of the potassium products.

To avoid this inconvenience, the author proposes a preliminary treatment of the manure with sulphuric acid at 1.845 sp. gr., to convert potassium nitrate and chloride into the fixed sulphate. The sulphuric acid attacks the manure energetically, and much facilitates the incineration, which may be effected at a dark red heat. The ignited portion (10 grms.) is exhausted with boiling distilled water acidulated with hydrochloric acid, and the filtrate, when cold, is made up to 500 c. c. Of this solution 50 c c., representing 1 grm. of the sample, are taken, and, after being heated until close upon ebullition, baryta-water is added until a strong alkaline reaction is obtained. The sulphuric and phosphoric acids, alumina, magnesia, etc, are thus precipitated. The filtrate is heated to a boil, and mixed with ammonia and ammonium carbonate, to precipitate the excess of baryta in solution. The last traces of lime are eliminated by means of a few drops of ammonium oxalate. The filtrate is evaporated down on the water-bath, and the ammoniacal salts are expelled by carefully raising the temperature to dull redness. After having taken up the residue in distilled water it is treated with platinum chloride, and the potassium chloro-platinate obtained is reduced with oxalic acid. The quantity of potassa present in the manure can be calculated from the weight of platinum obtained.--_Bull. de la Soc. Chim. de Paris_.

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THE ORIGIN AND RELATIONS OF THE CARBON MINERALS.

[Footnote: Read before the New York Academy of Sciences, February 6, 1882.]

By J.S. NEWBERRY.

What are called the carbon minerals--peat, lignite, coal, graphite, asphalt, petroleum, etc.--are, properly speaking, not minerals at all, as they are organic substances, and have no definite chemical composition or crystalline forms. They are, in fact, chiefly the products or phases of a progressive and inevitable change in plant-tissue, which, like all organic matter, is an unstable compound and destined to decomposition.

In virtue of a mysterious and inscrutable force which resides in the microscopic embryo of the seed, a tree begins its growth. For a brief interval, this growth is maintained by the prepared food stored in the cotyledons, and this suffices to produce and to bring into functional activity--some root-fibrils below and leaves above, with which the independent and self-sustained life of the individual begins. Henceforward, perhaps for a thousand years, this life goes on, active in summer and dormant in winter, absorbing the sunlight as a motive power which it controls and guides. Its instruments are the discriminating cells at the extremities of the root-fibrils, which search for, select, and absorb the crude aliment adapted to the needs of the plant to which they belong, and the chlorophyl cells--the lungs and stomach of the tree--in the leaves. During all the years of the growth of the plant, these organs are mainly occupied in breaking the strongly riveted bonds that unite oxygen and carbon in carbonic acid; appropriating the carbon and driving off most of the oxygen. In the end, if the tree is, e. g., a _Sequoia_, some hundreds of tons of solid, organized tissue have been raised into a column hundreds of feet in height, in opposition to the force of gravitation and to the affinities of inorganic chemistry.

The time comes, however, sooner or later, when the power which has created and the life that has pervaded this wonderful structure abandon it. The affinities of inorganic chemistry immediately reassert themselves, in ordinary circumstances rapidly tearing down the ephemeral fabric.

The disintegration of organic tissue, when deserted by the force which has animated and preserved it, gives rise to the phenomena which form the theme of this paper.

Most animal-tissue decomposes with great rapidity, and plant tissue, when not protected, soon decays. This decay is essentially oxidation, since its final result is the restoration to the atmosphere of carbonic acid, which is broken up in plant-growth by the appropriation of its carbon. Hence it is a kind of combustion, although this term is more generally applied to very rapid oxidation, with the evolution of sensible light and heat. But, whether the process goes on rapidly or slowly, the same force is evolved that is absorbed in the growth of plant-tissue; and by accelerating and guiding its evolution, we are able to utilize this force in the production at will of heat, light, and their correlatives, chemical affinity, motive power, electricity, and magnetism. The decomposition of plants may, however, be more or less retarded, and it then takes the form of a destructive distillation, the constituents reacting upon each other, and forming temporary combinations, part of which are evolved, and part remain behind. Water is the great extinguisher of this as of the more rapid oxidation that we call combustion; and the decomposition of plant-tissue under water is extremely slow, from the partial exclusion of oxygen. Buried under thick and nearly impervious masses of clay, where the exclusion of oxygen is still more nearly complete, the decomposition is so far retarded that plant-tissue, which is destroyed by combustion almost instantaneously, and if exposed to "the elements"--moisture with a free access of oxygen--decays in a year or two, may be but partially consumed when millions of years have passed. The final result is, however, inevitable, and always the same, viz., the oxidation and escape of the organic mutter, and the concentration of the inorganic matter woven into its composition--in it, but not of it--forming what we call the ash of the plant.

Since the decomposition of organic matter commences the instant it is abandoned by the creative and conservative vital force, and proceeds uninterruptedly, whether slowly or rapidly, to the final result, it is evident that each moment in the progress of this decomposition presents us with a phase of structure and composition different from that which preceded and from that which follows it. Hence the succession of these phases forms a complete sliding scale, which is graphically shown in the following diagram, where the organic constituents of plant tissue--carbon, hydrogen, oxygen, and nitrogen--appear gradually diminishing to extinction, while the ash remains nearly constant, but relatively increasing, till it is the sole representative of the fabric.

We may cut this triangle of residual products where we please, and by careful analysis determine accurately the chemical composition of a section at this point, and we may please ourselves with the illusion, as many chemists have done, that the definite proportions found represent the formula of a specific compound; but an adjacent section above or below would show a different composition, and so in the entire triangle we should find an infinite series of formulae, or rather no constant formulae at all. We should also find that the slice, taken at any point while lying in the laboratory or undergoing chemical treatment, would change in composition, and become a different substance.

In the same way we can snatch a brand from the fire at any stage of its decomposition, or analyze a decaying tree trunk during any month of its existence, and thus manufacture as many chemical formulae as we like, and give them specific names; but it is evident that this is child's play, not science. The truth is, the slowly decomposing tissue of the plants of past ages has given us a series of phases which we have grouped under distinct names, and we have called one group peat, one lignite, another coal, another anthracite, and another graphite. We have spaced off the scale, and called all within certain lines by a common name; but this does not give us a common composition for all the material within these lines. Hence we see that any effort to define or describe coal, lignite, or anthracite accurately must be a failure, because neither has a fixed composition, neither is a distinct substance, but simply a conventional group of substances which form part of an infinite and indivisible series.

But this sliding scale of solid compounds, which we designate by the names given above, is not the only product of the natural and spontaneous distillation of plant tissue. Part of the original organic mass remains, though constantly wasting, to represent it; another part escapes, either completely oxidized as carbonic acid and water, or in a volatile or liquid form, still retaining its organic character, and destined to future oxidation, known as carbureted hydrogen, olefiant gas, petroleum, etc.

Hence, in the decomposition of vegetable tissue, two classes of resultant compounds are formed, one residual and the other evolved; and the genesis and relation of the carbon minerals may be accurately shown by the following diagram:

PLANT TISSUE _________________ | _Residual Products_ | _Evolved Products_ | Peat. } | } Lignite. } | } { Carbonic Acid. Bitumious Coal. } { Carbonic Oxide. | } { Carbureted Hydrogen, etc. Semi-bitumious " } { Water. | } { {Maltha. Anthracite. } { { | | } { {Asphalt etc. Graphitie Anthracite. } { Petro- { | | } { leum {Asphaltic Coal. Graphite. } { | | } {Asphaltic Anthracite. Ash. } { | { " Graphite.

[NOTE.--In this diagram, the vertical line connecting the names of the residual products (and of the derivatives of petroleum) indicates that each succeeding one is produced by further alteration from that which precedes it, and not independently. Also, the arrangement of the braces is designed to show that any or all of the evolved products are given off at each stage of alteration.]

The theory here proposed has not been evolved from my inner consciousness, but has grown from careful study, through many years, of facts in the field. A brief sketch of the evidence in favor of it is all that we have space for here.

RESIDUAL PRODUCTS.

_Peat_.--Dry plant-tissue consists of about 50 per cent, of carbon, 44 per cent, of oxygen, with a little nitrogen, and 6 per cent. of hydrogen. In a peat-bog, we find the upper part of the scale represented above very well shown: plants are growing on the surface with the normal composition of cellulose. The first stratum of peat consists of browned and partially decomposed plant-tissue, which is found to have lost perhaps 20 per cent. of the components of wood, and to have acquired an increasing percentage of carbon. As we descend in the peat, it becomes more homogeneous and darker until at the bottom of the marsh ten or twenty feet from the surface, we have a black, carbonaceous paste, which, when dried, resembles some varieties of coal, and approaches them in composition. It has lost half the substance of the original plant, and shows a marked increase in the relative proportion of carbon.

_Lignite_.--Each inch in vertical thickness of the peat-bog represents a phase in the progressive change from wood-tissue to lignite, using this term with its common signification to indicate, not necessarily carbonized ligneous tissue, but plant-tissue that belongs to a past though modern geological age--i.e., Tertiary, Cretaceous, Jurassic, or Triassic. These lignites or modern coals are only peat beds which have been buried for a longer or shorter time under clay, sand, or solidified rock, and have progressed farther or less far on the road to coal. As with peats, so with lignites, we find that at different geological levels they exhibit different stages of this distillation--the Tertiary lignites being usually distinguished without difficulty by the presence of a larger quantity of combined water and oxygen, and a less quantity of carbon, than the Cretaceous coals, and these in turn differ in the same respects from the Triassic.

All the coals of the Tertiary and Mesozoic ages are grouped under one name; but it is evident that they are as different from each other as the new and spongy from the old and well-rotted peat in the peat-bog.

_Coal_.--By mere convention, we call the peat which accumulated in the Carboniferous age by the name of bituminous coal; and an examination of the Carboniferous strata in different countries has shown that the peat-beds formed in the Carboniferous age, though varying somewhat, like others, with the kind of vegetation from which they were derived, have a common character by which they may be distinguished from the more modern coals; containing less water, less oxygen, and more carbon, and usually exhibiting the property of coking, which is rare in coals of later date. Though there is great diversity in the Carboniferous coals, and it would be absurd to express their composition by a single formula, it may be said that, over the whole world, these coals have characteristics, as a group, by which they can be recognized, the result of the slow decomposition of the tissue of plants which lived in the Carboniferous age, and which have, by a broad and general change, approximated to a certain phase in the spontaneous distillation of plant-tissue. An experienced geologist will not fail to refer to their proper horizon a group of coals of Carboniferous age any more than those of the Cretaceous or Tertiary.

_Anthracite_--In the ages anterior to the Carboniferous, the quantity of land vegetation was apparently not sufficient to form thick and extensive beds of peat; but the remains of plant-tissue are contained in all the older formations, though there only as anthracite or graphite--the last two groups of residual products. Of these we have examples in the beds of graphite in the Laurentian rocks of Canada, and of anthracite of the lower Silurian strata of Upper Church and Kilnaleck, Ireland.

From these facts it is apparent that the carbon series is graded geologically, that is, by the lapse of time during which plant-tissue has been subjected to this natural and spontaneous distillation. But we have better evidence than this of the derivation of one from another of the groups of residual products which have been enumerated. In many localities, the coals and lignites of different ages have been exposed to local influences--such as the outbursts of trap-rock, or the metamorphism of mountain chains--which have hastened the distillation, and out of known earlier groups have produced the last. For example, trap outbursts have converted Tertiary lignites in Alaska into good bituminous coals; on Queen Charlotte's Island, on Anthracite Creek, in southwestern Colorado, and at the Placer Mountains, near Santa Fe, New Mexico, Cretaceous lignites into anthracite; those from Queen Charlotte's Island and southwestern Colorado are as bright, hard, and valuable as any from Pennsylvania. At a little distance from the focus of volcanic action, the Cretaceous coals of southwestern Colorado have been made bituminous and coking, while at the Placer Mountains the same stratum may be seen in its anthracitic and lignitic stages.

A still better series, illustrating the derivation of one form of carbon solids from another, is furnished by the coals of Ohio, Pennsylvania, and Rhode Island. These are of the same age; in Ohio, presenting the normal composition and physical characters of bituminous coals, that is, of plant tissue generally and uniformly descending the scale in the lapse of time from the Carboniferous age to the present. In the mountains of Pennsylvania the same coal beds, somewhat affected by the metamorphism which all the rocks of the Alleghanies have shared, have reached the stage of _semi-bituminous_ coals, where half the volatile constituents have been driven off; again, in the anthracite basins of eastern Pennsylvania, the distillation further effected has formed from these coals _anthracite_, containing only from three to ten per cent. of volatile matter; while in the focus of metamorphic action, at Newport, Rhode Island, the Carboniferous coals have been changed to _graphitic anthracite_, that is, are half anthracite and half graphite. Here, traveling from west to east, a progressive change is noted, similar to that which may be observed in making a vertical section of a peat bog, or in comparing the coals of Tertiary, Mesozoic, and Carboniferous age, only the latter is the continuation and natural sequence of the former series of changes.

In the Laurentian rocks of Canada are large accumulations of carbonaceous matter, all of which is graphite, and that which is universally conceded to be derived from plant-tissue. The oxidation of graphite is artificially difficult, and in nature's laboratory slow; but it is inevitable, as we see in the decomposition of its outcrops and the blanching of exposed surfaces of clouded marbles, where the coloring is graphite. Thus the end is reached, and by observations in the field, the origin and relationship of the different carbon solids derived from organic tissue are demonstrated.

It only remains to be said, in regard to them, that all the changes enumerated may be imitated artificially, and that the stages of decomposition which we have designated by the names graphite, anthracite, coal, lignite, are not necessary results of the decomposition of plant-tissue. A fallen tree may slowly consume away, and all its carbonaceous matter may be oxidized and dissipated without exhibiting the phases of lignite, coal, etc.; and lignite and coal, when exposed to air and moisture, are burned away to ashes in the same manner, simply because in these cases complete oxidation of the carbon takes place, particle by particle, and the mass is not affected as a whole in such a way as to assume the intermediate stages referred to. Chemical analysis, however, proves that the process is essentially the same, although the physical results are different.

EVOLVED PRODUCTS.

The gradual wasting of plant-tissue in the formation of peat, lignite, coal, etc., may be estimated as averaging for peat, 20 to 30 per cent.; lignite, 30 to 50 per cent.; coal, 50 to 70 per cent.; anthracite, 70 to 80; and graphite, 90 per cent. of the original mass. The evolved products ultimately represent the entire organic portion of the wood--the mineral matter, or ash, being the only residuum. These evolved products include both liquids and gases, and by subsequent changes, solids are produced from some of them. Carbonic acid, carbonic oxide, nitrogenous and hydrocarbon gases, water, and petroleum, are mentioned above as the substances which escape from wood-tissue during its decomposition. That all these are eliminated in the decay of vegetable and animal structures is now generally conceded by chemists and geologists, although there is a wide difference of opinion as to the nature of the process.

It has been claimed that the evolved products enumerated above are the results of the primary decomposition of organic matter, and never of further changes in the residual products; i.e., that in the breaking-up of organic tissue, variable quantities of coal, anthracite, petroleum, marsh gas, etc., are formed, but that these are never derived, the one from the other. This opinion is, however, certainly erroneous, and the formation of any or all the evolved products may take place throughout the entire progress of the decomposition. Marsh gas and carbonic acid are seen escaping from the surface of pools where recent vegetable matter is submerged, and they are also eliminated in the further decomposition of peat, lignite, coal, and carbonaceous shale. Fire damp and choke-damp, common names for the gases mentioned above, are produced in large quantities in the mines where Tertiary or Cretaceous lignites, or Carboniferous coals or anthracites are mined. It has been said that these gases are simply locked up in the interstices of the carbonaceous matter and are liberated in its excavation; but all who have worked coal mines know that such accumulations are not sufficient to supply the enormous and continuous flow which comes from all parts of the mass penetrated. We have ample proof, moreover, that coal, when exposed to the air, undergoes a kind of distillation, in which the evolution of carbonic acid and hydrocarbon gases is a necessary and prominent feature.

The gas makers know that if their coal is permitted to lie for months or years after being mined, it suffers serious deterioration, yielding a less and less quantity of illuminating gas with the lapse of time. So coking coals are rendered dry, non-caking, and valueless for this purpose by long exposure.