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to be done for the protection of the freedmen could best bel which is defended by an ancient castle, affords shelter to large 'accomplished by new associations formed for that purpose. The ships, and is the natural outlet for the commerce of a thriving Liberalor was discontinued at the end of the same year, after an agricultural and mining district. Despite its small size and the existence of thirty-five years. He visited England for the second want of railway communication, Garrucủa has thus a considertime in 1846, and again in 1867, when he was received with able trade in lead, silver, copper, iron, esparto grass, fruit, &c. distinguished honours, public as well as private. In 1877, when Besides sca-going ships, many small coasters enter in ballast, and he was there for the last time, he declined every form of public clear with valuable cargocs. In 1902, 135 vessels of 390,000 tons recognition. He died in New York on the 24th of May 1879, in entered the harbour, the majority being British or Spanish; and the seventy-fourth year of his age, and was buried in Boston, in the same year the value of the exports reached £478,000, and after a most impressive funeral service, four days later. In that of the imports £128,000. Both imports and exports trebled 1843 a small volume of his Sonnels and other Poems was published, their value in the ten years 1897-1902. and in 1852 appeared a volume of Selections from his Writings GARSTON, a seaport in the Widnes parliamentary division of and Speeches. His wife, Helen Eliza Benson, died in 1876. Lancashire, England, on the Mersey, 6 m. S.E. of Liverpool. Four sons and one daughter survived them.

Pop. (1891) 13,444; (1901) 17,289. The docks, belonging to the Garrison's son, WILLIAM LLOYD GARRISON (1838–1909), was a London & North Western railway company, employ most of the prominent advocate of the single tax, free trade, woman's working population. There is about a mile of quayage, with suffrage, and of the repeal of the Chinese Exclusion Act, and an special machinery for the shipping of coal, which forms the chief opponent of imperialism; another son, WENDELL PHILLIPS article of export. GARRISON (1840-1907), was literary editor of the New York GARTH, SIR SAMUEL (1661-1719), English physician and Nation from 1865 to 1906.

poet, was born of a good Yorkshire family in 1661. He entered The above article, with certain modifications, reproduces the Peterhouse, Cambridge, in 1676, graduating B.A. in 1679 and account given in the 9th edition of this work by Oliver Johnson M.A. in 1684. He took his M.D. and became a member of the (reprinted from his Garrison: an Outline of his Life, New York, College of Physicians in 1691. In 1697 he delivered the Harveian editor, and an intimate friend of Garrison he edited the Liberator oration, in which he advocated á scheme dating from some ten during Garrison's absence in England in 1833. and later was an editor years back for providing dispcnsaries for the relief of the sick or an associate editor of various journals, including, after the Civil poor, as a protection against the greed of the apothecaries. In War, the New York Tribune and the New York Evening Post. He 1699 he published a mock-heroic poem, The Dispensary, in six also published an excellent brief biography in William Löyd Garrison cantos, which had an instant success, passing through three and his Times (Boston, 1880).

The great authority on the life of Garrison is the thorough and editions within a year. In this he ridiculed the apothecaries and candid work of his sons, W. P. and F. J. Garrison, William Lloyd their allies among the physicians. The poem has little interest at Garrison 1805-1879: The Story of his life lold by his Children (4 the present day, except as a proof that the heroic couplet was vols., New York, 1885-1889), which is indispensable for the student of the anti-slavery struggle in America. Goldwin Smith's The Moral

written with smoothness and polish before the days of Pope. Crusader: a Biographical Essay on William Lloyd Garrison (New Garth was a member of the Kit-Kat Club, and became the leading York, 1892) is a brilliant sketch.

physician of the Whigs, as Radcliffe was of the Tories. In 1714 GARRISON, originally a term for stores or supplies, also a he was knighted by George I. and he died on the 18th of January defence or protection, now confined in meaning to a body of 1719. He wrote little besides his best-known work The Dispentroops stationed in a town or fortress for the purpose of defence. sary and Claremont, a moral espistle in verse. He made a Latin In form the word is derived from 0. Fr. garison, modern oration (1700) in praise Dryden and translated the Life of guérison, from guérir, to furnish with stores, to preserve, but in Olho in the fifth volume of Dryden's Plutarch. In 1717 he edited ils later meaning it has been confused with the Fr. garnison, the a translation of Ovid's Mclamorphoses, himself supplying the regular word for troops stationed for purposes of defence. In fourteenth and part of the fifteenth book. English "garnison " was used till the 16th century, when“


GARTOK, a trade-market of Tibet, situated on the bank of the rison " took its place. In the British army " garrison troops," Indus on the road between Shigatse and Leh, to the east of Simla. especially“ garrison artillery,” are troops trained and employed in accordance with the "Tibet treaty of 1904, Gartok, together for garrison work as distinct from field operations.

with Yatung and Gyantse, was thrown open to British trade. GARROTE (Spanish for "cudgel "), an appliance used in on the return of the column from Lhasa in that year Gartok was Spain and Portugal for the execution of criminals condemned visited by a party under Captain Ryder, wbd found only a few to death. The criminal is conducted to the place of execution dozen people in winter quarters, their houses being in the midst (which is public) on horseback or in a cart, wearing a black of a bare plain. In summer, however, all the trade between tunic, and is attended by a procession of priests, &c. He is Tibet and Ladakh passes through this place. seated on a scaffold fastened to an upright post by an iron collar GARY, a city of Lake county, Indiana, U.S.A., at the southern (the garrote), and a knob worked by a screw or lever dislocates end of Lake Michigan, about 25 m. S.E. of Chicago, Il. Pop. his spinal column, or a small blade severs the spinal column at (1910 census) 16,802. Gary is served by the Baltimore & the base of the brain. (Sec CAPITAL PUNISHMENT.) Originally a Ohio, the Lake Shore & Michigan Southern, thc Michigan Central, stout cord or bandage was tied round the neck of the criminal, the Pennsylvania, the Wabash, and (for freight only) the who was seated in a chair fixed to a post. Between the cord and Chicago, Lake Shore & Eastern, and the Indiana Harbor Belt the neck a stick was inserted (hence the name) and twisted till railways, and by several steamship lines plying the Great Lakes, strangulation ensued.

There are about 21 sq. m. within the municipal limits, but the “Garrotting” is the name given in England to a form of city lies chiefly within a tract of about 8000 acres composed at the robbery with violence which became rather common in the time of its settlement mainly of sand dupes and swamps interwinter of 1862-1863. The thief came up behind his victim, sected from east to west by the Grand Calumet and the Little threw a cord over his head, and tightened it nearly to strangula- Calumet rivers, small streams respectively about i and 3 m. S. tion point, while robbing him. An act of 1863, imposing the of the lake shore. In 1906 the United States Steel Corporation penalty of flogging in addition to penal servitude for this offence, bought this tract to establish on it a great industrial community, had the effect of stopping garrotting almost entirely. At any as direct water connexion with the Lake Superior ore region was rate, the practice was checked; and, though the opponents of possible, and it was comparatively accessible to West Virginia any sort of flogging refuse to admit that this was due to the coal and Michigan limestone, with unusual railroad facilities. penalty, that view has always been taken by the English judges The Steel Corporation began the actual building of the town in who had experience of such cases.

June 1906, the first step being the installation of an elaborate GARRUCHA, a seaport of south-eastern Spain, in the province system of sewers, and of mains

and conduits, for the distribution of Almeria; on the Mediterranean Sea and on the right bank of of water, gas and electricity. The water supply is taken from the the river Antas. Pop. (1900) 4461. The harbour of Garrucha, I lake at a point 2 m, offshore by means of a tunnel. These public

utilities the Steel Corporation controls, and it has built about | imaginary substance in which there is no frictional retardation soo dwellings, two hotels, a bank, and its own plant. A small of molecular motion; or, in other words, the time during which patch of land, now within the limits of the city, has been from the any molecule is influenced by other molecules is infinitesimally beginning in the hands of private owners, but the remainder of small compared with the time during which it traverses its mean the lots (except those already sold) are owned by the Steel free path. It serves as a means of research, more particularly Corporation, and are sold under certain restrictions intended to in mathematical investigations, the simple laws thus deduced prevent real estate speculation, to guarantee bona fide improve being subsequently modified by introducing assumptions in ment of the property, and to restrict the sale of intoxicating order to co-ordinate actual experiences. drinks. Between the Grand Calumet river (which has been The gaseous state was well known to the ancients; for in. dredged out into a canal) and the lake lies the plant of the Steel stance, in Greek cosmology,“ air ” (Tvellua) was one of the fundaCorporation, covering about 1200 acres. All the machinery in mental elements. The alchemists used such terms as spiritus, this great plant is driven by electricity from generators whose Natus, halitus, cura, emanatio nubila, &c., words implying a motive power is supplied by the combustion of gases from the wind" or "breath.” The word “ gas was invented by blast furnaces. From the same sources is also supplied the J. B. van Helmont in his Ortus medicinae, posthumously published electricity for lighting the city. The rail mill is operated by in 1648, in the course of his description of the gas now known three-phase induction motors of from 2000 to 6000 horse-power as carbon dioxide. He found that charcoal on burning yielded capacity. The city was chartered in 1906 and was named in a “spirit,” which he named spiritus sylvestris on account of its honour of Elbert Henry Gary (b. 1846), chairman of the board of supposed untamable nature (“Gas sylvestre sive incoërcibile, directors and chairman of the finance committee of the United quod in corpus cogi non potest visibile "); and he invented States Steel Corporation.

the word “gas” in the expression: "... this spirit, hitherto GAS, a general term for one of the three states of aggregation unknown, ... I call by a new name gas” (“hunc spiritum, of matter; also more specifically applied to coal-gas, the gaseous incognitum hactenus, novo nomine gas voco"). The word was product formed in the destructive distillation of coal or other suggested by the Gr. xáos, chaos, for he also writes: “I have carbonaceous matter (see below, section Gas Manufacture; for called this spirit gas, it being scarcely distinguishable from the gas engines see the separate heading Gas ENGINE).

Chaos of the ancients” (“ halitum illum Gas vocavi, non longe The Gaseous State.-Matter is studied under three physical a Chao veterum secretum "). The view that the word was phases-solids, liquids and gases, the latter two being sometimes suggested by the Dutch geesi, spirit, is consequently erroneous. grouped as “fluids.” The study of the physical properties of Until the end of the 18th century the word "air," qualified by Huids in general constitutes the science of hydromechanics, and certain adjectives, was in common use for most of the gases known ibeir applications in the arts is termed hydraulics; the special-a custom due in considerable measure to the important part science dealing with the physical properties of gases is named which common air played in chemical and physical investigations. pneumatics.

The study of gases may be divided into two main branches: The gaseous fluid with which we have chiefly to do is our the physical and the chemical. The former investigates essenatmosphere. Though practically invisible, it appeals in its tially general properties, such as the weight and density, the properties to other of our senses, so that the evidences of its relation between pressure, volume and temperature (piezometric presence are manifold. Thus we feel it in its motion as wind, and thermometric properties), calorimetric properties, diffusion, and observe the dynamical effects of this motion in the quiver viscosity, electrical and thermal conductivity, &c., and generally of the leaf or the motion of a sailing ship. It offers resistance to properties independent of composition. These subjects are the passage of bodies through it, destroying their motion and discussed in the articles DENSITY; THERMOMETRY; CALORI. transforming their energy-as is betrayed to our hearing in the METRY; DIFFUSION; CONDUCTION OF HEAT; and CONDENSAwhiz of the rifle bullet, to our sight in the flash of the meteor. TION OF Gases. The latter has for its province the preparation,

The practically obvious distinction between solids and fluids collection and identification of gases, and the volume relations may be stated in dynamical language thus:--solids can sustain in which they combine; in general it deals with specific proa longitudinal pressure without being supported by a lateral perties. The historical development of the chemistry of gasespressure; fluids cannot. Hence any region of space enclosed pneumatic chemistry—is treated in the article CHEMISTRY; the by a rigid boundary can be easily filled with a fluid, which then technical analysis of gaseous mixtures is treated below under takes the form of the bounding surface at every point of it. But Gas Analysis. Connecting the experimental study of the physical here we distinguish between fluids according as they are gases and chemical properties is the immense theoretical édifice or liquids. The gas will always completely fill the region, however termed the kinetic theory of gases. This subject, which is dissmall the quantity put in. Remove any portion and the re-cussed in the article MOLECULE, has for its purpose (1) the derivamainder will expand so as to fill the whole space again. On the tion of a physical structure of a gas which will agree with the other hand, it requires a definite quantity of liquid to fill the experimental observations of the diverse physical properties, region. Remove any portion and a part of the space will be and (2) a correlation of the physical properties and chemical left unoccupied by liquid. Part of the liquid surface is then composition. Otherwise conditioned than by the form of the wall or bounding Gas Analysis.-The term "gas analysis " is given to that surface of the region; and if the portion of the wall not in con- branch of analytical chemistry which has for its object the tact with the liquid is removed the form and quantity of the quantitative determination of the components of a gaseous liquid are in no way affected. Hence a liquid can be kept in an mixture. The chief applications are found in the analysis of flue open vessel; a gas cannot so be. To quote the differentia of gases (in which much information is gained as to the completeSir Oliver Lodge: “A solid bas volume and shape; a liquid ness and efficiency of combustion), and of coal gas (where it is has volume, but no shape; a gas has neither volume nor shape.” necessary to have a product of a definite composition within

It is necessary to distinguish between a gas and a "vapour.” certain limits). There are, in addition, many other branches The latter possesses the physical property stated above which of chemical technology in which the methods are employed. distinguishes a gas from a fluid, but it differs from a gas by being In general, volumetric methods are used, i.e. a component is readily condensible to a liquid, either by lowering the temperature absorbed by a suitable reagent and the diminution in volume or moderately increasing the pressure. The study of the effects noted, or it is absorbed in water and the amount determined of pressure and temperature on many gases led to the introduction by titration with a standard solution. Exact analysis is difficult of the term “permanent gases” to denote gases which were and tedious, and consequently the laboratory methods are not apparently not liquefiable. The list included hydrogen, nitrogen employed in technology, where time is an important factor and and oxygen; but with improved methods these gases have been moderate accuracy is all that is necessary. In this article an liquefied and even solidified, thus rendering the term meaningless outline of the technical practice will be given. (see LIQUID GASES). The term “perfect gas " is applied to an The apparatus consists of (1) a measuring vessel, and (2) a

series of absorption pipettes. A convenient form of measuring The choice of absorbents and the order in which the gases are vessel is that devised by W Hempel. It consists of two to be estimated is strictly limited. Confining ourselves to cases vertical tubes provided with feet and connected at the bottom where titration methods are not employed, the general order is by flexible rubber tubing. One tube, called the “ measuring as follows: carbon dioxide, olefines, oxygen, carbon monoxide, tube,” is provided with a capillary stopcock at the top and hydrogen, methane and nitrogen (by difference). This scheme is graduated downwards; the other tube, called the “ level tube," particularly applicable to coal-gas Carbon dioxide is absorbed is plain and open. To use the apparatus, the measuring tube by a potash solution containing one part of potash to between is completely filled with water by pouring water into both tubes, two and three of water; the stronger solution absorbs about 40 raising the level tube until water overflows at the stopcock, volumes of the gas. The olefines-ethylene, &c.—are generally which is then turned. The test gas is brought to the stopcock, absorbed by a very strong sulphuric acid prepared by adding by means of a fine tube which has been previously filled with sulphur trioxide to sulphuric acid to form a mixture which water or in which the air has been displaced by running the gas solidifies when slightly cooled. Bromine water is also employed. through. By opening the stopcock and lowering the level tube Oxygen is absorbed by stick phosphorus contained in a tubulated any desired quantity of the gas can be aspirated over. In cases pipette filled with water. The temperature must be above 18°; where a large quantity of gas, i.e. sufficient for several tests, is and the absorption is prevented by ammonia, olefines, alcohol, to be collected, the measuring tube is replaced by a large bottle. and some other substances. An alkaline solution of pyrogallo

The volume of the gas in the measuring tube is determined by is also used; this solution rapidly absorbs oxygen, becoming bringing the water in both tubes to the same level, and reading black in colour, and it is necessary to prepare the solution the graduation on the tube, avoiding parallax and the other errors immediately before use. Carbon monoxide is absorbed by a associated with recording the coincidence of a graduation with a solution of cuprous chloride in hydrochloric acid or, better, in

ammonia. When small in amount, it is better to estimate as carbon dioxide by burning with oxygen and absorbing in potash; when large in amount, the bulk is absorbed in ammoniacal cuprous chloride and the residue burned. Hydrogen may be estimated by absorption by heated palladium contained in a capillary through which the gas is passed, or by exploding (under reduced pressure) with an excess of oxygen, and measuring the diminution in volume, two-thirds of which is the volume of hydrogen. The explosion method is unsatisfactory when the gas is contained over water, and is improved by using mercury. Methane cannot be burnt in this way even when there is much hydrogen present, and several other methods have been proposed, such as mixing with air and aspirating over copper oxide heated to redness, or mixing with oxygen and burning in a

platinum tube heated to redness, the carbon dioxide formed (By permission of Messrs Baird & Tatlock.)

being estimated by absorption in potash. Gases soluble in water, FIG. I.

FIG. 2,

such as ammonia, hydrochloric acid, sulphuretted hydrogen,

sulphur dioxide, &c., are estimated by passing a known volume cf meniscus. The temperature and atmospheric pressure are simul- the gas through water and titrating the solution with a standard taneously noted. If the tests be carried out rapidly, the tem- solution. Many types of absorption vessel are in use, and the perature and pressure may be assumed to be constant, and any standard solutions are generally such that i c.c. of the solution diminution in volume due to the absorption of a constituent may corresponds to I c.c. of the gas under normal conditions. be rcadily expressed as a percentage. If, however, the tem Many forms of composite gas-apparatus are in use. One of the perature and pressure vary, the volumes are reduced to oo and commonest is the Orsat shown in fig. 3. The gas is measured in 760 mm. by means of the formula V = V(P-p)/(1+.003661)760, the graduated cylinder on the right, which is surrounded by a in which V is the observed volume, P the barometric pressure, water jacket and provided with a levelling bottle. At the top it is the vapour tension of water at the temperature i of the experi- connected by a capillary tube bent at right angles to a series of ment. This reduction is facilitated by the use of tables. absorbing vessels, the connexion

Some common forms of absorption pipettes are shown in figs. being effected by stopcocks. These 1 and 2. The simpler form consists of two bulbs connected vessels consist of two vertical at the bottom by a wide tube. The lower bulb is provided with cylinders joined at the bottom a smaller bulb bearing a capillary through which the gas is led to by a short tube. The cylinder the apparatus, the higher bulb has a wider outlet tube. The in direct communication with the arrangement is mounted vertically on a stand. Sometimes the capillary is filled with glass tubes so small bulb on the left is omitted. The form of the pipette varies as to expose a larger surface of the with the nature of the absorbing material. For solutions which absorbing solution to the gas. The remain permanent in air the two-bulbed form suffices; in other other cylinder is open to the air cases a composite pipette (fig. 2) is employed, in which the and serves to hold the liquid absorbent is protected by a second pipette containing water. In ejected from the absorbing cylinthe case of solid reagents, e.g. phosphorus, the absorbing bulb der. Any number of bulbs can be has a tubulure at the bottom. To use a pipette, the absorbing attached to the horizontal capillary; liquid is brought to the outlet of the capillary by tilting or by in the form illustrated there are squeezing a rubber ball fixed to the wide end, and the liquid is four, the last being a hydrogen maintained there by closing with a clip. The capillary is con- pipette in which the palladium is nected with the measuring tube by a fine tube previously filled heated in a horizontal tube by (By permission of Messrs Baird & with water. The clip is removed, the stopcock opened, and the a spirit lamp. At the end of the level tube of the measuring apparatus raised, so that the gas horizontal tube there is a threepasses into the first bulb. There it is allowed to remain, the way cock connecting with the air or an aspirator. To use pipette being shaken from time to time. It is then run back into the apparatus, the measuring tube is completely filled with the measuring tube by lowering the level tube, the stopcock is water by raising the levelling bottle. The absorbing vessels closed, and the volume noted. The operation is repeated until are then about half filled with the absorbents, and, by there is no further absorption.

opening the cocks and aspirating, the liquid is brought so as


FIG. 3.


tive dis



Pet cent.

Marsh gas




in the retort, with the length of time the distillation has been going The effect produced by alteration in the temperature of the retort on, and with an infinity of other factors of a more or less complex upon the composition of both gas and tar is very marked. As the

nature. If bituminous coal is distilled at a low tempera, temperature is raised, the yield of gas from a given weight of coal Destruc

ture, the tar is found to contain considerable quantities of increases; but with the increase of volume there is a marked decrease

light paraffin oils; and there is no doubt that paraffin in the illuminating value of the gas evolved. Lewis T. Wright found, Ullation

hydrocarbons are present in the original coal.' These in a series of experiments, that, when four portions of the same coal of coal.

paraffins, under the influence of heat, split up into simples were distilled at temperatures ranging from a dull red heat to the members of the same series and into olefines; and if we imagine the highest temperature attainable in an iron retort, he obtained the action in its simplest form, we should have the gases, as they were following results as to yield and illuminating power:evolved, consisting of (say) ethane and ethylene. These have now to pass down the heated retort on their way to the ascension pipe,

Illuminating Total

Cubic st. of and the contact with the heated sides of the retort, and the baking Temperature.

Power, Candles from the radiant heat in the retort, set up an infinity of changes,

Gas per ton.


per ton. Ethane, when heated to this degree, splits up into ethylene and hydrogen, whilst ethylene decomposes to methane and acetylene, I. Dull red


20.5 33.950 and the acetylene at once polymerizes to benzene, styrolene, retene, 2. Hotter



34.510 &c. A portion also condenses, and at the same time loses some 3.



36.140 hydrogen, becoming naphthalene; and the compounds so formed 4. Bright orange


15.6 37.460 by interactions amongst themselves build up the remainder of the hydrocarbons present in the coal tar, whilst the organic substances

Composition of the Gas. containing oxygen in the coal break down, and cause the formation of the phenols in the tar. There is very little doubt that the general course of the decom.

Per cent. Per cent. positions follows these lines; but any such simple explanation of the actions taking place is rendered impossible by the fact that, Hydrogen

38.09 43.77 48.02 instead of the breaking-down of the hydrocarbons being completed


30.70 in the coal, and only secondary reactions taking place in the retort, Olefines


4.51 in practice the hydrocarbons to a great extent leave the coal as the Carbon monoxide


13.96 vapours of condensible hydrocarbons, and the breaking down of these Nitrogen



obs. 2.81 to such simple gaseous compounds as ethylene is proceeding in the retort at the same time as the breaking up of the ethylene already formed into acetylene and mechane, and ihe polymerization of the former into higher compounds.. Starting with a solid hydrocarbon The gas analysis of No. 3 was lost, but the illuminating power of definite composition, it would be theoretically possible to decom shows that it was intermediate in composition between Nos. 2 and 4 pose it entirely into carbon, hydrogen, ethylene and methane, From this it will be seen that, with the increase of temperature, the and, by rapidly removing these from the heating zone before any hydrocarbons--the olefines and marsh gas series-gradually break secondary actions took place, to prevent formation of tar. But any such ideal is hopeless in practice, as the coal is not a definite com- hydrogen, the percentage of which steadily increases with the rise of

up, depositing carbon in the crown of the retort, and liberating pound, and it is impossible to subject it to a fixed temperature.

temperature. If the retorts are at a temperature of 1000° C. when the charge of The tar formed is affected to an even greater extent than the gas by coal is put in, the temperature of the distillation will vary from about

alterations in the temperature at which the destructive distillation 800°C. close to the walls, to about 400°C. in the centre of takes place. The lower the temperature, the smaller will be the effect of

the coal; and in the same way, in the space above the coal, tempera

volume of gas produced, and the lighter the specific gravity of the the products which come in contact with the sides of the ture la the

tar, whilst with increase of temperature, the volume of gas rapidly retort are heated to 1000°C., whilst the gas near the coal rises, and so does the specific gravity of the tar. Working with a retort.

is probably heated to only 600°C. Moreover, the gases caking coal Wright obtained the following results:and vapours in the retort are subjected to a period of heating which varies widely with the distance from the mouth of the retort of the

Yicld of Gas coal that is undergoing carbonization. The gas developed by the

Specific Gravity

per ton, coal near the mouth of the retort is quickly washed out into the

of Tar.

Cub. st. ascension pipe by the push of the gas behind, and the period for which it has been exposed to the radiant heat from the walls of the


1.086 retort is practically nil; whilst the gas evolved in the portion of the


1.120 retort farthest from the mouthpiece has only its own rate of evolution


1.140 to drive it forward, and has to traverse the longest run possible in


1.154 the retort, exposed during the whole of that period to radiant heat


1.206 and to contact with the highly heated surface of the retort itself. Hence we find that the tar is formed of two distinct sets of products,

Analysis of the tar showed that the increase of the specific gravity the first due to incomplete decomposition and the second to secondary was due to the increase in the quantity of pitch, which rose from reactions due to the products of the decomposition being kept too 28.89 to 64.08% in the residuals; whilst the ammonia, naphtha long in the zone of heat.

and light oils steadily fell in quantity, the creosote and anthracene of the first class, the light paraffin oils and pitch may be taken as examples; whilst benzene, naphthalene and retort carbon represent begins to show in quantity in the tar as soon as the yield of gas reaches

oils doing the same, but to a smaller extent. Naphthalene also the second. The formation of the second class of bodies is a great

10,000 cub. st. per ton of coal carbonized. loss to the gas manufacturer, as, with the exception of the trace of benzene carried with the gas as vapour, these products are not only characteristics will remain the same. They may be divided into

In spite of these variations, however, the products in their main useless in the gas, but one of them, naphthalene, is a serious trouble, (a) Solids, such as the coke and retort carbon; (6) liquids, consisting because any trace carried forward by the gas condenses with

sudden of the tar and ammoniacal liquor; and (c) gases, consisting of the changes of temperature, and causes obstructions in the service pipes, unpurified coal gas. The proportions in which the products are whilst their

presence in the tar means the loss of a very large pro- approximately obtained from a ton of gas coal have been given as portion of the illuminating constituents of the gas. Moreover, these

follows: secondary products cannot be successfully reduced, by further heating, to simpler hydrocarbons of any high illuminating value, and

10,000 cub. ft. of gas 380 lb = 17.0 per cent. such bodies as naphthalene and anthracene have so great a stability

10 gallons of tar

= 5:1 that, when once formed, they resist any efforts again to decompose

Gas liquor

= 7.9 them by heat, short of the temperature which breaks them up into


= 1568 =70.0 methane, carbon and hydrogen. The ammonia is derived from the nitrogen present in the coal


10000 combining with hydrogen during destructive distillation, the nitrogen becoming distributed amongst all three classes of products. The contains the mineral non-volatile constituents which remain behind

The chief solid residue, coke, is not absolutely pure carbon, as it following table will give an approximate idea of the proportions as ash when the original coal is burnt, and which, to a which go to each:

great extent, existed in the sap that filled the cells of the

Solid Per cent.

plant from which the coal was formed. The retort carbon products. Nitrogen as ammonia

14.50 formed as a dense deposit on the crown of the retort by the action as cyanogen

1-56 of the high temperature on the hydrocarbons is, however, carbon in free in gas and combined in tar

35.26 a very pure form, and, on account of its density, is largely used remaining in coke


for electrical purposes.

Liquor condensed from gas alone, without wash water.

= 115 , = 177


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