1210
INDUSTRIAL AND ENGINEERING CHEMISTRY
of 1000 pounds per hour on the dry basis. The air leaves a t 130’ F. Calculate (a) humidity of entering air, ( b ) humidity of exit air, (c) evaporation of water from stock in pounds per hour, (d) volume of entering air, ( e ) volume of exit air. Solution (shown on chart). (a) Connect wet- and dry-bulb temperatures of entering air with a straight line and read the humidity of the entering air on the scale a t the right-hand edge as 0.0538 pound water per pound dry air. ( b ) Since wet-bulb temperature is constant throughout drier, draw a straight line through the intersection of the line drawn to solve part (a) with the wet-bulb temperature scale and through 130’ F. on the dry-bulb scale. Read the humidity of the exit air on the right-hand humidity scale as 0.0645 pound water per pound dry air. (c) Water evaporated = lOOO(0.0645 0.0538) = 10.7 pounds per hour. (d) Connect 170’ F. on the dry-bulb temperature scale with 0.0538 on the left-hand humidity scale and read the humid volume as 17.25 cubic feet wet air per pound dry air. Volume of entering air is therefore 17,250 cubic feet per hour, (e) By similar method, volume of exit air is 16,380 cubic feet per hour.
-
Conclusion There is a similarity between line coordinate charts and the more familiar nomographic charts. The two should not
Vol. 21, No. 12
be confused, however. The five charts described in this article are examples of the wide adaptability of line coordinates to chemical engineering data. The reader may adopt this method to construct other charts to suit his particular needs. Literature Cited (1) Brodetsky, “A First Course in Nomography,” G. Bell & Sons, Ltd., London, 1920. (2) Carr and Murphy, J . A m . Chem. Soc.. 51, 116 (1929). (3) d’Ocagne, “Traite de Nomographie,” p. 158, Gauthier-Villars, Paris, 1921. (4) Grosvenor, T r a m . 4 m . Znst. Chem. Eng., 1, 184 (1912). ( 5 ) International Critical Tables, Vol. V, McGraw-Hill Book Co., Inc. (6) Leslie and Carr, IND.ENG.CHEM.,17,810 (1925). (7) Monrad and Badger, Zbid., 21, 40 (1929). (8) Partington and Schilling. “Specific Heats of Gases.” E. Benn, t t d . , 1924. (9) Rechenberg, “Distillation,” Selbstverlag von Schimmel & Co., 1923. (10) Runge, “Graphical Methods,” Columbia University Press, 1912. (11) Walker, Lewis, and McAdams, “Principles of Chemical Engineering,” p. 458, RIcGraw-Hill Book Co.. Inc., 1927. (12) Young, Sci. Proc. R o y . Dublin Soc., 12,374 (1910).
Effects of Temperature and Pressure on the Upper Explosive Limit of Methane-Oxygen Mixtures‘ C. M. Cooper and P. J. Wiezevich DEPARTMENT OF CHEMICAL EKOINEERING, MASSACHUSETTS INSTITUTE OF TECHNOLOGY. CAMBRIDGE, MASS.
A new apparatus of the make-and-break type has surprising to find that anybeen developed for the ignition of gaseous mixtures a t mentation has been done thing which alters the heat high temperatures and pressures. With this apparatus losses to the s u r r o u n d i n g s by various investigators the explosive limits of methane-oxygen mixtures have affects the explosive limits. o n t h e explosive limits of been investigated a t pressures up to 230 atmospheres methane-air mixtures a t ordiThus, by gradually decreasand temperatures up to 480’ C. ing the diameter of the tube nary temperatures and presIt has been found t h a t the lower the oxygen concenused for the determinations, sures. Recently ($) higher tration or the temperature, the higher the pressure repressures have been used with the explosive l i m i t s come quired for the successful ignition of the mixture; and the same materials, but few closer and closer together unconversely, as either pressure or temperature is indata are available for methtil finally, for v e r y n a r r o w creased, the amount of oxygen necessary to form a ane-oxygen mixtures. This tubes, it appears that there combustible mixture is decreased. A t temperatures work was u n d e r t a k e n in is no gas composition which above 400” C. spontaneous reaction begins to occur. will ignite a n d p r o p a g a t e order to obtain information Complete consumption of the oxygen does not take flame. concerning the effects of templace on the explosion of the mixtures a t high pressure. perature a n d p r e s s u r e o n Previous Work the upper explosive limit of methane-oxygen mixtures. The limits of inflammability for gases and vapors a t orThe “expl&ve limit” or “limit of inflammability” of an dinary conditions have been determined by various investiinflammable gas, vapor, or solid suspension with oxygen or gators (9, 10, $0, 33). The effect of pressures up to 10 any medium capable of supporting combustion may be atmospheres has also been studied (2, 29, 24, $5, /to),and defined as that composition which when ignited will just sup- results published after the completion of the present study (2) port its own combustion. Consider a typical case. If meth- give the effect of pressures up to 400 to 500 atmospheres ane is mixed with air a t room temperature and pressure, for various gas and vapor mixtures with air. At atmosit is found that mixtures containing less than about 5 per pheric pressure and room temperature the upper and lower cent methane will not burn. Compositions from 6 per cent limit mixtures of methane and air contain, respectively, 14.02 to 14 per cent burn when ignited, while those containing more and 5.24 per cent oxygen. At pressures below atmospheric than 14 per cent will not ignite. The composition containing the limits gradually narrow and meet a t about 9 per cent 6 per cent methane is known as the lower limit mixture. methane for a pressure of 140 mm. (20” (2.). At 10 atmosSimilarly the 14 per cent mixture is the upper limit mixture. pheres pressure the upper limit becomes 14 and the lower 6.5 When a limit mixture burns, part of the heat liberated by per cent, while a t 100 atmospheres the corresponding limits the burning of one layer of gas is used in heating the adjacent are 36 and 7 per cent. layer to the ignition temperature. The remainder of the Experiments on the effect of temperature a t low pressures heat is lost by radiation and conduction. It is therefore not have also been made (,9, 25, 38) with methane-air mixtures. The limits widen continually as the temperature is increased, 1 Received August 12, 1929.
I
1 T H E past much experi-
ISDUSTRIAL Ah'D ENGINEERING CHEMISTRY
December, 1929
MOVPBLE ELECTRODE FIXED ELECTRODE
S T E U S M E T I 31%
EXPLOSION CHAMBER AMMETER
1211
factorily when severe explosions occurred, although it withstodd static pressures of 340 atmospheres. The reaction space was cylindrical, 3.18 cm. in diameter and 3.81 cm. long. The wall surfaces were n o t p r o t e c t e d in any way, and soon formed a perceptible layer of oxides. ~ I E T HOO FD IGhmroN-The customary means of ignition has been an electrical discharge across a gap in the reaction space with some form of induction coil supplying the necessary potential difference. With this arrangement there appears to be a definite minimum amount of energy required in the spark in order to ignite a mixture at the existing conditions of temDerature and Dressure. Thus. Wheeler t4S) required about 0.5 ampere in the primary circuit of his induction coil to ignite the mixture a t 1atmosphere while a t 8 100 mm. pressure 7 amperes were required. The first series of experiments in the p r e s e n t work were made with a hightension electrical discharge employing a 0.5-kilowatt transformer, allowing the current to flow intermittently. When higher pressures than atmospheric were encountered, results became uncertain, and at pressures above 400 pounds per square inch (27.2 atmospheres) violent explosions occurred with certain mixtures. An ammeter inserted in the primary circuit of the transformer showed a
4iq u -1
Figure 1-Diagrammatic
View of Apparatus
until beyond 700" C. the results begin to become uncertain, possibly owing to surface reactions. As already mentioned, it has been found that anything which alters the rate a t which heat is conducted away from an advancing flame front alters the limit composition. Thus, small tubes with a high coefficient of heat conductivity will give entirely different results (24, 34) than larger heatinsulated tubes. The effect of tube diameters above 50 mm. was found to be slight, but below that value the range of explosive compositions was narrowed. This fact is important in designing apparatus for high-pressure determinations where it is necessary to keep the apparatus as small as possible. Other factors which influence the determination of the limit mixtures are the method and point of ignition. TThen the point of ignition lies near the top of the reaction space, the range of explosive limit compositions is slightly narrower than when located either a t the bottom or the side. This difference is probably due to convection effects which can scarcely exist in the first case where flame is propagated downwards. An electric spark has been the usual method of ignition. As the gas pressure is reduced below one atmosphere, the energy necessary to ignite a limit mixture increases rapidly (49). On the other hand, discharges pass with difficulty through gases a t high pressures. A more positive method of ignition under these conditions has been the electrical fusion of a fine silver wire in the reaction chamber
(4). Apparatus
Figure 1 shows the apparatus used for the present experiments. A mixture of methane and oxygen was made up in the water-sealed gasometer, compressed by a minature twostage compressor, passed through an oil and water trap, and admitted through a small needle valve to the explosion chamber. The latter was provided with a make-and-break electrical ignition system, thermocouple for temperature measurement, and a steel safety disk of such a thickness that failure would occur before dangerous pressures could build up in the apparatus. EXPLOSION CHAMBER-The assembled reaction unit or explosion chamber is shown in Figure 2. It was turned from alloy-steel stock, and had a thickness sufficient to stand about 2000 atmospheres pressure a t 350' C. The cold-rolled safety disk had a thickness of about 1.2 mm., and failed satis-
GUIDE
Figure 2-Apparatus for Determination of Pressure and Temperature Effects on Limlts of Gas Mixtures
constant current of 2.2 amperes at pressures above 400 pounds per square inch (27.2 atmospheres), while at lower pressures over 15 amperes were drawn. Apparently no spark occurred a t the higher pressures, so the ignition must have taken place from a silent discharge.
1212
INDUSTRIAL A N D ENGINEERING CHEMISTRY
I n their high pressure work Berl and Werner ( 2 ) melted fine silver wires by passing through them a heavy electric current. The metallic vapor allowed an arc to form for an instant. This method had the disadvantage of requiring a new wire after every attempted ignition. Another series of experiments in the present work attempted the use of an incandescent platinum wire, quickly heated by an electric c u r r e n t , but no consistent data could b e o b t a i n e d with this m e t h o d . Evidently surface reaction occurred during the warming up of the wire, causing the formation of a n i n s u l a t i n g layer of inert gas around the wire. This conclusion was also r e a c h e d in the work of Coward and Guest ( I @ , which showed that when hot metal bars were used to ignite an inflammable gas mixture, good 1,-wc*F~+*R~ o xi d a t i o n catalysts such as platinum had to be much h o t t e r than relatively inert surfaces. The make-andbreak method finally chosen for this work ( F i g u r e 2) was the only one to work satisfactorily. Two contacts in the center of t h e r e a c t i o n space were arranged to be Figure 3-Two-Stage Compressor rapidly pulled a p a r t by means of an electromagnet, breaking the flow of a current of 8 amperes in a circuit containing a large inductance. This produced an intense spark which could be depended on a t any pressure. The energy in the spark was that stored up in that magnetic field of the inductance, and hence was independent of the pressure in the chamber. This method had several advantages over any of the others so far considered. In the first place, ignition was positive since. if current flowed in the circuit and ceased to flow when the contacts were opened, a spark must have been produced. Moreover, the spark worked equally well a t low and high pressure and released a constant amount of energy. The size of the spark depended on the speed with which the contacts were opened. This is the reason for the steel hammer employed in the igniting mechanism. The hammer was accelerated by the electromagnet and had a high velocity a t the time it hit the top, lifting the movable contact. Furthermore, it was not necessary to dismantle the apparatus after each sparking as in the case of the silver-wire fusion. TEMPERATURE MEASUREMENT-The initial temperature of the gas was determined by means of a small copper-ideal thermocouple (No. 36 B. and S. gage) placed in a steel well projecting into the reaction space. This well was of about 1.6 mm. outside diameter with an 0.8-mm. bore, and because of this small size and consequent low heat capacity temperature fluctuations were registered very quickly. The thermoelectric potential was measured by a Leeds 8: Korthrup
Vol. 21, No. 12
potentiometer which could be read to about 2" C. The thermocouple was insulated by a coating of low-melting glass applied by running the fine wires through a molten glass prepared by fusing a mixture of borax and litharge. PRESSURE MEAsuREJIENTs-Several ranges of calibrated Bourdon tube gages were used for the pressure determinations. The precision to be expected from these was about as follows: RANGE in. Almos. Atmospheric to 250 To 17 250 to 2000 17-136 Above 2000 Above 136
Lbs.
-fie7 so.-
PROBABLE ERROR Lbs. .bet sa. Almos. - in. * 3 0.204 *20 1.36 * 50 3.4
TEMPEIt4TURE Co?mRoL-The reaction chamber extended into the center of an electric heater made by winding alternate layers of asbestos tape and chrome1 wire on a steel tube, the whole being surrounded by a layer of kieselguhr 1 inch (2.5 cm.) thick, for heat insulation. Since the tube leading to the chamber was of small cross section, the heat flowing along it was also slight. Consequently the temperature of the chamber was quite uniform. The insulation and sparking mechanism in the top of the apparatus were kept cool by means of a water jacket. COMPRESSOR-The gas mixture was compressed in a small two-stage compressor (Figure 3) having a capacity of about 200 liters per hour. With the exception of frequent valve cleaning and grinding, the operation was satisfactory. PIPINa-The gas mixture a t high pressure was distributed in brass and copper capillary tubing of approximately 4.75 mm. outside diameter with 1.6 mm. diameter bore.
Experimental Procedure
PREPARATION AND ANALYSISOF Gas ?VIIxTuRE-The mixture of methane and oxygen was made up in the 200-liter water-sealed gasometer. The methane was of natural-gas origin, subsequently purified by liquefaction and distillation, and contained 0.5 per cent ethane (determined by fractionation a t low temperature) and 5 per cent nitrogen (determined as residual gas after combustion). The oxygen was obtained by air liquefaction and was better than 99 per cent pure. A few runs were made on an unpurified n a t u r a l g a s w h i c h contained, bes i d e s methane, 2 per cent ethane and 5 per c e n t nitrogen. Howeyer, no a p p r e c i a b l e difference in the results was noticed. The mixture was allowed t o stand about 12 hours in the gasometer to insure uniformity of composition. The mixture was then analyzed for oxygen in a Burrell gasanalysis apparatus, and similar analyses w ere made from time to time during the course of the experiments t o m a k e certain that the composition did not change. PROCEDURE-The reaction c h a m b e r w a s brought up to the de-
INDUSTRIAL A N D ENGINEERING CHEMISTRY
December, 1929
1213
Payman's (33)values of 40.8 per cent oxygen and 59.2 per cent methane. It can be seen from the figure that pressure has a marked effect on the upper limit. Starting with about 39 per cent oxygen in the limit mixture a t atmospheric pressure, the oxygen content necessary for combustion decreases to about 17 per cent a t 34 atmospheres and then to about 14 per cent a t 68 atmospheres. At 170 atmospheres the limit mixture contains only about 11 per cent oxygen. Figures 5, 6, and 7 give the temperature-pressure data for single gas compositions. These have been combined in Figure 8 where, in order to condense the pressure scale, logarithms of pressure have been plotted versus oxygen concentrations. It will be observed that, in general, the lower the oxygen concentration or the temperature, the higher the pressure required for successful ignition of the mixture. As either pressure or temperature was increased, the amount of oxygen necessary to form a combustible mixture decreased, and a t temperatures above 400" C. spontaneous reaction began to occur. Under this condition the oxygen content of the gas de40 creased on standing to such an extent that no 2 3 0 combustion could be E obtained on sparking. For instance, when a E 2o mixture originally anal y z i n g 22.6 per cent 10 oxygen was allowed to stand in the chamber 1 o minute without sparkloo '0° 400 TCMPERATURE 'C. ing at a temperature of 371" C. and a pressure of 215 pounds per square inch (14.62 atmospheres), the exit gas analyzed 1.6 per cent carbon dioxide and 21.4 per cent oxygen with no carbon monoxide. Figure 9 shows the variations of the gas composition resulting when a gas mixture, a t constant initial temperature, is ignited a t various initial pressures. This again emphasizes Results and Discussion the incompleteness of reaction. No attempt has been made The data obtained in this work are summarized in Table I. to account for the shapes of these curves. Runs 1 to 5 were made a t atmospheric pressure using a jump spark for ignition. All other experiments a t higher Table I-Summarized Data pressures were made using the make-and-break device for GAS ignition. INITIAL INITIAL P R E S S U R E LIMIT
sired temperature by manipulation of the heater rheostat, and carefully purged out with the gas mixture. The exit valve of the chamber was then closed and the pressure allowed to build up slowly. -4s the pressure rose, sparks were discharged a t intervals by means of the ignition apparatus until ignition occurred. This point was checked by repeating the procedure, except that no sparks were discharged until the limit pressure as shown by the first experiment was almost I ;cached. By a suffi00 FIGURE 5 cient number of exEFFECT OF TEMPERATURE periments two p r e s sures were determined for each condition of temperature and gas composition investig a t e d - ( I ) a point w h e r e reaction was f i r s t distinctly perc e p t i b l e , and (2) a point as near as possible to (1) yet where reaction could not be
ll77ll
-I
'
RUN
'RRSSURE
INITIAL
LIMIT
TEMP. N O
reaction RUNS 152 - l e a
50
GAS
COMPOSITION:
c.
c
z
$
40
m w
;
30
L J
i
20
z
IO
0 0
100
200
300
400
500
1-5 80-54 85-95 96-106 107-11; 118-123 124-127 127-132 132-135 136-142 143-147 148-151 152-164 165-168 169-172 173- 176 177-186 187-188
20 10 10 19 19 173 256 385 530 20 20 20 100 228 288 332 410 480
180-198 199-213 214-219 220-225 226-230
20 20 132 240 380
INITIAL TEMPE RATURE 'C.
Figure 4 shows graphically the effect of pressure a t 20" C. on the upper explosive limit of methane-oxygen mixtures. The limit mixture a t atmospheric pressure was found to be 38.5 per cent oxygen and 58.4 per cent methane, which check
4
b
Lbs./ I.bs,/ sq. In. At mos . q . in. Almos 15 1.0 15 1.0 38.5 58.4 3.1 15 1.0 2.0 30 38.0 59.0 3 . 0 55 3.7 5.4 t;O 20.3 67.0 3 7 8.2 8 . 2 115 120 26.7 6 9 . 6 3 . 7 615 4 7 . 8 500 8 4 . 0 17.2 78.6 4 . 2 435 2 9 . 0 395 2 6.9 17.2 78.6 4 . 2 29.6 17.2 78.6 4 . 2 436 iii ip:o 2;. 1 2z5 17.2 78.6 4 . 2 17.2 78.6 4 . 2 2000 136 1 1 . 5 8 4 . 0 4 . 5 2220 151 9 . 0 5 6 . 4 4 . 6 3365 229 895 14.0 8 1 . 7 4 . 3 6 0 . 8 865 5 8 . 8 550 14.0 81.7 4 . 3 3 7 . 4 495 3 3 . 7 505 14.0 81.7 4 . 3 3 4 . 3 410 2 7 . 9 875 2 5 . 5 345 2 3 . 4 1 4 . 0 81.7 4 . 3 345 14.0 81.7 4 . 3 2 3 . 4 285 1 9 . 4 li.9 14.0 81.7 4 . 3 . . . . 0 a 2z5 14.0 81.7 4 . 3 Unpurified natural gas 2 1 . 2 75 0 3 . 8 415 2 8 . 2 315 2 1 . 4 270 1 8 . 3 215 1 4 . 6 22.6 73.5 3 9 200 13 6 190 1 2 . 9 22.6 73.5 3.9 22.6 73.5 3 9 135 9 . 2 145 9.9 b b b b 22.6 73.5 3 9
%
%
%
rRAPHICAL
METHOD
bs./ sq.
in. :Almos.
400- 2 7 . 2 380 A 2 5 . 9 248- 1 6 . 7
...
Would not ignite. Would not ignite after standing 1 minute.
350 260
23.8 17.7
INDUSTRIAL AND ENGINEERI,VG CHEMISTRY
1214
FIGURE
8
EFFECT O f TEMPERATURE AND PRESSURE ON THE UPPER EXPLOSIVE LIMIT Of
w 80 3
6 eo
Acknowledgment The writers are indebted to Per K. Frolich, who suggested and supervised the work, and to the Research Laboratory of Applied Chemistry of Massachusetts Institute of Technology for placing its facilities a t t'heir disposal.
a
s 40
i
$
for the pressure range investigated. Complete consumption of the oxygen does not take place on the explosion of methaneoxygen mixtures a t high pressure.
METHANE- OXYGEN MIXTURES V-REACTION A-NO REACTION 0 WlNTS OBTAINED BY EXTRAWLATION
100 h
30
e
g 20
Bibliography
! 2
(I.)
10
2
(2) (3) (4) (5) (6) (7)
8 6 4
3
(S) 2
I
IO
!
12
14 I6 18 20 24 2a PERCENT OXYGEN IN MIXTURE
!
524
32
36
40
45
FIGURE 9 COMWSITION O f CAS AFTER IGMTION
RUNS 109-213
AT 2O.C.
INITIAL GAS COMPOSITION
L
Oi22.SX
CH,-73.5%
Nt-3.S*/,
E
5
l2
5
t-l
8* IW
8
Vol. 21, Yo, 12
4
0
0
20
40 INITIAL
60
80
PRESSURE
(ATM.)
100
Conclusions Both temperature and pressure markedly affect the upper explosive limit of methane-oxygen mixtures. The greater either variable, the smaller the amount of oxygen necessary for reaction. Spontaneous reaction occurs above 400" C.
(9) (10) (11) (12) (13) (14) (15) (16) (17) (18) (19) (20) (21) (22) (23) (24) (25) (26) (27) (28) (29) (30) (31) (32) (33) (34) (35) (36) (37) (38) (39) (40) (41) (42) (43) (44) (45)
hllner, Z . Ver. deul. Ing., 71, 411 (1927). Berl and Werner, Z . angew. Chem., 42, 245 (1929). Bone, Phil. Trans., A216, 275 (1915). Bone and Others, Proc. Roy. Soc. (London), llOA, 615, 634 (1926). Bone, Townend, and Piewit, Ibid., 108, 393 (1925). Brown, Leslie, and Hunn, I N D .ENG.CHEM.,17, 397 (1925). Brown and Watkins, I b i d . , 19, 366 (1927). Burgess and Wheeler, Safety in Mines Research Board, Paper 16. Burrell and Robertson, Bur. Mines, Tech. Paper 121 (1916). Clark and Thiele, IND.ENG.CHEM.,17, 1219 (1925). Coward, Carpenter, and Payman, J. Chem. Soc., 116, 27 (1919). Coward and Guest, J . Am. Chem. Soc., 49, 2479 (1927). Coward and Meiter, Ibid., 49, 386 (1927). Coward and Wheeler, B7ennsto.f- Wdrmevirt., 9, 431 (1927). Cowen and Finch, Proc. Roy. SOC.(London), 111A, 257 (1926). Crouch and Carver, IND.END.CHEM.,17, 641 (1925). Dodge, Chem. Met. Eng., 26, 416 (1922). Egerton and Gates, Proc. Roy. Soc. (London), 116A, 516 (1927). Ellis, J . Chem. Soc., 123, 1450 (1923). Fischer and Werner, Z . Elektrochem., 30, 29 (1924). Jorissen and Kayser, Rec. trav. chim., 46, 373 (1927). Kundt and Warburg, J. phys., 6, 118 (1876). Lovell, Coleman, and Boyd, I N D .ENG.CHEM.,19, 389 (1927). Mallard and LeChatelier, A n n mines, 4, 274 (1885). Mason and Wheeler, J . Chem. Soc., 113, 47 (1918). Mason and Wheeler, Ibid., 121, 2084 (1922). Morgan, "Electric Spark Ignition," Crosby, Lockwood and Son, London, 1922. Morgan, Phil. M a g . , 45, 968 (1923). Morgan and Wheeler, J. Chem. Soc., 119, 239 (1921). Nagai, J. Facully Eng. Tokyo Imp. Uniu., 17, 3 (1927). Xeumann, Z. Ver. deul. Ing., 70, 1071 (1926). Paterson and Campbell, Proc. Phys. Soc. London, 31, 168 (1919). Payman, J. Chem. Soc., 115, 1436 (1919). Payman and Wheeler, Ibid., 112, 664 (1918). Payman and Wheeler, Ibid., 123, 430 (1923). Payman and Wheeler, Chem. Soc., A n n . Repts., 19, 20 (1923). Richardson and Sutton, IND. END.CHEM.,20, 187 (1928). Taffanel, Compl. rend., 167, 593 (1913). Terada and Yumoto, Proc. Imp. Acad. Japan, 2, 261 (1926). Terres and Plenz, J . Gasbel., 67, 990 (1914). Thornton, Phil. Mag., 6, 28, 734 (1914); PYOC.Roy. SOL. (London), 91A, 17 (1914). Townend, Ibid., 1 1 6 8 , 637 (1927). Wheeler, J . Chem. Soc., 111, 112 (1917). Wheeler, Ibid., 126, 1859 (1924); 121, 2079 (1922). White, Ibid., 127, 672 (1925).
Wood Flour Opens New Field for Industry Industrial plants in the United States are developing overnight new uses for wood flour, according to the National Committee on Wood Utilization of the Department of Commerce. Wood plastics of the type that can be pressed or molded are now working into specialized fields, where apparently their use is meeting an economical approval. Only recently have wood plastics entered the furniture and other industries. The committee stated that it is impossible to tell exactly the amounts of wood flour consumed by various industries. Phenolresin products, linoleum and its use in dynamite cartridges as filler consume many thousands of pounds yearly. The increasing demand for wood flour in the manufacture of various articles has resulted in an increased consumption of the product from 7000 tons in 1924 to 24,000 tons in 1927, and approximately 40,000 tons in 1928. During 1928 imports of wood flour into the United States totaled 14,490,401 pounds, valued a t $94,723, it was stated. It was pointed out by the committee that whereas American operators are spending money to dispose of sawdust and shavings,
European lumber manufacturers are converting these materials into wood flour, exporting it to this country, paying duty, and evidently selling it at a profit. European wood flour has been claimed to have certain advantages over the domestic product, but the validity of the claim has been disproved, it was stated. Increased experience and care in the selection of raw material by American manufacturers have resulted in a product equal in every way to that produced by foreign mills, according to the committee. The wood substance of various species of trees differs very little in composition, it was explained. However, there are certain infiltrations of gums and resins in some woods, and in others certain coloring, that preclude their use as wood flour for some products. Spruce, fir, and pine are the chief woods used in Europe to produce the highest grades of wood flour. Similar species are represented in the United States by true firs, white pines, and spruces.
