INDUSTRIAL A N D ENGINEERIXG! CHEMISTRY
June, 1928
617
Board method gives results that agree more closely with the oil-shale method than with the Fischer method. Yields of tar by this method are usually high, owing to experimental error. The small sample of 20 grams yielded only a small amount of tar, which was hard to separate accurately from the watery distillate. Comparative Reliability of Methods
-1
-
Figure 4-Relation
G
~_______
- _
2:
35 40 45 O \ > G E \ ( I S H FPEE PER CE\T)
ZD
20
_, 4,
between Tar Yield a n d Oxygen Content
each case sum up to nearly 100 per cent, except Fischer. off 3 per cent, so there are no consistent errors inherent in the method favoring wrong figures. On an average, the oil-shale method gives somewhat low yields of tar and high yields of gas. The residue and water are also slightly low, but hardly to a significant extent. Evidently this method, as compared with the other two, makes gas a t the expense of tar. This could result from higher retort temperatures and more extensive cracking. It will be recalled that temperature is not measured in this method; control is effected solely by observing the rate of formation of the distillate. The Fischer method gives the largest residue and the lowest gas figures, together with a slightly higher tar yield than the oil-shale method. Cracking was therefore minimized in this method. The Fuel Research
With all empirical methods such as these, careful attention to details of procedure is required to insure that the tests are all carried out in exactly the same manner. Long experience with a given method will render this easy, and an experienced analyst will turn out results of a quality impossible to the beginner. Realizing this, the writers believe that all three methods can give fair results in the hands of their originators or of others with more experience than themselves. Nevertheless, on the basis of their work, the writers believe that the Fischer method is superior to the other two, both for accuracy and facility of manipulation. The oil-shale method was not designed for the assay of coal, and for coal the rate of distillation does not give such satisfactory control as that based on temperature measurement. The iron retort corrodes and is difficult to keep gas-tight. The main difficulty with the Fuel Research Board method is that the sample taken for assay is so small as to render difficult the accurate handling of recovered distillation products. Table I11 gives variations between duplicate determinations for each constituent determined by the several methods, also the maximum variation found in each case. Agreement between duplicates is clearly best by the Fischer method. Between the two other methods there does not seem to be much choice.
Effect of Physical Characteristics of Coke on Reactivity’pz J. D. Davis and D. A. Reynolds PITTSBURGH
E X P B R I M I ~S TXATT I O N ,
u. s. BCREACOF
?rXI.?.ES, P I T T S B U R G H , P A .
Results of reactivity tests of low- and high-temperar e a c t i n g w i t h substances S APPLIED to coke ture cokes in air, steam, and carbon dioxide over temother than oxygen, but such the term “reactivity” perature ranges from 800” to 1100” C. are given. The a distinction hardly seems is rather i n d e f i n i t e . effects on reactivity of bulk density, volatile matter, warranted. “Reactivity” is Every coke user thinks of that adsorptive power, size of test particles, and varying perhaps the best general term quality in connection with the reactivity of particles of the same sample have been to use; where it is necessary use of which he intends to estimated. to be more s p e c i f i c , t h e put the coke. Thus, if he method of test should also wants to make water gas, he thinks of the rate a t which the coke will produce water gas be stated. under practical working conditions. The producer man The character of coal used and the method of coking deis interested in rate of reduction of carbon dioxide. Others termine the physical characteristics of the coke and hence consider ease of ignition, rate of combustion, etc. As a its reactivity. I n measuring the effect of physical properties result, various empirical test methods have been developed one should have a test method for reactivity applicable to as for determining reactivity, each being based on a particular wide a range of uses as possible, that conclusions of general use for the coke. The quantity measured is usually called significance may be drawn. The test method used in this reactivit3, although it is realized that all test methods by paper was selected after comparing various available methods which it is determined do not measure the same thing. The (in modified form when this seemed advisable) for sensiterm “combustibility” is also used. Smith and his collabo- tivity and reproducibility of results. The physical characterr a t o r ~define ~ “combustibility” as the property of com- istics studied were: (1) bulk density, (2) volatile-matter bining with oxygen, and “reactivity” as the property of content, (3) adsorptive power, (4) size of particles, and (5) coke luster. 1 Presented before the Division of Gas and Fuel Chemistry at the 74th
A
Meeting of the American Chemical Society, Detroit, Mich., September 5 to 10, 1927. 2 Published by permission of the Director, U. S. Bureau of Mines (Not subject to copyright ) 8 Smith, Finlayson, Spiers and Townsend, Gas J . , 1926, Coke No.3-16.
Cokes Used
With the exception of the one made in superheated steam, the cokes used in this investigation were produced on an
I N D U S T R I A L A N D ENGINEERING CHEMISTRY
618
Vol. 20, No. 6
a n d Analysis of Cokes Tested
Table I-Description
ULTIMATE ANALYSIS
PROXIMATE ANALYSIS
1 Utah (Mesa Verda) 2 German coking 3 Pittsburgh 4 Illinois 5 Pittsburgh 6 Pittsburgh 7 Pittsburgh 8 Pittsburgh 9 Pittsburgh 10 Pittsburgh 11 Pittsburgh
Distilled in steam at 750' C. Rotary retort Externally heated retort, 2-stage Externally heated retort, 2-stage, 750' C. U. G. I. intermittent vertical retort U. G. I. intermittent vertical retort Russel, horizontal trough Woodall-Duckham, continuous vertical Becker oven Beehive oven Beehive oven
%
%
%
2.8 1.5 3.7 1.3 1.3 0.7 0.8 0.7 0.7 0.7 0.5
10.6 14.2 11.9 2.4 2.5 1.2 1.4 1.6 2.0 1.7 1.6
75.4 66.2 72.5 84.7 86.3 88.0
industrial scale by processes well known in this country. Table I gives their general description and analyses. It should be noted that the low-temperature cokes 1 to 4, inclusive, were made from coals of different ranks, so that here the kind of coal, as well as the method of coking, is a factor which might be expected to influence reactivity. High-temperature cokes 5 to 9, inclusive, were made from the same coal, and any variation in their reactivity is directly chargeable to the method of coking. Beehive cokes 10 and 11 were made from a coal similar to, but not identical with, that used for cokes 5 to 9.
k
I-i
Ial
U Figure I-Apparatus
for Determination of Reactivity of Coke
Apparatus and Test Procedure The apparatus used and the method of testing are described a t length in an earlier paper;4 accordingly, a brief description will suffice here. Figure 1shows the set-up of apparatus used for determining reactivity in carbon dioxide. That used with air and water vapor is essentially the same. Gas flow from the carbon dioxide tank, a, was regulated by valve b and measured by flowmeter c. The gas was dried over calcium chloride in d and led upward through a 3/4-in~h (2-cm.) quartz tube which was packed below the coke with cracked quartz to insure preheating to the test temperature. The 2-inch (5-cm.) column of coke supported on a perforated porcelain plate was placed in the furnace, f, at the center of a zone of uniform temperature. Two platinum, platinumrhodium thermocouples, j , were placed outside the quartz tube a t the top and bottom of the coke column, as shown in the enlarged sketch, s, and one protected bya l/rinch (3-mm.) quartz sheath, h, was placed centrally inside the coke with its junction 1/8 inch (3 mm.) above the porcelain plate. I n all cases except with air, the three couples indicated the same temperature after equilibrium had been reached. A fourth couple placed outside the quartz tube just below the coke 4
Davis and Green, Prqc. Am. Cas Assocn,,,S, 1160 (1926).
88.0
86.1 85.3 86.7 86.8
11.2 18.1 11.9 11.6 9.9 10.1 9.8 11.6 12.0 10.9 11 2
,
%
%
%
%
%
%
2.7 3.1 2.9 0.7 1.1 0.8 0.7 0.6 0 6 0.7 0.6
77.4 70.7 75.2 83.2 85.4 86.8 86.8 84.4 84.6 85.0 85.4
1.7 1.4 1.5 1.2 1.4 1.2 1.1 1.1 1.2 1.0 1.2
6.4 5.2 6.7 1.8 1.5 0.5 0.9 1.7 0.9 1.4 0.9
0.6 1.5 1.8 1.3 0.7 0.6 0.7 0.6 0.7 1.0 0.8
11.2 18.1 11.9 11.6 9.9 10.1 9.8 11.6 12.0 10.9 11.1
ii,tiio
,
12,480 12,440 12,770 12,780 12,820 12,530 12,550 12,620 12,570
led to a temperature controller which maintained the temperature constant to within * 7" C. A water seal, n, permitted the gases not collected for analysis to pass out of the system, a t all times maintaining a slight positive pressure, thus avoiding leakage of air into the apparatus. The gas sample for analysis was collected in the mercury bell jar, 0 , from which it was drawn off and analyzed in the mercury Orsat gas apparatus, p . The test sample of coke, which was sized to pass 10 mesh and remain on 20 mesh, was measured by a container which when filled and leveled held an amount just sufficient to occupy 2 inches (5 cm.) of the 3/d-inch (2-cm.) quartz tube. Care was taken to have the same volume of coke in the tube for each determination. Weighings of samples used in repeated tests proved that this method of measurement gave practically constant weights for a given coke. This volume of coke was filled into the furnace tube in the same manner for every determination by pouring through a funnel inserted in the T-tube, i, and made to fall into the tube by gentle uniform tapping of the funnel. The fuel bed was therefore uniform for all tests. After charging in this manner and making the necessary connections, the furnace was heated up to temperature and carbon dioxide was admitted a t the rate of 200 cc. per minute for 10 minutes to sweep out the apparatus before a test gas sample was taken. A gas sample was now collected and the gas flow to the furnace was nearly stopped during the time required to make the analysis. The gas flow was again adjusted to 200 cc. per minute and another sample taken. Three samples were taken in this manner and their analyses averaged. From the average the reactivity of the coke in carbon dioxide was calculated by the formula: Reactivity =
2
co+ co x (cod '
100
Results of Reactivity Tests Table I1 gives the results of reactivity tests of the cokes at three different temperatures, 800", 950", and 1100" C., and with three different reacting gases-air, water vapor, and carban dioxide. In general, they are listed in the order of decreasing reactivity. Although the order is noticeably reversed in several instances, it may be observed that it is, in general, the same for all test temperatures and in the three different test media. The variations may be due to actual variations in reactivity of portions of the same sample used for test. In what follows it will be shown that there is a fairly large variation in reactivity of different particles of the same coke sample not detectable before testing. However, from these results it may be concluded that reactivity means the same thing relatively regardless of whether it is defined by the air, steam, or carbon dioxide method of determination. Increase in test temperature over the range studied seems for the most part merely to increase the velocity coefficient of the effective reaction. Reversal of order of reactivity for different temperatures where the same medium is used may be interpreted as indicating a different rate of
INDUSTRIAL A N D ENGINEERING CHEMISTRY
June, 1928
increase in the temperature coefficient of reaction velocity for the different cokes. This is an effect to be expected. Koppers6 recently noticed it, particularly where cokes of quite different character were tested in carbon dioxide over wide temperature ranges. The low-temperature cokes are of a distinctly higher order of reactivity than the high-temperature cokes; there is no great variation between the members of the two kinds. I n the latter instance the results
619
for the determination of reactivity based on the temperature of self-heating, Parr8 has shown that reactivity of coke varies i ~ i \ e re y mith the maximum temperature used in coking, and it is well known that low-temperature coke is characterized by high volatile-matter content. Furthermore, in the test method used here the samples were heated for 10 minutes a t 950" C. (called for in the standard method for determining volatile matter) before gas samples for reactivity determination were drawn. This treatment would tend to reduce all samples to the same volatile-matter content. Owing to the necessity of heating the sample to temperature before making the test by this method, it is probably not possible to make a fair comparison between volatile-matter content and reactivity. Table III-E5ect on Reactivity in CO? a t 950° C. of Bulk Density, Volatile Matter, a n d Adsorptive Power COKE
1 2 3 4 5 6 7 8 9 10 11
REACTIVITY
36.8 22.3 10.5 27.5 6.0 3.6 4.8 3.2 4.6 3 0 3 0
DB:k:y 0.41 0.46 0:45 0.60 0.61 0.56 0.52 0.60 0 57 0 56
MATTER
CO? ABSORBED PER 10 GRAMS COKEA T 250
Per cent 10.6 14.2 11.9 2.4 2.5 1.2 1.4 1.6 2.0 1 7 1 6 Active charcoal
c.
CC. 195.5 82.0
...
20.1 3.55 1.96 1.11 5.60 0.97 1 37 0 93 531 00
Reactivity and Adsorptive Capacity
Sutcliffe and Evansg have indicated that the more reactive cokes are those with a large number of minute cells per unit Figure 2-Apparatus for Determination of t h e Volume of Gas Absorbed by Pulverized Coke mass. They attribute the high reactivity of low-temperature cokes and charcoal to the large proportion of pore volume indicate that variation of the method of coking within the contributed by the smaller pores. High-temperature cokes, range of American high-temperature coking practice has no on the other hand, are less reactive because after formation very pronounced effect on reactivity of the coke produced. in the initial stages of carbonization the small cells become clogged through deposition of graphitic carbon by decompoTable 11-Reactivities of Cokes i n Air, S t e a m , a n d Carbon Dioxide sition of volatile matter during the subsequent high-temperaa t Three Temperatures ture stages. Bunte and Fitzlo held similar views and furI AIR I STEAM 1 CARBONDIOXIDE nished evidence of their correctness by tests of the gas-absorbCOKE 800' 950' 11000 8000 9500 11000 800' 950' l l O O o ing capacities of various cokes. It is well known that a subC. c. c. c. c. c. C. c. c. -. stance having a large proportion of very small cells will have 1 60.7 81.4 9 8 . 6 7 . 1 29.0 50.3 3.6 36.8 76.9 a large absorption capacity, particularly for the more easily 2 9 . 3 25.7 42.2 3 . 1 22.3 59.8 58.5 74.3 95.8 3 5 . 5 21.5 48.0 2 . 1 10.5 5 7 . 5 59.6 73.1 96.6 condensable gases, and the amount of such absorption may 4 4 . 4 27.9 47.4 1 . 3 27.5 63.1 56.8 65.1 94.7 be taken as a measure of cell volume of this sort. 5 0 . 5 6 . 0 31.1 58.1 65.4 81.3 1.7 13.9 28.9 0.7 3 . 6 24.6 6 57.6 63.0 73.7 1 . 4 10.9 27.9 The relative absorption capacities for carbon dioxide of 7 58.7 6 3 . 3 7 4 . 1 1 . 3 10.8 27.3 0.5 4 . 6 24.1 8 1 . 6 10.2 25.1 0 . 5 3 . 2 22.5 59.4 62.8 74.4 cokes used in this investigation were measured with the 9 60.0 6 3 . 7 7 4 . 4 1 . 8 11.2 27.7 0 . 4 4 . 6 16.1 apparatus shown in Figure 2. Tube t was filled to a constant 10 59.0 63.3 79.2 1.4 11.8 26.9 0.4 3 . 0 21.9 11 60.0 61.2 63.3 1.6 10.2 24.7 0 . 4 3.0 14.5 level with coke and evacuated to a pressure of less than 1 mm. by pump p . The stopcock s1 was then closed and s2 opened, permitting the gas to enter t . The volume of Variation of Reactivity with Bulk Density gas necessary to restore atmospheric pressure in the coke From Table 111, it is seen that the low-temperature cokes was measured by gas buret o, which also served as a gas hare the lower bulk density and the higher reactivity, but reservoir. I n all tests the coke was maintained a t constant that there is no very close relation between the two properties. temperature (25"C.) by the water bath surrounding t. From This agrees with results reported by Perrott and FieldneP the true specific gravity of the cokes11 and the weight of samand also with those found by Nichols, Brewer, and Taylor.' ple used the true coke volume was calculated. Then, knowing the volume of gas as measured and the volume of the coke Reactivity and Volatile-Matter Content container, the volume of gas (25" C. and 740 mm.) absorbed by the sample was determined. Table I11 also shows the relation between the reactivity Table I11 gives the relation between the volume of carbon and the original volatile-matter content, of each coke. High dioxide per unit weight absorbed by the cokes and their reactivity usually corresponds to high volatile-matter con8 Parr and Staley, IND. ENG.CHEM.,19, 820 (1927). tent, but this is probably purely incidental. By a method
1
* J . SOC.Ckem. I n d . , 41, 196T (1922).
6 8
'
Koppers Mitteilungen, 192S, Heft 2, S. 37. Proc. A m . SOC.Tesfing Materials, 23, 475, 501 (1923). Proc. A m . Gas Assocn.. 8, 1129 (1926).
Gas Wasserfack, 67, 241 (1924). Standard method of test for volume of cell space of lump coke, Am. SOC.Testing Materials, Standards, 1924, p. 1028. 10
11
renctivitie; d e t c r u i i d a t YSU' C'. iii c;rriruii rliosidr. 'l'licsr results show, in general, that the capacity of these cokes for absorption of carbon dioxide is proportional to their reacti7,ity It will be noted, liowever, that sample 8 is a n exception; it absorbs inore carbon dioxide than ot,her cokes of approximately the same reactivity. Evidently there me factors which may modiiy the &et of \-oliinie of small cells, or c n p
Pisure S--Appearance of Coke 4 sffer 'Teafin8 in Steam
illary surface, on reactivity. Usually, but not invariably. reactivity will be proportional to the amount of such surface, Table IV-Variation
Mesh 8-14 14-20 2W85 8- 14 14-20 20-85 8-14 14-u) 20-83 8-14
14-21> 210-3.3
of Reactivity with Size of Coke Particle8
33.2 97 3
ds 3 23.1
30.8 27.8 5.5
si
Cr. 383.5 204.6 197.8 18.7 22.8
23.8 0.5 1.5
P F I
rrni
(1.7 8.5 9.9 10.1
$1.8 9.5 R.8 8.4
R !J
12
s
8.1
:3 R 4.5
I .iI 11.9 1 4
10 13
4.0
10 a 10.4
P"
iP,i*
Variation in Reactivity of Different Particles of Same Coke
Sample
It has bwn s h w tlmt different size coke particles of ,me sainplr ~ n n ydiffer in composition and therefore vity may not have the snme proportionality to coke surfare as expected. Fiirtlier results dJtaiiied show that oven iiniform size p:iriielcs of t,he same cokc sample vary noticeably in rwiclivity. It was noticed thut all the coke samples were of uniform liistcr before testing. Borne of tlie samples were of lighter color than others, but there was no readily distinguishable rliffmence in nppeamm:e of individud particles. After t,estiiig in steam, air, or cartion dioxide, all the cokes showed varying nimbers d distinct,ly blackened particles, as illnsIrat,ed in Figiires 3 and 4. These dark particles were found t,o be very soft+ easily crushed in the fingers. Microscopic examination sliiiwed that blackening extended throughout the particle arid that the gas had completely penetrated the particle ntLacking it uniformly. There was no evidence of precipitated c:irb(m. All colres exhibited the phenomenon of blackening, but with the more react.ive cokes the blackening of particles washy far the more pronounced (more perticles affected). These cokes nlso loolced driller originally. Blackening increased quite rriarkedly u.ith the test temperature: in all cases. When two different samples were made irom one of the brightest portions (oent,er of the piece) and one of the dullest port,ions (end near& tlic retort center) of rt large piece of coke and reactivit,ics of btie two samples compared, the results shown in Table V were obtained. I n every case the dull sample was the mure reactive. When these samples were examined after test---that is, after having been exposed to carbon dioxide and iiir at 950"and 1100" C . 4 t was clearly seen that these from the dull coke contained by far the most t,l;irlieried particlcs. This dcfinitrly wnnect,s blackening with
14.4 14.2 34.4
4.0 4.7
4.8
1.4 2.8 1 8 11 x 11 9 (1.8
Reactivity and Size of Coke Particles
In the preceding pariigralh tlic e.ff(wt (I( wryiug cnpiliary surface on reactivity was detemiinetl. the extcrliiil surface or particle sire remaining consi.ant. Table IT' gives results of tests wherein the external surface was varied and both reactivity in rarbon diiixide and absorptive capacity in car. bon dioxide were determined. It will be noted that reactivity is in all cases inversely proportional to part.icle size. Adsorptive capacity also tends t,o vary inversely witli particle size in the case of lowtemperature cokes 1 and 4. With high-teniperat,ure cokes 7 and 10, no such proportionality is evident. Here, however, the quantities determined are so small that variations found are near the limit of experimental error. Furthermore, the results b u n d for ash and volatile matter show that some segregation took place during separation of the sizes. The different sizes of the same coke were thus identical neither in coke substance nor mineralmatterconbent. It seems clear that with the high-temperature cokes external surface has a greater effect on reactivity than capillary surface, which is in accord with the views of S u e cliffe and Evans9 and nlso wit.h the findings of Sherman and Kinney.12 "Iron A s . 111, 1839 11928).
W u r e 4~~- A p p ~ ~ r a of n ~Coke e after Testins in Air
the original appearance of the coke. The duller the coke originally the more blackened particles it will produce under test and the more reactive it will bo found. The dull coke used here came from near tbe center of the charge where t,he time of exposure to high temperature waq relatively short. Tlius one may say thrtt not only (as found by Parr8) will reactivity decrease as the maximum temperat,ure of coking increases, but also that it will decrease as time of exposure to high temperature decreases. Kopperss also found that enkc near the center of the oven was the most reactive. The effect of long preheating on the reactivity of roke has recent.ly been well shown by Nettlenhusch.lJ He 94
Hiinnrroff-Chrm.. 8. 37 (1927).
I,\-DUSTRIdL
June, 1928
;1-VD E.VGINEERI.VG CHEAWISTRY
ascribes decrease in reactivity brought about thereby to shrinkage of cell space and (at temperatures above 850" C.) to graphitization through decomposition of methane. It may be observed further that in the preparation of active carbon by carbonization of bituminous coal the temperature is kept below 700" C. because if higher temperatures are used it is well known that the high-temperature product cannot be satisfactorily activated. Table V-Reactivities COKE
5
of Bright and Dull Portions of Cokes 4 a n d 5
TESTCONDITIONS
In air at llOOo C. for 60 minutes I n C 0 2 a t 1100°C.for60minutes
4
In air at 950' C.
In Cor at 950' C.
PORTIONREACTIVITY
Bright Dull Bright Dull Bright Dull Bright Dull
Per cent 73.4 82.4 16.9 24.9 63.6 69.9 9.6 32.4
Grams
1.0670 1.9940 1.7500 2.4860
.... .... .... ....
From this study of the phenomena of bIackening during the reactivity test it is evident that there is a separation of reactive and non-reactive particles by the action of the gas. The porous reactive particles are completely penetrated and the reaction progresses throughout the whole particle, whereas with the non-porous (bright) particles the reaction is confined mostly to the external surface. Reduction in size would be expected to have the greatest effect on reactivity of the latter. Whether the effect is due more largely to shrinkage, to stoppage of the pores by other forms of carbon, or to graphitization, it is difficult to tell. It seems certain that any of the gases used in the reactivity test would activate the porous particles and that the rate of reaction would be
621
increased as the test progressed. This was not noticed in any of the cokes tested in this investigation, but it was observed that the surface was gradually reduced by a coating of ash which would tend to counteract the activation tendency. Koppers,6 however, found that a number of samples showed increased reactivity while others showed decreased reactivity, as the test progressed. Conclusions
1-In general, reactivity varies inversely as bulk density and directly as volatile-matter content, but this relation does not always hold, particularly with cokes varying only slightly in reactivity. The effect of volatile-matter content h probably only incidental; it indicates the temperature conditions under which the coke was made, which are the governing factors. 2-Reactivity varies inversely with the size of test particles and will in general vary directly as the adsorptive power. Both properties affect the extent of reactive surface and hence are interrelated. Size of particles has perhaps the greatest influence on reactivity of high-temperature cokes, because their adsorptive capacity is very low. The reactions here appear to take place almost entirely at the external surface. 3-Different coke particles of the same sample show different reactivities, as is manifested by selective blackening of the more reactive particles during test. The duller portions of the same piece of coke, provided they come from the center of the coke charge, are much more reactive than the brighter portions-because they have not been subjected to severe heating conditions. Blackened particles found after making the reactivity test came originally from the dullest portions of the coke.
Carbon Blacks and Their Use in Rubber' I-Comparative Properties of Blacks and Tests in Uncured Rubber Norris Goodwin and C. R. Park DELANO LANI)CO.,2312 EAST52ND ST., LOS
XNGFLES, CALIF
UR howledge regardThe physical and chemical characteristics of several to explain experimental reing the physical and carbon blacks and of rubber stocks containing them sults where the information is chemical characterishave been investigated in order to determine their suitnot complete will be excused ability as Pigments in tire-tread stocks. Five blacks tics of pigments which make in consideration of the chief them more or less suitable as have been Studied-CharltOn lampblack, Micronex, aim of the work, which is only Super Spectra, Thermatomic, and Goodwin. Part I repre nforcing agents in cured to point out the facts, for the rubber goods is very incomresents a study of the Properties of the blacks themauthors realize that certain selves and their use in raw rubber. Part 11, to be pubplete. I n spite of s e v e r a l conclusions may have to be brilliant contributions in the lished in a subsequent issue, will describe tests on variqualified as new information field! we are still far from a ous cured rubber stocks containing the same blacks. becomes available. satisfactory understanding of F i v e b l a c k s h a v i n g as the principles involved in the preparation of compounds. widely different characteristics as possible have been chosen Lack of systematically arranged information is perhaps partly for study: responsible for this state of affairs. The object of this paper Charlton lampblack-an O i l black. was to assemble more detailed and well-organized informamade 'Or and tion in a small field. It is believed that a sufficient number w i & , gas of systematic efforts will place us in a position to understand for use (3) super spectra-^ channel-processgas black more completely the colloidal behavior of pigments in rubber in varnishes and enamels and perhaps in other media. (4) Therrnatomic-A gas black made by thermal decomposiThis study has been confined to the pigments most com- tion of natural gas. combustion monly used in tire treads-namely, carbon blacks-although ~ t w ( ~ by $ ~ ~ ~ ~ in rare cases other pigments have been introduced to illus- of ~ trate some particular point. It is hoped that a few attempts It was hoped that, by a large number of the 1 Received January 30, 1928 various physical and chemical properties of the blacks with
0
~~~~~~~~~$l;PardoecesS
~
~
