Anna Garlin Spencer - "The Family and it's Members"

Charles Miner Thompson - "The Calico Cat"

Charles Asbury Stephens - "Left on Labrador"

Wilhelm Ruland - "Legends of the Rhine"

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




It cannot altogether be granted that the value of a process for diluting
acetylene with carbon dioxide has been established, except in so far as
the mere presence of the diluent may somewhat diminish the tendency of
the acetylene to polymerise as it passes through a hot burner (_cf._
Chapter VIII.). Certainly as a fuel-gas the mixture would be less
efficient, and the extra amount of carbon dioxide produced by each flame
is not wholly to be ignored. Moreover, since properly generated and
purified acetylene can be consumed in proper burners without trouble, all
reason for introducing carbon dioxide has disappeared.

MIXTURES OF ACETYLENE AND AIR.--A further proposal for diluting acetylene
was the addition to it of air. Apart from questions of explosibility,
this method has the advantage over that of adding carbon dioxide that the
air, though not inflammable, is, in virtue of its contained oxygen, a
supporter of combustion, and is required in a flame; whereas carbon
dioxide is not only not a supporter of combustion, but is actually a
product thereof, and correspondingly more objectionable. According to
some experiments carried out by Dufour, neat acetylene burnt under
certain conditions evolved between 1.0 and 1.8 candle-power per litre-
hour; a mixture of 1 volume of acetylene with 1 volume of air evolved 1.4
candle-power; a mixture of 1 volume of acetylene with 1.2 volumes of air,
2.25 candle-power; and a mixture of 1 volume of acetylene with 1.3
volumes of air, 2.70 candle-power per litre-hour of acetylene in the
several mixtures. Averaging the figures, and calculating into terms of
acetylene (only) burnt, Dufour found neat acetylene to develop 1.29
candle-power per litre-hour, and acetylene diluted with air to develop
1.51 candle-power. When, however, allowance is made for the cost and
trouble of preparing such mixtures the advantage of the process
disappears; and moreover it is accompanied by too grave risks, unless
conducted on a largo scale and under most highly skilled supervision, to
be fit for general employment.

Fouche, however, has since found the duty, per cubic foot of neat
acetylene consumed in a twin injector burner at the most advantageous
rate of 3.2 inches, to be as follows for mixtures with air in the
proportions stated:

Percentage of air 0 17 27 33.5
Candles per cubic feet 38.4 36.0 32.8 26.0

At lower pressures, the duty of the acetylene when diluted appears to be
relatively somewhat higher. Figures which have been published in regard
to a mixture of 30 volumes of air and 70 volumes of acetylene obtained by
a particular system of producing such a mixture, known as the "Molet-
Boistelle," indicate that the admixture of air causes a slight increase
in the illuminating duty obtained from the acetylene in burners of
various sizes. The type of burner and the pressure employed in these
experiments were not, however, stated. This system has been used at
certain stations on the "Midi" railway in France. Nevertheless even where
the admixture of air to acetylene is legally permissible, the risk of
obtaining a really dangerous product and the nebulous character of the
advantages attainable should preclude its adoption.

In Great Britain the manufacture, importation, storage, and use of
acetylene mixed with air or oxygen, in all proportions and at all
pressures, with or without the presence of other substances, is
prohibited by an Order in Council dated July 1900; to which prohibition
the mixture of acetylene and air that takes place in a burner or
contrivance in which the mixture is intended to be burnt, and the
admixture of air with acetylene that may unavoidably occur in the first
use or recharging of an apparatus (usually a water-to-carbide generator),
properly designed and constructed with a view to the production of pure
acetylene, are the solitary exceptions.

MIXED CARBIDES.--In fact the only processes for diluting acetylene which
possess real utility are that of adding vaporised petroleum spirit or
benzene to the gas, as was described in Chapter X. under the name of
carburetted acetylene, and one other possible method of obtaining a
diluted acetylene directly from the gas-generator, to which a few words
will now be devoted. [Footnote: Mixtures of acetylene with relatively
large proportions of other illuminating gases, such as are referred to on
subsequent pages, are also, from one aspect, forms of diluted acetylene.]
Calcium carbide is only one particular specimen of a large number of
similar metallic compounds, which can be prepared in the electric
furnace, or otherwise. Some of those carbides yield acetylene when
treated with water, some are not attacked, some give liquid products, and
some yield methane, or mixtures of methane and hydrogen. Among the latter
is manganese carbide. If, then, a mixture of manganese carbide and
calcium carbide is put into an ordinary acetylene generator, the gas
evolved will be a mixture of acetylene with methane and hydrogen in
proportions depending upon the composition of the carbide mixture. It is
clear that a suitable mixture of the carbides might be made by preparing
them separately and bulking the whole in the desired proportions; while
since manganese carbide can be won in the electric furnace, it might be
feasible to charge into such a furnace a mixture of lime, coke, and
manganese oxide calculated to yield a simple mixture of the carbides or a
kind of double carbide. Following the lines which have been adopted in
writing the present book, it is not proposed to discuss the possibility
of making mixed carbides; but it may be said in brief that Brame and
Lewes have carried out several experiments in this direction, using
charges of lime and coke containing (_a_) up to 20 per cent. of
manganese oxide, and (_b_) more than 60 per cent. of manganese
oxide. In neither case did they succeed in obtaining a material which
gave a mixture of acetylene and methane when treated with water; in case
(_a_) they found the gas to be practically pure acetylene, so that
the carbide must have been calcium carbide only; in case (_b_) the
gas was mainly methane and hydrogen, so that the carbide must have been
essentially that of manganese alone. Mixed charges containing between 20
and 60 per cent. of manganese oxide remain to be studied; but whether
they would give mixed carbides or no, it would be perfectly simple to mix
ready-made carbides of calcium and manganese together, if any demand for
a diluted acetylene should arise on a sufficiently large scale. It is,
however, somewhat difficult to appreciate the benefits to be obtained
from forms of diluted acetylene other than those to which reference is
made later in this chapter.

There is, nevertheless, one modification of calcium carbide which, in a
small but important sphere, finds a useful _role_. It has been
pointed out that a carbide containing much calcium phosphide is usually
objectionable, because the gas evolved from it requires extra
purification, and because there is the (somewhat unlikely) possibility
that the acetylene obtained from such material before purification may be
spontaneously inflammable. If, now, to the usual furnace charge of lime
and coke a sufficient quantity of calcium phosphate is purposely added,
it is possible to win a mixture of calcium phosphide and carbide, or, as
Bradley, Read, and Jacobs call it, a "carbophosphide of calcium," having
the formula Ca_5C_6P_2, which yields a spontaneously inflammable mixture
of acetylene, gaseous phosphine, and liquid phosphine when treated with
water, and which, therefore, automatically gives a flame when brought
into contact with the liquid. The value of this material will be
described in Chapter XIII.

GAS-ENRICHING.--Other methods of diluting acetylene consist in adding a
comparatively small proportion of it to some other gas, and may be
considered rather as processes for enriching that other gas with
acetylene. Provided the second gas is well chosen, such mixtures exhibit
properties which render them peculiarly valuable for special purposes.
They have, usually, a far lower upper limit of explosibility than that of
neat acetylene, and they admit of safe compression to an extent greatly
exceeding that of acetylene itself, while they do not lose illuminating
power on compression. The second characteristic is most important, and
depends on the phenomena of "partial pressure," which have been referred
to in Chapter VI. When a single gas is stored at atmospheric pressure, it
is insensibly withstanding on all sides and in all directions a pressure
of roughly 15 lb. per square inch, which is the weight of the atmosphere
at sea-level; and when a mixture of two gases, X and Y, in equal volumes
is similarly stored it, regarded as an entity, is also supporting a
pressure of 15 lb. per square inch. But in every 1 volume of that mixture
there is only half a volume of X and Y each; and, ignoring the presence
of its partner, each half-volume is evenly distributed throughout a space
of 1 volume. But since the volume of a gas stands in inverse ratio to the
pressure under which it is stored, the half-volume of X in the 1 volume
of X + Y apparently stands at a pressure of half an atmosphere, for it
has expanded till it fills, from a chemical and physical aspect, the
space of 1 volume: suitable tests proving that it exhibits the properties
which a gas stored at a pressure of half an atmosphere should do.
Therefore, in the mixture under consideration, X and Y are both said to
be at a "partial pressure" of half an atmosphere, which is manifestly 7.5
lb. per square inch. Clearly, when a gas is an entity (either an element
or one single chemical compound) partial and total pressure are
identical. Now, it has been shown that acetylene ceases to be a safe gas
to handle when it is stored at a pressure of 2 atmospheres; but the limit
of safety really occurs when the gas is stored at a _partial_
pressure of 2 atmospheres. Neat acetylene, accordingly, cannot be
compressed above the mark 30 lb. shown on a pressure gauge; but diluted
acetylene (if the diluent is suitable) may be compressed in safety till
the partial pressure of the acetylene itself reaches 2 atmospheres. For
instance, a mixture of equal volumes of X and Y (X being acetylene)
contains X at a partial pressure of half the total pressure, and may
therefore be compressed to (2 / 1/2 =) 4 atmospheres before X reaches the
partial pressure of 2 atmospheres; and therewith the mixture is brought
just to the limit of safety, any effect of Y one way or the other being
neglected. Similarly, a mixture of 1 volume of acetylene with 4 volumes
of Y may be safely compressed to a pressure of (2 / 1/5 =) 10
atmospheres, or, broadly, a mixture in which the percentage of acetylene
is _x_ may be safely compressed to a pressure not exceeding (2 /
_x_/100) atmospheres. This fact permits acetylene after proper
dilution to be compressed in the same fashion as is allowable in the case
of the dissolved and absorbed gas described above.

If the latent illuminating power of acetylene is not to be wasted, the
diluent must not be selected without thought. Acetylene burns with a very
hot flame, the luminosity of which is seriously decreased if the
temperature is lowered. As mentioned in Chapter VIII., this may be done
by allowing too much air to enter the flame; but it may also be effected
to a certain extent by mixing with the acetylene before combustion some
combustible gas or vapour which burns at a lower temperature than
acetylene itself. Manifestly, therefore, the ideal diluent for acetylene
is a substance which possesses as high a flame temperature as acetylene
and a certain degree of intrinsic illuminating power, while the lower the
flame temperature of the diluent and the less its intrinsic illuminating
power, the less efficiently will the acetylene act as an enriching
material. According to Love, Hempel, Wedding, and others, if acetylene is
mixed with coal-gas in amounts up to 8 per cent. or thereabouts, the
illuminating power of the mixture increases about 1 candle for every 1
per cent. of acetylene present: a fact which is usually expressed by
saying that with coal-gas the enrichment value of acetylene is 1 candle
per 1 per cent. Above 8 per cent., the enrichment value of acetylene
rises, Love having found an increase in illuminating power, for each 1
per cent. of acetylene in the mixture, of 1.42 candles with 11.28 per
cent. of acetylene; and of 1.54 candles with 17.62 per cent. of
acetylene. Theoretically, if the illuminating power of acetylene is taken
at 240 candles, its enrichment value should be (240 / 100 =) 2.4 candles
per 1 per cent.; and since, in the case of coal-gas, its actual
enrichment value falls seriously below this figure, it is clear that
coal-gas is not an economical diluent for it. Moreover, coal-gas can be
enriched by other methods much more cheaply than with acetylene. Simple
("blue") water-gas, according to Love, requires more than 10 per cent. of
acetylene to be added to it before a luminous flame is produced; while a
mixture of 20.3 per cent. of acetylene and 79.7 per cent. of water-gas
had an illuminating power of 15.47 candles. Every addition to the
proportion of acetylene when it amounted to 20 per cent. and upwards of
the mixture had a very appreciable effect on the illuminating power of
the latter. Thus with 27.84 per cent. of acetylene, the illuminating
power of the mixture was 40.87 candles; with 38.00 per cent. of acetylene
it was 73.96 candles. Acetylene would not be an economical agent to
employ in order to render water-gas an illuminating gas of about the
quality of coal-gas, but the economy of enrichment of water-gas by
acetylene increases rapidly with the degree of enrichment demanded of it.
Carburetted water-gas which, after compression under 16 atmospheres
pressure, had an illuminating power of about 17.5 candles, was enriched
by additions of acetylene. 4.5 per cent. of acetylene in the mixture gave
an illuminating power of 22.69 candles; 8.4 per cent., 29.54 candles;
11.21 per cent., 35.05 candles; 15.06 per cent., 42.19 candles; and 21.44
per cent., 52.61 candles. It is therefore evident that the effect of
additions of acetylene on the illuminating power of carburetted water-gas
is of the same order as its effect on coal-gas. The enrichment value of
the acetylene increases with its proportion in the mixture; but only when
the proportion becomes quite considerable, and, therefore, the gas of
high illuminating power, does enrichment by acetylene become economical.
Methane (marsh-gas), owing to its comparatively high flame temperature,
and to the fact that it has an intrinsic, if small, illuminating power,
is a better diluent of acetylene than carbon monoxide or hydrogen, in
that it preserves to a greater extent the illuminative value of the
acetylene.

Actually comparisons of the effect of additions of various proportions of
a richly illuminating gas, such as acetylene, on the illuminative value
of a gas which has little or no inherent illuminating power, are largely
vitiated by the want of any systematic method for arriving at the
representative illuminative value of any illuminating gas. A statement
that the illuminating power of a gas is _x_ candles is, strictly
speaking, incomplete, unless it is supplemented by the information that
the gas during testing was burnt (1) in a specified type of burner, and
(2) either at a specified fixed rate of consumption or so as to afford a
light of a certain specified intensity. There is no general agreement,
even in respect of the statutory testing of the illuminating power of
coal-gas supplies, as to the observance of uniform conditions of burning
of the gas under test, and in regard to more highly illuminating gases
there is even greater diversity of conditions. Hence figures such as
those quoted above for the enrichment value of acetylene inevitably show
a certain want of harmony which is in reality due to the imperfection or
incompleteness of the modes of testing employed. Relatively to another,
one gas appears advantageously merely in virtue of the conditions of
assessing illuminating power having been more favourable to it. Therefore
enrichment values, such as those given, must always be regarded as only
approximately trustworthy in instituting comparisons between either
different diluent gases or different enriching agents.

ACETYLENE MIXTURES FOR RAILWAY-CARRIAGE LIGHTING.--In modern practice,
the gases which are most commonly employed for diluents of acetylene,
under the conditions now being considered, are cannel-coal gas (in
France) and oil-gas (elsewhere). Fowler has made a series of observations
on the illuminating value of mixtures of oil-gas and acetylene. 13.41 per
cent. of acetylene improved the illuminating power of oil-gas from 43 to
49 candles. Thirty-nine-candle-power oil-gas had its illuminating power
raised to about 60 candles by an admixture of 20 per cent. of acetylene,
to about 80 candles by 40 per cent. of acetylene, and to about 110
candles by 60 per cent. of acetylene. The difficulty of employing
mixtures fairly rich in acetylene, or pure acetylene, for railway-
carriage lighting, lies in the poor efficiency of the small burners which
yield from such rich gas a light of 15 to 20 candle-power, such as is
suitable for the purpose. For the lighting of railway carriages it is
seldom deemed necessary to have a flame of more than 20 candle-power, and
it is somewhat difficult to obtain such a flame from oil-gas mixtures
rich in acetylene, unless the illuminative value of the gas is wasted to
a considerable extent. According to Bunte, 15 volumes of coal-gas, 8
volumes of German oil-gas, and 1.5 volumes of acetylene all yield an
equal amount of light; from which it follows that 1 volume of acetylene
is equivalent to 5.3 volumes of German oil-gas.

A lengthy series of experiments upon the illuminating power of mixtures
of oil-gas and acetylene in proportions ranging between 10 and 50 per
cent. of the latter, consumed in different burners and at different
pressures, has been carried out by Borck, of the German State Railway
Department. The figures show that per unit of volume such mixtures may
give anything up to 6.75 times the light evolved by pure oil-gas; but
that the latent illuminating power of the acetylene is less
advantageously developed if too much of it is employed. As 20 per cent.
of acetylene is the highest proportion which may be legally added to oil-
gas in this country, Borck's results for that mixture may be studied:

______________________________________________________________________
| | | | | | | |
| | | | | | | Propor- |
| | | | Consump- | | Consump- | tionate |
| Kind of | No. of | Pres- | tion per | Candle- | tion per | Illum- |
| Burner. | Burner | sure. | Hour. | Power. | Candle- | inating |
| | | mm. | Litres. | | Hour. | Power |
| | | | | | Litres. | to Pure |
| | | | | | | Oil-Gas.|
|___________|________|_______|__________|_________|__________|_________|
| | | | | | | |
| Bray | 00 | 42 | 82 | 56.2 | 1.15 | 3.38 |
| " | 000 | 35 | 54 | 28.3 | 1.91 | 4.92 |
| " | 0000 | 35 | 43.3 | 16 | 2.71 | 4.90 |
| Oil-gas | | | | | | |
| burner | 15 | 24 | 21 | 7.25 | 2.89 | 4.53 |
| " " | 30 | 15 | 22 | 10.5 | 2.09 | 3.57 |
| " " | 40 | 16 | 33.5 | 20.2 | 1.65 | 3.01 |
| " " | 60 | 33 | 73 | 45.2 | 1.62 | 3.37 |
| |
| The oil-gas from which this mixture was prepared showing: |
| |
| Bray | 00 | 34 | 73.5 | 16.6 | 4.42 | ... |
| " | 000 | 30 | 48 | 6.89 | 6.96 | ... |
| " | 0000 | 28 | 39 | 3.26 | 11.6 | ... |
| Oil-gas | | | | | | |
| burner | 15 | 21 | 19 | 1.6 | 11.8 | ... |
| " " | 30 | 14 | 21.5 | 2.94 | 7.31 | ... |
| " " | 40 | 15 | 33 | 6.7 | 4.92 | ... |
| " " | 60 | 25 | 60 | 13.4 | 4.40 | ... |
|___________|________|_______|__________|_________|__________|_________|

It will be seen that the original oil-gas, when compressed to 10
atmospheres, gave a light of 1 candle-hour for an average consumption of
7.66 litres in the Bray burners, and for a consumption of 7.11 litres in
the ordinary German oil-gas jets; while the mixture containing 20 per
cent. of acetylene evolved the same amount of light for a consumption of
2.02 litres in Bray burners, or of 2.06 litres in the oil-gas jets.
Again, taking No. 40 as the most popular and useful size of burner, 1
volume of acetylene oil-gas may be said to be equal to 3 volumes of
simple oil-gas, which is the value assigned to the mixture by the German
Government officials, who, at the prices ruling there, hold the mixture
to be twice as expensive as plain oil-gas per unit of volume, which means
that for a given outlay 50 per cent. more light may be obtained from
acetylene oil-gas than from oil-gas alone.

This comparison of cost is not applicable, as it stands, to compressed
oil-gas, with and without enrichment by acetylene, in this country, owing
to the oils from which oil-gas is made being much cheaper and of better
quality here than in Germany, where a heavy duty is imposed on imported
petroleum. Oil-gas as made from Scotch and other good quality gas-oil in
this country, usually has, after compression, an illuminating duty of
about 8 candles per cubic foot, which is about double that of the
compressed German oil-gas as examined by Borck.

Hence the following table, containing a summary of results obtained by H.
Fowler with compressed oil-gas, as used on English railways, must be
accepted rather than the foregoing, in so far as conditions prevailing in
this country are concerned. It likewise refers to a mixture of oil-gas
and acetylene containing 20 per cent. of acetylene.

______________________________________________________________________
| | | | | | |
| | | | | | Ratio of |
| | |Consumption| |Candles per| Illuminating |
| Burner. |Pressure.| per Hour. |Candle| Cubic Foot| Power to that |
| | Inches. |Cubic Feet.|Power.| per Hour. |of Oil-gas [1] |
| | | | | | in the same |
| | | | | | Burner. |
|_____________|_________|___________|______|___________|_______________|
| | | | | | |
| Oil-gas . . | 0.7 | 0.98 | 12.5 | 12.72 | 1.65 |
| Bray 000 . | 0.7 | 1.17 | 14.4 | 12.30 | 1.57 |
| " 0000 . | 0.7 | 0.97 | 10.4 | 10.74 | 1.41 |
| " 00000 | 0.7 | 0.78 | 5.6 | 7.16 | 1.08 |
| " 000000 | 0.7 | 0.55 | 1.9 | 3.52 | 1.14 |
|_____________|_________|___________|______|___________|_______________|

[Footnote 1: Data relating to the relative pecuniary values of acetylene
(carburetted or not), coal-gas, paraffin, and electricity as heating or
illuminating agents, are frequently presented to British readers after
simple recalculation into English equivalents of the figures which obtain
in France and Germany. Such a method of procedure is utterly incorrect,
as it ignores the higher prices of coal, coal-gas, and especially
petroleum products on the Continent of Europe, which arise partly from
geographical, but mainly from political causes.]

The mixture was tried also at higher pressures in the same burners, but
with less favourable results in regard to the duty realised. The oil-gas
was also tried at various pressures, and the most favourable result is
taken for computing the ratio in the last column. It is evident from this
table that 1 volume of this acetylene-oil-gas mixture is equal at the
most to 1.65 volume of the simple oil-gas. Whether the mixture will prove
cheaper under particular conditions must depend on the relative prices of
gas-oil and calcium carbide at the works where the gas is made and
compressed. At the prevailing prices in most parts of Britain, simple
oil-gas is slightly cheaper, but an appreciable rise in the price of gas-
oil would render the mixture with acetylene the cheaper illuminant. The
fact remains, however, that per unit weight or volume of cylinder into
which the gas is compressed, acetylene oil-gas evolves a higher candle-
power, or the same candle-power for a longer period, than simple,
unenriched British oil-gas. Latterly, however, the incandescent mantle
has found application for railway-carriage lighting, and poorer
compressed gases have thereby been rendered available. Thus coal-gas, to
which a small proportion of acetylene has been added, may advantageously
displace the richer oil-gas and acetylene mixtures.

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