I j36
I < , ( ; E O K G l < F.4I.K
Second-The helium coiltent of t h e gas tends to increase a s the nitrogen increases, though no direct relation is observed. Third-In Kansas, lines of iso-heliuni and iso-paraffin content can lie traced across tlie state and these foliow approximately the lilies of outcrop of the various geological strata. Fourth-A very wide variation in composition is rioted in the gases exainined ; hydrocarbons varying from 15.00 per ceiit. to $ 8 . 0 0 Fer cent., and helium from a trace up to 1.84 per cent. LA\l"HSCU,
KASSAS.
.-~llgllst26, 1p;.
[ C O S TR 111L-T I OS
12 K O M
TFi IS
H A V EJI X T E R L.4 BOR A TORIES SITY, S O . 1 4 j . I
0 I:
c OLI' 31111A
XI 1
THE IGNITION TEMPERATURES OF GASEOUS MIXTURES. s E C O S I > I'AI'IIK.
HY K. G I ~ O R G F EALX. Keceived July 20, 1907.
Introduction. I n a paper published about a year ago' a new method was described for determining t h e ignition temperatures of gaseous mixtures arid the results obtained for mixtures of hydrogen and oxygen were given in detail. T h e ignition temperature was defined as the teniperature at which a gaseous mass would ignite if left entirely to itself for sonie tiin?, the catalytic action of the walls of the vessel in which the gas was enclosed being eliminated. T h e new method for determining these teniperatures consisted of instantaneously compressing t h e mixtures enclosed in a suitable vessel. This compression raises the temperatiire of t h e gas, and, if carried out with sufficient rapidity, is adiabatic, no heat being lost by radiation or conduction. Tlir rise in temperature of the mixture niay then be calculated from the initial and final volumes oi ti;e gas, its initial temperature, and the ratio of the specific heats of tlic gas at constant pressure and constant volume. I n compressing the n i i s t u r t s , a s so011 a s t h e teniperature of ignition is reached there is R sudderi reaction (explosion), enough force 1,ei:ig developed by the reaction to mal;:. the determination of the final uoluiiie of the r1iixtL:re a comparatively siniple.matter as was shown in the first paper. I n t h e present paper, the results obtained by this method for mixtures made u p of carbon monoxide atid oxygen ; hydrogen, oxygen and nitrogen ; carbon inonoxide, oxygen and nitrogen ; and carbon monoxide, oxygeii a n d hydrogen are given, arid tlie results obtained before for mixtures of hydrogen and oxygen coiifirmed. 111 the results given for mixtures of hydrogeri and oxyger iii the first paper a sinall correction was overlooked, but this has been introduced here and will be discussed later. Thi\ Journal, 28,
I j1 j
IGXITION TEMPERATURES O F GASEOUS MIXTURES
I537
Although there has been a considerable amount of work done on the determination of the ignition temperatures of mixtures of hydrogen and oxygen, there has been comparatively little with mixtures of other gases. V. Meyer and Krause' found the ignition temperature of the mixture 2CO 0, to lie between 791' and 879' absolute, using the method of enclosing the mixture in sealed bulbs which were plunged into baths heated to definite temperatures. They found the same ignition temperature for the mixture 2H2 0,. ( F o r adiscussion of this method, cf. first paper, p. 1531.) Mallard and L e Chatelier,' by passing the gas into a tube heated to a definite temperature, found the ignition temperature of the mixture containing 7 0 per cent. carbon monoxide and 30 per cent. oxygen to be about 923'. They also found that diluting this mixture, as well a s the detonating gas mixture, with one of the active constituents or with an inert gas, modified the ignition temperature only slightly. Description of Apparatus and Method of Experimenting, In the determination of the ignition temperatures of mixtures containing hydrogen and oxygen, two pieces of apparatus (I and 11) of different sizes were used. I n the work to be described here, two new pieces of apparatus (I11 and IV) entirely of steel, were constructed. Apparatus I11 is shown in Figure I . Apparatus IV is of exactly the same construction, only larger. T h e general plan of all four is the same, and since I and I1 were described in detail before, the cut of 111 and the dimensions of I11 and IV will suffice here :
+
+
Apparatus 111.
Inner length of cylinder .............................. 25.460 cm. Inner diameter of cylinder, a n d diameter of piston head 2,580 cni. Thickness of walls of upper portion of cylinder . . . . . . . . r.3zj cni. Thickness of walls of lower (thickest) portion of cylitider .......................................... 2.823 cm. Distance from lower inner edge of iiilet tube t o bottom of 19.500 cm. cylinder ........................................ Thickness of steel a t bottom of cylinder . . . . . . . . . . . . . . . 3.514 cm. Length of piston. ..................................... 37.688 cm. Volume of gas measured a t atmospheric pressure used in each experiment ................................ 101.7 cc. .
Apparatus IV.
24.142 cm. 5.078 cm. 1.278 cm. 5.276 cm. 18.640 mi. 5.163 cui. 36.405 cm. 377.5 cc.
With Apparatus I, 69 8 cc. gas were used, with 11, 283.9 cc. T h e method of experimenting was essentially the same as used before. T h e mixture was passed into the cylinder through a thin rubber tube passing through the inlet tube, E, the piston being clamped in position so that the lower edge of t h e piston head was just above the opening of the inlet tube. T h e air displaced passed out through the inlet tube around the rubber tubing. A s soon as sufficient of the mixture had been Ann., 264, 85. Annales des Mines ( 8 ) , 4, 274.
'
run in to ensure of the air being completely dispiaced, the rubber tube was rapidly withdrawn, and the piston pushed down past the opening of t h e inlet tube. The height of the piston head from tlic base was then measured, from which the initial volume of tlie mixture was calculated. To cause adiabatic compression, a weight was dropped 011 the piston. ~ Figure 2 , which requires T h e device for accomplishi~igthis is S ~ O T T Iiii no further explanatioii. Apparatus IV is showvn here ready for an experiment. By the compression brought about in this way. the piston was iorced down until the heat developed by the compression was sufficient to ignite the gas, when aii explosion occurred, the entire mass of gas reacting a t once, aiid the downward niotion of the piston stopped. From the position of the movable ring, A , which was forced u p ns tlie piston desceuded, the final volume (i. r . the volume a t the instant of iguitioii), was calculated. T h e ring was made of fiber board and was clamped to the piston rod by a s c r a v by nieaiis of which it could be tightened as much as was desired. T h e piston head was furnished n ith two leather rings ( a s shown 111 Fig. I ) , which werc renewed when tiecess:iry. 1,aiioliiie was again used as lubricant, and the two pieces of apparatus were a s air-tight :ISApparatus I1 had been found to be. 'I'he iriitini temperatiire of tlie mixture was taken to be the room teniperature. Tlie initial p r e s u r e was alwa! s greater than one atmosphere, and was calculated by tli~.idingtlie distance from the lower edge of the inlet tube to the bottom of the cylinder by h l , tlie initial height of the enclosed mixture. T h e hydrogen used Tvas obtaiiietl in cylinders from 1;imer M .\mend, and was made froin zinc and sulpliuric acid. "lie ox>.gen was prepared by the S . S. White Ilental Xauufacturing Cornpaiiy for medicinal purposes, and x i s the purest obtaiiiablt.. 'rhe carbon monoxide was prepared by droppiiig formic acid 90 per cent. iiito concentrated sulphuric acid, pure carbon moiioxide being. erolred i n large amounts rer!. convcniently by this method. Wheii ; i n inert gas (nitrogen I was used, air was taken and the mixtures calculated on the nssiuiiptioii that it colisisted of 80 per cent. nitrogen arid -30 per cent. oxygen by volume. Although this is not exactly true, the igiiitioii temperature of a iuisture whose composition varies a t most 2-3 per cent., as is the case here, is practically constant. T h i s i s shown most clearly b y the cun'es for the ignitioii temperatures of mixtures of iiydrogeii and osygeri and of carbon monoxide and ox!.geii. T h e gases were inixed orer water in a twoliter graduated glass gasometer. from which the!. were run directly into t h e cylinder, passing through a sinal1 n.ash bottle cotitairling water. In this way thc gas was always saturated \vitli water at the ordiiiary temperature. Apparatus I11 was first constructed and used, theii AlpparatiisI\- was ~
IGNITION TEMPERATURES O F GASEOUS M I X T U R E S
I539
constructed in order to have as greatly differing amounts of gases to work with as possible. I t was found, however, that the mechanical difficulties, which need not be detailed here, connected with the use of the larger apparatus, due to the large mass of exploding gas and the consequent violence of the explosion, resulted in so much time being taken u p for repairs, etc., that after the results shown in Tables I O and 16 were obtained, after working two months, this apparatus was abandoned temporarily, since the same results were obtained with Apparatus 111, which could be handled much more easily. With Apparatus 111, a 2 2 . 7 kg. weight was used, with Apparatus I V , a 31.8 k g . weight. T h e distances were measured with a steel measuring rod graduated directly to 0.5 millimeters, and carrying a circular vernier ivith which readings to 0.01 millimeter could be made. T h e initial height was read to 0. I millimeter, and the final height to 0.01 millimeter. Although the readings map appear to be more accurate than the method apparently justifies, it was thought best to make the actual experimental measurements as exact as possible. T h e experimental work was carried out in the laboratory of Professor Charles E. Lucke, of the Mechanical Engineering Department of Columbia University, and it is due to his aid in assisting to overcome the mechanical difficulties, and in having the repairs which were constantly required made, that it was possible to proceed with this investigation a s rapidly as has been the case. Calculation of Results. T h e method of calculating is the same as already given. The formulas used are :
in which T, represents the initial (absolute) temperature of the mixture. T,, the ignition temperature (absolute). h,, the height in centimeters of the initial volume of the mixture (heights may be used in place of volumes since the diameter is constant). h,, the final height in centimeters of the mixture ( a t the ignition temperature). p , , the initial pressure of the gas in atmospheres. P I , the pressure of the gas in atniospheres at the ignition temperature. h, the ratio of the specific heats of the gases at constant pressure and constant volume, taken as equal to 1.4 for the gases (H2, 0,, CO, K2) used.' Since these are diatoniic gases, k is the same for all. This brings u p the question of a small error which was overlooked in the first The possible source of error introduced in this way will be discussed later.
Ij40
1;.
GEOKGF: 1:AI.K
paper. T h e gases are saturated with water vapor a t the ordinary t e n perature and are tlien compressed adiabatically. T h e rise in temperature produced in this way is the same for the diatomic gases, but miter vapor being triatouiic would not be heated to such a temperature arid woultl consequently lower the temperature of the mixture. Since the gases were saturated a t the ordinary t e n i ~ e r a t u r e(17'-23'') the aniount of water vapor present is perfectly definite and may be corrected for. Since k= I . 29 for water vapor, the rise in temperature of t h e water vapor a s well as of the other gases present may be calculated, and since their specific heats are known by applying the method of mixtiires, the teniperature of the mixture at the ignition point niay be calculated. This ignition temperature would be lower than the one calculated on the assumption t h a t t h e water vapor had no effect on the heating, but t h e difference is small. T h e correction will be applied in detail t o one case. T h e initial temperature being 293' (20' C . ) t h e temperatures produced by t h e same compression in a diatomic ( k = 1.4) and in a triatomic ( k = 1.29) gas are : k=
fi = 1 . 2 9
1.4
57'' 630' 678' 718'
736' 842' 931' 1009'
+
For t h e mixture 4H, 0,. Table I , t h e average ignition temperature, omitting the correction for water vapor, was calculated to be 874'. T h e temperature to which water vapor would be raised by the same compression is 647'. One cubic centimeter of the mixture contains 0 . 0 7 2 mg. H,, 0.286 mg. 0,,and 0 . 0 [ 73 mg. H,O. T h e specific heat at constant volume of hydrogen at 874' in thousandths of calories is 2.75, of oxygen at 874', 0.17,and of water vapor a t 647', 0.38.' By the method of mix0, is : tures', the corrected ignition temperature of t h e mixture 4H,
+
(0.72 X 2.7j 874) (0.2S6 .(0.0173 . ~ . X 0.3s j< 647j (0.0173 X 0.3s) i - (0,072 >< 2.75) -r ( 0 . 2 8
+
74)
~
8680
T h e method is exactly the same for the other rnixtures. T h e corrected final average results will only be given, however. T h e corrections are small and of t h e same order of magnitude throughout.
Experimental Results. Only the corrected results for Tables 1-8 are given. T h e complete results will be taken up and discussed in groups after the possible sources Mallard and Le Chatelier, Compt. rend., 96, 1358. The cooling effect of the water vapor on the gases is of course exerted continuously from t h e beginning of the compression, hut the final result is essentially the same if the total effect is assumed to take place at the final volume, as has been done i n t h e calculations.
I G N I T I O N T E M P E R A T U R E S O F GASEOUS M I X T U R E S
of error have been spoken of, T h e corrected values of correction due to water vapor just explained.
T, refer
TABLE I . 4H, 0,. Apparatus I. Corrected T, - 868. TABLE 2. zH, 0,. Apparatus I. Corrected T, - 806. TABLE 3. H, 0,. Apparatus I. Corrected T, - 781. TABLE 4. 4H, 0,. Apparatus 11. Corrected T, ~- 887. TABLE 5. zH, 0,. Apparatus 11. Corrected T, - 8i4. TABLE ti. H, f 0,. Apparatus 11. Corrected T, - 791. TABLE 7 . H, 20,. Apparatus 11. Corrected T, - 803. TABLE S. H, 4 0,. Apparatus 11. Corrected T, - 844. TABLE 9. 2H, 0,. Apparatus 111.
+.
+
+
+
+
+
+
+
TI
hi
h,
14.78 13.48 13.31 13.29
1.076 290. S27. 1.004 291. s12. 290. 0.994 819. 826. 0.979 291. Average . . . . . . . . . 323 Corrected T, - SIS.
H, hl
14.50
hi
14.12 '3.92 13.75
1.185
T?
PI 1.32 1.45 1.47 1.47
51.7 55.0 55.6 56.6
PI 1.29
43.0
Pr
TABLE IO. 0,. A4pparatusI\'. Ti
Tn
291. 793. Corrected T, - 788.
TABLE I I . H, 1- 0,. Apparatus 111. hz TI PI 0.852 293. 901. 1.38 0.906 294. 877. 1.40 0.903 294. 874. I .42 Average SS4. Corrected T, - 87s.
............
A
PI
70.4 64.2 64.2
1541 to the
K . GEORGE F A L K
~ ~ m . 1I 2 3.
6C0
+ 0,.
Appnrxtus 111.
'I.,
/I ''
PI
1 ' .:
0.669 2S9. 100~~. 1.3' 0.65 I 291. I 006. I.3.i 991. I. j6 0.669 291. 0.575 29~1. 1036. 1.41 0,637 290. 979. I . .46 A v e r a g e . . . . . . . . . . . . 1002. Corrected T, - 994. 'I'.lBLF: ' 3 . .$CO i 0,. Apparatus 111. hl
15.70 14.86 13.83 14.09 12.j
3
111
15.13 14. j l
14.63 14.40 13.99 13.80 '3.55 13.47 12.37
hy
'T3
0.900
29c.
0.333 0.83;
2sg. 290.
'4.49 13.87 13.85
1.24 1.~71 1.;1
S90. 1.3s 0.869 292. 902. I . .i2 0,740 , 289. Averrig?. . . . . . . . . . . . 907. Corrected T,- - 9 0 : . TABI,I3 14. 2 C O -4 0:. Apparatus 111. I.
lis
I?
I,
241, S6s. 0.975 0.S91 292. 890. 0.960 290. b62. 290. 8SS. 0.S78 0.908 291. 369. s93. 0.Sjl 293. 0. so7 2'12. y),'. 0.8s; :9.. 867. Si.;. 0. 735 291. ..!vrr;ige.. ..........SSu. Corrected T, S73.
Pi
1.24
1.53 I.?.: I
.36
I
. ~?(J
1.41 Id
.1 1.45 1.58
10.7.8
99. 1 121.4
103. I
A
67.9 74.0 73.3 68. I Sr.6
Pi 59.9 67.4 60.3 68.3 67.0 69. S 74.7 65.4
--
/3 0
PI.
Jt 1
15.39 15.35 14.68
Pl
'Ti.
910. 915. 916.
P? 100.8
0.860 0.93s o.Sjj O. 86 I 0.82j
913. $93,
2ss. 292.
j1.o
29".
290.
916.
75.8
290.
Avt.r;igc.
63.6
901. 897. s97.
2Y9.
0.jS2
72. I
70.3 73.3
. . . . . . . . . . .90.7.
Corrected T, 89;. 'I'XnLF!! 16. C O r f tI. Apparatus 11..
'r2
P.
0.81 I
289.
925.
73.4
0.82:
292.
91 7. I S.
in.i
'TI
11
Average. .
.......
C'orrvctrd
T1
912.
IGNITION TEMPERATURES O F GASEOUS MIXTURES TABLE 17. Apparatus 111. h? Ti T? h I .40 294. 816. 1.083 824. I .40 293. 1.046 826. 1.42 294. 1.041 I .003 293. 832. 1.43 Average.. . . . . . .&5. Corrected T, - 820.
+ 0, + N,.
H,
hl
13.90 13.89 13 7s 13.61
..
H,
..
TABLE IS. Apparatus 111.
+ 0, + 2N2.
T,
TI
hl
h2
14.60 14.16 14.14 13.80 13.75
0.982 292. 0.913 293. I .007 294. 293. 0.971 0.962 293, Average.. . . . . . . Corrected T,
.
hi
860. 877. 846. 847. 849. .S56. - 85 I ,
..
$1
1.34 1.38 1.38 I .41 1.42
TABLE 19. Apparatus I11 'rl 'r! PI h? 901. 1.38 291. 0.863 924. 1.38 0.808 294. 921. 1.40 294. 0.802 1.41 294. 926. 0.786 0.815 294. 908. I .43 Average,. .. . . . .. . .916. Corrected T, - 910.
H,
14.18 14.15 '3.92 13.85 13.67
P? 50.0 52 5 52.6 55.2
P2
58.5 63.9 5 7 58. I 58.7
+ 0, + 4N2.
.
P? 69.2 75.8 76. I 78.2 73.9
TABLE 2 0 . 2H2 7 0, $- N,. Apparatus 111. T1
T1
h1
hi
14.65
294. 1.061 1.035 291. 294.. 0.957 0.895 292. 0.953 294. Average.. . Corrected
14.22
14.00 13.84 13.55
.. . . ..... 8 j z .
hl
PI 7.33 7.37 1.39 1.41 1.44
P? 52.5 53.7 59.6 65.2 59.2
T,-- S46.
TABLE 21. Apparatus 111. Irl 1'1 *r? P1 0.797 294. 930. 1.37 0.829 294. 9'5. 1.38 0.813 294. 921. I .3s 0.793 294. 926. I .40 0.736 294. 952. 1.44 Average. . . . . . .. .. .929 Corrected T, - 922.
2H,
14.27 14.16 14.10 13.95 13.90
840. 839. 860. 873. 849.
+ 0, + 4N,.
.
P? 77.5 73.2 75. I 77.4 5j.3
15
1%;
K . GEORGE FALK
TABLE
H,
.'
2
O2
22.
S1. Apparatus 111.
Ti 'I., PI 294. s44. I .3S 8j6. I .;s 294, 294. 1.051 830. 1.39 294. I ,025 s;s. I .39 Average. ...........842. Corrected T, - 1137. T X R L E 23, H, 2 0, - .IS,. Apparatus 111. 112
1.009 0.974
11I
14.26 14.18
13.90 13.8j I3.2Q
'r ,
122
0.833 0.S49 0. 7 j 3
29.3.
,
OL . X! ( 2 4 ) . ........ CO 4-O? -1- 2h-, ( 2 j ). . . . . . . . . CO+O,-; N, ( 2 6 ) . . . . . . . . CO 0, 1-2N:,( 2 7 ) . . . . . . . . . 4 C O + O , + - x2 ( 2 8 ) . . . . . . . . . 4 CO 0, 2W:, (29) . . . . . . . . 2 2
+
2
94r
IGNITION TEMPERATURES
OF GASEOUS M I X T U R E S
15.51
T h e values T (calc.) are obtained by meatis of the empirical equation ( b ) T = T, $- 80%' in which T denotes the calculated ignition temperatures, TC , the ignition temperatures of the mixtures without the inert gas as obtained volume inert gas. With the aid of from curve 11, and n' = ___ volume carbon monoxide. curve I1 and equation (b), the ignition temperature of any mixture of carbon monoxide and oxygen, alone and i n the presence of an inert gas, may be calculated u p to the point where ignition is impossible. TABLE E. HYDROGEN, C A R B O N MONOXIDE AND O X Y G E N . T (obs.) Tn (calc.) T6 (calc.)
H,+ 02+ CO(30) H, 0, - t - z C 0 (31) H, 0, 4 C O (32) 2H2 + 0, f-2CO ( 3 3 ) 2H2 0, 4CO (34) H?+2O2f2CO(35) H2+20,+4CO(36) 213~ 30, zco ( 3 7 )
.......
+ + +
+ +
....... .......
+
+
......
812
. . . . . . . 8s I . . . . . . . 895
....... .......
877 938 869 888 825
817 847 907 8i3 933 563 923 822
984 9'4 921 954 941 944 894 1030
T h e values under T, (calc.) were obtained from equation (a) and curve I, assuming carbon monoxide to act as a neutral gas, under 'I'a (calc.) from equation ( b ) and curve 11, assuming hydrogen to be neutral. As seen from the table, the experimentally determined value agrees in .every case with the lower of the calculated values, indicating that the ignition temperature is fixed by two of the constituents, the third simply acting as an inert gas. T h i s evidently holds also if nitrogen, carbon dioxide, or any other inert gas is present, so that tocalculate the ignition temperature of any mixture of hydrogen, carbon monoxide, oxygen, and an inert gas, it is simply necessary t o calculate first the ignition temperature of the hydrogen and oxygen, assuming the rest of the mixture t o be inert (curve I, equation (a) ), and then, to do the same with the carbon monoxide and oxygen with the other constituents inert (curve 11, equation ( b ) ). The lower of these two temperatures will be t h e required ignition temperature of the mixture. A number of experiments were tried with hydrogen and nitrogen, nitrogen and oxygen, and carbon monoxide and hydrogen mixtures, but in no case could any sign of a reaction having taken place under the conditions described, be perceived. Producer gas which is used in gas eugines consists essentially of hydrogen, carbon monoxide, oxygen, nitrogen, and carbon dioxide. T h e results given in this paper show how t h e ignition temperature of any such mixture may be calculated. A general discussion of this phase of the subject would not be of much value without a large number of
I
