IN D USTR I A L A N D EN G IN EE R I N G CH E M I ST R Y
October, 1934
temperature drop. No obvious relation seems to exist. The correlation of the liquid film heat-transfer coefficients calcu-
OVER-ALL TEMP. -4pparent True F. F. 42.1 36.4 42.1 36.6 42.2 38.3 42.3 38.8
AP140 AP240 AP340 AP440
lated on the basis of the apparent temperature drop will be the subject of a later paper. .kCBNOWLEDGMENT
OF APPARENT AKD TRUE TABLE I. COMPARISON TEMPERATURE DROPS
RUN No.
1047
LIQUIDFILMTEMP Apparent True F. ' F. 24.4 18.7 16.4 21.9 20.6 16.7 18.6 15.1
BP140 BP240 BP340 BP440
42.2 42.3 42.3 42.3
34.6 35.2 36.1 36.9
30.7 28.9 25.2 23.4
23.1 21.8 19.0 18.0
CP140 CP240 CP340
42.6 42.6 42.5
32.4 32.3 31.2
36.0 33.4 31.8
25.8 23.1 20.5
4L140 AL240 .4L340 -4L442
42.2 42.6 42.0 42.0
36.1 37.5 37.5 38.0
30.4 22.8 18.8 18.2
24.3 17.7 14.3 14.2
BL140 BL240 BL340
41.5 42.0 41.9
34.7 35.4 39.1
31.6 29.0 23.7
24.8 22.4 20.9
BL160 BL260
60.4 62.6
53.1 53.6
45.0 42.7
37.7 33.3
CL144 CL542 CL642
43.1 43.2 43.2
33.1 32.5 32.1
36.7 34.7 33.1
26.7 24.0 22.0
Appreciation is expressed to W. R. Kleckner and E. D. Allen for their assistance in obtaining the experimental data. Especial acknowledgment is also made to the National Research Council for a Grant-in-Aid that greatly expedited this work. LITER.4TURE CITED
(1) Badger and Shepard. Trans. A m . Inst. Chem. Enyi's., 16, 159 (1928). (2) Claassen, Mitt.Forschungsarb., 7, 75 (1902). (3) Cryder and Gilliland, IND.ENG.CHEM.,24, 1382 (1932). (4) Hebbard and Badger, Ibid., Anal. Ed., 5 , 359 (1933). ( 5 ) Jacob and Fritz, Forsch. Gebiete Ingenieurw., 2, 434 (1931). (6) Kerr, E. W., Trans. A m . SOC.Mech. Engrs., 35,731 (1913). (7) Linden and Montillon, Trans. Am. Inst. Chem. Engrs., 24, 1 2 0 (1930). (8) McAdams, "Heat Transmission," p. 169, McGraw-Hill Book Co., New York, 1933. RECEIVED July 26, 1934. Presented before the Division of Industrial and Engineering Chemistry a t the 88th Meeting of the American Chemical Society, Cleveland, Ohio, September 10 t o 14, 1934. This article is part of the dissertation submitted by L. A. Logan in partial fulfilment of the requirements for the degree of doctor of science in the University of Michigan.
White Lead Effect of Chemical Structure on Physical Properties A. W. ,~NDERSOR;,Anaconda Zinc Oxide Department, International Lead Refining Company, East Chicago, Ind.
W
HITE lea,d is a basic carbonate of lead in which are
found two components: lead carbonate is considered crystalline, while lead hydroxide is considered amorphous. There are some differences of opinion as to the reaction involved in the formation of basic carbonates of lead. According t o Liebig (5) it proceeds as follows:
+
+
Pb ~ C H ~ C O O H - + P ~ ( C H I C O O ) ~ Hz 2Pb(CHaC00)2 ~H~O+P~(CH~COO)~.P~I(OH)~ 2CH8COOH 3Pb(CH3COO)a.Pb(OH)2 4C02+2[2PbC03,Pb(OH)c] GCH&OOH
+
+
+
FIGURE 1
+
COhSTITUTION4L
DI4GR411
It is not definitely known what the actual constitutional formula is. However, according to Heaton ( 3 ) it is probable that a definite chemical compound is not formed b u t rather a mixture of complex basic carbonates which come to equilibrium a t the approximate ratio of 2PbCOJ Pb(0H)n. To correspond exactly to this formula the pigment s h o d d show the folloning percentage composition, Ha0
PbO
2.32 86.32
Pb
cot
80.14 11.35
corresponding to a component equivalent (given by Lambert, 4) of PbCOi Pb(0H)n
68.9 31.1
Theoretically the above formula is correct, and, as Thorpe
(7) found, the best samples show a ratio of components of two molecules of lead carbonate to one molecule of lead hydroxide. But the basic-carbonate white leads as used in the paint trade in many cases deviate from the above theoretical 'structure. Pigments having a lead carbonate content as low as 60 per cent and as high as 80 per cent have been encountered. Beyond these limits the valuable properties of the pigment may be lost. According to A. S. T. M. specifications the maximum lead carbonate content should be 75 per cent and the minimum 65 (1). The paint manufacturer, however, is interested in basiccarbonate white lead from the standpoint of its physical prope r t i e s , s u c h as oil a b s o r p t i o n , tinting s t r e n g t h , opacity, etc., rather than the c h e m i c a l structure. Severtheless, i t has been found that the physical p r o p e r t i es of w h i t e l e a d a r e FIGURE 2. SIZE-FREQUENCY CURVES affected by the chemical structure. The degree and direction of this change in physical properties will follow the varying ratio of lead carbonate to lead hydroxide. It may be that the older processes of manufacture limited the chemical structure
u
.A
k'rounc 3.
c
PWUTUMICROGRAPHS OF E L
nor.KlYc WHITE
I.,
