Ernest Seton Thompson - "The Biography of a Grizzly"

Maurice Hewlett - "The Forest Lovers"

William James - "Memories and Studies"

Arthur Schnitzler - "Casanova's Homecoming"

Annual Bibliography of Commonwealth Literature 2007
This paper argues that discourses of love in Ghanaian market literature for youth offer a view into complex negotiations of agency and empowerment. Drawing on Deborah Durham's notion of youth as "social `shifters'" and Francis Nyamnjoh's conception of the "interconnectedness" of agency, I take Ghanaian market literature as one specific case of how African literature for youth foregrounds questions of continuity and change as African societies enter into increasingly complex global relations. In this literature for youth, received notions of love, often constructed out of impressions from American pop and hip hop music, carry new notions of agency that compete with existing "domesticated" forms. Authors like Ike Tandoh and Evelyn Tay employ discourses of love to offer youth alternative avenues for empowerment in a context of socio-economic disenfranchizement. In a creative process of "straddling", this writing both reveals and reproduces the contradictions that obtain in youth configurations of agency.

Acetylene, The Principles Of Its Generation And Use

F >> F. H. Leeds and W. J. Atkinson Butterfield >> Acetylene, The Principles Of Its Generation And Use




Numerous experiments have been performed to determine the temperature of the
acetylene flame. According to an exhaustive research by L. Nichols, when the
gas burns in air it attains a maximum temperature of 1900 deg. C. +- 20 deg.,
which is 120 deg. higher than the temperature he found by a similar method
of observation for the coal-gas flame (fish-tail burner). Le Chatelier had
previously assigned to the acetylene flame a temperature between 2100 deg.
and 2400 deg., while Lewes had found for the dark zone 459 deg., for the
luminous zone 1410 deg., and for the tip 1517 deg. C, Fery and Mahler have
also made measurements of the temperatures afforded by acetylene and other
fuels, some of their results being quoted below. Fery employed his optical
method of estimating the temperature, Mahler a process devised by Mallard
and Le Chatelier. Mahler's figures all relate to flames supplied with air
at a temperature of 0 deg. C. and a constant pressure of 760 mm.

Hydrogen . . . . . . . . . . . 1900 1960
Carbon monoxide . . . . . . . . . -- 2100
Methane . . . . . . . . . . . -- _ 1850
Coal-gas (luminous) . . . . . . . . 1712 |
" (atmospheric, with deficient supply of air) . 1812 | 1950
" (atmospheric, with full supply of air) . . 1871 _|
Water-gas . . . . . . . . . . -- 2000
Oxy-coal-gas blowpipe . . . . . . . 2200 --
Oxy-hydrogen blowpipe . . . . . . . 2420 --
Acetylene . . . . . . . . . . 2548 2350
Alcohol . . . . . . . . . . . 1705 1700
Alcohol (in Denayrouze Bunsen) . . . . . 1862 --
Alcohol and petrol in equal parts . . . . 2053 --
Crude petroleum (American) . . . . . . -- 2000
Petroleum spirit " . . . . . . . -- 1920
Petroleum oil " . . . . . . . -- 1660

Catani has published the following determinations of the temperature
yielded by acetylene when burnt with cold and hot air and also with
oxygen:

Acetylene and cold air . . . . . . 2568 deg. C.
" air at 500 deg. C . . . . 2780 deg. C.
" air at 1000 deg. C . . . . 3000 deg. C.
" oxygen . . . . . . 4160 deg. C.

EXPLOSIVE LIMITS.--The range of explosibility of mixtures of acetylene
and air has been determined by various observers. Eitner's figures for
the lower and upper explosive limits, when the mixture, at 62.6 deg. F.,
is in a tube 19 mm. in diameter, and contains 1.9 per cent. of aqueous
vapour, are 3.35 and 52.3 per cent. of acetylene (_cf._ Chapter X.).
In this case the mixture was fired by electric spark. In wider vessels,
the upper explosive limit, when the mixture was fired by a Bunsen flame,
was found to be as high as 75 per cent. of acetylene. Eitner also found
that when 13 of the 21 volumes of oxygen in air are displaced by carbon
dioxide, a mixture of such "carbon dioxide air" with acetylene is
inexplosive in all proportions. Also that when carbon dioxide is added to
a mixture of acetylene and air, an explosion no longer occurs when the
carbon dioxide amounts to 46 volumes or more to every 54 volumes of air,
whatever may be the proportion of acetylene in the mixture. [Footnote:
According to Caro, if acetylene is added to a mixture composed of 55 per
cent. by volume of air and 45 per cent. of carbon dioxide, the whole is
only explosive when the proportion of acetylene lies between 5.0 and 5.8
per cent. Caro has also quoted the effect of various inflammable vapours
upon the explosive limits of acetylene, his results being referred to in
Chapter X.] These figures are valuable in connexion with the prevention
of the formation of explosive mixtures of air and acetylene when new
mains or plant are being brought into operation (_cf._ Chapter
VII.). Eitner has also shown, by direct investigation on mixtures of
other combustible gases and air, that the range of explosibility is
greatly reduced by increase in the proportion of aqueous vapour present.
As the proportion of aqueous vapour in gas standing over water increases
with the temperature the range of explosibility of mixtures of a
combustible gas and air is naturally and automatically reduced when the
temperature rises, provided the mixture is in contact with water. Thus at
17.0 deg. C., mixtures of hydrogen, air, and aqueous vapour containing from
9.3 to 65.0 per cent, of hydrogen are explosive, whereas at 78.1 deg. C.,
provided the mixture is saturated with aqueous vapour, explosion occurs
only when the percentage of hydrogen in the mixture is between 11.2 and
21.9. The range of explosibility of mixtures of acetylene and air is
similarly reduced by the addition of aqueous vapour (though the exact
figures have not been experimentally ascertained); and hence it follows
that when the temperature in an acetylene generator in which water is in
excess, or in a gasholder, rises, the risk of explosion, if air is mixed
with the gas, is automatically reduced with the rise in temperature by
reason of the higher proportion of aqueous vapour which the gas will
retain at the higher temperature. This fact is alluded to in Chapter II.
Acetone vapour also acts similarly in lowering the upper explosive limit
of acetylene (_cf._ Chapter XI.).

It may perhaps be well to indicate briefly the practical significance of
the range of explosibility of a mixture of air and a combustible gas,
such as acetylene. The lower explosive limit is the lowest percentage of
combustible gas in the mixture of it and air at which explosion will
occur in the mixture if a light or spark is applied to it. If the
combustible gas is present in the mixture with air in less than that
percentage explosion is impossible. The upper explosive limit is the
highest percentage of combustible gas in the mixture of it and air at
which explosion will occur in the mixture if a light or spark is applied
to it. If the combustible gas is present in the mixture with air in more
than that percentage explosion is impossible. Mixtures, however, in which
the percentage of combustible gas lies between these two limits will
explode when a light or spark is applied to them; and the comprehensive
term "range of explosibility" is used to cover all lying between the two
explosive limits. If, then, a naked light is applied to a vessel
containing a mixture of a combustible gas and air, in which mixture the
proportion of combustible gas is below the lower limit of explosibility,
the gas will not take fire, but the light will continue to burn, deriving
its necessary oxygen from the excess of air present. On the other hand,
if a light is applied to a vessel containing a mixture of a combustible
gas and air, in which mixture the proportion of combustible gas is above
the upper limit of explosibility, the light will be extinguished, and
within the vessel the gaseous mixture will not burn; but it may burn at
the open mouth of the vessel as it comes in contact with the surrounding
air, until by diffusion, &c., sufficient air has entered the vessel to
form, with the remaining gas, a mixture lying within the explosive
limits, when an explosion will occur. Again, if a gaseous mixture
containing less of its combustible constituent than is necessary to
attain the lower explosive limit escapes from an open-ended pipe and a
light is applied to it, the mixture will not burn as a useful compact
flame (if, indeed, it fires at all); if the mixture contains more of its
combustible constituent than is required to attain the upper explosive
limit, that mixture will burn quietly at the mouth of the pipe and will
be free from any tendency to fire back into the pipe--assuming, of
course, that the gaseous mixture within the pipe is constantly travelling
towards the open end. If, however, a gaseous mixture containing a
proportion of its combustible constituent which lies between the lower
and the upper explosive limit of that constituent escapes from an open-
ended pipe and a light is applied, the mixture will fire and the flame
will pass back into the pipe, there to produce an explosion, unless the
orifice of the said pipe is so small as to prevent the explosive wave
passing (as is the case with a proper acetylene burner), or unless the
pipe itself is so narrow as appreciably to alter the range of
explosibility by lowering the upper explosive limit from its normal
value.

By far the most potent factor in altering the range of explosibility of
any gas when mixed with air is the diameter of the vessel containing or
delivering such mixture. Le Chatelier has investigated this point in the
case of acetylene, and his values are reproduced overleaf; they are
comparable among themselves, although it will be observed that his
absolute results differ somewhat from those obtained by Eitner which are
quoted later:

_Explosive Limits of Acetylene mixed with Air._--(Le Chatelier.)

___________________________________________________________
| | | |
| | Explosive Limits. | |
| Diameter of Tube |_______________________| Range of |
| in Millimetres. | | | Explosibility. |
| | Lower. | Upper. | |
|__________________|___________|___________|________________|
| | | | |
| | Per Cent. | Per Cent. | Per Cent. |
| 40 | 2.9 | 64 | 61.1 |
| 30 | 3.1 | 62 | 58.9 |
| 20 | 3.5 | 55 | 51.5 |
| 6 | 4.0 | 40 | 36.0 |
| 4 | 4.5 | 25 | 20.5 |
| 2 | 5.0 | 15 | 10.0 |
| 0.8 | 7.7 | 10 | 2.3 |
| 0.5 | ... | ... | ... |
|__________________|___________|___________|________________|

Thus it appears that past an orifice or constriction 0.5 mm. in diameter
no explosion of acetylene can proceed, whatever may be the proportions
between the gas and the air in the mixture present.

With every gas the explosive limits and the range of explosibility are
also influenced by various circumstances, such as the manner of ignition,
the pressure, and other minor conditions; but the following figures for
mixtures of air and different combustible gases were obtained by Eitner
under similar conditions, and are therefore strictly comparable one with
another. The conditions were that the mixture was contained in a tube 19
mm. (3/4-inch) wide, was at about 60 deg. to 65 deg. F., was saturated with
aqueous vapour, and was fired by electric spark.

_Table giving the Percentage by volume of Combustible Gas in a Mixture
of that Gas and Air corresponding with the Explosive Limits of such a
Mixture._--(Eitner.)

____________________________________________________________________
| | | | |
| Description of | Lower | Upper | Difference between the |
| Combustible Gas. | Explosive | Explosive | Lower and Upper Limits, |
| | Limit. | Limit. | showing the range |
| | | | covered by the |
| | | | Explosive Mixtures. |
|__________________|___________|___________|_________________________|
| | | | |
| | Per Cent. | Per Cent. | Per Cent. |
| Carbon monoxide | 16.50 | 74.95 | 58.45 |
| Hydrogen | 9.45 | 66.40 | 57.95 |
| Water-gas | | | |
| (uncarburetted) | 12.40 | 66.75 | 54.35 |
| ACETYLENE | 3.35 | 52.30 | 48.95 |
| Coal-gas | 7.90 | 19.10 | 11.20 |
| Ethylene | 4.10 | 14.60 | 10.50 |
| Methane | 6.10 | 12.80 | 6.70 |
| Benzene (vapour) | 2.65 | 6.50 | 3.85 |
| Pentane " | 2.40 | 4.90 | 2.50 |
| Benzoline " | 2.40 | 4.90 | 2.50 |
|__________________|___________|___________|_________________________|

These figures are of great practical significance. They indicate that a
mixture of acetylene and air becomes explosive (_i.e._, will explode
if a light is applied to it) when only 3.35 per cent. of the mixture is
acetylene, while a similar mixture of coal-gas and air is not explosive
until the coal-gas reaches 7.9 per cent. of the mixture. And again, air
may be added to coal-gas, and it does not become explosive until the
coal-gas is reduced to 19.1 per cent. of the mixture, while, on the
contrary, if air is added to acetylene, the mixture becomes explosive as
soon as the acetylene has fallen to 52.3 per cent. Hence the immense
importance of taking precautions to avoid, on the one hand, the escape of
acetylene into the air of a room, and, on the other hand, the admixture
of air with the acetylene in any vessel containing it or any pipe through
which it passes. These precautions are far more essential with acetylene
than with coal-gas. The table shows further how great is the danger of
explosion if benzene, benzoline, or other similar highly volatile
hydrocarbons [Footnote: The nomenclature of the different volatile
spirits is apt to be very confusing. "Benzene" is the proper name for the
most volatile hydrocarbon derived from coal-tar, whose formula is C_6H_6.
Commercially, benzene is often known as "benzol" or "benzole"; but it
would be generally advantageous if those latter words were only used to
mean imperfectly rectified benzene, _i.e._, mixtures of benzene with
toluene, &c., such as are more explicitly understood by the terms "90.s
benzol" and "50.s benzol." "Gasoline," "carburine," "petroleum ether,"
"benzine," "benzoline," "petrol," and "petroleum spirit" all refer to
more or less volatile (the most volatile being mentioned first) and more
or less thoroughly rectified products obtained from petroleum. They are
mixtures of different hydrocarbons, the greater part of them having the
general chemical formula C_nH_2n+2 where n = 5 or more. None of them is a
definite chemical compound as is benzene; when n = 5 only the product is
pentane. These hydrocarbons are known to chemists as "paraffins,"
"naphthenes" being occasionally met with; while a certain proportion of
unsaturated hydrocarbons is also present in most petroleum spirits. The
hydrocarbons of coal-tar are "aromatic hydrocarbons," their generic
formula being C_nH_2^n-6, where n is never less than 6.] are allowed to
vaporise in a room in which a light may be introduced. Less of the vapour
of these hydrocarbons than of acetylene in the air of a room brings the
mixture to the lower explosive limit, and therewith subjects it to the
risk of explosion. This tact militates strongly against the use of such
hydrocarbons within a house, or against the use of air-gas, which, as
explained in Chapter I., is air more or less saturated with the vapour of
volatile hydrocarbons. Conversely, a combustible gas, such as acetylene,
may be safely "carburetted" by these hydrocarbons in a properly
constructed apparatus set up outside the dwelling-house, as explained in
Chapter X., because there would be no air (as in air-gas) in the pipes,
&c., and a relatively large escape of carburetted acetylene would be
required to produce an explosive atmosphere in a room. Moreover, the
odour of the acetylene itself would render the detection of a leak far
easier with carburetted acetylene than with air-gas.

N. Teclu has investigated the explosive limits of mixtures of air with
certain combustible gases somewhat in the same manner as Eitner, viz.: by
firing the mixture in an eudiometer tube by means of an electric spark.
He worked, however, with the mixture dry instead of saturated with
aqueous vapour, which doubtless helps to account for the difference
between his and Eitner's results.

_Table giving the Percentages by volume of Combustible Gas in a
Dehydrated Mixture of that Gas and Air between which the Explosive Limits
of such a Mixture lie._--(Teclu).

____________________________________________________________________
| | | |
| | Lower Explosive Limit. | Upper Explosive Limit. |
| Description of |________________________|________________________|
| Combustible Gas. | | |
| | Per Cent. of Gas. | Per Cent. of Gas. |
|__________________|________________________|________________________|
| | | |
| ACETYLENE | 1.53-1.77 | 57.95-58.65 |
| Hydrogen | 9.73-9.96 | 62.75-63.58 |
| Coal-gas | 4.36-4.82 | 23.35-23.63 |
| Methane | 3.20-3.67 | 7.46- 7.88 |
|__________________|________________________|________________________|

Experiments have been made at Lechbruch in Bavaria to ascertain directly
the smallest proportion of acetylene which renders the air of a room
explosive. Ignition was effected by the flame resulting when a pad of
cotton-wool impregnated with benzoline or potassium chlorate was fired by
an electrically heated wire. The room in which most of the tests were
made was 8 ft. 10 in. long, 6 ft. 7 in. wide, and 6 ft. 8 in. high, and
had two windows. When acetylene was generated in this room in normal
conditions of natural ventilation through the walls, the volume generated
could amount to 3 per cent. of the air-space of the room without
explosion ensuing on ignition of the wool, provided time elapsed for
equable diffusion, which, moreover, was rapidly attained. Further, it was
found that when the whole of the acetylene which 2 kilogrammes or 4.4 lb.
of carbide (the maximum permissible charge in many countries for a
portable lamp for indoor use) will yield was liberated in a room, a
destructive explosion could not ensue on ignition provided the air-space
exceeded 40 cubic metres or 1410 cubic feet, or, if the evolved gas were
uniformly diffused, 24 cubic metres or 850 cubic feet. When the walls of
the room were rendered impervious to air and gas, and acetylene was
liberated, and allowed time for diffusion, in the air of the room, an
explosion was observed with a proportion of only 2-1/2 per cent. of
acetylene in the air.

_Solubility of Acetylene in Various Liquids._

_____________________________________________________________________
| | | | |
| | | Volumes of | |
| | Tem- | Acetylene | |
| Solvent. |perature.|dissolved by| Authority. |
| | | 100 Vols. | |
| | | of Solvent.| |
|___________________________|_________|____________|__________________|
| | | | |
| | Degs. C | | |
| Acetone . . . . | 15 | 2500 | Claude and Hess |
| " . . . . | 50 | 1250 | " |
| Acetic acid; alcohol . | 18 | 600 | Berthelot |
| Benzoline; chloroform . | 18 | 400 | " |
| Paraffin oil . . . | 0 | 103.3 | E. Muller |
| " . . . | 18 | 150 | Berthelot |
| Olive oil . . . . | -- | 48 | Fuchs and Schiff |
| Carbon bisulphide . . | 18 | 100 | Berthelot |
| " tetrachloride . | 0 | 25 | Nieuwland |
| Water (at 4 65 atmospheres| | | |
| pressure) . . | 0 | 160 | Villard |
| " (at 755 mm. pressure)| 12 | 118 | Berthelot |
| " (760 mm. pressure) . | 12 | 106.6 | E. Mueller |
| " " . | 15 | 110 | Lewes |
| " " . | 18 | 100 | Berthelot |
| " " . | -- | 100 | E. Davy (in 1836)|
| " " . | 19.5 | 97.5 | E. Mueller |
| Milk of lime: about 10 | | | |
| grammes of calcium hy- | 5 | 112 | Hammerschmidt |
| droxide per 100 c.c. . | | | and Sandmann |
| " " " | 10 | 95 | " |
| " " " | 20 | 75 | " |
| " " " | 50 | 38 | " |
| " " " | 70 | 20 | " |
| " " " | 90 | 6 | " |
| Solution of common salt,5%| 19 | 67.9 | " |
| (sodium chloride) " | 25 | 47.7 | " |
| " 20%| 19 | 29.6 | " |
| " " | 25 | 12.6 | " |
| "(nearly saturated, | | | |
| 26%) . . | 15 | 20.6 | " |
| "(saturated, sp. gr.| | | |
| 1-21) . . | 0 | 22.0 | E. Mueller |
| " " " | 12 | 21.0 | " |
| " " " | 18 | 20.4 | " |
| Solution of calcium | | | Hammerschmidt |
| chloride (saturated) . | 15 | 6.0 | and Sandmann |
| Berge and Reychler's re- | | | |
| agent . . . . | -- | 95 | Nieuwland |
|___________________________|_________|____________|__________________|

SOLUBILITY.--Acetylene is readily soluble in many liquids. It is
desirable, on the one hand, as indicated in Chapter III., that the liquid
in the seals of gasholders, &c., should be one in which acetylene is
soluble to the smallest degree practically attainable; while, on the
other hand, liquids in which acetylene is soluble in a very high degree
are valuable agents for its storage in the liquid state. Hence it is
important to know the extent of the solubility of acetylene in a number
of liquids. The tabular statement (p. 179) gives the most trustworthy
information in regard to the solubilities under the normal atmospheric
pressure of 760 mm. or thereabouts.

The strength of milk of lime quoted in the above table was obtained by
carefully allowing 50 grammes of carbide to interact with 550 c.c. of
water at 5 deg. C. A higher degree of concentration of the milk of lime
was found by Hammerschmidt and Sandmann to cause a slight decrease in the
amount of acetylene held in solution by it. Hammerschmidt and Sandmann's
figures, however, do not agree well with others obtained by Caro, who has
also determined the solubility of acetylene in lime-water, using first, a
clear saturated lime-water prepared at 20 deg. C. and secondly, a milk of
lime obtained by slaking 10 grammes of quicklime in 100 c.c. of water. As
before, the figures relate to the volumes of acetylene dissolved at
atmospheric pressure by 100 volumes of the stated liquid.

_________________________________________________
| | | |
| Temperature. | Lime-water. | Milk of Lime. |
|_______________|_______________|_________________|
| | | |
| Degs C. | | |
| 0 | 146.2 | 152.6 |
| 5 | 138.5 | -- |
| 15 | 122.8 | 134.8 |
| 50 | 43.9 | 62.6 |
| 90 | 6.2 | 9.2 |
|_______________|_______________|_________________|

Figures showing the solubility of acetylene in plain water at different
temperatures have been published in Landolt-Boernstein's Physico-
Chemical Tables. These are reproduced below. The "Coefficient of
Absorption" is the volume of the gas, measured at 0 deg. C. and a
barometric height of 760 mm. taken up by one volume of water, at the stated
temperature, when the gas pressure on the surface, apart from the vapour
pressure of the water itself, is 760 mm. The "Solubility" is the weight
of acetylene in grammes taken up by 100 grammes of water at the stated
temperature, when the total pressure on the surface, including that of
the vapour pressure of the water, is 760 mm.

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