When all the fittings, burners excepted,_Acetylene, the Principles of Its Generation and Use A Practical Handbook on the Production, Purification, and Subsequent Treatment of Acetylene for the Development of Light, Heat, and Power

system of pipes must be tested by putting it under a gas (or air)

pressure of 9 or 12 inches of water, and observing on an attached

pressure gauge whether any fall in pressure occurs within fifteen minutes

after the main inlet tap has been shut. The pressure required for this

purpose can be obtained by temporarily weighting the holder, or by the

employment of a pump. If the gauge shows a fall of pressure of one

quarter of an inch or more in these circumstances, the pipes must be

examined until the leak is located. In the presence of a meter, the

installation can conveniently be tested for soundness by throwing into

it, through the meter, a pressure of 12 inches or so of water from the

weighted holder, then leaving the inlet cock open, and observing whether

the index hand on the lowest dial remains perfectly stationary for a

quarter of an hour--movement of the linger again indicating a leak. The

search for leaks must never be made with a light; if the pipes are full

of air this is useless, if full of gas, criminal in its stupidity. While

the whole installation is still under a pressure of 12 inches thrown from

the loaded holder, whether it contains air or gas, first all the likely

spots (joints, &c.), then the entire length of pipe is carefully brushed

over with strong soapy water, which will produce a conspicuous "soap-

bubble" wherever the smallest flaw occurs. The tightness of a system of

pipes put under pressure from a loaded holder cannot be ascertained

safely by observing the height of the bell, and noting if it falls on

standing. Even if there is no issue of gas from the holder, the position

of the bell will alter with every variation in temperature of the stored

gas or surrounding air, and with every movement of the barometer, rising

as the temperature rises and as the barometer falls, and _vice

versâ_, while, unless the water in the seal is saturated with

whatever gas the holder contains, the bell will steadily drop a little an

part of its contents are lost by dissolution in the liquid.

PIPES AND FITTINGS.--As a general rule it is unadvisable to use lead or

composition pipe for permanent acetylene connexions. If exposed, it is

liable to be damaged, and perhaps penetrated by a blow, and if set in the

wall and covered with paper or panel it is liable to be pierced if nails

or tacks should at any time be driven into the wall. There is also an

increased risk in case of fire, owing to its ready fusibility. If used at

all--and it has obvious advantages--lead or composition piping should be

laid on the surface of the walls, &c., and protected from blows, &c., by

a light wooden casing, outwardly resembling the wooden coverings for

electric lighting wires. It has been a common practice, in laying the

underground mains required for supplying the villages which are lighted

by means of acetylene from a central works in different parts of France,

to employ lead pipes. The plan is economical, but in view of the danger

that the main might be flattened by the weight of heavy traction-engines

passing over the roads, or that it might settle into local dips from the

same cause or from the action of subterranean water, in which dips water

would be constantly condensing in cold weather, the use of lead for this

purpose cannot be recommended. Steam-barrel would be preferable to cast

pipe, because permanently sound joints are easier to make in the former,

and because it is not so brittle.

The fittings used for acetylene must have perfectly sound joints and

taps, for the same reasons that the service-pipes must be quite sound.

Common gas-fittings will not do, the joints, taps, ball-sockets, &c., are

not accurately enough ground to prevent leakage. They may in many cases

be improved by regrinding, but often the plug and barrel are so shallow

that it is almost impossible to ensure soundness. It is therefore better

to procure fittings having good taps and joints in the first instance;

the barrels should be long, fairly wide, and there should be no sensible

"play" between plug and barrel when adjusted so that the plug turns

easily when lightly lubricated. Fittings are now being specially made for

acetylene, which is a step in the right direction, because, in addition

to superior taps and joints being essential, smaller bore piping and

smaller through-ways to the taps than are required for coal-gas serve for

acetylene. It is perhaps advisable to add that wherever a rigid bracket

or fitting will answer as well as a jointed one, the latter should on no

account be used; also water-slide pendants should never be employed, as

they are fruitful of accidents, and their apparent advantages are for the

most part illusory. Ball-sockets also should be avoided if possible; if

it is absolutely necessary to have a fitting with a ball-socket, the

latter should have a sleeve made of a short length of sound rubber-tubing

of a size to give a close fit, slipped over so as to join the ball

portion to the socket portion. This sleeve should be inspected once a

quarter at least, and renewed immediately it shows signs of cracking.

Generally speaking all the fittings used should be characterised by

structural simplicity; any ornamental or decorative effects desired may

be secured by proper design without sacrifice of the simplicity which

should always mark the essential and operative parts of the fitting.

Flexible connexions between the fixed service-pipe and a semi-portable or

temporary burner may at times be required. If the connexion is for

permanent use, it must not be of rubber, but of the metallic flexible

tubing which is now commonly employed for such connexions in the case of

coal-gas. There should be a tap between the service-pipe and the flexible

connexion, and this tap should be turned off whenever the burner is out

of use, so that the connexion is not at other times under the pressure

which is maintained in the service-pipes. Unless the connexion is very

short--say 2 feet or less--there should also be a tap at the burner.

These flexible connexions, though serviceable in the case of table-lamps,

&c., of which the position may have to be altered, are undesirable, as

they increase the risk attendant on gas (whether acetylene or other

illuminating gas) lighting, and should, if possible, be avoided. Flexible

connexions may also be required for temporary use, such as for conveying

acetylene to an optical lantern, and if only occasionally called for, the

cost of the metallic flexible tubing will usually preclude its use. It

will generally be found, however, that the whole connexion in such a case

can be of composition or lead gas-piping, connected up at its two ends by

a few inches of flexible rubber tubing. It should be carried along the

walls or over the heads of people who may use the room, rather than

across the floor, or at a low level, and the acetylene should be turned

on to it only when actually required for use, and turned off at the fixed

service-pipe as soon as no longer required. Quite narrow composition

tubing, say 1/4-inch, will carry all the acetylene required for two or

three burners. The cost of a composition temporary connexion will usually

be less than one of even common rubber tubing, and it will be safer. The

composition tubing must not, of course, be sharply bent, but carried by

easy curves to the desired point, and it should be carefully rolled in a

roll of not less than 18 inches diameter when removed. If these

precautions are observed it may be used very many times.

Acetylene service-pipes should, wherever possible, be laid with a fall,

which may be very slight, towards a small closed vessel adjoining the

gasholder or purifier, in order that any water deposited from the gas

owing to condensation of aqueous vapour may run out of the pipe into that

apparatus. Where it is impossible to secure an uninterrupted fall in that

direction, there should be inserted in the service-pipe, at the lowest

point of each dip it makes, a short length of pipe turned downwards and

terminating in a plug or sound tap. Water condensing in this section of

the service-pipe will then run down and collect in this drainage-pipe,

from which it can be withdrawn at intervals by opening the plug or tap

for a moment. The condensed water is thus removed from the service-pipe,

and does not obstruct its through-way. Similar drainage devices may be

used at the lowest points of all dips in mains, though there are special

seal-pots which take the place of the cock or plug used to seal the end

of the drainage-pipe. Such seal-pots or "syphons" are commonly used on

ordinary gas-distributing systems, and might be applied in the case of

large acetylene installations, as they offer facilities for removing the

condensed water from time to time in a convenient and expeditious manner.

EXPULSION OF AIR FROM MAINS.--After a service-pipe system has been proved

to be sound, it is necessary to expel the air from it before acetylene

can be admitted to it with a view to consumption. Unless the system is a

very large one, the expulsion of air is most conveniently effected by

forcing from the gasholder preliminary batches of acetylene through the

pipes, while lights are kept away from the vicinity. This precaution is

necessary because, while the acetylene is displacing the air in the

pipes, they will for some time contain a mixture of air and acetylene in

proportions which fall within the explosive limits of such a mixture. If

the escaping acetylene caught fire from any adjacent light under these

conditions, a most disastrous explosion would ensue and extend through

all the ramifications of the system of pipes. Therefore the first step

when a new system of pipes has to be cleared of air is to see that there

are no lights in or about the house--either fires, lamps, cigars or

pipes, candles or other flames. Obviously this work must be done in the

daytime and finished before nightfall. Burners are removed from two or

more brackets at the farthest points in the system from the gasholder,

and flexible connexions are temporarily attached to them, and led through

a window or door into the open air well clear of the house. One of the

brackets selected should as a rule be the lowest point supplied in the

house. The gasholder having been previously filled with acetylene, the

tap or taps on the pipe leading to the house are turned on, and the

acetylene is passed under slight pressure into the system of pipes, and

escapes through the aforesaid brackets, of which the taps have been

turned on, into the open. The taps of all other brackets are kept closed.

The gas should be allowed to flow thus through the pipes until about five

times the maximum quantity which all the burners on the system would

consume in an hour has escaped from the open brackets. The taps on these

brackets are then closed, and the burners replaced. Flexible tubing is

then connected in place of the burners to all the other brackets in the

house, and acetylene is similarly allowed to escape into the open air

from each for a quarter of an hour. All taps are then closed, and the

burners replaced; all windows in the house are left open wide for half an

hour to allow of the dissipation of any acetylene which may have

accumulated in any part of it, and then, while full pressure from the

gasholder is maintained, a tap is turned on and the gas lighted. If it

burns with a good, fully luminous flame it may be concluded that the

system of pipes is virtually free from air, and the installation may be

used forthwith as required. If, however, the flame is very feebly

luminous, or if the escaping gas does not light, lights must be

extinguished, and the pipes again blown through with acetylene into the

open air. The burner must invariably be in position when a light is

applied, because, in the event of the pipes still containing an explosive

mixture, ignition would not be communicated through the small orifices of

the burner to the mixture in the pipes, and the application of the light

would not entail any danger of an explosion.

Gasfitters familiar with coal-gas should remember, when putting a system

of acetylene pipes into use for the first time, that the range over which

mixtures of acetylene and air are explosive is wider than that over which

mixtures of coal-gas and air are explosive, and that greater care is

therefore necessary in getting the pipes and rooms free from a dangerous

mixture.

The mains for very large installations of acetylene--_e.g._, for

lighting a small town--may advisedly be freed from air by some other plan

than simple expulsion of the air by acetylene, both from the point of

view of economy and of safety. If the chimney gases from a neighbouring

furnace are found on examination to contain not more than about 8 per

cent of oxygen, they may be drawn into the gasholder and forced through

the pipes before acetylene is admitted to them. The high proportion of

carbon dioxide and the low proportion of oxygen in chimney gases makes a

mixture of acetylene and chimney gases non-explosive in any proportions,

and hence if the air is first wholly or to a large extent expelled from a

pipe, main, or apparatus, by means of chimney gases, acetylene may be

admitted, and a much shorter time allowed for the expulsion by it of the

contents of the pipe, before a light is applied at the burners, &c. This

plan, however, will usually only be adopted in the case of very large

pipes, &c.; but on a smaller scale the air may be swept out of a

distributing system by bringing it into connexion with a cylinder of

compressed or liquefied carbon dioxide, the pressure in which will drive

the gas to any spot where an outlet is provided. As these cylinders of

"carbonic acid" are in common employment for preparing aerated waters and

for "lifting" beer, &c., they are easy to hire and use.

TABLE (B).

Giving the Sizes of Pipe which should be used in practice for Acetylene

when the fall of pressure in the Pipe is not to exceed 0.1 inch. (Based

on Morel's formula.)

_________________________________________________________

| | |

| Cubic Feet of | Diameters of Pipe to be used up to |

| Acetylene | the lengths indicated. |

| which the Pipe |_______________________________________|

| pass in | 1/4 | 3/8 | 1/2 | 3/4 | 1 |

|________________|_______|_______|_______|_______|_______|

| | | | | | |

| 1 | 520 | 3960 | 16700 | ... | ... |

| 2 | 130 | 990 | 4170 | ... | ... |

| 3 | 58 | 440 | 1850 | ... | ... |

| 4 | 32 | 240 | 1040 | ... | ... |

| 5 | 21 | 150 | 660 | 5070 | ... |

| 6 | 14 | 110 | 460 | 3520 | ... |

| 7 | 10 | 80 | 340 | 2590 | ... |

| 8 | ... | 62 | 260 | 1980 | ... |

| 9 | ... | 49 | 200 | 1560 | ... |

| 10 | ... | 39 | 160 | 1270 | 5340 |

| 15 | ... | 17 | 74 | 560 | 2370 |

| 20 | ... | 10 | 41 | 310 | 1330 |

| 25 | ... | ... | 26 | 200 | 850 |

| 30 | ... | ... | 18 | 140 | 590 |

| 35 | ... | ... | 13 | 100 | 430 |

| 40 | ... | ... | 10 | 79 | 330 |

| 45 | ... | ... | ... | 62 | 260 |

| 50 | ... | ... | ... | 50 | 210 |

|________________|_______|_______|_______|_______|_______|

TABLE (A).

Showing the Quantities [Q] (in cubic feet) of Acetylene which will pass

in One Hour through Pipes of various diameters (in inches) under

different Falls of Pressure. (Based on Morel's formula.)

____________________________________________________________________

| | | | | | | | | | | | |

| of Pipe | 1/4| 3/8| 1/2| 3/4 | 1 | 1 | 1 | 1 | 2 | 2 | 3 |

| [_d_] = | | | | | | 1/4 | 1/2| 3/4| | 1/2| |

|__________|____|____|____|_____|_____|_____|____|____|____|____|____|

| | |

| Length | |

| of Pipe | |

| [_l_] = | Fall of Pressure in the Pipe [_h_] = 0.10 inch. |

| Feet | |

|__________|_________________________________________________________|

| | | | | | | | | | | | |

| 10 | 7.2|19.9|40.8|112 |230 |405 | 635| 935|1305|2285|3600|

| 25 | 4.5|12.6|25.8| 71.2|146 |255 | 400| 590| 825|1445|2280|

| 50 | 3.2| 8.9|18.3| 50.3|103 |180 | 285| 420| 585|1020|1610|

| 100 | 2.3| 6.3|12.9| 35.6| 73.1|127 | 200| 295| 410| 720|1140|

| 200 | 1.6| 4.4| 9.1| 25.2| 51.7| 90.3| 142| 210| 290| 510| 805|

| 300 | 1.3| 3.6| 7.4| 20.5| 42.2| 73.7| 116| 171| 240| 415| 655|

| 400 | 1.1| 3.1| 6.4| 17.8| 36.5| 63.8| 100| 148| 205| 360| 570|

| 500 | 1.0| 2.8| 5.8| 15.9| 32.7| 57.1| 90| 132| 185| 320| 510|

|__________|____|____|____|_____|_____|_____|____|____|____|____|____|

| | |

| Length | |

| of Pipe | |

| [_l_] = | Fall of Pressure in the Pipe [_h_] = 0.25 inch. |

| Feet | |

|__________|_________________________________________________________|

| | | | | | | | | | | | |

| 25 | 7.2|19.9|40.8|112 |230 |405 | 635| 935|1305|2285|3600|

| 50 | 5.1|14.1|28.9| 79.6|163 |285 | 450| 660| 925|1615|2550|

| 100 | 3.6| 9.9|20.4| 56.3|115 |200 | 320| 470| 655|1140|1800|

| 250 | 2.3| 6.3|12.9| 35.6| 73.1|127 | 200| 295| 410| 720|1140|

| 500 | 1.6| 4.4| 9.1| 25.2| 51.7| 90.3| 142| 210| 290| 510| 805|

| 1000 | 1.1| 3.1| 6.4| 17.8| 36.5| 63.8| 100| 148| 205| 360| 570|

|__________|____|____|____|_____|_____|_____|____|____|____|____|____|

| | |

| Length | |

| of Pipe | |

| [_l_] = | Fall of Pressure in the Pipe [_h_] = 0.50 inch. |

| Feet | |

|__________|_________________________________________________________|

| | | | | | | | | | | | |

| 25 |10.2|28.1|57.8|159 |325 |570 | 900|1325|1850|3230|5095|

| 50 | 7.2|19.9|40.8|112 |230 |405 | 635| 935|1305|2285|3600|

| 100 | 5.1|14.1|28.9| 79.6|163 |285 | 450| 660| 925|1615|2550|

| 250 | 3.2| 8.9|18.3| 50.3|103 |180 | 285| 420| 585|1020|1610|

| 500 | 2.3| 6.3|12.9| 35.6| 73.1|127 | 200| 295| 410| 720|1140|

| 1000 | 1.6| 4.4| 9.1| 25.2| 51.7| 90.3| 142| 210| 290| 510| 805|

|__________|____|____|____|_____|_____|_____|____|____|____|____|____|

| | |

| Length | |

| of Pipe | |

| [_l_] = | Fall of Pressure in the Pipe [_h_] = 0.75 inch. |

| Feet | |

|__________|_________________________________________________________|

| | | | | | | | | | | | |

| 50 | 8.8|24.4|50.0|138 |280 |495 | 780|1145|1160|2800|4410|

| 100 | 6.2|17.2|35.4| 97.5|200 |350 | 550| 810|1130|1980|3120|

| 250 | 3.9|10.9|22.4| 61.7|126 |220 | 350| 510| 715|1250|1975|

| 500 | 2.8| 7.7|15.8| 43.6| 89.5|156 | 245| 360| 505| 885|1395|

| 1000 | 2.0| 5.4|11.2| 30.8| 63.3|110 | 174| 255| 360| 625| 985|

| 2000 | 1.4| 3.8| 7.9| 21.8| 44.8| 78.2| 123| 181| 250| 440| 695|

|__________|____|____|____|_____|_____|_____|____|____|____|____|____|

| | |

| Length | |

| of Pipe | |

| [_l_] = | Fall of Pressure in the Pipe [_h_] = 1.0 inch. |

| Feet | |

|__________|_________________________________________________________|

| | | | | | | | | | | | |

| 100 | 7.2|19.9|40.8|112 |230 |405 | 635| 935|1305|2285|3600|

| 250 | 4.5|12.6|25.8| 71.2|146 |255 | 400| 590| 825|1445|2280|

| 500 | 3.2| 8.9|18.3| 50.3|103 |180 | 285| 420| 585|1020|1610|

| 1000 | 2.3| 6.3|12.9| 35.6| 73.1|127 | 200| 295| 410| 720|1140|

| 2000 | 1.6| 4.4| 9.1| 25.2| 51.7| 90.3| 142| 210| 290| 510| 805|

| 3000 | 1.3| 3.6| 7.4| 20.5| 42.2| 73.7| 116| 171| 240| 415| 655|

|__________|_________________________________________________________|

| | |

| Length | |

| of Pipe | |

| [_l_] = | Fall of Pressure in the Pipe [_h_] = 1.5 inch. |

| Feet | |

|__________|_________________________________________________________|

| | | | | | | | | | | | |

| 250 | 5.6|15.4|31.6| 87.2|179 |310 | 495| 725|1010|1770|2790|

| 500 | 3.9|10.9|22.4| 61.7|126 |220 | 350| 510| 715|1250|1975|

| 1000 | 2.8| 7.7|15.8| 43.6| 89.5|156 | 245| 360| 505| 885|1395|

| 2000 | 2.0| 5.4|11.2| 30.8| 63.3|110 | 174| 255| 360| 625| 985|

| 3000 | 1.6| 4.4| 9.1| 25.2| 51.7| 90.3| 142| 210| 290| 510| 805|

| 4000 | 1.4| 3.8| 7.9| 21.8| 44.8| 78.2| 123| 181| 250| 440| 695|

|__________|____|____|____|_____|_____|_____|____|____|____|____|____|

| | |

| Length | |

| of Pipe | |

| [_l_] = | Fall of Pressure in the Pipe [_h_] = 2.0 inches. |

| Feet | |

|__________|_________________________________________________________|

| | | | | | | | | | | | |

| 500 | 4.5|12.6|25.8| 71.2|146 |255 | 400| 590| 825|1445|2280|

| 1000 | 3.2| 8.9|18.3| 50.3|103 |180 | 285| 420| 585|1020|1610|

| 2000 | 2.3| 6.3|12.9| 35.6| 73.1|127 | 200| 295| 410| 720|1140|

| 3000 | 1.8| 5.1|10.5| 29.1| 59.7|104 | 164| 240| 335| 590| 930|

| 4000 | 1.6| 4.4| 9.1| 25.2| 51.7| 90.3| 142| 210| 290| 510| 805|

| 5000 | 1.4| 4.0| 8.1| 22.5| 46.2| 80.8| 127| 187| 260| 455| 720|

| 6000 | 1.3| 3.6| 7.4| 20.5| 42.2| 73.7| 116| 171| 240| 415| 655|

|__________|____|____|____|_____|_____|_____|____|____|____|____|____|

NOTE.--In order not to impart to the above table the appearance of the

quantities having been calculated to a degree of accuracy which has no

practical significance, quantities of less than 5 cubic feet have been

ignored when the total quantity exceeds 200 cubic feet, and fractions of

a cubic foot have been included only when the total quantity is less than

100 cubic feet.

TABLE (C).

Giving the Sizes of Pipe which should be used in practice for Acetylene

when the fall of pressure in the Pipe is not to exceed 0.25 inch. (Based

on Morel's formula.)

____________________________________________________________________

| | |

| Cubic feet | |

| of | |

| Acetylene | Diameters of Pipe to be used up to the lengths stated.|

| which the | |

| Pipe is | |

| required |_______________________________________________________|

| in One | 1/4 | 1/2 | 3/4 | 1 | 1-1/4| 1-1/2| 1-3/4| 2 |

|____________|______|______|______|______|______|______|______|______|

| | | | | | | | | |

| 2-1/2 | 1580 | 6680 | 50750| ... | ... | ... | ... | ... |

| 5 | 390 | 1670 | 12690| 53160| ... | ... | ... | ... |

| 7-1/2 | 175 | 710 | 5610| 23760| ... | ... | ... | ... |

| 10 | 99 | 410 | 3170| 13360| 40790| ... | ... | ... |

| 15 | 41 | 185 | 1410| 5940| 18130| 45110| ... | ... |

| 20 | 24 | 105 | 790| 3350| 10190| 25370| 54840| ... |

| 25 | 26 | 67 | 500| 2130| 6520| 16240| 35100| ... |

| 30 | 11 | 46 | 350| 1480| 4530| 11270| 24370| 47520|

| 35 | ... | 34 | 260| 1090| 3330| 8280| 17900| 34910|

| 40 | ... | 26 | 195| 830| 2550| 6340| 13710| 26730|

| 45 | ... | 20 | 155| 660| 2010| 5010| 10830| 21120|

| 50 | ... | 16 | 125| 530| 1630| 4060| 8770| 17110|

| 60 | ... | 11 | 88| 370| 1130| 2880| 6090| 11880|

| 70 | ... | ... | 61| 270| 830| 2070| 4470| 8730|

| 80 | ... | ... | 49| 210| 630| 1580| 3420| 6680|

| 90 | ... | ... | 39| 165| 500| 1250| 2700| 5280|

| 100 | ... | ... | 31| 130| 400| 1010| 2190| 4270|

| 150 | ... | ... | 14| 59| 180| 450| 970| 1900|

| 200 | ... | ... | ... | 33| 100| 250| 540| 1070|

| 250 | ... | ... | ... | 21| 65| 160| 350| 680|

| 500 | ... | ... | ... | ... | 16| 40| 87| 170|

| 1000 | ... | ... | ... | ... | ... | 10| 22| 42|

|____________|______|______|______|______|______|______|______|______|

TABLE (D).

Giving the Sizes of Pipe which should be used in practice for Acetylene

Mains when the fall of pressure in the Main is not to exceed 0.5 inch,

(Based on Morel's formula.)

____________________________________________________________________

| | |

| Cubic feet | |

| of | |

| Acetylene | Diameters of Pipe to be used up to the lengths stated.|

| which the | |

| Main is | |

| required |_______________________________________________________|

| in One | 3/4 | 1 | 1-1/4| 1-1/2| 1-3/4| 2 | 2-1/2| 3 |

|____________|______|______|______|______|______|______|______|______|

| | | | | | | | | |

| 10 | 5.05 | ... | ... | ... | ... | ... | ... | ... |

| 25 | 0.80 | 2.45 | 6.15 | ... | ... | ... | ... | ... |

| 50 | 0.20 | 0.60 | 1.50 | 3.30 | 6.45 | ... | ... | ... |

| 100 | 0.05 | 0.15 | 0.35 | 0.80 | 1.60 | 4.95 |12.30 | ... |

| 200 | ... | 0.04 | 0.09 | 0.20 | 0.40 | 1.20 | 3.05 |12.95 |

| 300 | ... | ... | 0.04 | 0.09 | 0.18 | 0.55 | 1.35 | 5.75 |

| 400 | ... | ... | ... | 0.05 | 0.10 | 0.30 | 0.75 | 3.25 |

| 500 | ... | .. | ... | 0.03 | 0.06 | 0.20 | 0.50 | 2.05 |

| 750 | ... | ... | ... | ... | 0.03 | 0.08 | 0.20 | 0.80 |

| 1100 | ... | ... | ... | ... | ... | 0.05 | 0.12 | 0.50 |

| 1500 | ... | ... | ... | ... | ... | 0.02 | 0.05 | 0.23 |

| 2000 | ... | ... | ... | ... | ... | ... | 0.03 | 0.13 |

| 2500 | ... | ... | ... | ... | ... | ... | 0.02 | 0.08 |

| 5000 | ... | ... | ... | ... | ... | ... | ... | 0.03 |

|____________|______|______|______|______|______|______|______|______|

TABLE (E).

Giving the Sizes of Pipe which should be used in practice for Acetylene

Mains when the fall of pressure in the Main is not to exceed 1.0 inch.

(Based on Morel's formula.)

__________________________________________________________________

| | |

| Cubic feet | |

| of | |

| Acetylene |Diameters of Pipe to be used up to the lengths stated|

| which the | |

| Main is | |

| required |_____________________________________________________|

| in One | 3/4 | 1 |1-1/4|1-1/2|1-3/4| 2 |2-1/2| 3 | 4 |

|____________|_____|_____|_____|_____|_____|_____|_____|_____|_____|

| | | | | | | | | | |

| 10 | 2.40|10.13|30.90| ... | ... | ... | ... | ... | ... |

| 25 | 0.38| 1.62| 4.94|12.30| ... | ... | ... | ... | ... |

| 50 | 0.09| 0.40| 1.23| 3.07| 6.65|12.96| ... | ... | ... |

| 100 | 0.02| 0.10| 0.30| 0.77| 1.66| 3.24| 9.88| ... | ... |

| 200 | ... | 0.02| 0.07| 0.19| 0.41| 0.81| 2.47| 6.15| ... |

| 300 | ... | 0.01| 0.03| 0.08| 0.18| 0.36| 1.09| 2.73|11.52|

| 400 | ... | ... | 0.0 | 0.05| 0.10| 0.20| 0.61| 1.53| 6.48|

| 500 | ... | ... | 0.0 | 0.03| 0.06| 0.13| 0.39| 0.98| 4.14|

| 750 | ... | ... | ... | 0.01| 0.03| 0.05| 0.17| 0.43| 1.84|

| 1000 | ... | ... | ... | ... | 0.01| 0.03| 0.10| 0.24| 1.03|

| 1500 | ... | ... | ... | ... | ... | 0.01| 0.01| 0.11| 0.46|

| 2000 | ... | ... | ... | ... | ... | ... | 0.02| 0.06| 0.26|

| 2500 | ... | ... | ... | ... | ... | ... | 0.01| 0.04| 0.16|

| 5000 | ... | ... | ... | ... | ... | ... | ... | 0.01| 0.04|

|____________|_____|_____|_____|_____|_____|_____|_____|_____|_____|

CHAPTER VIII

COMBUSTION OF ACETYLENE IN LUMINOUS BURNERS--THEIR DISPOSITION

NATURE OF LUMINOUS FLAMES.--When referring to methods of obtaining

artificial light by means of processes involving combustion or oxidation,

the term "incandescence" is usually limited to those forms of burner in

which some extraneous substance, such as a "mantle," is raised to a

brilliant white heat. Though convenient, the phrase is a mere convention,

for all artificial illuminants, even including the electric light, which

exhibit a useful degree of intensity depend on the same principle of

incandescence. Adopting the convention, however, an incandescent burner

is one in which the fuel burns with a non-luminous or atmospheric flame,

the light being produced by causing that flame to play upon some

extraneous refractory body having the property of emitting much light

when it is raised to a sufficiently high temperature; while a luminous

burner is one in which the fuel is allowed to combine with atmospheric

oxygen in such a way that one or more of the constituents in the gas

evolves light as it suffers combustion. From the strictly chemical point

of view the light-giving substance in the incandescent flame lasts

indefinitely, for it experiences no change except in temperature; whereas

the light-giving substance in a luminous flame lasts but for an instant,

for it only evolves light during the act of its combination with the

oxygen of the atmosphere. Any fluid combustible which burns with a flame

can be made to give light on the incandescent system, for all such

materials either burn naturally, or can be made to burn with a non-

luminous flame, which can be employed to raise the temperature of some

mantle; but only those fuels can be burnt on the self-luminous system

which contain some ingredient that is liberated in the elemental state in

the flame, the said ingredient being one which combines energetically

with oxygen so as to liberate much local heat. In practice, just as there

are only two or three substances which are suitable for the construction

of an incandescent mantle, so there is only one which renders a flame

usefully self-luminous, viz., carbon; and therefore only such fuels as

contain carbon among their constituents can be burnt so as to produce

light without the assistance of the mantle. But inasmuch as it is

necessary for the evolution of light by the combustion of carbon that

that carbon shall be in the free state, only those carbonaceous fuels

yield light without the mantle in which the carbonaceous ingredient is

dissociated into its elements before it is consumed. For instance,

alcohol and carbon monoxide are both combustible, and both contain

carbon; but they yield non-luminous flames, for the carbon burns to

carbon dioxide in ordinary conditions without assuming the solid form;

ether, petroleum, acetylene, and some of the hydrocarbons of coal-gas do

emit light on combustion, for part of their carbon is so liberated. The

quantity of light emitted by the glowing substance increases as the

temperature of that substance rises: the gain in light being equal to the

fifth or higher power of the gain in heat; [Footnote: Calculated from

absolute zero.] therefore unnecessary dissipation of heat from a flame is

one of the most important matters to be guarded against if that flame is

to be an economical illuminant. But the amount of heat liberated when a

certain weight (or volume) of a particular fuel combines with a

sufficient quantity of oxygen to oxidise it wholly is absolutely fixed,

and is exactly the same whether that fuel is made to give a luminous or a

non-luminous flame. Nevertheless the atmospheric flame given by a certain

fuel may be appreciably hotter than its luminous flame, because the

former is usually smaller than the latter. Unless the luminous flame of a

rich fuel is made to expose a wide surface to the air, part of its carbon

may escape ultimate combustion; soot or smoke may be produced, and some

of the most valuable heat-giving substance will be wasted. But if the

flame is made to expose a large surface to the air, it becomes flat or

hollow in shape instead of being cylindrical and solid, and therefore in

proportion to its cubical capacity it presents to the cold air a larger

superficies, from which loss of heat by radiation, &c., occurs. Being

larger, too, the heat produced is less concentrated.

It does not fall within the province of the present book to discuss the

relative merits of luminous and incandescent lighting; but it may be

remarked that acetylene ranks with petroleum against coal-gas,

carburetted or non-carburetted water-gas, and semi-water-gas, in showing

a comparatively small degree of increased efficiency when burnt under the

mantle. Any gas which is essentially composed of carbon monoxide or

hydrogen alone (or both together) burns with a non-luminous flame, and

can therefore only be used for illuminating purposes on the incandescent

system; but, broadly speaking, the higher is the latent illuminating

power of the gas itself when burnt in a non-atmospheric burner, the less

marked is the superiority, both from the economical and the hygienic

aspect, of its incandescent flame. It must be remembered also that only a

gas yields a flame when it is burnt; the flame of a paraffin lamp and of

a candle is due to the combustion of the vaporised fuel. Methods of

burning acetylene under the mantle are discussed in Chapter IX.; here

only self-luminous flames are being considered, but the theoretical

question of heat economy applies to both processes.

Heat may be lost from a flame in three several ways: by direct radiation

and conduction into the surrounding air, among the products of

combustion, and by conduction into the body of the burner. Loss of heat

by radiation and conduction to the air will be the greater as the flame

exposes a larger surface, and as a more rapid current of cold air is

brought into proximity with the flame. Loss of heat by conduction, into

the burner will be the greater as the material of which the burner is

constructed is a better conductor of heat, and as the mass of material in

that burner is larger. Loss of heat by passage into the combustion

products will also be greater as these products are more voluminous; but

the volume of true combustion products from any particular gas is a fixed

quantity, and since these products must leave the flame at the

temperature of that flame--where the highest temperature possible is

requisite--it would seem that no control can be had over the quantity of

heat so lost. However, although it is not possible in practice to supply

a flame with too little air, lest some of its carbon should escape

consumption and prove a nuisance, it is very easy without conspicuous

inconvenience to supply it with too much; and if the flame is supplied

with too much, there is an unnecessary volume of air passing through it

to dilute the true combustion products, which air absorbs its own proper

proportion of heat. It is only the oxygen of the air which a flame needs,

and this oxygen is mixed with approximately four times its volume of

nitrogen; if, then, only a small excess of oxygen (too little to be

noticeable of itself) is admitted to a flame, it is yet harmful, because

it brings with it four times its volume of nitrogen, which has to be

raised to the same temperature as the oxygen. Moreover, the nitrogen and

the excess of oxygen occupy much space in the flame, making it larger,

and distributing that fixed quantity of heat which it is capable of

generating over an unnecessarily large area. It is for this reason that

any gas gives so much brighter a light when burnt in pure oxygen than in

air, (1) because the flame is smaller and its heat more concentrated, and

(2) because part of its heat is not being wasted in raising the

temperature of a large mass of inert nitrogen. Thus, if the flame of a

gas which naturally gives a luminous flame is supplied with an excess of

air, its illuminating value diminishes; and this is true whether that

excess is introduced at the base of the actual flame, or is added to the

gas prior to ignition. In fact the method of adding some air to a

naturally luminous gas before it arrives at its place of combustion is

the principle of the Bunsen burner, used for incandescent lighting and

for most forms of warming and cooking stoves. A well-made modern

atmospheric burner, however, does not add an excess of air to the flame,

as might appear from what has been said; such a burner only adds part of

the air before and the remainder of the necessary quantity after the

point of first ignition--the function of the primary supply being merely

to insure thorough admixture and to avoid the production of elemental

carbon within the flame.

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 æsthetic 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° 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-Beaupré 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°, 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 Phôs 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 Phôs 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 Phôs 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 PHÔS 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 Phôs

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 |

|_________|___________|____________|__________|_____________|

| | | | | |

| 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 |

|_________|___________|____________|__________|_____________|

| | | | | |

| 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 |

|_________|___________|____________|__________|_____________|

Neuberg gives these figures for different burners (1900) as supplied by

Pintsch:

______________________________________________________________________

| | | | | |

| | Gas | | Candles | |"w

|____________________|___________|____________|__________|_____________|

| | | | | |

| No. 0, slit burner | 3.9 | 1.59 | 59.2 | 37.3 |

| " 00000 fishtail | 1.6 | 0.81 | 31.2 | 38.5 |

| Twin burner No. 1 | 3.2 | 0.32 | 13.1 | 40.8 |

| " " " 2 | 3.2 | 0.53 | 21.9 | 41.3 |

| " " " 3 | 3.2 | 0.74 | 31.0 | 41.9 |

| " " " 4 | 3.2 | 0.95 | 39.8 | 41.9 |

|____________________|___________|____________|__________|_____________|

The actual candle-power developed by each burner was not quoted by

Neuberg, and has accordingly been calculated from his efficiency values.

It is noteworthy, and in opposition to what has been found by other

investigators as well as to strict theory, that Neuberg represents the

efficiencies to be almost identical in all sizes of the same description

of burner, irrespective of the rate at which it consumes gas.

Writing in 1902, Capelle gave for Stadelmann's twin injector burners the

following figures; but as he examined each burner at several different

pressures, the values recorded in the second, third, and fourth columns

are maxima, showing the highest candle-power which could be procured from

each burner when the pressure was adjusted so as to cause consumption to

proceed at the most economical rate. The efficiency values in the fifth

column, however, are the mean values calculated so as to include all the

data referring to each burner. Capelle's results have been reproduced

from the original on the basis that 1 _bougie décimale_ equals 0.98

standard English candle, which is the value he himself ascribes to it (1

_bougie décimale_ equals 1.02 candles is the value now accepted).

_____________________________________________________________________

| | | | | |

|_____________|_________|_____________________|__________|____________|

| | | | | |

| 10 | 3.5 | 0.40 | 8.4 | 21.1 |

| 15 | 2.8 | 0.46 | 16.6 | 33.3 |

| 20 | 3.9 | 0.64 | 25.1 | 40.0 |

| 25 | 3.5 | 0.84 | 37.8 | 46.1 |

| 30 | 3.5 | 0.97 | 48.2 | 49.4 |

|_____________|_________|_____________________|__________|____________|

Some testings of various self-luminous burners of which the results were

reported by R. Granjon in 1907, gave the following results for the duty

of each burner, when the pressure was regulated for each burner to that

which afforded the maximum illuminating duty. The duty in the original

paper is given in litres per Carcel-hour. The candle has been taken as

equal to 0.102 Carcel for the conversion to candles per cubic foot.

___________________________________________________________________

| | | | |

|_______________________|_____________|__________ |_________________|

| | | | |

| Twin . . . . | 10 | 2.76 | 21.2 |

| " . . . . | 20 | 2.76 | 23.5 |

| " . . . . | 25 | 3.94 | 30.2 |

| " . . . . | 30 | 3.94-4.33 | 44.8 |

| ", (pair of flames) | 35 | 3.55-3.94 | 45.6 |

| Bray's "Manchester" | 6 | 1.97 | 18.8 |

| " | 20 | 1.97 | 35.6 |

| " | 40 | 2.36 | 42.1 |

| Rat-tail . . . | 5 | 5.5 | 21.9 |

| " . . . | 8 | 4.73 | 25.0 |

| Slit or batswing . | 30 | 1.97-2.36 | 37.0 |

|_______________________|_____________|___________|_________________|

Granjon has concluded from his investigations that the Manchester or

fish-tail burners are economical when they consume 0.7 cubic foot per

hour and when the pressure is between 2 and 2.4 inches. When these

burners are used at the pressure most suitable for twin burners their

consumption is about one-third greater than that of the latter per

candle-hour. The 25 to 35 litres-per-hour twin burners should be used at

a pressure higher by about 1 inch than the 10 to 20 litres-per-hour twin

burners.

At the present time, when the average burner has a smaller hourly

consumption than 1 foot per hour, it is customary in Germany to quote the

mean illuminating value of acetylene in self-luminous burners as being 1

Hefner unit per 0.70 litre, which, taking

1 Hefner unit = 0.913 English candle

1 English candle = 1.095 Hefner units,

works out to an efficiency of 37 candles per foot in burners probably

consuming between 0.5 and 0.7 foot per hour.

Even when allowance is made for the difficulties in determining

illuminating power, especially when different photometers, different

standards of light, and different observers are concerned, it will be

seen that these results are too irregular to be altogether trustworthy,

and that much more work must be done on this subject before the economy

of the acetylene flame can be appraised with exactitude. However, as

certain fixed data are necessary, the authors have studied those and

other determinations, rejecting some extreme figures, and averaging the

remainder; whence it appears that on an average twin-injector burners of

different sizes should yield light somewhat as follows:

_______________________________________________________

| | | |

| Size of Burner in | Candle-power | Candles |

| Cubic Feet per Hour. | Developed. | per Cubic Foot. |

|______________________|______________|_________________|

| | | |

| 0.5 | 18.0 | 35.9 |

| 0.7 | 27.0 | 38.5 |

| 1.0 | 45.6 | 45.6 |

|______________________|______________|_________________|

In the tabular statement in Chapter I. the 0.7-foot burner was taken as

the standard, because, considering all things, it seems the best, to

adopt for domestic purposes. The 1-foot burner is more economical when in

the best condition, but requires a higher gas pressure, and is rather too

powerful a unit light for good illuminating effect; the 0.5 burner

naturally gives a better illuminating effect, but its economy is

surpassed by the 0.7-foot burner, which is not too powerful for the human

eye.

For convenience of comparison, the illuminating powers and duties of the

0.5- and 0.7-foot acetylene burners may be given in different ways:

ILLUMINATING POWER OF SELF-LUMINOUS ACETYLENE.

_0.7-foot Burner._ | _Half-foot Burner._

1 litre = 1.36 candles. | 1 litre = 1.27 candles.

1 cubic foot = 38.5 candles. | 1 cubic foot = 35.9 candles.

1 candle = 0.736 litre. | 1 candle = 0.79 litre.

1 candle = 0.026 cubic foot. | 1 candle = 0.028 cubic foot.

If the two streams of gas impinge at an angle of 90°, twin-injector

burners for acetylene appear to work best when the gas enters them at a

pressure of 2 to 2.5 inches; for a higher pressure the angle should be

made a little acute. Large burners require to have a wider distance

between the jets, to be supplied with acetylene at a higher pressure, and

to be constructed with a smaller angle of impingement. Every burner, of

whatever construction and size, must always be supplied with gas at its

proper pressure; a pressure varying from time to time is fatal.

It is worth observing that although injector burners are satisfactory in

practice, and are in fact almost the only jets yet found to give

prolonged satisfaction, the method of injecting air below the point of

combustion in a self-luminous burner is in some respects wrong in

principle. If acetylene can be consumed without polymerisation in burners

of the simple fish-tail or bat's-wing type, it should show a higher

illuminating efficiency. In 1902 Javal stated that it was possible to

burn thoroughly purified acetylene in twin non-injector burners, provided

the two jets, made of steatite as usual, were arranged horizontally

instead of obliquely, the two streams of gas then meeting at an angle of

180°, so as to yield an almost circular flame. According to Javal,

whereas carbonaceous growths were always produced in non-injector

acetylene burners with either oblique or horizontal jets, in the former

case the growths eventually distorted the gas orifices, but in the latter

the carbon was deposited in the form of a tube, and fell off from the

burner by its own weight directly it had grown to a length of 1.2 or 1.5

millimetres, leaving the jets perfectly clear and smooth. Javal has had

such a burner running for 10 or 12 hours per day for a total of 2071

hours; it did not need cleaning out on any occasion, and its consumption

at the end of the period was the same as at first. He found that it was

necessary that the tips should be of steatite, and not of metal or glass;

that the orifices should be drilled in a flat surface rather than at the

apex of a cone, and that the acetylene should be purified to the utmost

possible extent. Subsequent experience has demonstrated the possibility

of constructing non-injector burners such as that shown in Fig. 13, which

behave satisfactorily even though the jets are oblique. But with such

burners trouble will inevitably ensue unless the gas is always purified

to a high degree and is tolerably dry and well filtered. Non-injector

burners should not be used unless special care is taken to insure that

the installation is consistently operated in an efficient manner in these

respects.

GLOBES, &C.--It does not fall within the province of the present volume

to treat at length of chimneys, globes, or the various glassware which

may be placed round a source of light to modify its appearance. It should

be remarked, however, that obedience to two rules is necessary for

complete satisfaction in all forms of artificial illumination. First, no

light much stronger in intensity than a single candle ought ever to be

placed in such a position in an occupied room that its direct rays can

reach the eye, or the vision will be temporarily, and may be permanently,

injured. Secondly, unless economy is to be wholly ignored, no coloured or

tinted globe or shade should ever be put round a source of artificial

light. The best material for the construction of globes is that which

possesses the maximum of translucency coupled with non-transparency,

_i.e._, a material which passes the highest proportion of the light

falling upon it, and yet disperses that light in such different

directions that the glowing body cannot be seen through the globe. Very

roughly speaking, plain white glass, such as that of which the chimneys

of oil-lamps and incandescent gas-burners are composed, is quite

transparent, and therefore affords no protection to the eyesight; a

protective globe should be rather of ground or opal glass, or of plain

glass to which a dispersive effect has been given by forming small prisms

on its inner or outer surface, or both. Such opal, ground, or dispersive

shades waste much light in terms of illuminating power, but waste

comparatively little in illuminating effect well designed, they may

actually increase the illuminating effect in certain positions; a tinted

globe, even if quite plain in figure, wastes both illuminating power and

effect, and is only to be tolerated for so-believed aesthetic reasons.

Naturally no globe must be of such figure, or so narrow at either

orifice, as to distort the shape of the unshaded acetylene flame--it is

hardly necessary to say this now, but some years ago coal-gas globes were

constructed with an apparent total disregard of this fundamental point.

CHAPTER IX

INCANDESCENT BURNERS--HEATING APPARATUS--MOTORS--AUTOGENOUS SOLDERING

MERITS OF LIGHTING BY INCANDESCENT MANTLES.--It has already been shown

that acetylene bases its chief claim for adoption as an illuminant in

country districts upon the fact that, when consumed in simple self-

luminous burners, it gives a light comparable in all respects save that

of cost to the light of incandescent coal-gas. The employment of a mantle

is still accompanied by several objections which appear serious to the

average householder, who is not always disposed either to devote

sufficient attention to his burners to keep them in a high state of

efficiency or to contract for their maintenance by the gas company or

others. Coal-gas cannot be burnt satisfactorily on the incandescent

system unless the glass chimneys and shades are kept clean, unless the

mantles are renewed as soon as they show signs of deterioration, and,

perhaps most important of all, unless the burners are frequently cleared

of the dust which collects round the jets. For this reason luminous

acetylene ranks with luminous coal-gas in convenience and simplicity,

while ranking with incandescent coal-gas in hygienic value. Very similar

remarks apply to paraffin, and, in certain countries, to denatured

alcohol. Since those latter illuminants are also available in rural

places where coal-gas is not laid on, luminous acetylene is a less

advantageous means of procuring artificial light than paraffin (and on

occasion than coal-gas and alcohol when the latter fuels are burnt under

the mantle), if the pecuniary aspect of the question is the only one

considered. Such a comparison, however, is by no means fair; for if coal-

gas, paraffin, and alcohol can be consumed on the incandescent system, so

can acetylene; and if acetylene is hygienically equal to incandescent

coal-gas, it is superior thereto when also burnt under the mantle.

Nevertheless there should be one minor but perfectly irremediable defect

in incandescent acetylene, viz., a sacrifice of that characteristic

property of the luminous gas to emit a light closely resembling that of

the sun in tint, which was mentioned in Chapter 1. Self-luminous

acetylene gives the whitest light hitherto procurable without special

correction of the rays, because its light is derived from glowing

particles of carbon which happen to be heated (because of the high flame

temperature) to the best possible temperature for the emission of pure

white light. The light of any combustible consumed on the "incandescent"

system is derived from glowing particles of ceria, thoria, or similar

metallic oxides; and the character or shade of the light they emit is a

function, apart from the temperature to which they are raised, of their

specific chemical nature. Still, the light of incandescent acetylene is

sufficiently pleasant, and according to Caro is purer white than that of

incandescent coal-gas; but lengthy tests carried out by one of the

authors actually show it to be appreciably inferior to luminous acetylene

for colour-matching, in which the latter is known almost to equal full

daylight, and to excel every form of artificial light except that of the

electric arc specially corrected by means of glass tinted with copper

salts.

CONDITIONS FOR INCANDESCENT ACETYLENE LIGHTING.--For success in the

combustion of acetylene on the incandescent system, however, several

points have to be observed. First, the gas must be delivered at a

strictly constant pressure to the burner, and at one which exceeds a

certain limit, ranging with different types and different sizes of burner

from 2 to 4 or 5 inches of water. (The authors examined, as long ago as

1903, an incandescent burner of German construction claimed to work at a

pressure of 1.5 inches, which it was almost impossible to induce to fire

back to the jets however slowly the cock was manipulated, provided the

pressure of the gas was maintained well above the point specified. But

ordinarily a pressure of about 4 inches is used with incandescent

acetylene burners.) Secondly, it is necessary that the acetylene shall at

all times be free from appreciable admixture with air, even 0.5 per cent,

being highly objectionable according to Caro; so that generators

introducing any noteworthy amount of air into the holder each time their

decomposing chambers are opened for recharging are not suitable for

employment when incandescent burners are contemplated. The reason for

this will be more apparent later on, but it depends on the obvious fact

that if the acetylene already contains an appreciable proportion of air,

when a further quantity is admitted at the burner inlets, the gaseous

mixture contains a higher percentage of oxygen than is suited to the size

and design of the burner, so that flashing back to the injector jets is

imminent at any moment, and may be determined by the slightest

fluctuation in pressure--if, indeed, the flame will remain at the proper

spot for combustion at all. Thirdly, the fact that the acetylene which is

to be consumed under the mantle must be most rigorously purified from

phosphorus compounds has been mentioned in Chapter V. Impure acetylene

will often destroy a mantle in two or three hours; but with highly

purified gas the average life of a mantle may be taken, according to

Giro, at 500 or 600 hours. It is safer, however, to assume a rather

shorter average life, say 300 to 400 burning hours. Fourthly, owing to

the higher pressure at which acetylene must be delivered to an

incandescent burner and to the higher temperature of the acetylene flame

in comparison with coal-gas, a mantle good enough to give satisfactory

results with the latter does not of necessity answer with acetylene; in

fact, the authors have found that English Welsbach coal-gas mantles of

the small sizes required by incandescent acetylene burners are not

competent to last for more than a very few hours, although, in identical

conditions, mantles prepared specially for use with acetylene have proved

durable. The atmospheric acetylene flame, too, differs in shape from an

atmospheric flame of coal-gas, and it does not always happen that a coal-

gas mantle contracts to fit the former; although it usually emits a

better light (because it fits better) after some 20 hours use than at

first. Caro has stated that to derive the best results a mantle needs to

contain a larger proportion of ceria than the 1 per cent. present in

mantles made according to the Welsbach formula, that it should be

somewhat coarser in mesh, and have a large orifice at the head. Other

authorities hold that mantles for acetylene, should contain other rare

earths besides the thoria and ceria of which the coal-gas mantles almost

wholly consist. It seems probable, however, that the composition of the

ordinary impregnating fluid need not be varied for acetylene mantles

provided it is of the proper strength and the mantles are raised to a

higher temperature in manufacture than coal-gas mantles by the use of

either coal-gas at very high pressure or an acetylene flame. The

thickness of the substance of the mantle cannot be greatly increased with

a view to attaining greater stability without causing a reduction in the

light afforded. But the shape should be such that the mantle conforms as

closely as possible to the acetylene Bunsen flame, which differs slightly

with different patterns of incandescent burner heads. According to L.

Cadenel, the acetylene mantle should be cylindrical for the lower two-

thirds of its length, and slightly conical above, with an opening of

moderate size at the top. The head of the mantle should be of slighter

construction than that of coal-gas mantles. Fifthly, generators belonging

to the automatic variety, which in most forms inevitably add more or less

air to the acetylene every time they are cleaned or charged, appear to

have achieved most popularity in Great Britain; and these frequently do

not yield a gas fit for use with the mantle. This state of affairs, added

to what has just been said, makes it difficult to speak in very

favourable terms of the incandescent acetylene light for use in Great

Britain. But as the advantages of an acetylene not contaminated with air

are becoming more generally recognised, and mantles of several different

makes are procurable more cheaply, incandescent acetylene is now more

practicable than hitherto. Carburetted acetylene or "carburylene," which

is discussed later, is especially suitable for use with mantle burners.

ATMOSPHERIC ACETYLENE BURNERS.--The satisfactory employment of acetylene

in incandescent burners, for boiling, warming, and cooking purposes, and

also to some extent as a motive power in small engines, demands the

production of a good atmospheric or non-luminous flame, _i.e._, the

construction of a trustworthy burner of the Bunsen type.

This has been exceedingly difficult to achieve for two reasons: first,

the wide range over which mixtures of acetylene and air are explosive;

secondly, the high speed at which the explosive wave travels through such

a mixture. It has been pointed out in Chapter VIII. that a Bunsen burner

is one in which a certain proportion of air is mixed with the gas before

it arrives at the actual point of ignition; and as that proportion must

be such that the mixture falls between the upper and lower limits of

explosibility, there is a gaseous mixture in the burner tube between the

air inlets and the outlet which, if the conditions are suitable, will

burn with explosive force: that is to say, will fire back to the air jets

when a light is applied to the proper place for combustion. Such an

explosion, of course, is far too small in extent to constitute any danger

to person or property; the objection to it is simply that the shock of

the explosion is liable to fracture the fragile incandescent mantle,

while the gas, continuing to burn within the burner tube (in the case of

a warming or cooking stove), blocks up that tube with carbon, and

exhibits the other well-known troubles of a coal-gas stove which has

"fired back."

It has been shown, however, in Chapter VI. that the range over which

mixtures of acetylene and air are explosive depends on the size of the

vessel, or more particularly on the diameter of the tube, in which they

are stored; so that if the burner tube between the air inlets and the

point of ignition can be made small enough in diameter, a normally

explosive mixture will cease to exhibit explosive properties. Manifestly,

if a tube is made very small in diameter, it will only pass a small

volume of gas, and it may be useless for the supply of an atmospheric

burner; but Le Chatelier's researches have proved that a tube may be

narrowed at one spot only, in such fashion that the explosive wave

refuses to pass the constriction, while the virtual diameter of the tube,

as far as passage of gas is concerned, remains considerably larger than

the size of the constriction itself. Moreover, inasmuch as the speed of

propagation of the explosion is strictly fixed by the conditions

prevailing, if the speed at which the mixture, of acetylene and air

travels from the air inlets to the point of ignition is more rapid than

the speed at which the explosion tends to travel from the point of

ignition to the air inlets, the said mixture of acetylene and air will

burn quietly at the orifice without attempting to fire backwards into the

tube. By combining together these two devices: by delivering the

acetylene to the injector jet at a pressure sufficient to drive the

mixture of gas and air forward rapidly enough, and by narrowing the

leading tube either wholly or at one spot to a diameter small enough, it

is easy to make an atmospheric burner for acetylene which behaves

perfectly as long as it is fairly alight, and the supply of gas is not

checked; but further difficulties still remain, because at the instant of

lighting and extinguishing, i.e., while the tap is being turned on or

off, the pressure of the gas is too small to determine a flow of

acetylene and air within the tube at a speed exceeding that of the

explosive wave; and therefore the act of lighting or extinguishing is

very likely to be accompanied by a smart explosion severe enough to split

the mantle, or at least to cause the burner to fire back. Nevertheless,

after several early attempts, which were comparative failures,

atmospheric acetylene burners have been constructed that work quite

satisfactorily, so that the gas has become readily available for use

under the mantle, or in heating stoves. Sometimes success has been

obtained by the employment of more than one small tube leading to a

common place of ignition, sometimes by the use of two or more fine wire-

gauze screens in the tube, sometimes by the addition of an enlarged head

to the burner in which head alone thorough mixing of the gas and air

occurs, and sometimes by the employment of a travelling sleeve which

serves more or less completely to block the air inlets.

DUTY OF INCANDESCENT ACETYLENE BURNERS.--Granting that the petty troubles

and expenses incidental to incandescent lighting are not considered

prohibitive--and in careful hands they are not really serious--

and that mantles suitable for acetylene are employed, the gas may be

rendered considerably cheaper to use per unit of light evolved by

consuming it in incandescent burners. In Chapter VIII. it was shown that

the modern self-luminous, l/2-foot acetylene burner emits a light of

about 1.27 standard English candles per litre-hour. A large number of

incandescent burners, of German and French construction, consuming from

7.0 to 22.2 litres per hour at pressures ranging between 60 and 120

millimetres have been examined by Caro, who has found them to give lights

of from 10.8 to 104.5 Hefner units, and efficiencies of from 2.40 to 5.50

units per litre-hour. Averaging his results, it may be said that

incandescent burners consuming from 10 to 20 litres per hour at pressures

of 80 or 100 millimetres yield a light of 4.0 Hefner units per litre-

hour. Expressed in English terms, incandescent acetylene burners

consuming 0.5 cubic foot per hour at a pressure of 3 or 4 inches give the

duties shown in the following table, which may advantageously be compared

with that printed in Chapter VIII., page 239, for the self-luminous gas:

ILLUMINATING POWER OF INCANDESCENT ACETYLENE.

HALF-FOOT BURNERS.

1 litre = 3.65 candles | 1 candle = 0.274 litre.

1 cubic foot = 103.40 candles. | 1 candle = 0.0097 cubic foot.

A number of tests of the Güntner or Schimek incandescent burners of the

10 and 15 litres-per-hour sizes, made by one of the authors in 1906, gave

the following average results when tested at a pressure of 4 inches:

_________________________________________________________________

| | | | |

|______________|_________________________|__________|_____________|

| | | | | |

| 10 | 0.472 | 13.35 | 46.0 | 97.4 |

| 15 | 0.663 | 18.80 | 70.0 | 105.5 |

|______________|____________|____________|__________|_____________|

These figures indicate that the duty increases slightly with the size of

the burner. Other tests showed that the duty increased more considerably

with an increase of pressure, so that mantles used, or which had been

previously used, at a pressure of 5 inches gave duties of 115 to 125

candles per cubic foot.

It should be noted that the burners so far considered are small, being

intended for domestic purposes only; larger burners exhibit higher

efficiencies. For instance, a set of French incandescent acetylene

burners examined by Fouché showed:

_________________________________________________________________

| | | | | |

|________________|__________|____________|__________|_____________|

| | | | | |

| 20 | 5.9 | 0.71 | 70 | 98.6 |

| 40 | 5.9 | 1.41 | 150 | 106.4 |

| 70 | 5.9 | 2.47 | 280 | 113.4 |

| 120 | 5.9 | 4.23 | 500 | 118.2 |

|________________|__________|____________|__________|_____________|

By increasing the pressure at which acetylene is introduced into burners

of this type, still larger duties may be obtained from them:

_________________________________________________________________

| | | | | |

|________________|__________|____________|__________|_____________|

| | | | | |

| 55 | 39.4 | 1.94 | 220 | 113.4 |

| 100 | 39.4 | 3.53 | 430 | 121.8 |

| 180 | 39.4 | 6.35 | 820 | 129.1 |

| 260 | 27.6 | 9.18 | 1300 | 141.6 |

|________________|__________|____________|__________|_____________|

High-power burners such as these are only fit for special purposes, such

as lighthouse illumination, or optical lantern work, &c.; and they

naturally require mantles of considerably greater tenacity than those

intended for employment with coal-gas. Nevertheless, suitable mantles can

be, and are being, made, and by their aid the illuminating duty of

acetylene can be raised from the 30 odd candles per foot of the common

0.5-foot self-luminous jet to 140 candles or more per foot, which is a

gain in efficiency of 367 per cent., or, neglecting upkeep and sundries

and considering only the gas consumed, an economy of nearly 79 per cent.

In 1902, working apparently with acetylene dissolved under pressure in

acetone (_cf._ Chapter XI.), Lewes obtained the annexed results with

the incandescent gas:

________________________________________________________

| | | | |

|___________|_____________|______________|______________|

| | | | |

| 8 | 0.883 | 65 | 73.6 |

| 9 | 0.94 | 72 | 76.0 |

| 10 | 1.00 | 146 | 146.0 |

| 12 | 1.06 | 150 | 141.2 |

| 15 | 1.25 | 150 | 120.0 |

| 20 | 1.33 | 166 | 124.8 |

| 25 | 1.50 | 186 | 123.3 |

| 40 | 2.12 | 257 | 121.2 |

|___________|_____________|______________|______________|

It will be seen that although the total candle-power developed increases

with the pressure, the duty of the burner attained a maximum at a

pressure of 10 inches. This is presumably due to the fact either that the

same burner was used throughout the tests, and was only intended to work

at a pressure of 10 inches or thereabouts, or that the larger burners

were not so well constructed as the smaller ones. Other investigators

have not given this maximum of duty with a medium-sized or medium-driven

burner; but Lewes has observed a similar phenomenon in the case of 0.7 to

0.8 cubic foot self-luminous jets.

Figures, however, which seem to show that the duty of incandescent

acetylene does not always rise with the size of the burner or with the

pressure at which the gas is delivered to it, have been published in

connexion with the installation at the French lighthouse at Chassiron,

the northern point of the Island of Oléron. Here the acetylene is

generated in hand-fed carbide-to-water generators so constructed as to

give any pressure up to nearly 200 inches of water column; purified by

means of heratol, and finally delivered to a burner composed of thirty-

seven small tubes, which raises to incandescence a mantle 55 millimetres

in diameter at its base. At a pressure of 7.77 inches of water, the

burner passes 3.9 cubic feet of acetylene per hour, and at a pressure of

49.2 inches (the head actually used) it consumes 20.06 cubic feet per

hour. As shown by the following table, such increment of gas pressure

raises the specific intensity of the light, _i.e._, the illuminating

power per unit of incandescent surface, but it does not appreciably raise

the duty or economy of the gas. Manifestly, in terms of duty alone, a

pressure of 23.6 inches of water-column is as advantageous as the higher

Chassiron figures; but since intensity of light is an important matter in

a lighthouse, it is found better on the whole to work the generators at a

pressure of 49.2 inches. In studying these figures referring to the

French lighthouse, it is interesting to bear in mind that when ordinary

six-wick petroleum oil burners wore used in the same place, the specific

intensity of the light developed was 75 candle-power per square inch, and

when that plant was abandoned in favour of an oil-gas apparatus, the

incandescent burner yielded 161 candle-power per square inch;

substitution of incandescent acetylene under pressure has doubled the

brilliancy of the light.

___________________________________________________________

| | | |

| | Duty. | Intensity. |

| Pressure in Inches. | Candle-power per | Candle-power per |

| | Cubic Foot. | Square Inch. |

|_____________________|__________________|__________________|

| | | |

| 7.77 | 105.5 | 126.0 |

| 23.60 | 106.0 | 226.0 |

| 31.50 | 110.0 | 277.0 |

| 39.40 | 110.0 | 301.0 |

| 47.30 | 106.0 | 317.0 |

| 49.20 | 104.0 | 324.9 |

| 196.80 | 110.0 | 383.0 |

|_____________________|__________________|__________________|

When tested in modern burners consuming between 12 and 18 litres per hour

at a pressure of 100 millimetres (4 inches), some special forms of

incandescent mantles constructed of ramie fibre, which in certain

respects appears to be better suited than cotton for use with acetylene,

have shown the following degree of loss in illuminating power after

prolonged employment (Caro):

_Luminosity in Hefner Units._

________________________________________________________

| | | | | |

|_________|_______|____________|____________|____________|

| | | | | |

| No. 1. | 53.2 | 51.8 | 50.6 | 49.8 |

| No. 2. | 76.3 | 75.8 | 73.4 | 72.2 |

| No. 3. | 73.1 | 72.5 | 70.1 | 68.6 |

|_________|_______|____________|____________|____________|

It will be seen that the maximum loss of illuminating power in 400 hours

was 6.4 per cent., the average loss being 6.0 per cent.

TYPICAL INCANDESCENT BURNERS.--Of the many burners for lighting by the

use of incandescent mantles which have been devised, a few of the more

widely used types may be briefly referred to. There is no doubt that

finality in the design of these burners has not yet been reached, and

that improvements in the direction of simplification of construction and

in efficiency and durability will continue to be made.

Among the early incandescent burners, one made by the Allgemeine Carbid

und Acetylen Gesellschaft of Berlin in 1900 depended on the narrowness of

the mixing tube and the proportioning of the gas nipple and air inlets to

prevent lighting-back. There was a wider concentric tube round the upper

part of the mixing tube, and the lower part of the mantle fitted round

this. The mouth of the mixing tube of this 10-litres-per-hour burner was

0.11 inch in diameter, and the external diameter of the middle

cylindrical part of the mixing tube was 0.28 inch. There was no gauze

diaphragm or stuffing, and firing-back did not occur until the pressure

was reduced to about 1.5 inches. The same company later introduced a

burner differing in several important particulars from the one just

described. The comparatively narrow stem of the mixing tube and the

proportions of the gas nipple and air inlets were retained, but the

mixing tube was surmounted by a wide chamber or burner head, in which

naturally there was a considerable reduction in the rate of flow of the

gas. Consequently it was found necessary to introduce a gauze screen into

the burner head to prevent firing back. The alterations have resulted in

the lighting duty of the burner being considerably improved. Among other

burners designed about 1900 may be mentioned the Ackermann, the head of

which consisted of a series of tubes from each of which a jet of flame

was produced, the Fouché, the Weber, and the Trendel. Subsequently a

tubular-headed burner known as the Sirius has been produced for the

consumption of acetylene at high pressure (20 inches and upwards).

The more recent burners which have been somewhat extensively used include

the "Schimek," made by W. Güntner of Vienna, which is shown in Fig. 19.

It consists of a tapering narrow injecting nozzle within a conical

chamber C which is open below, and is surmounted by the mixing tube over

which telescopes a tube which carries the enlarged burner head G, and the

chimney gallery D. There are two diaphragms of gauze in the burner head

to prevent firing back, and one in the nozzle portion of the burner. The

conical chamber has a perforated base-plate below which is a circular

plate B which rotates on a screw cut on the lower part of the nozzle

portion A of the burner. This plate serves as a damper to control the

amount of air admitted through the base of the conical chamber to the

mixing tube. There are six small notches in the lower edge of the conical

chamber to prevent the inflow of air being cut of entirely by the damper.

The mixing tube in both the 10-litre and the 15-litre burner is about

0.24 inch in internal diameter but the burner head is nearly 0.42 inch in

the 10-litre and 0.48 inch in the 15-litre burner. The opening in the

head of the burner through which the mixture of gas and air escapes to

the flame is 0.15 and 0.17 inch in diameter in these two sizes

respectively. The results of some testings made with Schimek burners have

been already given.

[Illustration: FIG. 19.--"SCHIMEK" BURNER.]

The "Knappich" burner, made by the firm of Keller and Knappich of

Augsburg, somewhat resembles the later pattern of the Allgemeine Carbid

und Acetylen Gesellschaft. It has a narrow mixing tube, viz., 0.2 inch in

internal diameter, and a wide burner head, viz., 0.63 inch in internal

diameter for the 25-litre size. The only gauze diaphragm is in the upper

part of the burner head. The opening in the cap of the burner head, at

which the gas burns, is 0.22 inch in diameter. The gas nipple extends

into a domed chamber at the base of the mixing tube, and the internal air

is supplied through four holes in the base-plate of that chamber. No

means of regulating the effective area of the air inlet holes are

provided.

The "Zenith" burner, made by the firm of Gebrüder Jacob of Zwickau, more

closely resembles the Schimek, but the air inlets are in the side of the

lower widened portion of the mixing tube, and are more or less closed by

means of an outside loose collar which may be screwed up and down on a

thread on a collar fixed to the mixing tube. The mixing tube is 0.24

inch, and the burner head 0.475 inch in internal diameter. The opening in

the cap of the burner is 0.16 inch in diameter. There is a diaphragm of

double gauze in the cap, and this is the only gauze used in the burner.

All the incandescent burners hitherto mentioned ordinarily have the gas

nipple made in brass or other metal, which is liable to corrosion, and

the orifice to distortion by heat or if it becomes necessary to remove

any obstruction from it. The orifice in the nipple is extremely small--

usually less than 0.015 inch--and any slight obstruction or distortion

would alter to a serious extent the rate of flow of gas through it, and

so affect the working of the burner. In order to overcome this defect,

inherent to metal nipples, burners are now constructed for acetylene in

which the nipple is of hard incorrodible material. One of these burners

has been made on behalf of the Office Central de l'Acétylène of Paris,

and is commonly known as the "O.C.A." burner. In it the nipple is of

steatite. On the inner mixing tube of this burner is mounted an elongated

cone of wire wound spirally, which serves both to ensure proper admixture

of the gas and air, and to prevent firing-back. There is no gauze in this

burner, and the parts are readily detachable for cleaning when required.

Another burner, in which metal is abolished for the nipple, is made by

Geo. Bray and Co., Ltd., of Leeds, and is shown in Fig. 20. In this

burner the injecting nipple is of porcelain.

[Illustration: FIG. 20.--BRAY'S INCANDESCENT BURNER.]

ACETYLENE FOR HEATING AND COOKING.--Since the problem of constructing a

trustworthy atmospheric burner has been solved, acetylene is not only

available for use in incandescent lighting, but it can also be employed

for heating or cooking purposes, because all boiling, most warming, and

some roasting stoves are simply arrangements for utilising the heat of a

non-luminous flame in one particular way. With suitable alterations in

the dimensions of the burners, apparatus for consuming coal-gas may be

imitated and made fit to burn acetylene; and as a matter of fact several

firms are now constructing such appliances, which leave little or nothing

to be desired. It may perhaps be well to insist upon the elementary point

which is so frequently ignored in practice, viz., that no stove, except

perhaps a small portable boiling ring, ought ever to be used in an

occupied room unless it is connected with a chimney, free from down-

draughts, for the products of combustion to escape into the outer air;

and also that no chimney, however tall, can cause an up-draught in all

states of the weather unless there is free admission of fresh air into

the room at the base of the chimney. Still, at the prices for coal,

paraffin oil, and calcium carbide which exist in Great Britain, acetylene

is not an economical means of providing artificial heat. If a 0.7 cubic

foot luminous acetylene burner gives a light of 27 candles, and if

ordinary country coal-gas gives light of 12 to 13 candles in a 5-foot

burner, one volume of acetylene is equally valuable with 15 or 16 volumes

of coal-gas when both are consumed in self-luminous jets; and if, with

the mantle, acetylene develops 99 candles per cubic foot, while coal-gas

gives in common practice 15 to 20 candles, one volume of acetylene is

equally valuable with 5 to 6-1/2 volumes of coal-gas when both are

consumed on the incandescent system; whereas, if the acetylene is burnt

in a flat flame, and the coal-gas under the mantle, 1 volume of the

former is equally efficient with 2 volumes of coal-gas as an artificial

illuminant. This last method of comparison being manifestly unfair,

acetylene may be said to be at least five times as efficient per unit of

volume as coal-gas for the production of light. But from the table given

on a later page it appears that as a source of artificial heat, acetylene

is only equal to about 2-3 times its volume of ordinary coal-gas.

Nevertheless, the domestic advantages of gas firing are very marked; and

when a properly constructed stove is properly installed, the hygienic

advantages of gas-firing are alone equally conspicuous--for the disfavor

with which gas-firing is regarded by many physicians is due to experience

gained with apparatus warming principally by convection [Footnote:

Radiant heat is high-temperature heat, like the heat emitted by a mass of

red-hot coke; convected heat is low-temperature heat, invisible to the

eye. Radiant heat heats objects first, and leaves them to warm the air;

convected heat is heat applied directly to air, and leaves the air to

warm objects afterwards. On all hygienic grounds radiant heat is better

than convected heat, but the latter is more economical. By an absurd and

confusing custom, that particular warming apparatus (gas, steam, or hot

water) which yields practically no radiant heat, and does all its work by

convection, is known to the trade as a "radiator."] instead of radiation;

or to acquaintance with intrinsically better stoves either not connected

to any flues or connected to one deficient in exhausting power. In these

circumstances, whenever an installation of acetylene has been laid down

for the illumination of a house or district, the merit of convenience may

outweigh the defect of extravagance, and the gas may be judiciously

employed in a boiling ring, or for warming a bedroom; while, if pecuniary

considerations are not paramount, the acetylene may be used for every

purpose to which the townsman would apply his cheaper coal-gas.

The difficulty of constructing atmospheric acetylene burners in which the

flame would not be likely to strike back to the nipple has already been

referred to in connexion with the construction atmospheric burners for

incandescent lighting. Owing, however, to the large proportions of the

atmospheric burners of boiling rings and stove and in particular to the

larger bore of their mixing tube, the risk of the flame striking back is

greater with them, than with incandescent lighting burners. The greatest

trouble is presented at lighting, and when the pressure of the gas-supply

is low. The risk of firing-back when the burner is lighted is avoided in

some forms of boiling rings, &c., by providing a loose collar which can

be slipped over the air inlets of the Bunsen tube before applying a light

to the burner, and slipped clear of them as soon as the burner is alight.

Thus at the moment of lighting, the burner is converted temporarily into

one of the non-atmospheric type, and after the flame has thus been

established at the head or ring of the burner, the internal air-supply is

started by removing the loose collar from the air inlets, and the flame

is thus made atmospheric. In these conditions it does not travel

backwards to the nipple. In other heating burners it is generally

necessary to turn on the gas tap a few seconds before applying a light to

the burner or ring or stove; the gas streaming through the mixing tube

then fills it with acetylene and air mixed in the proper working

proportions, and when the light is applied, there is no explosion in the

mixing tube, or striking-back of the flame to the nipple.

Single or two-burner gas rings for boiling purposes, or for heating

cooking ovens, known as the "La Belle," made by Falk Stadelmann and Co.,

Ltd., of London, may be used at as low a gas pressure as 2 inches, though

they give better results at 3 inches, which is their normal working

pressure. The gas-inlet nozzle or nipple of the burner is set within a

spherical bulb in which are four air inlets. The mixing tube which is

placed at a proper distance in front of the nipple, is proportioned to

the rate of flow of the gas and air, and contains a mixing chamber with a

baffling pillar to further their admixture. A fine wire gauze insertion

serves to prevent striking-back of the flame. A "La Belle" boiling ring

consumes at 3 inches pressure about 48 litres or 1.7 cubic feet of

acetylene per hour.

ACETYLENE MOTORS.--The question as to the feasibility of developing

"power" from acetylene, _i.e._, of running an engine by means of the

gas, may be answered in essentially identical terms. Specially designed

gas-engines of 1, 3, 6, or even 10 h.p. work perfectly with acetylene,

and such motors are in regular employment in numerous situations, more

particularly for pumping water to feed the generators of a large village

acetylene installation. Acetylene is not an economical source of power,

partly for the theoretical reason that it is a richer fuel even than

coal-gas, and gas-engines would appear usually to be more efficient as

the fuel they burn is poorer in calorific intensity, _i.e._, in

heating power (which is explosive power) per unit of volume. The richer,

or more concentrated, any fuel in, the more rapidly does the explosion in

a mixture of that fuel with air proceed, because a rich fuel contains a

smaller proportion of non-inflammable gases which tend to retard

explosion than a poor one; and, in reason, a gas-engine works better the

more slowly the mixture of gas and air with which it is fed explodes.

Still, by properly designing the ports of a gas-engine cylinder, so that

the normal amount of compression of the charge and of expansion of the

exploded mixture which best suit coal-gas are modified to suit acetylene,

satisfactory engines can be constructed; and wherever an acetylene

installation for light exists, it becomes a mere question of expediency

whether the same fuel shall not be used to develop power, say, for

pumping up the water required in a large country house, instead of

employing hand labour, or the cheaper hot-air or petroleum motor. Taking

the mean of the results obtained by numerous investigators, it appears

that 1 h.p.-hour can be obtained for a consumption of 200 litres of

acetylene; whence it may be calculated that that amount of energy costs

about 3d. for gas only, neglecting upkeep, lubricating material

(which would be relatively expensive) and interest, &c.

Acetylene Blowpipes--The design of a satisfactory blowpipe for use with

acetylene had at first proved a matter of some difficulty, since the jet,

like that of an ordinary self-luminous burner, usually exhibited a

tendency to become choked with carbonaceous growths. But when acetylene

had become available for various purposes at considerable pressure, after

compression into porous matter as described in Chapter XI, the troubles

were soon overcome; and a new form of blowpipe was constructed in which

acetylene was consumed under pressure in conjunction with oxygen. The

temperature given by this apparatus exceeds that of the familiar oxy-

hydrogen blowpipe, because the actual combustible material is carbon

instead of hydrogen. When 2 atoms of hydrogen unite with 1 of oxygen to

form 1 molecule of gaseous water, about 59 large calories are evolved,

and when 1 atom of solid amorphous carbon unites with 2 atoms of oxygen

to form 1 molecule of carbon dioxide, 97.3 calories are evolved. In both

cases, however, the heat attainable is limited by the fact that at

certain temperatures hydrogen and oxygen refuse to combine to form water,

and carbon and oxygen refuse to form carbon dioxide--in other words,

water vapour and carbon dioxide dissociate and absorb heat in the process

at certain moderately elevated temperatures. But when 1 atom of solid

amorphous carbon unites with 1 atom of oxygen to form carbon monoxide,

29.1 [Footnote: Cf. Chapter VI., page 185.] large calories are produced,

and carbon monoxide is capable of existence at much higher temperatures

than either carbon dioxide or water vapour. In any gaseous hydrocarbon,

again, the carbon exists in the gaseous state, and when 1 atom of the

hypothetical gaseous carbon combines with 1 atom of oxygen to produce 1

molecule of carbon monoxide, 68.2 large calories are evolved. Thus while

solid amorphous carbon emits more heat than a chemically equivalent

quantity of hydrogen provided it is enabled to combine with its higher

proportion of oxygen, it emits less if only carbon monoxide is formed;

but a higher temperature can be attained in the latter case, because the

carbon monoxide is more permanent or stable. Gaseous carbon, on the other

hand, emits more heat than an equivalent quantity of hydrogen, [Footnote:

In a blowpipe flame hydrogen can only burn to gaseous, not liquid,

water.] even when it is only converted into the monoxide. In other words,

a gaseous fuel which consists of hydrogen alone can only yield that

temperature as a maximum at which the speed of the dissociation of the

water vapour reaches that of the oxidation of the hydrogen; and were

carbon dioxide the only oxide of carbon, a similar state of affairs would

be ultimately reached in the flame of a carbonaceous gas. But since in

the latter case the carbon dioxide does not tend to dissociate

completely, but only to lose one atom of oxygen, above the limiting

temperature for the formation of carbon dioxide, carbon monoxide is still

produced, because there is less dissociating force opposed to its

formation. Thus at ordinary temperatures the heat of combustion of

acetylene is 315.7 calories; but at temperatures where water vapour and

carbon dioxide no longer exist, there is lost to that quantity of 315.7

calories the heat of combustion of hydrogen (69.0) and twice that of

carbon monoxide (68.2 x 2 = 136.4); so that above those critical

temperatures, the heat of combustion of acetylene is only 315.7 - (69.0 +

136.4) = 110.3. [Footnote: When the heat of combustion of acetylene is

quoted as 315.7 calories, it is understood that the water formed is

condensed into the liquid state. If the water remains gaseous, as it must

do in a flame, the heat of formation is reduced by about 10 calories.

This does not affect the above calculation, because the heat of

combustion of hydrogen when the water remains gaseous is similarly 10

calories less than 69, _i.e._, 59, as mentioned above in the text.

Deleting the heat of liquefaction of water, the calculation referred to

becomes 305.7 - (59.0 + l36.4) = 110.3 as before.] This value of 110.3

calories is clearly made up of the heat of formation of acetylene itself,

and twice the heat of conversion of carbon into carbon monoxide,

_i.e._, for diamond carbon, 58.1 + 26.1 x 2 = 110.3; or for

amorphous carbon, 52.1 + 29.1 x 2 = 110.3. From the foregoing

considerations, it may be inferred that the acetylene-oxygen blowpipe can

be regarded as a device for burning gaseous carbon in oxygen; but were it

possible to obtain carbon in the state of gas and so to lead it into a

blowpipe, the acetylene apparatus should still be more powerful, because

in it the temperature would be raised, not only by the heat of formation

of carbon monoxide, but also by the heat attendant upon the dissociation

of the acetylene which yields the carbon.

Acetylene requires 2.5 volumes of oxygen to burn it completely; but in

the construction of an acetylene-oxygen blowpipe the proportion of oxygen

is kept below this figure, viz., at 1.1 to 1.8 volumes, so that the

deficiency is left to be made up from the surrounding air. Thus at the

jet of the blowpipe the acetylene dissociates and its carbon is oxidised,

at first no doubt to carbon monoxide only, but afterwards to carbon

dioxide; and round the flame of the gaseous carbon is a comparatively

cool, though absolutely very hot jacket of hydrogen burning to water

vapour in a mixture of oxygen and air, which protects the inner zone from

loss of heat. As just explained, theoretical grounds support the

conclusions at which Fouché has arrived, viz., that the temperature of

the acetylene-oxygen blowpipe flame is above that at which hydrogen will

combine with oxygen to form water, and that it can only be exceeded by

those found in a powerful electric furnace. As the hydrogen dissociated

from the acetylene remains temporarily in the free state, the flame of

the acetylene blowpipe, possesses strong reducing powers; and this,

coupled probably with an intensity of heat which is practically otherwise

unattainable, except by the aid of a high-tension electric current,

should make the acetylene-oxygen blowpipe a most useful piece of

apparatus for a large variety of metallurgical, chemical, and physical

operations. In Fouché's earliest attempts to design an acetylene

blowpipe, the gas was first saturated with a combustible vapour, such as

that of petroleum spirit or ether, and the mixture was consumed with a

blast of oxygen in an ordinary coal-gas blow-pipe. The apparatus worked

fairly well, but gave a flame of varying character; it was capable of

fusing iron, raised a pencil of lime to a more brilliant degree of

incandescence than the eth-oxygen burner, and did not deposit carbon at

the jet. The matter, however, was not pursued, as the blowpipe fed with

undiluted acetylene took its place. The second apparatus constructed by

Fouché was the high-pressure blowpipe, the theoretical aspect of which

has already been studied. In this, acetylene passing through a water-seal

from a cylinder where it is stored as a solution in acetone (_cf._

Chapter XI.), and oxygen coming from another cylinder, are each allowed

to enter the blowpipe at a pressure of 118 to 157 inches of water column

(_i.e._, 8.7 to 11.6 inches of mercury; 4.2 to 5.7 lb. per square

inch, or 0.3 to 0.4 atmosphere). The gases mix in a chamber tightly

packed with porous matter such as that which is employed in the original

acetylene reservoir, and finally issue from a jet having a diameter of 1

millimetre at the necessary speed of 100 to 150 metres per second.

Finding, however, that the need for having the acetylene under pressure

somewhat limited the sphere of usefulness of his apparatus, Fouché

finally designed a low-pressure blowpipe, in which only the oxygen

requires to be in a state of compression, while the acetylene is drawn

directly from any generator of the ordinary pattern that does not yield a

gas contaminated with air. The oxygen passes through a reducing valve to

lower the pressure under which it stands in the cylinder to that of 1 or

1.5 effective atmosphere, this amount being necessary to inject the

acetylene and to give the previously mentioned speed of escape from the

blowpipe orifice. The acetylene is led through a system of long narrow

tubes to prevent it firing-back.

Acetylene, the Principles of Its Generation and Use A Practical Handbook on the Production, Purification, and Subsequent Treatment of Acetylene for the Development of Light, Heat, and Power · 第 19 / 22 章

When all the fittings, burners excepted, have been connected, the whole