INTERMETALLIC COMPOUNDS BETWEEN LITHIUM AND LEAD
June, 1958
in the calculated values for (H+). Further, when the data for pKz‘ 3 A f i in Table I11 are extrapolated to zero ionic strength, the value 7.198 is obtained for pK2. This is in fair agreement with the value of 7.183 at 38’ given by Bates and Acree, and the value of 7.165 a t 37’ calculated by Bjerrum and Unmack. ExtraDolation of the data for pKa‘ in Table IV leads to-the value of 12.185 for pKn which is in good agreement with the value of 12.180 a t 37’ calculated by Bjerrum and Unmack, and the value 12.00 given by Latimer. To summarize, at ionic strengths from 0.1 to
+
689
0.5, the range of ionic strengths occurring in urine, the apparent dissociation constants for phosphoric acid at 38’ may be expressed by pK1’ = 2.137 - 0.522 fi + 0.041 /.t
-
pKz‘ = 7.198 1.566 fi pKa‘ = 12.483 - 2.61 d;
+0.937~ + 1.OOGp
01
,
pK1‘ = 2.120 - 0.467 d p pKz‘ = 6.944 - 0.562 dji pKs‘ = 12.185 - 1.494 C i j
INTERMETALLIC COMPOUNDS BETWEEN LITHIUM AND LEAD. THE CRYSTAL STRUCTURE OF Li2,Pbs1 BYA. ZALKINAND W. J. RAMSEY University of California, Radiation Laboratory, Livermore Site, Livermore, California Received J a n u a r y S4#1868
The crystal structure of L i ~ P h has s been determined. The face-centered cubic cell contains 80 Pb atoms in space group F23; the cell constant is 20.08 A. The packing of the Li and Pb atoms is analogous to that found for LiPb, Li8Pbs, LiaPb and LilPbz; these structures resemble the body-centered cubic array present in Li metal, with the appropriate number of Li atoms replaced by Pb.
Introduction The work described below completes crystalstructure determinations of the five intermetallic compounds in the lithium-lead system. Structures of the other four compounds, LiPb,2j3LisPbs,4 Li3Pb,bLi7Pb2,6have been reported previously. I n the lithium-lead phase diagram (Fig. 1) determined by Grube and Klaiber,B the most lithium-rich compound in the system is called “Li4Pb.” X-Ray and analytical data presented below indicate that the composition of this “Li4Pb” phase is LizzPb5. Experimental
rected for the Lorentz,’ polarization,? and velocity factors.8 The data suffer badly from absorption effects; due to the anhedral shape of the crystal, the computation of this correction would be extremely complex and was thus omitted. Powder diffraction patterns also were obtained with a Norelco 11.46 cm.-diameter camera, using Cu KCX X-rays.
Crystal Structure Determination Li22Pbb has a face-centered cubic cell of a = 20.08 fi. The measured density, as determined with a helium densitometer on the powdered material, is 3.88 0.04 g./cc. There are 80 Pb atoms per unit cell; the unit cell volume is 8038 fie8; the X-ray density is 3.90 g./cc. There are 16 The material was prepared by fusing the two metals in an argon atmosphere in a manner previously described.6 formula units per unit cell. A Patterson projection was perfprmed on twentyLit~Pb5is formed by a peritectic reaction between LiVPbl and the melt at about 650O.8 By.very slowly cooling a melt two hkO intensities. containing 85 atom % Li, it was possible to obtain a sample
in which the phases (LiztPbb and eutectic) could be cleanly separated mechanically. Single-phase samples were analyzed chemically, and the composition found corresponded to LizzPb,(Li/Pb = 4.40). The compound has a black, shiny, metallic luster and is rapidly attacked by air. X-Ray diffraction samples were pre ared in an argonfilled dry box. A small single crystal 0.3 mm. across) was isolated in a thin-walled glass capillary and photographed with the Weissenberg single crystal camera using the standard equi-inclination techniques. The crystal was, by chance, oriented with its rotation axis in the [110] direction; rotation and zero-through fifth-layer Weissenberg patterns were obtained. Cu K a radiation (A = 1.5418 A . ) was used. Reflection intensities were measured from the Weissenberg patterns by visually comparing the diffraction spots with a set of calibrated spots. These data were then cor-
&
(1) This work was performed under the auspices of the U. 9. Atomic Energy Commission. (2) H. Nowotny, Z . Melallkunde, S3, 388 (1941). (3) A. Zalkin and W. J. Ramsev, _ . UCRL-4860. Mar. 1957. (4) A. Zalkin, W. J. Ramsey and D. H. Templeton, THISJOURNAL, 60. 1275 (1956). i5) A. &kin and W. J. Ramsey, ibid., 60, 234 (1956). (6) G. Grube and H. Klaiber, 2. Elektrochem., 40, 745 (1934).
*
P(z, y ) =
c h
IFhklZ
k
cos 27r (hz 4-ky)
(1)
The resulting pattern is shown in Fig. 2, where the contours are drawn at arbitrary intervals. The projection has peaks at distances corresponding approximately to multiples of twelfths (twelfths, sixth, thirds, etc.). This pattern has the approximate appearance of a body-centered cubic sub-cell of size ‘/B a on an edge. This type of subcell is characteristic of the structures of the other Li-Pb intermetallics, where the atoms are in a body-centered cubic arrangement (like the lithium metal structure) with the appropriate number of P b atoms uniformly distributed in an ordered fashion amid the Li atoms. The real cell (a = 20.08 fi.) contains 6 X 6 X 6 = 216 sub-cells of 2 atoms each, giving a total of 432 atoms per unit cell. The density calculation yields (7) C. S. Barrett, “Structure of Metals,” McGraw-Hill Book Co., Inc., N. Y., 1952, p. 621. (8) G. Tunell, Am. Mineral., 24, 448 (1939).
A. ZALKINAND W. J. RAMSEY
690
+
+
The general parameters x - 1/4, y 1/4, x structure factor formula would then be
A
In
e
.
Vol. 62
9ook
(2)
where fn is the scattering factor for atom n, and xn, yn and z,, are the coordinates of atom n in the general position. When - h k I = 4m 2(mis an integer), the first term in the equation IS zero. It was necessary to investigate the positions in a lower symmetry space group than the systematic absences indicated. This can be viewed as another example of false symmetry, a subject discussed by Kitaigorod~kii~ and by Templeton. lo The space group F23 was found suitable for investigation of the atomic locations in this structure. Several trial structures utilizing pairs of 16-fold and pairs of 24-fold positions in space group F23 were investigated. One such model was unique in that no two lead atoms were touching; a cursory comparison of some of the observed data with valuescalculated from this model showed good agreement. This model is that of a large cube consisting of a G X 6 X 6 matrix of body centered cubic sub-cells; this sub-cell is analogous to the lithium metal unit cell. The positions used for the lead atoms are indicated in Table 11; these positions are such that no two lead atoms occupy the same sub-cell. All of the atomic parameters would be multiples of twelfths if this were an ideal structure of equal sized atoms; since the lithium and lead atoms are different in size, the parameters do deviate by small but significant amounts from an ideal structure. Trial parameters for the P b positions were estimated from the Patterson projection; these were refined by a least-squares treatment on 185 nonzero reflections. Structure factors were calculated from formula 3 below. This formula assumes that the parameters of the two sets of 16-fold positions are exactly of a unit cell apart, and likewise for the two 24-fold positions.
+ +
800
ATOM -% Pb. composition in parentheses Fig. 1.-The system Li-Pb: are those determined in this series of articles. 2
4
cos 2akx1
+ cos
27rZXl
+
+ 2(COS 2ThX2 cos 27rkxz cos 27r ZXZ)] (3)
The resulting Pb atom parameters obtained from the least-squares refinements are tabulated in 4 12 6 Fig. 2.-Patterson projection in the (100) plane for Li22Pbb. Table I. The standard deviations were estimated by the method described by Cruikshank.l' 80 Pb atoms, the remaining 352 being the Li TABLE I atoms; this results in the formula LizzPbs. An accurate chemical analysis of a carefully prepared THE P b ATOM POSITIONS AND PARAMETERB IN Li22Pl), sample confirmed this formulation rather than the No. of positions and Wyckoff 4:1 compound previously reported.6 notationla Parameters The space group was taken as F23. I n addition 16 e X I = -0.0859 f 0.0003 to the face-centering extinctions, additional ab16 e XI' = XI - '/d = -0.3359 k +I sences were observed for reflections with h 24 f xz = 0.3211 f 0.0003 = 4n 2. Although this type of extinction is 0.0711 x i r = 22 - 1/4 24 g characteristic of special positions in Fd3, F4132, and Fd%, it was found impossible to derive a where structure based on these symmetries. This type (9) A. I. Kitaigorodskii, Izuest. Akad. Nauk, S.S.B.R.,Oldel. Khim. of extinction can be obtained by taking a general Nauk, 263 (1949). set (and certain special sets) of positions with (10) D. H. Templeton, Acta Cryst., 9, 199 (1956). (11) D. W. J. Cruikshank, Acta Cryst., 2, 154 (1949). parameters x,y,x and making a companion set with c
+
+
b
i FOR LizzPb5 (" Unobserved or zero observed intensity.) :ULATF,D STRUCTURE FACTORE AND CAL( TABLE 11: OBSERVED
h
k
l
IFol
lFol
3 4 3 4 3 5 4 5 6 5 4 5 7 6 5 7 8 7 6 8 5 7 8 7 9 6 9 8 7 7 9 8 10 7 9 9 10 7 11 8 9 11 9 8 10 9 11 8 12 7 11 10 12 9 11 12 9 10 9 11 13
1 0 3 2 3 1 4 3 2 3 4 5 1 4 5 3 0 3 6 2 5 5 4 5 1 6 3 4 7 5 3 6 2 7 5 5 4 7 1 8 7 3 5 6 6 7 3 8 0 7 5 6 2 7 5 4 9 8 9 5 1 7 4 7 7 3 6 9 3
1 0 1 2 3 1 0 1 0 3 4 1 1 2 3 1 0 3 0 2 5 1 0 3 1 4 1 4 1 5 3 2 0 3 1 3 2 5 1 0 1 1 5 6 0 3 3 4 0 7 1 4 2 5 3 0 1 2 3 5 1 1 4 7 3 1 2 5 3
10 25 46 70 76 64 49 14 10 25 41 17 42 17 17 17 17 57 185 91 80 10 10 10 17 14 38 71 27 83 66 10 45 27 14 20 41 46 10 14
1 8 36 11 57 13 89 14 105 10 108 10 59 11 6 13 16 12 39 11 47 9 20 10 68 12 27 14 22 11 20 13 15 13 63 12 212 15 103 11 119 13 1 14 13 15 4 11 3 13 21 9 39 15 66 14 21 12 84 11 80 15 11 11 49 13 27 16 19 15 28 13 37 16 53 10 13 14 20 11 4 13 15 16 16 12 8 1 3 34 15 48 15 26 12 82 11 171 15 29 16 97 12 60 13 8 17 7 11 19 14 12 14 29 16 55 13 64 15 26 17 17 13 68 12 27 15 24 17 2 14 23 17 1 1 5 20 13 616
11
12 9 11 13 12 9 13
."
20
"
27 49 10 89 164
"
83 63 10
" " "
34 59 72 23 20 63 25 25 10 17 (I
7
h
k
E
lFal
8 7 5 2 8 10 9 5 8 9 9 10 6 4 7 7 5 8
8 5 1 0 6 0 1 3 0 3 7 4 6 2 7 1 5 4 1 5 3 0 1 1 5 9 3 4 2 3 1 7 1 0 3 3 2 8 2 5 7 0 8 5 1 5 6 9 3 4 0 1 1 7 6 0 2 3 5 1 7 4 1 3 4 1 3 5 0
116 10 29 " 17 77
1 9 7 6 3 11 7 9 3 6
10 11 5 9 9 0 5 9 2 10 8 11 7 4
8 9 7 5 10 9 7 4 12 11 1 11 8 10 6 11 7 3 9 12 9 3 10 5 9 11
8
(1
17
" " 42 17 127 71 10 25 23 37
" 10 "
"
70 59
"
14
" " 10 14 29 a
64 31 29 89 96 41 68 31 a
" 29 "
" 37 17 92 a
5G 64
" " 44 a a a
17
" " 10 42
' 45 48 14
IFol
h
k
E
97 11 11 9 10 15 7 7 46 17 5 3 1 3 1 8 0 0 24 16 6 6 76 15 9 5 9 1 3 9 9 17 16 8 4 1 1 7 7 1 1 9 1 7 5 5 36 13 11 7 5 13 13 1 141 18 4 0 65 14 12 2 518 4 2 25 12 10 10 17 15 11 1 3 1 7 7 3 18 13 13 3 28 12 12 8 34 15 9 7 13 15 11 3 22 16 10 2 2 0 1 8 6 0 16 14 10 8 51 11 11 11 52 13 13 5 017 7 5 24 19 1 1 25 13 11 9 8 1 5 1 1 5 9 1 7 9 1 21 19 3 1 38 14 12 6 14 17 9 3 47 19 3 3 27 16 8 8 22 13 13 7 78 15 9 9 90 17 7 7 30 19 5 1 64 14 14 0 27 16 10 6 5 1 8 8 2 9 1 5 1 1 7 32 17 9 5 1 6 1 9 5 3 15 18 12 0 28 20 0 0 6 15 13 3 117 17 9 5 419 5 3 65 16 12 0 67 14 14 4 25 17 11 1 1 7 1 9 5 5 44 19 7 1 7 2 0 4 8 16 16 12 4 ' 8 1 5 1 3 5 21 17 9 7 0 1 7 1 1 3 1 6 1 9 7 3 19 13 13 9 32 18 8 6 14 18 10 0 42 15 11 9 49 12 12 12 34 20 4 4
mI
Ihl
h
IC
E
lFoI IF01
18 17 11 5 19 2 19 7 5 ' 1 7 18 14 12 10 " 5 11 18 10 4 24 29 20 6 2 12 12 15 13 7 21 38 19 9 1 " 17 20 21 1 1 5 2 15 15 1 " 11 76 17 9 9 10 30 21 3 1 " 10 26 19 9 3 43 40 60 16 10 10 10 21 16 14 2 30 3 14 14 8 70 65 48 13 13 11 15 28 17 11 7 " 9 2 1 9 7 7 " l 34 15 15 3 35 28 9 17 13 1 26 33 26 21 3 3 33 29 10 16 12 8 " 21 7 2 0 8 0 " 1 7 100 15 11 11 35 46 21 5 1 30 27 24 20 6 6 15 18 15 15 5 0 55 21 5 3 5 18 15 13 9 24 24 16 20 8 4 53 44 16 17 13 5 1 18 19 11 1 " 29 25 18 10 8 0 1 22 2 0 33 42 16 17 11 9 " 25 48 19 11 3 " 14 33 19 9 7 18 26 0 21 7 1 21 13 33 21 5 5 24 16 37 15 15 7 " 13 10 21 7 3 " 18 2 3 2 2 4 3 " 9 63 18 12 6 69 72 24 20 10 2 39 29 2 1713 7 a 9 13 19 11 5 " 2 17 13 13 i 3 50 31 22 16 16 0 87 66 17 15 13 11 8 31 17 15 1 " 8 1 3 2 1 7 5 @ 4 17 18 14 0 6 22 22 6 0 26 27 54 17 15 3 7 65 21 9 1 8 31 19 9 9 38 33 21 16 16 4 a 9 0 20 8 8 61 55 141 19 13 1 0 8 2 3 1 1 " 4 1 17 11 11 59 64 16 19 11 7 11 12 29 15 15 9 32 23 30 21 9 3 32 24 11 10 10 6 " 9 6 18 14 4 24 14 4 14 14 12 11 24 83 22 6 4 45 48 33 17 13 9 ' 0 (I
' " (I
" 47 27
'
68 23 27
' " 53
" (I
33
" (I
( I
101 56 a
" 59 11
" " a
21
" a
65 45 36 38 18 (I
72 26
" " "
26 33 (I
" a
61 66 21 30
" 32 (I
a
24 28
" " 78 38
(I
(I
(I
(I
(I
h
k
,
E
[Fol \Fa1
19 13 13 2 1 7 7 " 2 3 3 1 " 17 15 5 11 16 12 12 " 20 12 0 2 1 9 5 " 23 3 3 " 16 14 10 22 8 2 18 19 13 5 " 23 5 1 39 20 12 4 15 13 13 " 17 15 7 19 11 9 21 11 1 2 3 5 3 ' 18 12 10 15 15 11 a 21 9 7 " 21 11 3 " 16 16 8 24 0 0 50 17 17 1 ' 19 13 7 " 23 5 5 " 17 13 11 28 23 7 1 30 18 16 2 " 18 14 8 26 22 8 6 21 22 10 0 77 24 2 2 21 17 17 3 a 19 15 1 " 2 3 7 3 ' 21 11 5 26 2 4 4 0 " 17 15 9 a 19 15 3 15 16 14 12 " 22 10 4 " 20 10 10 31 20 14 2 46 2 3 7 5 ' 17 17 5 35 19 11 11 15 21 9 9 24 2 4 4 4 " 20 12 8 11 19 15 5 a 21 11 7 a 21 13 1 a 2 3 9 1 " 19 13 9 11 18 12 12 " 24 6 2 a 18 16 6 21 15 15 13 " 23 9 3 21 13 3 18 17 13 13 " 2 3 7 7 " 17 17 7 42 25 1 1 15 16 14 14 15 20 2 2 57 13 11 11 (I
(I
(I
(I
(I
36 8 6 24 12 10 l 19 10 17 20 47 8 16 15 6 12 8 2 1 11 0 2 66 12 30 12 37 33 19 28 27 58 21 12 17 4 31 9 6 28 3 6 10 47 3 56 30 20 2 19 2 23
T 3 24 5 16 8 22 14 17 18 6 42 12 25 52 5
A. ZALKINAND W. J. RAMSEY
692
++
16e x x x* x,32,12; flx,32; 3,32,x; face centering 24f x,O,O;O,x,O; O,O,x;;) face centering 24g x i 1 4i1/4; '/4iXl1/4; '/?i1/4jX; *i1/4ia/4; l/dla/+f; face centermg
'1'
+
a/41R11/4;
The observed and calculated structure factors are shown in Table 11. The least-squares calculations were performed on the IBM-650 computer. The scaling factor of the observed t o the calculated intensities was adjusted by leastsquares also. An isotropic temperature factor was included, where 0 is the diffraction angle, X is the e - B sinB@/A2 Fcalo = Fobs
(4)
X-ray wave length, and B is related to the mean atomic displacement; the B was treated by least squares, and the resultant value for the Pb atoms was ~ 1 . X4 10-l6 cmS2. The reliability indices are
I n the least-squares procedure, Rz is the error quantity that is minimized. The large R1 value is attributed to the very heavy X-ray absorption by the crystal; corrections for this absorption were omitted because of the anhedral crystal shape and because of the difficulty of such a calculation. In the simple body-centered cubic sub-cell structure, which is assumed here, the lithium atoms occupy all sites not occupied by Pb. The approximate lithium atom positions are shown in Table 111. The Pb atoms deviate from the ideal parameters of 1/3 and - '/I2 by 0.012 and 0.002 parts of a unit cell for the 24- and 16-fold positions, respectively, One would then expect deviations of this order of magnitude for the Li atoms; however,
Vol. 62
these deviations cannot be determined by X-ray diffraction techniques. Discussion The ratio 352/80 of Li/Pb atoms in the structure, as well as chemical analysis of single-phase samples, show the stoichiometry of this compound to be LizzPbs. Grube and Klaibere refer to this phase as LirPb on the basis of thermal analysis data, while the difference between the compositions of Li22Pbb and LirPb is only 1.5 atom % or 1.0 weight yo. For the idealized structure, each Pb atom would have eight nearest Li neighbors, and each Li atom, eight nearest neighbors of which three or less are Pb and the rest are Li. The actual nearestneighbor situation may be quite different due to minor shifts from the ideal structure, whence the Pb would have more neighbors through better packing; in Li7Pbz, this variation from ideality gives P b eleven Li neighbors (five nearest and six near). A Li-Pb distance in Li22Pbs is 2.99A.; this particular distance was calculated from the Li atom at (O,O,O) to the Pb atoms at *(-0.0859, 0.0859, 0.0859). The remaining distances cannot be calculated because the Li positions are not known to a sufficient accuracy.
summary The crystallographic properties of all of the lithium-lead intermetallic compounds are tabulated in Table IV. The five compounds have basically the same type of packing whereby there is a bodycentered cubic packing of the atoms (analogous to Li metal) with the appropriate ratio of Li and P b atoms spaced in such a way as to distribute uni-
TABLE I11 THE APPROXIMATELITHIUMATOM POSITIONS IN Li22Pbb No. of po8itions
Li (b.c. cubic)
and Wyckoff notstionla
.
where 16e 24f 24g 4%
Positions or parameters
0, 0, 0;
4a 4b 4c 4d 16 e 10 e 16 e 16 e 16 e 16 e 24 f 24 g 48 h 48 h 48 h 48 h
+ face centering + face centering + face centering a/4; + face centering
I/Z, 1 / ~ ; I/',
I/,,
a/4,
*/4,
1/4;
2 = 1/12
x= x= x=
L i P b (Rhombohedral S c u b i c )
'/6
6/12
x
= '/12 x = 6/6 x = '/a x = ~/IZ x = 6/6, y =
z,y,z; ZAY;
z =0
1/6,
=
2/3)
= x =
'/41
= 1/8, z = 0 1/ = '/I21 z = '/12
8/d,
y=
x
Y,Z~X;xI9&
Li,Pb (f.c. cubic)
y
1/12,
see Table I see Table I see Table I ?,z,R;
L i s Pb3 (monoclinic)
1/8
z,f,%
z =
L i P b 2 (hexagonal)
1/12
Y,W; %Y?%
~,T,z;~ ~ 3 2 , y,s,x; ~; + face centering
Z,X,T;
(12) Terminology from "International Tablee for X-Ray Crystallography," Vol. 1, Kynoch Presa, Birmingham, England, 1952.
L i 2 , P b 5 (f.c. c u b i c )
Fig. 3.-Comparison of the atomic arrangements in the compounds of the Li-Pb system.
U
DETERMINATION OF HYDROGEN ATOMSIN BURNTGAS
June, 1958
693
TABLE IV SUMMARY OF CRYSTALLOQRAPHIC DATAOF Compound
Cell tY w
Space group
Cubic Cubic Hexagonal
Ini3vn F23 P321
LiaPb LisPba
Cubic Monoclinic
Fm3m C2/m
4 2
p-LiPb b'-LiPb
Cubic Rhombohedral
Pm 3m R3m
1 1
Pb a
LITHIUM-LEADINTERMETALLIC COMPOUNDS' Cell constants
z 2 16
Li LizzPbs Li7Pb2
THE
a = 3.508A. a = 20.08 A. a = 4.751 c = 8.589A. a = 6.687A. a = 8.24A: b = 4.757A. c = 11.03A. b = 104.5" a = 3.563A. (220') a = 3.542-k. (Y = 89.5" a = 4.950A. .
h.
1
Cubic Fm3m 4 All values a t room temperature except for @-LiPb.
formly the Pb atoms amid the Li atoms. Figure 3 shows a two-dimensional representation of the ideal structures pictured in the layer corresponding t o the (110) plane of the body-centered sub-cell. I n LizzPbsthere are two types of layers which differ only by the number of Pb atoms per layer. These layers stack upon each other in such a way as to distribute the Pb atoms uniformly. Small deviations from the model positions exist in most of the structures. Only in Li6Pb3 do the P b atoms actually touch each other; however, given the 8/3 ratio, this aPpears t o be the most efficient way of distributing the Pb atoms. The pairing of Pb atoms is a common feature in the Na-Pb system, more so than in the
X-Ray density, g./cc.
Mole
Wt.
% Li
Yo Li
Ref.
0.53 3.86 4.59
100.0 81.5 77.8
100.0 12.8 10.5
13
5.06 5.37
75.0 72.7
9.1 8.2
5 4
7.86 8.00
50.0 50.0
3.2 3.2
3 3
11.35
0.0
0.0
14
.. 5
Li-Pb system.16 No evidence has been found for the compound LiloPbereported by Rollier and Arreghini.I6 I n the powder patterns there exist similarities in the spacings between the various compounds; probably a mixture of phases (LiaPb and LilPbz, possibly) was misinterpreted as being a single phase. Ac~owledgments.-we would like to thank Mr. vernonsilveira for much of the photography, Mr. LeRoy Green for preparing a pure sample, Mr. Robert Lim for the chemical analysis, and Dr. D. HaTempleton for his interest and his discussions On false symmetry. (15) N.E.Weston, D. P. Shoemaker, Abstracts of the Communications, 4th International Congress, Internatirnal Union of Crystallography, Montreal 10-19, July, 1957. (16) M. A. Rollier and E. Arreghini, 2. Krisl., 101, 470 (1939).
(13) H. Perlitz and E. Aruja, Phil. Mag., 80,55 (1940). (14) H.P. Klug, J . Am. Chem. Soc., 68, 1493 (1946).
DETERMINATION OF HYDROGEN ATOMS IN RICH, FLAT, PREMIXED FLAMES BY REACTION WITH HEAVY WATER BY C. P. FENIMORE AND G. W. JONES Research Laboratory, General Electric Co., Schenectady, N . Y . Received January dq9 1968
The concentration of hydrogen atoms in the burnt gas from flames burning on a cooled porous burner is determined by adding D 2 0 to the reactants and measuring the rate of formation of H D in the products. [HI can be inferred if the rate kz D20 +HD OD is known. kz is taken from Avromenko and Lorentso with a small change, constant of the reaction H and the consistency of [HI by this method with [HI as measured by Bulewicz, James and Sugden in a quite different manner is evidence that both methods are correct. In a 1300°K. hydrogen flame, or hydrogen plus carbon monoxide flame, [HI is about 2500 times the equilibrium concentration of H atoms in the burnt gas, [HI,,,. The ratio [H]/[H].,, decreases with rising temperature; it is about 140 in the burnt gas from a 1500°K. flame. The average rate of consumption of oxygen
+
+
+ e.+ k4
in such flames is equal to the rate of the reaction H OZ OH 0 if k d has a steric factor of order unity and if E, = 20 f 2 kcal. The great excess of hydrogen atoms is a peculiarity of hydrogen and hydrogen plus carbon monoxide flames. I n the burnt gas from rich hydrocarbon flames [HI = [HI,,,. Furthermore, the burnt gas from mixed fuels of hydrogen plus a little hydrocarbon possess much smaller ratios of [HI/ [Hle,, than the burnt gas from hydrogen flames at the same temperature.
Introduction This report describes measurement of the concentration of hydrogen atoms in the burnt gas from rich flames. A flame of known burning velocity and temperature is established on a water cooled,
porous metal burner. A little DzO is added to the reactants and the concentration of hydrogen atoms is inferred from the rate of appearance of HD. With rich hydrogen flames, our results prove to be consistent with those of Bulewicz, James and
