Jean de La Fontaine - "The Fables of La Fontaine"

Mrs. Humphry Ward - "Marriage a la mode"

Burton Egbert Stevenson - "The Home Book of Verse, Volume 1"

Joel Barlow - "The Columbiad"

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




ILLUMINATING POWER.--It is very necessary to observe that, as the
combined losses of heat from a flame must be smaller in proportion to the
total heat produced by the flame as the flame itself becomes larger, the
more powerful and intense any single unit of artificial light is, the
more economical does it become, because economy of heat spells economy of
light. Conversely, the more powerful and intense any single unit of light
is, the more is it liable to injure the eyesight, the deeper and, by
contrast, the more impenetrable are the shadows it yields, and the less
pleasant and artistic is its effect in an occupied room. For economical
reasons, therefore, one large central source of light is best in an
apartment, but for physiological and aesthetic reasons a considerable
number of correspondingly smaller units are preferable. Even in the
street the economical advantage of the single unit is outweighed by the
inconvenience of its shadows, and by the superiority of a number of
evenly distributed small sources to one central large source of light
whenever the natural transmission of light rays through the atmosphere is
interfered with by mist or fog. The illuminating power of acetylene is
commonly stated to be "240 candles" (though on the same basis Wolff has
found it to be about 280 candles). This statement means that when
acetylene is consumed in the most advantageous self-luminous burner at
the most advantageous rate, that rate (expressed in cubic feet per hour)
is to 5 in the same ratio as the intensity of the light evolved
(expressed in standard candles) is to the said "illuminating power."
Thus, Wolff found that when acetylene was burnt in the "0000 Bray" fish-
tail burner at the rate of 1.377 cubic feet per hour, a light of 77
candle-power was obtained. Hence, putting x to represent the illuminating
power of the acetylene in standard candles, we have:

1.377 / 5 = 77 / x hence x = 280.

Therefore acetylene is said to have, according to Wolff, an illuminating
power of about 280 candles, or according to other observers, whose
results have been commonly quoted, of 240 candles. The same method of
calculating the nominal illuminating power of a gas is applied within the
United Kingdom in the case of all gases which cannot be advantageously
burnt at the rate of 5 cubic feet per hour in the standard burner
(usually an Argand). The rate of 5 cubic feet per hour is specified in
most Acts of Parliament relating to gas-supply as that at which coal-gas
is to be burnt in testings of its illuminating power; and the
illuminating power of the gas is defined as the intensity, expressed in
standard candles, of the light afforded when the gas is burnt at that
rate. In order to make the values found for the light evolved at more
advantageous rates of consumption by other descriptions of gas--such as
oil-gas or acetylene--comparable with the "illuminating power" of coal-
gas as defined above, the values found are corrected in the ratio of the
actual rate of consumption to 5 cubic feet per hour.

In this way the illuminating power of 240 candles has been commonly
assigned to acetylene, though it would be clearer to those unfamiliar
with the definition of illuminating power in the Acts of Parliament which
regulate the testing of coal-gas, if the same fact were conveyed by
stating that acetylene affords a maximum illuminating power of 48 candles
(_i.e._, 240 / 5) per cubic foot. Actually, by misunderstanding of
the accepted though arbitrary nomenclature of gas photometry, it has not
infrequently been assorted or implied that a cubic foot of acetylene
yields a light of 240 candle-power instead of 48 candle-power. It should,
moreover, be remembered that the ideal illuminating power of a gas is the
highest realisable in any Argand or flat-flame burner, while the said
burner may not be a practicable one for general use in house lighting.
Thus, the burners recommended for general use in lighting by acetylene do
not develop a light of 48 candles per cubic foot of gas consumed, but
considerably less, as will appear from the data given later in this
chapter.

It has been stated that in order to avoid loss of heat from a flame
through the burner, that burner should present only a small mass of
material (_i.e._, be as light in weight as possible), and should be
constructed of a bad heat-conductor. But if a small mass of a material
very deficient in heat-conducting properties comes in contact with a
flame, its temperature rises seriously and may approach that of the base
of the flame itself. In the case of coal-gas this phenomenon is not
objectionable, is even advantageous, and it explains why a burner made of
steatite, which conducts heat badly, in always more economical (of heat
and therefore of light) than an iron one. In the case of acetylene the
same rule should, and undoubtedly does, apply also; but it is
complicated, and its effect sometimes neutralised, by a peculiarity of
the gas itself. It has been shown in Chapters II. and VI. that acetylene
polymerises under the influence of heat, being converted into other
bodies of lower illuminating power, together with some elemental carbon.
If, now, acetylene is fed into a burner which, being composed of some
material like steatite possessed of low heat-conducting and radiating
powers, is very hot, and if the burner comprises a tube of sensible
length, the gas that actually arrives at the orifice may no longer be
pure acetylene, but acetylene diluted with inferior illuminating agents,
and accompanied by a certain proportion of carbon. Neglecting the effect
of this carbon, which will be considered in the following paragraph, it
is manifest that the acetylene issuing from a hot burner--assuming its
temperature to exceed the minimum capable of determining polymerisation--
may emit less light per unit of volume than the acetylene escaping from a
cold burner. Proof of this statement is to be found in some experiments
described by Bullier, who observed that when a small "Manchester" or
fish-tail burner was allowed to become naturally hot, the quantity of gas
needed to give the light of one candle (uncorrected) was 1.32 litres, but
when the burner was kept cool by providing it with a jacket in which
water was constantly circulating, only 1.13 litres of acetylene were
necessary to obtain the same illuminating value, this being an economy of
16 per cent.

EARLY BURNERS.--One of the chief difficulties encountered in the early
days of the acetylene industry was the design of a satisfactory burner
which should possess a life of reasonable length. The first burners tried
were ordinary oil-gas jets, which resemble the fish-tails used with coal-
gas, but made smaller in every part to allow for the higher illuminating
power of the oil-gas or acetylene per unit of volume. Although the flames
they gave were very brilliant, and indeed have never been surpassed, the
light quickly fell off in intensity owing to the distortion of their
orifices caused by the deposition of solid matter at the edges. Various
explanations have been offered to account for the precipitation of solid
matter at the jets. If the acetylene passes directly to the burner from a
generator having carbide in excess without being washed or filtered in
any way, the gas may carry with it particles of lime dust, which will
collect in the pipes mainly at the points where they are constricted; and
as the pipes will be of comparatively large bore until the actual burner
is readied, it will be chiefly at the orifices where the deposition
occurs. This cause, though trivial, is often overlooked. It will be
obviated whenever the plant is intelligently designed. As the phosphoric
anhydride, or pentoxide, which is produced when a gas containing
phosphorus burns, is a solid body, it may be deposited at the burner
jets. This cause may be removed, or at least minimised, by proper
purification of the acetylene, which means the removal of phosphorus
compounds. Should the gas contain hydrogen silicide siliciuretted
hydrogen), solid silica will be produced similarly, and will play its
part in causing obstruction. According to Lewes the main factor in the
blocking of the burners is the presence of liquid polymerised products in
the acetylene, benzene in particular; for he considers that these bodies
will be absorbed by the porous steatite, and will be decomposed under the
influence of heat in that substance, saturating the steatite with carbon
which, by a "catalytic" action presumably, assists in the deposition of
further quantities of carbon in the burner tube until distortion of the
flame results. Some action of this character possibly occurs; but were it
the sole cause of blockage, the trouble would disappear entirely if the
gas were washed with some suitable heavy oil before entering the burners,
or if the latter were constructed of a non-porous material. It is
certainly true that the purer is the acetylene burnt, both as regards
freedom from phosphorus and absence of products of polymerisation, the
longer do the burners last; and it has been claimed that a burner
constructed at its jets of some non-porous substance, e.g., "ruby," does
not choke as quickly as do steatite ones. Nevertheless, stoppages at the
burners cannot be wholly avoided by these refinements. Gaud has shown
that when pure acetylene is burnt at the normal rate in 1-foot Bray jets,
growths of carbon soon appear, but do not obstruct the orifices during
100 hours' use; if, however, the gas-supply is checked till the flame
becomes thick, the growths appear more quickly, and become obstructive
after some 60 hours' burning. On the assumption that acetylene begins to
polymerise at a temperature of 100 deg. C., Gaud calculates that
polymerisation cannot cause blocking of the burners unless the speed of
the passing gas is so far reduced that the burner is only delivering one-
sixth of its proper volume. But during 1902 Javal demonstrated that on
heating in a gas-flame one arm of a twin, non-injector burner which had
been and still was behaving quite satisfactorily with highly purified
acetylene, growths were formed at the jet of that arm almost
instantaneously. There is thus little doubt that the principal cause of
this phenomenon is the partial dissociation of the acetylene (i.e.,
decomposition into its elements) as it passes through the burner itself;
and the extent of such dissociation will depend, not at all upon the
purity of the gas, but upon the temperature of the burner, upon the
readiness with which the heat of the burner is communicated to the gas,
and upon the speed at which the acetylene travels through the burner.

Some experiments reported by R. Granjon and P. Mauricheau-Beaupre in 1906
indicate, however, that phosphine in the gas is the primary cause of the
growths upon non-injector burners. According to these investigators the
combustion of the phosphine causes a deposit at the burner orifices of
phosphoric acid, which is raised by the flame to a temperature higher
than that of the burner. This hot deposit then decomposes some acetylene,
and the carbon deposited therefrom is rendered incombustible by the
phosphoric acid which continues to be produced from the combustion of the
phosphine in the gas. The incombustible deposit of carbon and phosphoric
acid thus produced ultimately chokes the burner.

It will appear in Chapter XI. that some of the first endeavours to avoid
burner troubles were based on the dilution of the acetylene with carbon
dioxide or air before the gas reached the place of combustion; while the
subsequent paragraphs will show that the same result is arrived at more
satisfactorily by diluting the acetylene with air during its actual
passage through the burner. It seems highly probable that the beneficial
effect of the earliest methods was due simply or primarily to the
dilution, the molecules of the acetylene being partially protected from
the heat of the burner by the molecules of a gas which was not injured by
the high temperature, and which attracted to itself part of the heat that
would otherwise have been communicated to the hydrocarbon. The modern
injector burner exhibits the same phenomenon of dilution, and is to the
same extent efficacious in preventing polymerisation; but inasmuch as it
permits a larger proportion of air to be introduced, and as the addition
is made roughly half-way along the burner passage, the cold air is more
effectual in keeping the former part of the tip cool, and in jacketing
the acetylene during its travel through the latter part, the bore of
which is larger than it otherwise would be.

INJECTOR AND TWIN-FLAME BURNERS.--In practice it is neither possible to
cool an acetylene burner systematically, nor is it desirable to construct
it of such a large mass of some good heat conductor that its temperature
always remains below the dissociation point of the gas. The earliest
direct attempts to keep the burner cool were directed to an avoidance of
contact between the flame of the burning acetylene and the body of the
jet, this being effected by causing the current of acetylene to inject a
small proportion of air through lateral apertures in the burner below the
point of ignition. Such air naturally carries along with it some of the
heat which, in spite of all precautions, still reaches the burner; but it
also apparently forms a temporary annular jacket round the stream of gas,
preventing it from catching fire until it has arrived at an appreciable
distance from the jet. Other attempts were made by placing two non-
injector jets in such mutual positions that the two streams of gas met at
an angle, there to spread fan-fashion into a flat flame. This is really
nothing but the old fish-tail coal-gas burner--which yields its flat
flame by identical impingement of two gas streams--modified in detail so
that the bulk of the flame should be at a considerable distance from the
burner instead of resting directly upon it. In the fish-tail the two
orifices are bored in the one piece of steatite, and virtually join at
their external ends; in the acetylene burner, two separate pieces of
steatite, three-quarters of an inch or more apart, carried by completely
separate supports, are each drilled with one hole, and the flame stands
vertically midway between them. The two streams of gas are in one
vertical plane, to which the vertical plane of the flame is at right
angles. Neither of these devices singly gave a solution of the
difficulty; but by combining the two--the injector and the twin-flame
principle--the modern flat-flame acetylene burner has been evolved, and
is now met with in two slightly different forms known as the Billwiller
and the Naphey respectively. The latter apparently ought to be called the
Dolan.

[Illustration: FIG. 8.--TYPICAL ACETYLENE BURNERS.]

The essential feature of the Naphey burner is the tip, which is shown in
longitudinal section at A in Fig. 8. It consists of a mushroom headed
cylinder of steatite, drilled centrally with a gas passage, which at its
point is of a diameter suited to pass half the quantity of acetylene that
the entire burner is intended to consume. The cap is provided with four
radial air passages, only two of which are represented in the drawing;
these unite in the centre of the head, where they enter into the
longitudinal channel, virtually a continuation of the gas-way, leading to
the point of combustion by a tube wide enough to pass the introduced air
as well as the gas. Being under some pressure, the acetylene issuing from
the jet at the end of the cylindrical portion of the tip injects air
through the four air passages, and the mixture is finally burnt at the
top orifice. As pointed out in Chapter VII., the injector jet is so small
in diameter that even if the service-pipes leading to the tip contain an
explosive mixture of acetylene and air, the explosion produced locally if
a light is applied to the burner cannot pass backwards through that jet,
and all danger is obviated. One tip only of this description evidently
produces a long, jet-like flame, or a "rat-tail," in which the latent
illuminating power of the acetylene is not developed economically. In
practice, therefore, two of these tips are employed in unison, one of the
commonest methods of holding them being shown at B. From each tip issues
a stream of acetylene mixed with air, and to some extent also surrounded
by a jacket of air; and at a certain point, which forms the apex of an
isosceles right-angled triangle having its other angles at the orifices
of the tips, the gas streams impinge, yielding a flat flame, at right-
angles, as mentioned before, to the plane of the triangle. If the two
tips are three-quarters of an inch apart, and if the angle of impingement
is exactly 90 deg., the distance of each tip from the base of the flame
proper will be a trifle over half an inch; and although each stream of
gas does take fire and burn somewhat before meeting its neighbour,
comparatively little heat is generated near the body of the steatite.
Nevertheless, sufficient heat is occasionally communicated to the metal
stems of these burners to cause warping, followed by a want of alignment
in the gas streams, and this produces distortion of the flame, and
possibly smoking. Three methods of overcoming this defect have been used:
in one the arms are constructed entirely of steatite, in another they are
made of such soft metal as easily to be bent back again into position
with the fingers or pliers, in the third each arm is in two portions,
screwing the one into the other. The second type is represented by the
original Phos burner, in which the curved arms of B are replaced by a
pair of straight divergent arms of thin, soft tubing, joined to a pair of
convergent wider tubes carrying the two tips. The third type is met with
in the Drake burner, where the divergent arms are wide and have an
internal thread into which screws an external thread cut upon lateral
prolongations of the convergent tubes. Thus both the Phos and the Drake
burner exhibit a pair of exposed elbows between the gas inlet and the two
tips; and these elbows are utilised to carry a screwed wire fastened to
an external milled head by means of which any deposit of carbon in the
burner tubes can be pushed out. The present pattern of the Phos burner is
shown in Fig. 9, in which _A_ is the burner tip, _B_ the wire
or needle, and _C_ the milled head by which the wire is screwed in
and out of the burner tube.

[Illustration: FIG. 9.--IMPROVED PHOS BURNER.]

[Illustration: FIG. 10.--"WONDER" SINGLE AND TWO-FLAME BURNERS.]

[Illustration: FIG. 11.--"SUPREMA" NO. 266651, TWO-FLAME BURNER.]

[Illustration: FIG. 12.--BRAY'S MODIFIED NAPHEY INJECTOR BURNER TIP.]

[Illustration: FIG. 13.--BRAY'S "ELTA" BURNER.]

[Illustration: FIG. 14.--BRAY'S "LUTA" BURNER.]

[Illustration: FIG. 15.--BRAY'S "SANSAIR" BURNER.]

[Illustration: FIG. 16.--ADJUSTABLE "KONA" BURNER.]

In the original Billwiller burner, the injector gas orifice was brought
centrally under a somewhat larger hole drilled in a separate sheet of
platinum, the metal being so carried as to permit entry of air. In order
to avoid the expense of the platinum, the same principle was afterwards
used in the design of an all-steatite head, which is represented at D in
Fig. 8. The two holes there visible are the orifices for the emission of
the mixture of acetylene with indrawn air, the proper acetylene jets
lying concentrically below these in the thicker portions of the heads.
These two types of burner have been modified in a large number of ways,
some of which are shown at C, E, and F; the air entering through saw-
cuts, lateral holes, or an annular channel. Burners resembling F in
outward form are made with a pair of injector jets and corresponding air
orifices on each head, so as to produce a pair of names lying in the same
plane, "end-on" to one another, and projecting at either side
considerably beyond the body of the burner; these have the advantage of
yielding no shadow directly underneath. A burner of this pattern, viz.,
the "Wonder," which is sold in this country by Hannam's, Ltd., is shown
in Fig. 10, alongside the single-flame "Wonder" burner, which is largely
used, especially in the United States. Another two-flame burner, made of
steatite, by J. von Schwarz of Nuremberg, and sold by L. Wiener of
London, is shown in Fig. 11. Burners of the Argand type have also been
manufactured, but have been unsuccessful. There are, of course, endless
modifications of flat-flame burners to be found on the markets, but only
a few need be described. A device, which should prove useful where it may
be convenient to be able to turn one or more burners up or down from the
same common distant spot, has been patented by Forbes. It consists of the
usual twin-injector burner fitted with a small central pinhole jet; and
inside the casing is a receptacle containing a little mercury, the level
of which is moved by the gas pressure by an adaptation of the
displacement principle. When the main is carrying full pressure, both of
the jets proper are alight, and the burner behaves normally, but if the
pressure is reduced to a certain point, the movement of the mercury seals
the tubes leading to the main jets, and opens that of the pilot flame,
which alone remains alight till the pressure is increased again. Bray has
patented a modification of the Naphey injector tip, which is shown in
Fig. 12. It will be observed that the four air inlets are at right-angles
to the gas-way; but the essential feature of the device is the conical
orifice. By this arrangement it is claimed that firing back never occurs,
and that the burner can be turned down and left to give a small flame for
considerable periods of time without fear of the apertures becoming
choked or distorted. As a rule burners of the ordinary type do not well
bear being turned down; they should either be run at full power or
extinguished completely. The "Elta" burner, made by Geo. Bray and Co.,
Ltd., which is shown in Fig. 13, is an injector or atmospheric burner
which may be turned low without any deposition of carbon occurring on the
tips. A burner of simple construction but which cannot be turned low is
the "Luta," made by the same firm and shown in Fig. 14. Of the non-
atmospheric type the "Sansair," also made by Geo. Bray and Co., Ltd., is
extensively used. It is shown in Fig. 15. In order to avoid the warping,
through the heat of the flame, of the arms of burners which sometimes
occurs when they are made of metal, a number of burners are now made with
the arms wholly of steatite. One of the best-known of these, of the
injector type, is the "Kona," made by Falk, Stadelmann and Co., of
London. It is shown in Fig. 16, fitted with a screw device for adjusting
the flow of gas, so that when this adjuster has been set to give a flame
of the proper size, no further adjustment by means of the gas-tap is
necessary. This saves the trouble of manipulating the tap after the gas
is lighted. The same adjusting device may also be had fitted to the Phos
burner (Fig. 9) or to the "Orka" burner (Fig. 17), which is a steatite-
tip injector burner with metal arms made by Falk, Stadelmann and Co.,
Ltd. A burner with steatite arms, made by J. von Schwarz of Nuremberg,
and sold in this country by L. Wiener of London, is shown in Fig. 18.

[Illustration: FIG. 17.--"ORKA" BURNER.]

[Illustration: FIG. 18.--"SUPREMA" NO. 216469 BURNER.]

ILLUMINATING DUTY.--The illuminating value of ordinary self-luminous
acetylene burners in different sizes has been examined by various
photometrists. For burners of the Naphey type Lewes gives the following
table:

___________________________________________________________
| | | | | |
| | | Gas | | Candles |
| Burner. | Pressure, | Consumed, | Light in | per |
| | Inches | Cubic Feet | Candles. | Cubic Foot. |
| | | per Hour. | | |
|_________|___________|____________|__________|_____________|
| | | | | |
| No. 6 | 2.0 | 0.155 | 0.794 | 5.3 |
| " 8 | 2.0 | 0.27 | 3.2 | 11.6 |
| " 15 | 2.0 | 0.40 | 8.0 | 20.0 |
| " 25 | 2.0 | 0.65 | 17.0 | 26.6 |
| " 30 | 2.0 | 0.70 | 23.0 | 32.85 |
| " 42 | 2.0 | 1.00 | 34.0 | 34.0 |
|_________|___________|____________|__________|_____________|

From burners of the Billwiller type Lewes obtained in 1899 the values:

___________________________________________________________
| | | | | |
| | | Gas | | Candles |
| Burner. | Pressure, | Consumed, | Light in | per |
| | Inches | Cubic Feet | Candles. | Cubic Foot. |
| | | per Hour. | | |
|_________|___________|____________|__________|_____________|
| | | | | |
| No. 1 | 2.0 | 0.5 | 7.0 | 11.0 |
| " 2 | 2.0 | 0.75 | 21.0 | 32.0 |
| " 3 | 2.0 | 0.75 | 28.0 | 37.3 |
| " 4 | 3.0 | 1.2 | 48.0 | 40.0 |
| " 5 | 3.5 | 2.0 | 76.0 | 38.0 |
|_________|___________|____________|__________|_____________|

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