Chapter XII: Gaseous and Liquid Fuels (1)

=Gaseous and Liquid Fuels.=--Gaseous and liquid fuels used for domestic illumination and heating may be divided into three general classes--coal gas, including carburetted water gas and producer gas and their various mixtures; oil gas, acetylene and gasoline gas. Of these the first is the most important as an illuminating gas, while for industrial and domestic purposes producer gas is of no importance as a fuel gas. Gasoline, acetylene and oil gases are generated and used to a remarkable extent in isolated dwellings as fuel and for illumination.

The value of any gas for domestic purposes will depend on the amount of heat that is produced when it is burned. In the earlier days of its use coal gas was employed entirely as an illuminant and its value was expressed in illuminating power; at the present time the standard often prescribed by regulation is that of its illuminating capability and is stated in candlepower. There is, however, a tendency to establish the more consistent standard of expressing the value of gas by its heat value. The reasons for this is the general use of mantle gas burners which depend on the heating value alone for their efficiency and the fact that coal gas is very extensively used for domestic fuel.

=Coal Gas.=--Coal gas is derived from the solid hydrocarbons of coal transformed into the more convenient, gaseous form of fuel by means of distillation. Coal gas was first made by distilling coal from an iron pot over a fire and to some extent this is still the principle of the present practice. The gas as it comes from the retort is subjected to a refining process of washing and scrubbing to remove the undesirable properties when it is stored in a large gasometer for distribution through pipes to its places of use. Coal gas is now used largely for fuel as well as for lighting. Unless the heating value of gas is regulated by law in any community and determinations of its quality are made regularly by some competent official, the amount of heat contained in coal gas is entirely at the option of the manufacturer and manager’s conscience. The value as given in the table on page 252 is the number of B.t.u. coal gas should contain. The heating value of any gas is determined by burning the gas in a calorimeter made expressly for the measurement of the heat of combustion for each foot of the gas consumed.

=All-oil Water Gas.=--In places where an abundant supply of cheap oil is available, all-oil water gas has met with a great deal of favor. It is made by atomizing crude oil by a blast of steam in a heated chamber where a combination of the vaporized oil and steam form a gas. In general the gas resembles coal gas and as given in the table on page 252 is slightly higher in heating value.

=Pintsch Gas.=--One of the commercial adaptations of oil gas is that of the Pintsch process of compressing the gas in tanks for transportation. In the Pintsch process, the gas is subjected to a pressure of 10 atmospheres--about 150 pounds. This condensation permits a sufficiently large volume of gas to be stored in tanks as to make possible the lighting of railroad trains, etc., by gaslight. The pressure of the gas is reduced by an automatic regulating valve to that required by the burner. The flame is very much the same as that produced by coal gas.

=Blau Gas.=--Another commercial adaptation of oil gas is that known as Blau gas. In this process of storage the gas is subjected to 100 atmospheres of pressure--about 1500 pounds. This pressure is sufficient to liquefy the gas and as a result a large amount can be transported in a relatively small space. According to Fulweiler 1 gallon of the liquefied gas will yield about 28 cubic feet of the expanded gas and there will remain a residue that may run up to 9 per cent.

=Water Gas.=--When the vapor of water is brought into contact with incandescent carbon, the water is decomposed and sufficient carbon is absorbed to produce a fuel gas. Its manufacture depends on the decomposition that takes place when steam is blown into a bed of incandescent coal. The gas made by this reaction is a water gas, but due to the fact that when burned it gives a blue flame, it is known as “blue gas.” It has a heating value of about 300 B.t.u. per cubic foot, and as compared with coal gas which gives 622 B.t.u. per cubic foot, would be reckoned at about one-half its value as a heating agent. Blue gas may be rendered luminous by the addition of some hydrocarbon that will liberate free carbon in the flame when burned. This is accomplished in the process of manufacture by the addition of vaporized oil.

The following table as stated by Fulweiler gives the heating values of the gases commonly used for domestic purposes in British thermal units per cubic foot.

Coal gas. 622 B.t.u.
Carburetted water gas 643 B.t.u.
Pintsch gas. 1,276 B.t.u.
Blau gas. 1,704 B.t.u.
All-oil water gas 680 B.t.u.
Acetylene gas 1,350 B.t.u.
Gasoline gas. 514 B.t.u.
Oil gas 1,320 B.t.u.
Blue water gas 300 B.t.u.

The cost and calorific values as computed by Dr. Willard of the State Agricultural College of Kansas, given below, shows the relative values of various kinds of domestic fuels.

Cost per Cal. per Cal. for
pound Gram 1 cent
cents

Wood, 20 per cent. H.O. $ 5.00 per cord 0.167 2.3 7,620
Bitu. coal $ 4.25 per ton. 0.213 7.5 16,009
Ant. coal $12.50 per ton 0.625 6.0 4,354
Gasoline, sp. gr. 68 $ 0.14 per gallon,
5⅔ pounds. 2.470 10.0 1,846
Kerosene, sp. gr. 80 $ 0.11 per gallon,
6⅔ pounds. 1.650 10.0 2,753
Coal gas, 1.50 per 1000 cubic feet. 3.100 20.0 2,927
Alcohol, 90 per cent., 50 per gallon, 7.140 6.4 404
7 pounds
Electricity, 0.15 per kilowatt-hour 57.4

The relatively high heat value of Blau gas (1704 B.t.u.) and the fact that it may be reduced to a liquid form for transportation has resulted in the manufacture of small lighting plants that may be used in places where other forms of liquid or gaseous fuel are not desirable.

For transportation the gas is compressed in seamless, steel bottles that contain about 20 pounds of liquid. The charged bottles are shipped to the consumer and when empty are returned to the manufacturers to be refilled.

The entire plant--ready to be attached to the distributing pipes in the house--is contained in a steel cabinet. The charged tanks are attached to a larger tank into which the liquid gas is first expanded. This expansion is accomplished by an automatic valve that maintains a constant pressure in the large tank. With this plant the lamps and burners of the stoves are operated as with city gas--no generating or preliminary preparation being necessary. As soon as the bottles are exhausted they are replaced by others and the empty bottles are shipped to the factory to be refilled.

=Measurement of Gas.=--When gas of any kind is purchased from a manufacturing company, the amount used is measured by a gas meter, located at the point where the gas main enters the building. The readings of the meter are taken by the company at stated intervals and the amount registered is charged to the account of the consumer. Gas is sold in cubic feet and is so registered by the meter. The price is quoted by the manufacturers at a definite rate per thousand cubic feet. The difference between the last two readings of the meter furnishes the amount from which the gas bill is reckoned.

The occupants of a building are responsible for all gas registered by the meter and, therefore, should be acquainted with the conditions under which the gas is sold. Gas bills are often the subject of dispute because of failure to understand the period of time covered by the amount claimed; again, the varying length of days due to the season of the year has a pronounced effect on the amount of gas consumed. Lack of care in the economical use of gas is probably the most prolific cause of disputed bills.

The amount due for gas may at any time be checked by the consumer who keeps a record of the meter readings. At any time the correctness of a meter is doubted, arrangement may be made with the gas company to have it tested for accuracy. This is done in the office of the company, by attaching the meter to a measuring device--called a meter prover--in which a definite measured amount of gas is passed through the meter and comparison made with meter registration. If it is found that the meter does not register correctly, the gas company is in duty bound to make good the difference. If, however, the meter is found to be correct, it is customary to charge for the services of proving the meter.

=Gas Meters.=--The gas meter as ordinarily used is shown in Fig. 177. In Fig. 178 the same meter is shown with the top and front exposed.

The meter is operated by the pressure of the gas which enters at the inlet pipe on the left-hand side of the meter as you face the index. The gas from this pipe comes into the valve chamber and passes alternately into the diaphragms and their chambers, as the valve ports _V_ are opened and closed by the action of the meter. The movement of the valve in opening the port which admits gas to the diaphragm closes the port to the chamber which has filled. The gas entering the diaphragm expands it like a bellows and forces the gas out of the chamber, through the middle part of the valve into the outlet pipe _F_. While this action is going on, the gas is entering the case compartment on the opposite side of the meter and also forcing the gas from its diaphragm through the opening _F_.

While the meter is in operation, one of the diaphragms and one of the case compartments are filling while the others are emptying. The movement of the diaphragm discs is transformed to the recording dial by the connecting levers shown at the top of the figure. The movement of these levers is such as to produce a rotary motion to a tangent which is attached to a shaft that operates the recording dial. The tangent is carried around in a circle by the action of the arms and its movement is registered on the index of each cycle of the diaphragms.

The measurement is accomplished by the displacement of a definite amount of gas with each movement of the discs; first, from the chamber and then from the diaphragms.

HOW TO READ THE INDEX

The index of a gas meter looks quite complicated, but it is really a very simple contrivance. The small circle on the top in Fig. 177 is for testing purposes only and need not be considered. The dial of Fig. 177 is shown in Fig. 177_A_. The first circle, marked 1 thousand, registers 100 feet for each figure, 1000 feet for the entire circle. If the pointer stood on 9 it would mean 900 cubic feet. The second circle registers 1000 for each figure, or 10,000 for the entire circle. When the pointer of the first circle has been around once, it reaches 0 on that circle, but the hand on the second has moved to figure 1, showing 1000 feet used. The process goes on until the pointer of the second circle has traveled around and stands at zero. The pointer on the third circle, however, has moved to 1, indicating 10,000. This explanation shows the general plan of the index. A few minutes study of it will render the index as easy to read as the face of a clock. Of course, the pointers do not always stand exactly on the figures as they move from figure to figure as the gas is used.

Suppose your index stood like this:

Take the figure 3 on the 100 thousand circle, the figure 8 on the 10 thousand, and the figure 6 on the 1 thousand, and you have 30,000, 8000, and 600, or 38,600 feet. To ascertain the quantity of gas used in the time elapsing between the readings of the meter, subtract the quantity registered at the previous reading. Thus, if the previous reading was 38,600 feet, and the next reading 40,100 feet, the pointers standing thus:

You have 40,100
Subtract your last reading 38,600 and you find
------
that your bill should be for 1,500 feet
]

When 100,000 feet have been passed, the index is at zero; that is, all the pointers stand at 0, and the registration begins all over again.

=Prepayment Meters.=--In many places it is desirable to sell gas in small quantities and to prepay the amount for a given supply of gas. This is accomplished by a meter such as that of Fig. 179. The meter is constructed much the same as the former but provided with a mechanism such that when a coin--usually 25 cents--is deposited, according to the printed directions in the instrument, an amount of gas representing the proportional current rate is allowed to pass the meter. The supply is cut off as soon as the amount paid for is used; when in order to receive more gas, another coin must be deposited as before.

=Gas-service Rules.=--The rules for the regulation of gas service are in many States under the control of a board or commission whose duty it is to form codes prescribing the measurement and sale of all public utilities. The following form, General Order No. 20, State Public Utilities Commission of Illinois, gives an idea of the requirements in that State for the sale of coal gas.

RULE 3. REQUEST TESTS.--Each utility furnishing metered service
shall make a test of the accuracy of any meter, upon written
request by a consumer: Provided, first, that the meter in question
has not been tested by the utility or by the commission within 6
months previous to such request; and second, that the consumer
will agree to accept the result of the test made by the utility
as determining the basis for settling the difference claimed.
No charge shall be made to the consumer for any such test. A
report, giving the result of every such test, shall be made to the
consumer.

RULE 4. ADJUSTMENT OF BILLS FOR METER ERROR.--If on any test of a
service meter, either by the utility or by the commission, such
meter shall be found to have a percentage of error greater than
that allowed in Rule 11 (see below) for gas meters, the following
provisions for the adjustment of bills shall be observed.

(_a_) _Fast Meters._--If the meter is faster than allowable, the
utility shall refund to the consumer a percentage of the amount of
his bills for the 6 months previous to the test or for the time
the meter was installed, not exceeding 6 months, corresponding
to the percentage of error of the meter. No part of a minimum,
service or demand charge need be refunded.

(_b_) _Slow Meters._--If the meter is found not to register or to
run slow, the utility may render a bill to the consumer for the
estimated consumption during the preceding 6 months, not covered
by bills previously rendered, but such action shall be taken only
in cases of substantial importance where the utility is not at
fault for allowing the incorrect meter to be in service.

RULE 11. GAS-METER ACCURACY.--(_a_) _Method of Testing._--All
tests to determine the accuracy of registration of a gas service
meter shall be made with a suitable meter prover. At least two
test runs shall be made on each meter, the results of which shall
agree with each other within one-half per cent. (1/2%).

(_c_) _Allowable Error._--Whenever a meter is tested to determine
the accuracy with which it has been registering in service, it may
be considered as correct if found not more than two per cent. (2%)
in error, and no adjustment of charges shall be entailed unless
the error is greater than this amount.

RULE 15. HEATING VALUE.--Each utility furnishing manufactured
gas shall supply gas which at any point at least 1 mile from the
plant, and tested in the place where it is consumed, shall have a
monthly average total heating value of not less than 565 B.t.u.
per cubic foot, and at no time shall the total heating value of
the gas at such point be less than 530 B.t.u. per cubic foot.

To arrive at the monthly average total heating value, the results
of all tests made on any one day shall be averaged and the average
of all such daily averages shall be taken as the monthly average.

RULE 8. RAILROAD COMMISSION OF WISCONSIN.--Each utility furnishing
gas service must supply gas giving a monthly average of not less
than 600 B.t.u. total heating value per cubic foot, as referred
to standard conditions of temperature and pressure. The minimum
heating value shall never fall below 550. The tests to determine
the heating value of the gas shall be made anywhere within a
1-mile radius of the center of distribution.

=Gas Ranges.=--Gas ranges and all other heaters using gas as a fuel are constructed to utilize the principle of the Bunsen burner. Fig. 180 illustrates the type of burner used in the Jewel gas range. This represents the form adapted to the top burners for all direct-contact cooking or heating. The burners are of different sizes and arranged as they appear in Fig. 181. This picture shows the top of the range as seen from above, looking directly downward. The gas supply pipe and individual valves for each burner are in position as they appear in front of the range.

FIG. 181. FIG. 182.

FIG. 181.--Showing top burners and valve attachment of a gas stove.

FIG. 182.--Section showing arrangement of oven burners and lighter of a gas oven.]

In operation, the nozzles of the gas valves stand directly in front of the opening _G_, in Fig. 180. The stream of gas in passing into the burner induces a flow of air through the opening _A_. The mixture of gas and air is such as will burn with the characteristic Bunsen flame without smoke.

The oven burners are different in form but the individual flames are the same as those of the top burners. They extend across the oven as shown in Fig. 182. In this the top of the oven is removed and burners as seen are viewed from above.

The top burners are lighted by direct application of a burning match but the oven burners must be lighted by first igniting a special torch or “pilot lighter.” The middle gas valve of Fig. 182 is turned and the torch lighted, then the other valves are opened and the jets are instantly ignited. As soon as they are burning the pilot lighter is extinguished by turning its valve.

The reason for this special lighter is because of the possibility of explosion at the time of lighting. The gas from the jets is mixed with air at the proper proportion to be violently explosive and if by chance the gas should be turned on a sufficient time to fill the oven with this explosive mixture and then lighted, an explosion would be certain, with every possibility of disastrous consequences. All gas ovens should be lighted in a manner similar to that described.

=Lighting and Heating with Gasoline.=--The remarkable growth of modern cities, the building of small towns in the west, and the improvement in suburban and rural homes has created a demand for efficient means of illumination in the form of small household lighting plants. The development and improvement in electric lighting has induced an equal, if not greater, improvement in gas lighting. Up to the year 1875, the open-flame gas jet represented the most improved form of city lighting. Then came electricity, which for a time bade fair to supplant all other forms of illumination; but the relative high cost of electric lighting, even with the advantages it afforded, was a stimulus to improvement in less expensive forms of illuminants.

The invention of the incandescent-mantle gas burner enormously increased the opportunities for gas lighting and opened an inviting field of endeavor. In a relatively short time, three distinct types of gasoline lighting plants for household illumination came into common use, with a great number of different systems in each type. As a means of economical illumination the only rival of any consequence to the small gasoline-gas plant of today is acetylene. The dangers attending the use of these agents of illumination have been rapidly eliminated, until today--when intelligently managed--they are fully as safe as any other means of artificial lighting. Gasoline plants are now in common use in cities where competition with all other forms of illumination require excellence in service to hold an established place.

In order that any mechanical appliance may be used with the best results, its principle of operation and mechanism must be thoroughly understood. In the case of gasoline plants, not only familiarity with the mechanism should be acquired but an intimate knowledge of gasoline and its characteristic properties should be gained, that the peculiarities of the plant may be more fully comprehended.

=Gasoline= is the first distillate of crude petroleum; that is, in the process of separation, the crude petroleum is distilled from a retort and the condensed vapors at different degrees of temperature form the various grades of gasoline, kerosene, lubricating oil, paraffin, etc. The crude oil is placed in the still and heated; the distillate that first comes from the condenser, at the lowest temperature of the still, is gasoline of a light spiritous nature. As the process of distillation continues, this part of the petroleum is entirely driven off and it is necessary to raise the temperature of the still in order to vaporize an additional portion of the oil. There is no distinct line of separation between the gasoline that first comes from the condenser and that which comes over after the temperature is raised, except that it is less of a spiritous nature and contains more oily matter. As the temperature of the retort is gradually raised, the distillate contains less and less of the spiritous and constantly more of the oily matter.

In order to grade gasoline for the market, the standard adopted was that of relative density. The distillations produced at various temperatures are mixed to produce various densities which form definite grades of gasoline. The Beaumé hydrometer is a scale of relative specific gravities in which the different densities are expressed in degrees. The highest grade of gasoline produced by the first distillation is 90°Bé.; that is, the hydrometer will sink in the gasoline to 90° on the scale. As the temperature of the retort is gradually raised, the distillate becomes heavier and the next commercial grade is 86° gasoline. The 86° gasoline contains a greater proportion of oily matter and a less amount of that of a spiritous nature. The next commercial grade that is produced, as the temperature is raised, is 76° gasoline, a still highly volatile spirit but containing more oil than the last. This process is kept up until there is an amount of oil in the distillate that can no longer be termed gasoline, when kerosene is distilled from the retort.

The following descriptions of gasoline and kerosene by B. L. Smith, State Oil Inspection Chemist of North Dakota, gives a definite idea of their properties and the requirements of the law in their regulation and sale.

“Gasoline is formed by the condensation of vapor that passes
off at comparatively low temperatures during the distillation
of crude petroleum. It has been common practice among refiners
to collect as ‘straight’ gasoline all that distillate having
a specific gravity above 60°Bé. At present, the name applies
broadly to all the lighter products of petroleum above 50°Bé. in
gravity, including products obtained from the ‘casing-head’ gases
of oil wells, by methods of compression and cooling, and also the
‘cracked’ gasoline formed by the decomposition of heavier oils
when subjected to high temperature and pressure.

“It has been the custom to grade and sell gasoline according to
‘high’ or ‘low’ gravity test. Recent study and investigation has
shown that specific gravity in itself is of very little value in
determining the quality of a gasoline. It may be taken as an index
of other properties, particularly its volatility, if information
as to its source and method of production are at hand; but under
present market conditions a specific-gravity determination is
entirely inadequate. The specific-gravity test alone may give a
high rating to a poor gasoline and a low rating to a good one. It
has been discarded as a standard of comparison by the U. S. Bureau
of Mines. It indicates nothing definite about the quality of a
gasoline and in many cases it does not even approximate relative
values. Volatility, that is, the ease with which it vaporizes, is
the fundamental property that determines the grade, quality, and
usefulness of gasoline. The Beaumé test, however, must remain the
standard for grading gasolene until a more definite measure is
adopted.

“The Oil Inspection Law (1917) for the State of North Dakota,
states, that: ‘all gasolines, sold or offered for sale in
this State for household use, shall, when one hundred cubic
centimeters are subjected to a distillation in a flask--as
described for distilling of oil--show not less than three (3) per
cent. distilling at one hundred and fifty-eight (158) degrees
Fahrenheit, and there shall not be more than six (6) per cent.
residue at two hundred and eighty-four (284) degrees Fahrenheit,
which shall be known as the chemical test for gasoline sold or
offered for sale in this State for domestic purposes.’

“Gasoline for household purposes, as for use in cold-process
lighting systems should contain not more than a very slight amount
of constituents that do not vaporize readily. It is obvious that
a gasoline for cleaning or drying purpose should contain no oily
or kerosene distillate. On the other hand, the gasoline for use
in a gasoline stove or other generator, where heat is employed in
its vaporization, may contain a considerable amount of the less
volatile oils. The amount of gasoline sold for household use is
in very minor proportion to the immense quantity used for motor
purposes.

“No hard and fast line differentiates good motor gasoline from
bad. In fact standards of quality seem to be varying with advances
in engine design, so that what once was poor gasoline can now be
successfully used. Improvement in carburetors seem to be keeping
pace with the ever increasing amount of kerosene in the ordinary
motor gasoline.

“Gravity test cannot be relied upon as indicating the kerosene
content. In the laboratories of the Oil Inspection Department for
the State of North Dakota, there have been examined two gasolines
of the same gravity, 56.2°Bé. at 60°F., but which contains 31
per cent. and 62 per cent. of kerosene respectively, and their
distillation range is quite different. On the other hand, there
are other gasolines whose boiling range is nearly parallel
and similar, yet whose gravities are 50.2°Bé. and 59.2°Bé.
respectively. Also a gasoline and a kerosene having a difference
in gravity of but 1°Bé. and a difference of nearly 100°F. in the
temperature at which they begin to boil and a difference at 200°F.
in the temperature at which all had distilled over. The so-called
‘low’-test gasolines average between 35 per cent. and 40 per
cent. kerosene. The chief element of advantage in the so-called
‘high’-test gasolines seems to be that they yield a maximum
efficiency over a larger range of engine conditions.

“We have a sample of gasoline sold as ‘high’-test gasoline which
contains 29 per cent. of kerosene. Indeed it has a high Beaumé
gravity (63.70) compared to the average low-gravity gasolines on
the market, and it also contains a large amount (14 per cent.)
of very easily volatile constituents. Such a product seems to be
a blend of very light ‘casing-head’ stock with kerosene of low
boiling range to give the ‘high’ gravity.

“It is desirable that a gasoline should contain a certain
percentage of very low-boiling constituents, so that engines
may start more readily, especially in unfavorable conditions of
weather or climate; but a large proportion would be undesirable
because of loss through evaporation and the liability of
accidental ignition and explosion. A reasonable amount of light
volatile material would probably be about 3-1/2 per cent. Again a
reasonably low percentage of the very less volatile constituents
is desirable to insure complete vaporization at a not too high
temperature, say not more than 10 per cent.; but such a gasoline
would be expensive. The producers and refiners claim that the
present immense demand necessitates the mixture of low-boiling
kerosene constituents with the true gasoline fraction.

=“Kerosene.=--The character of this fuel is best understood by
comparing it with gasoline, which it in general resembles, except
that it is much less volatile. It is obtained from crude petroleum
at a temperature just above that (300°F.) at which gasoline passes
off. Its chief use is as an illuminant in lamps. It is also
increasingly used as a fuel in cooking stoves, small portable
heaters, and as a motor fuel for engines and tractors.

“The laws of most States stipulate certain tests which kerosene
must meet in order to be approved for general sale. These tests
include color, flash point, fire test, sulphur determination, and
candlepower tests. The North Dakota Oil Inspection Law (1917)
specifies that the color shall be water-white when viewed by
transmitted light through a layer of oil 4 inches deep. It shall
not give a flash test below 100°F. and shall not have a fire test
below 125°F. Such illuminating oils shall not contain water or
tar-like matter, nor shall they contain more than a trace of any
sulphur compound. The photometric test, when burning under normal
conditions, shall not show a fall of more than 25 per cent. in
candlepower in a burning test of not less than 6 hours nor more
than 8 hours’ duration, consuming 95 per cent. of the oil.

“The flash point of an oil is the lowest temperature at which
vapors arising therefrom ignite, without setting fire to the oil
itself, when a small test flame is quickly approached near the
surface in a test cup and quickly removed.

“The fire test of an oil is the lowest temperature at which the
oil itself ignites from its vapors and continues to burn when a
test flame is quickly approached near its surface and quickly
removed.

“When oils containing sulphur are burned, the sulphur is thrown
off in the form of gaseous sulphur compounds. Because of their
poisonous nature and their bleaching and disintegrating action on
clothing, hangings, wall coverings, etc., it is obvious that to
safeguard the health and preserve the furnishings of the home,
illuminating oils should contain not more than a trace of sulphur
compounds, and that their flash and fire limits should be high
enough to insure safety in ordinary use in lamps and stoves.

“The law further specifies as to the boiling limits of kerosene:
‘It shall be the duty of the State Oil Inspector ... to have
chemical tests made ... demonstrating whether or no such oils
contain more than 4 per cent. residue after being distilled at a
temperature of 570°F., and shall not contain more than 6 per cent.
of oil distilling at 310°F., when one hundred cubic centimeters of
the oil is distilled from a side-neck distilling flask’ of certain
specified dimensions.

“This is to insure the kerosene against an excess of easily
inflammable material of the gasoline range and thus render it
dangerous to the user. In addition it is to insure against
an undue proportion of heavy constituent of lubricating oil
distillate, which would clog the wick and reduce the efficiency,
heating and illuminating value of the oil.”

LIGHTING AND HEATING WITH GASOLINE

The extended use of gasoline as a lighting and heating agent, has brought about the development of a great number of mechanical devices that are intended to furnish the house with an efficient source of illumination and at the same time provide the kitchen with a convenient and relatively inexpensive fuel. These machines are generally simple in mechanical construction and so designed as to eliminate most of the dangers involved in the use of gasoline. In operation, they require a minimum amount of attention when suited to the purpose for which they are intended. That the object of the plants is attained is attested by the great number in use and the degree of satisfaction afforded the users.

The three systems of gasoline lighting referred to above are known commercially by terms which are characteristic of the process involved:

1. The _cold-process_ system, in which the gasoline is vaporized, at the temperature of an underground supply tank, and after being mixed with the required amount of air is sent through the building in ordinary gas pipes exactly as in the case of city gas.

2. The _hollow-wire_ system, in which the gasoline is sent from the supply tank to the burners in a liquid form, where it is vaporized by heat and the vapor mixed with the necessary air to afford complete combustion.

3. The _central-generator_ or _tube_ system, in which the gasoline is sent to a central generator from a supply tank and there vaporized by heat, at the same time being mixed with air in sufficient amounts to render it a completely combustible gas without further dilution.

THE COLD-PROCESS GAS MACHINE

The gas machine of the cold-process type is so constructed that air is forced through a tank or carburetor, containing gasoline and remains in its presence until saturated with gasoline vapor. This saturated air is afterward diluted with additional air, to produce a quality of gas that contains proportions of air and gasoline vapor which will produce complete combustion when burned with an open flame.

Combustion is a rapid chemical change in which heat is evolved due to the union of carbon and oxygen. If the carbon is completely oxidized, the combination produces carbon dioxide (CO₂) and the greatest amount of heat is evolved.

Gasoline being a highly volatile liquid will vaporize at temperatures as low as -10°F., but as the temperature is higher vaporization will be more rapid. In a confined space, at relatively low temperature, such as the carburetor of a gas machine, the vaporization will at first be very rapid; but after the more highly spiritous portion has been evaporated, a considerable part, even of the lighter grades, will be vaporized very slowly. In the cold-process machines, only the lighter grades can be used with success and even then, in inefficient machines, a portion of the lesser volatile gasoline will have to be thrown away. For this reason and for others that will appear later, it is advisable to consider very closely the working properties of the entire plant.

In order to obtain gas that will always be of the same quality and at the same time use gasoline in an efficient manner, the gas machine must be composed of three essential parts: the blower, the carburetor and the mixer.

The blower is that part of the machine which supplies air for absorbing the gasoline vapor and maintaining a constant pressure on the system. It is usually made in the form of a rotary pump, the motive power for which is a heavy weight. The pump may, however, be driven by water pressure furnished by city water pipes or other water supply.

The carburetor is a tank which contains the supply of gasoline and is so constructed as to permit the air from the blower to most readily take up the gasoline vapor. It should be so arranged that when the contained gasoline becomes old and less volatile, the air may remain in its presence a sufficient time to become saturated by slow absorption.

The mixer is that part of the machine which regulates the amount of gasoline vapor contained in the gas entering the distributing pipes. In order to satisfactorily perform its function, it should be so arranged as to permit a constant amount of gasoline vapor to enter the mixture which composes the finished gas. This amount should be such as to produce a bright clear flame in an open gas jet. If the gas contains too great an amount of gasoline vapor, the flame will smoke. If too little gasoline vapor is present, the flames will be pale and lacking in heat.

1 Carburator
2 Mixer
3 Blower
4 Weight
5 Gas Range
6 Water Heater
7 Water Tank

FIG. 183.--Cold-process system of gasoline lighting with kitchen range and water heater.]

In Fig. 183, the entire plant is shown in place. It occupies a place inside the building, usually in the basement. In the figure the carburetor is marked 1; the mixer 2 stands at the end of the blower, which is numbered 3. The motive power of the blower is furnished by a heavy weight, which is raised by a block and tackle, the cord of which is attached to the drum and fastened to the shaft of the blower. The force furnished by the weight 4 drives the blower and maintains a constant pressure on the gas in the system. The pipe 8 conducts the air from the blower to the carburetor, which is located underground, below the frost line and 25 or 30 feet away from the building.

The carburetor in this case is also the storage tank, as shown in detail in Fig. 184. The carburetor is divided laterally into two or more compartments, depending on the size of the plant to be accommodated. That shown in Fig. 184 contains four compartments and is intended for a large plant. The construction is such that the compartments are only partly filled with gasoline, and arranged to permit the air from the blower, which enters at the pipe marked air, to pass through each compartment in succession, beginning at the bottom, in order that it may become completely saturated with gasoline vapor. As an additional means of aiding the saturation of the passing air, the compartments in this carburetor are provided with spiral passages through which the air must pass, so that when it reaches the outlet pipe, marked gas, the air is completely filled with gasoline vapor.

The vapor-saturated air now leaves the carburetor by pipe 9, in Fig. 183, and enters the mixing chamber 2, where it is mixed with the required amount of atmospheric air, to make it completely combustible when burned at the burner.

The mixing chamber is shown in detail in Fig. 185. The mixing is done automatically and the quality of the gas is uniform, regardless of the varying conditions of the attending temperature and the quality of the gasoline in the carburetor.

The vitally important feature of any gas machine is, that a constant amount of gasoline vapor be carried to the burners. If the gas contains too great an amount of gasoline vapor, a smoky flame will be the result; if an insufficient amount of gasoline is present, the flame will be pale and give out little light. When freshly charged, the gasoline in the carburetor will vaporize very readily, and a large amount of air must be added to the gas to reduce it to the proper consistency; but from old gasoline, which has lost most of the highly volatile matter, a smaller proportion of atmospheric air will be demanded. For this reason, a mixing regulator that will always deliver gas containing the same amount of gasoline vapor is necessary to give satisfactory service. The mixer shown in Fig. 185 accomplishes this office by reason of the specific gravity of the gas.

As the air in the carburetor takes up gasoline vapor, its specific gravity is increased until the air is saturated; and by adding the amount of atmospheric air necessary for complete combustion the weight is reduced to a definite amount which will be constant. The required mixture will, therefore, always weigh the same amount. The principle on which this mixer works is that described in physics as the principle of Archimedes: “that a body immersed in a fluid will lose in weight an amount equal to the liquid displaced.” In the application of the law, the gas in the mixer is the fluid, and the float--to be described--is the displacing body.

The mixer in Fig. 185, is shown cut across lengthwise. The outside casing is indicated by the heavy black lines. The gas which leaves the opening at the top--marked gas outlet--is a mixture of gasoline and air that may be used for exactly the same purpose and in the same manner as coal gas. It may be used in open-flame gas jets or in the mantle gas lamps for lighting purposes and also as fuel gas for domestic heating. The gas is distributed through the building in ordinary gas pipes which are installed as for any other kind of gas. In Fig. 183 the distributing pipes are indicated by the heavy lines.

The valve in the air inlet, in the bottom of the mixer, controls the amount of air to be admitted. The entering gas from the carburetor being heavier than the desired mixture, will raise the float and in so doing will open the air valve and allow the air from the blower to enter. The float and valve are so adjusted that the desired mixture is attained when the balance beam is level. Any variation in the mixture will change its weight and the valve corrects the change whether it be too much or too little air.

The openings at the bottom, marked _gas inlet_ and _air inlet_, are intended for the admission of the saturated vapor from the carburetor, and the atmospheric air, as required. The float which fills the greater part of the inner space is a light sheet-metal drum, that is tightly sealed and nicely balanced by a counterweight on the opposite end of the suspending bar. The counterweight is made adjustable by the device marked _movable adjusting weight_--in the drawing--which permits the quantity of entering gas to be slightly changed as the gasoline in the carburetor grows old.

The adjustment of the counterweight to suit the gas given off from old gasoline in the carburetor, and the occasional rewinding, to elevate the blower weight, is practically all the attention this plant requires. It is a real gas plant which gives every service that may be obtained from coal gas.

THE HOLLOW-WIRE SYSTEM OF GASOLINE LIGHTING AND HEATING

The hollow-wire system of gasoline lighting possesses the advantage of simplicity in construction and ease of installation that makes it attractive, particularly for use in small dwellings. The ease with which plants of this character are installed in buildings already constructed and its relatively low cost has made it a popular means of lighting. The same principle as that used in the hollow-wire system is applied to portable gasoline lamps in which a remarkably convenient and brilliant lamp is made to take the place of the customary kerosene lamp. Small portable gasoline lamps are now extensively used for the same purpose as ordinary oil lanterns. These lamps are convenient as a source of light, make a handsome appearance and are relatively inexpensive to operate.

The hollow-wire system as commonly employed is illustrated in Figs. 186 and 187. In the gravity type of the system as illustrated in Fig. 186, the supply of gasoline is stored in the upper part of the house in a tank _T_ and conducted to the burners below, through a system of small copper tubes as indicated by the heavy lines in the drawing. The same tank is used to supply the gasoline for the stove _R_ in the kitchen and the lamps _L_ in the different apartments. The gasoline supply in this case, is obtained entirely by gravity. This type of plant is not approved by the National Board of Underwriters but its use is quite generally permitted. The storage of gasoline in this form should be done with caution as carelessness or accident might lead to serious results. With an arrangement of this kind the force of gravity gives the pressure which supplies the burners below but it would not be possible to use the lamps on the same floor with the tank.

Where it is desired to use lamps on both floors, a pressure tank is employed for supplying the gasoline to the lamps, as indicated in Fig. 187. In this plant the pressure tanks _S_, _T_ in the basement, furnish the pressure which forces the supply of gasoline through the small tubes to the lamps _L_ in the different rooms and also to the stove _R_ in the kitchen.

The means of furnishing the pressure for supplying the gasoline to the burners may be a simple tank as that in Fig. 188, or the more elaborate apparatus shown in the double tank of Fig. 189. Either style will give good results but the double tank requires the least attention in operation and is therefore more satisfactory in use.

The tank in Fig. 188 is made of sheet metal of such weight as will safely withstand the pressure necessary in its use. It is arranged with an opening _E_, for filling with gasoline, a pressure gage for indicating the air pressure to which the gasoline is subjected, and two needle valves; _C_, for attaching an air pump and _D_, to which the hollow wire is attached for distributing the gasoline to the places of use. The tank is filled with gasoline to about the line _A_, and then air pressure is applied with an ordinary air pump to say 20 pounds to the square inch. This pressure will be much more than will be necessary to force the gasoline through the tubes but it is intended to last for a considerable length of time.

FIG. 188.--Simple gasoline pressure-tank.

FIG. 189.--Double-pressure tank for constant pressure service in gasoline lighting systems.]

The principle of operation is that known in physics as Boyle’s law, that “the temperature being constant, the pressure of a confined gas will be inversely as its volume.” That is, if the tank is perfectly tight, the pressure above the line _A_, in the tank, will gradually become less as the gasoline is used and when its level is at the line _B_, where the volume is twice the original amount, the pressure will be one-half what it was originally, and will still be sufficient to force the gasoline through the tubes to the lamps. It is evident that once the tank is charged and the air pressure applied it will require no further attention until a considerable part of the gasoline is consumed. If at any time the pressure in the tank becomes too low to feed the lamps, a few strokes of the pump will raise it to the required amount.

While the single tank does the required work, its use is not perfect because the pressure is constantly varying. If a lamp is set to burn at a definite pressure, any decrease in the gasoline supply due to falling pressure will change the amount of light given by the lamp; while the variation in the pressure of the single supply tank is not great, a more perfect effect is attained in the double type of tank as that of Fig. 189.

The object attained in the use of two tanks differs with different manufacturers. The tank shown in Fig. 183, being intended to maintain a constant pressure on the gasoline, is quite different from those described in Fig. 197 in use with the central-generator system of lighting, to be described later. In Fig. 189 tank No. 1 is for air supply alone and tank No. 2 is the storage tank for gasoline. Between the two tanks is a pressure-regulating valve 6-7, which keeps a constant pressure on tank No. 2 so long as the air pressure of the tank No. 1 is equal or greater than the other. The gasoline in tank No. 2 will therefore be always under the same pressure and when the lamps are once burning the gasoline supply to each lamp will be a constant amount.

Tank No. 2 is separated by the head 13 into two compartments, marked 18 and 19. The connection between the two compartments is made by the valve 15 and the connection 16. The gasoline supply for the lighting system is taken from the lower chamber at the valve marked 17.

It is possible to refill this tank with gasoline while the system is working. To accomplish this, the air supply is cut off from tank No. 1, by closing valve 9 and the valve 15 is closed to retain the pressure on the lower chamber of tank No. 2. The screw-plug is then taken from the tube 12 and the tank refilled. The screw-plug is then returned to its place, the valves 9 and 15 are again opened and the regulating valve immediately restores the desired pressure.

The amount of pressure required on the system will depend on the height to which the gasoline is carried within the building. The pressure is generally 1 pound to each foot in height and to do the best work the pressure must be constant.

These plants may serve as a fuel supply for gasoline stove as indicated at _R_ or any other source of domestic heating. The usual gravity supply tank is replaced by the hollow wire through which is the gasoline from the tank in the basement.

=Mantle Gas Lamps.=--Mantle lamps that are intended for using city gas are much the same in construction as those using the cold-process gasoline gas; the styles of mechanism differ somewhat with manufacturers but all lamps of this kind possess the essential features that are common to all. Either of these gases may be used with open-flame burners, such as Fig. 193, but since the introduction of mantle lamps, the open-flame burners are rarely used for household illumination.

In the incandescent-mantle lamp, the light is produced by heating to incandescence a filmy mantle of highly refractory material. The higher the temperature to which the mantle of a lamp is raised, the greater is the quantity of light produced. The office of the burner is to produce a uniform heat throughout the mantle with the use of the least amount of gas. As ordinarily furnished from the mains, coal gas or gasoline gas is too rich in carbon to be used in mantle lamps without dilution. When gas is burned in a mantle lamp, it must contain sufficient oxygen--which is supplied by the air--to combine completely with the contained carbon and reduce it to carbon dioxide. If insufficient air is supplied, the lamp will smoke and the mantle will soon be filled with soot.

In the use of the various gases--made from coal, gasoline, kerosene, alcohol, etc.--as a fuel for the production of either heat or light, the form of the burner in which the gas is consumed is the most important factor of the system. Without burners in which to generate a satisfactory supply of heat for the desired purposes, mantle gas lamps would never have come into common use. An understanding of the mechanism of the burners of a system is of first importance because of the possibility of the failure of the entire plant through an improper adjustment of the lamps.

If complete combustion of the gas is attained in the burner, the greatest amount of heat will be evolved and the residue will be an odorless gas, carbon dioxide (CO₂). If the gas is not completely burned the odor of the gas is noticeable in the air. Incomplete combustion may be caused by an insufficient air supply, which causes a smoky flame; or if a larger flame is used than the burner is designed to carry, some of the gas will escape unburned. In either case the greatest amount of heat is not developed by the burner.

In most burners, whether for heating or lighting--in which gas, gasoline or alcohol is used as a fuel--the principle of operation is that of the Bunsen tube. One noticeable exception to this rule is the burners used with the central-generating systems where the Bunsen tube is a part of the generator.

The gas generated from any hydrocarbon will burn completely, only after being mixed with air or other incombustible gas, in proportions such as will completely oxidize the carbon contained in the fuel.

In Fig. 190 the familiar laboratory Bunsen burner affords an excellent illustration of the Bunsen principle which forms a part of all burners using gas as a fuel. The gas from the supply pipe issues from a small opening _A_ into a tube _B_ and by the force of its velocity the entering gas carries into the tube above it a quantity of air that may be regulated by the size of the opening. If the gas is burned without being first mixed with air, the flame will be dull and smoky but if air is admitted to mix with the gas, an entirely different flame is produced, the characteristic shape of which is shown in the figure.