Jan., 1921
T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
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obtained at t h e Middlefork mine, in addition t o t h e face samples collected in t h e mine. A large coalwashing plant is maintained at t h e mine for washing t h e entire tonnage. Each sample represents a day’s production for t h e mine, which varies between 2400 and 2800 tons. A sample of washed coal representing one day’s operation of t h e washery, on an average day, was also obtained. The sulfur forms in these samples are shown in Table 11.
grateful acknowledgment is made. Mr. C. A . Meissner, Chairman of the Coke Committee, U. S. Steel Corporation, and Mr. Thomas Moses, General Superin. tendent, U. S. Fuel Co., have followed t h e progress of the work with cordial cooperation.
TABLE11-FORMSOF SULFUR I N RAWAND WASHED ?OALS
By S. E. Sheppard
(Values in per cent o n moisture-free basis) Total Pyritic Sample No. Sulfur Sulfur 72 Raw coal.. 3.68 2.42 73 Raw coal.. 3.20 1.90 3.22 1.99 74 Raw coal.. 3.59 2.07 75 R a w coal.. 3.33 1.93 76 R a w coal.. 2.08 77 Raw coal.. . . . . . . . . . . . . . . . . 3.27 7 8 Raw coal., 2.77 1.55 1.99 Average of raw coal., . . . . . . . . 3.29 Average of face samples for m i n e . . .................... 3.30 1.92 2.25 0.92 Washed coal.. ............... Refuse.. 13.45
................ ................ ................ ................ ................ ...............
....................
Organic Sulfur 1.26 1.30 1.23 1.52 1.40 1.19 1.22 1.30 1.38 1.33
The values for organic sulfur in t h e average for t h e run-of-mine raw coal, and in t h e washed coal are nearly identical, namely, 1.30 per cent for the raw coal, and 1.33 per cent for t h e washed coal. Though t h e washed coal sample does not necessarily represent t h e product obtained by washing the identical coal of t h e run-ofmine samples, it must be taken as further evidence t o show t h a t organic sulfur is not segregated with or concentrated around the high specific gravity pieces of pyrite, nor is organic sulfur removable by gravitational methods. The average values for the sulfur forms in the run-of-mine raw coal are in close agreement with t h e average for the sectional face samples collected in t h e mine. CONCLUSIONS
I-Extreme irregularity of distribution is characteristic of t h e pyritic sulfur of coal. This offers a possibility of securing a low sulfur product by separate mining of parts of t h e seam. 2-In comparison with t h e large variations of pyritic sulfur in t h e vertical span of the bed, the organic sulfur is quite uniform. 3-There is little evidence of a definite relationship in t h e occurrence of organic and of pyritic sulfur. High pyritic sulfur in a bench or section of the bed is not indicative of high organic sulfur content. 4-The proportion of t h e sulfur t h a t is in organic combination in various raw coals varies within wide limits. High sulfur coals are ordinarily higher both in organic and pyritic sulfur t h a n low sulfur coals, though organic sulfur makes up a greater percentage of t h e total sulfur in t h e case of low sulfur coals (Table I). j-The organic sulfur content of some coals is sufficiently high t o limit seriously t h e extent t o which these coals can be cleaned of sulfur b$ washing. A C K N 0 W L E D G MEN T
This investigation was carried out under t h e general direction of Mr. E. A. Holbrook, Assistant Director, and Mr. Geo. S. Rice, Chief Mining Engineer, U. S. Bureau of Mines. To them and t o Professors S. W. Parr and H. H. Stoek, of t h e University of Illinois,
COLLOIDAL FUELS, THEIR PREPARATION AND PROPERTIES RE~EARC LABORATORY, H EASTMAN KODAKCo., ROCHESTER, N. Y.
“Colloidal fuels” is the name given t o a distinct class of liquid t o semiliquid blended fuels. They were developed in this country during and subsequent t o the last two years of the Great War. I n physical consistency they range from liquids with a viscosity a t normal temperatures of some j o o Engler t o very plastic pastes, and weak jellies, these latter becoming, however, relatively mobile and fluid when heated. They are composites, in which either finely divided carbonaceous solids or semisolids, or both, are so suspended in and blended with liquid hydrocarbons as t o form relatively stable and atomizable fuels. They have been developed primarily for burning with t h e regular types of atomizing burners using ordinary fuel oils, b u t have also possibilities for use in internal combustion engines of the Diesel and semi-Diesel type. WHY COLLOIDAL?
It may be said t h a t there is nothing in this outline description t o warrant t h e term “colloid.” The term, however, has a considerable elasticity. I do not propose t o add t o t h e excess of definitions of colloids; but will note two recent ones. According t o Dr. Wiley, colloid chemistry is t h e chemistry of “matter without form and void,” and is mentioned in t h e first chapter of Genesis. This gives it a respectable antiquity, and a latitude sufficient t o embrace anything. As agaihst this universal scope, Professor Bancroft tells us “it is t h e chemistry of finely divided masses, in other words, of bubbles, drops, grains, filaments, and films,” and this more specific dictum is certainly applicable t o t h e systems under discussion. However, without striving for a dictionary precision, it may be said t h a t t h e term is conveniently employed to describe the product, both owing t o certain of the fuels’ import a n t colloidal characteristics, and because t h e process of preparation may be justly termed “colloidalizing,” in view of its essential dependence upon colloid chemical processes and conceptions. HISTORICAL
,
Before entering into details of t h e application of colloid chemistry t o t h e fuel problem, let me say a few words on t h e history of t h e present Glass of materials. The idea of burning a suspension of carbonaceous matter in mineral oils appears t o be nearly as old as t h e use of fuel oil, b u t no attempt appears t o have been made t o investigate systematically i t s possibilities. The developments now described date from t h e summer of 1917. A t t h a t time a fellow-worker in this laboratory, Mr. J. G. Capstaff, asked t h e author
38
T U E JOL’RNAL O F I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
as t o t h e possibility of t h e use of powdered coal in conjunction with oil t o supplement t h e latter for oilburning ships. Actually, a n adequate supply of fuel oil was no less vital to t h e Allies than gasoline and lubricants. The German submarine campaign was threatening all of these. Having much faith in t h e possibilities of colloid chemistry, t h e author prepared some composites. They contained up t o 30 per cent of pulverized coal incorporated by a paint mill with an ancient specimen of oil from a laboratory oil bathplus one or two things thrown in for luck. These composites appeared promising as regards stability, and we succeeded in burning them satisfactorily in a n air-pressure oil-fired furnace. Through Dr. Mees these results were referred t o Mr. Lindon W. Bates, Engineering Chairman of t h e Submarine Defense Association, who was already devoting his attention to this very problem. At his instance and with Mr. Eastman’s sanction, t h e possibility of colloidally combining pulverized coal and fuel oil was taken u p by t h e research laboratory, in close and constant cooperation with t h e Submarine Defense Association, under hlr. Bates’ coordinating leadership; b u t for this, and without his catholic knowledge and experience of fuels and fuel problems, our initial experiment would probably have remained a laboratory incident. By “colloidally combining” is t o be understood “stably dispersing pulverized coal in fuel oil,” t h a t is, forming a uniform composite, t h e stability of which a t ordinary temperatures should be reckoned in months, while amply sufficient a t higher temperatures t o permit atomization by fuel oil burners. As stated, Mr. Bates had already been actively considering t h e possibility of supplementing oil for marine purposes by pulverized coal, or oil and coal combined. T h e Association had had assigned by Admiral Benson, Chief of Naval Operation, t h e U. S. S. Gem, which was operated under Mr. Bates’ direction for research work during t h e war. She was fitted with t h e highest class Normand destroyer boilers. Whatever t h e ultimate rating of , colloidal fuels in commercial practice, t h e technical objective was effected when, from April t o July 1918, this craft was successfully operated on a colloidal fuel, containing 30 per cent pulverized coal, as efficiently as with regular fuel oil. I shall return t o these trials in dealing with t h e properties of colloidal fuels. It must be remembered t h a t where a new paint or varnish requires pounds and gallons for practical trial, a fuel requires tons and t a n k loads. Much of t h e technology of preparation and control had t o be remodified as t h e amount prepared increased t o this scale, and in this connection I take pleasure in referring t o t h e constant and invaluable help of m y associate and assistant chemist, Mr. L. W. Eberlin. First let US consider briefly som6 chemical and technical aspects of their preparation. S O M E P A R A D O X E S OB C O L L O I D C H E M I S T R Y
I n many ways t h e science of colloids is a science of paradoxes. So much is evident in its development. As is well known, t h e term colloid was first applied by Graham t o a group of substances, such as gelatin, starch, silicic acid, or white of egg. He contrasted these
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with crystalloids such as sugar, salt, etc., because of their low or negligible diffusibility, difficulty in assuming definite crystalline form, and relative chemical inertness. Graham grouped these properties under t h e conception t h a t colloids had inergia, t h a t is, an inertia of energy which made their s t a t e a t any moment dependent upon their previous history; whereas t h e s t a t e of a crystalloid a t a n y moment can be defined without reference t o its history, b u t is completely defined by quantities independent of duration previous t o t h a t moment. He considered t h a t t h e y formed a dynamic state of matter as compared with t h e static s t a t e of crystalloids. And he believed t h a t this depended ultimately upon a difference in t h e molecules of colloids, a greater content of idiochemical affinity. Paradox shows itself now. The development of colloid science i n t h e last twenty years has been toward quite opposite conclusions, on the whole. It has been i n t h e direction of regarding colloids as physically rather t h a n chemically specific. Briefly, it is argued t h a t any substance in t h e solid or liquid s t a t e can be brought t o t h e colloid condition if i t be mechanically subdivided so t h a t its particles or droplets are approximately between I,U and ~ p inp diameter, t h a t is, less t h a n O . O O O O I cm., but greater t h a n O.OOOOOOI cm., and kept so in suspension in an indifferent medium. In terms of this conception, colloids form a particular intermediate region of dispersed systems or dispersoids, expressed in t h e table: Coarse Dispersoids Diameters greater t h a n 0.1 p , do not pass fitter paper, can be resolved with microscope (up t o 2000) Suspensions Emulsions
DISPERSOIDS Colloids Increasing Dispersity 0 1 p t o 1M P , pass through filter paper, not microscopically resolved, do not dialyze or diffuse
--f
---f
Suspensoids Emulsoids
>
Molecular Dispersoids Diameters smaller t h a n 1 p p , pass through filter paper, not microscopically resolved, diffusible and dialyzable True solutions
It is admitted explicitly t h a t t h e boundaries a r e not sharply defined, b u t t h a t we have a gradation. It will be seen t h a t this relatively clear-cut conception marks a great change. Colloids and crystalloids are not antithetic, b u t connected by continuous transitions. T h e crystalloid condition, involving directed symmetry relations in space, is a n internal molecular condition; t h e colloid state is a n external one, depending upon t h e subdivision of multimolecular masses, and possible t o all chemical substances. T h e properties of colloids, on this view, depend chiefly upon t h e large accession of surface energy, parallel with dispersity. Dispersity is defined most generally total surface Thus, a sphere has a lower as ratio of total volume‘ specific dispersity t h a n a cube of t h e same volume, because its surfaceis smaller in proportion t o its volume. A large number of properties of colloids can be explained very reasonably on t h e view t h a t spontaneous changes in dispersoids will be in t h e direction of reducing t h e dispersity, t h u s diminishing t h e free surface energy, and b y t h e conception of adsorption, i. e . , of surface concentration of (molecularly) dissolved substances on dispersed material. So far S O ’
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Jan., 1 9 2 1
good. But paradox again asserts itself. Considerations of this type are found t o be most satisfactory when applied t o so-called suspensoids, i. e . , colloid or pseudo-colloid systems in which no intimate relation exists between the dispersion medium (solvent) and the dispersed substance. Colloidal solution of noble (nonoxidizable) metals, of many metallic oxides, sulfides, and “insoluble salts” are largely covered. They show themselves optically heterogeneous by Tyndall beam and ultramicroscope, and their behavior is largely representable by supporting the idea of mechanical subdivision with t h a t of specific adsorption of electrically charged “ions” t o their surface, giving them an electric charge opposite t o t h a t of t h e medium. But, it is precisely for t h e emulsoid colloids primarily considered b y Grahamgelatin, albumin, globulin, rubber-the colloids p a y exceZZence-that t h e conception just outlined appears inadequate. Their properties and behavior appear better explainable on a development of Graham’s original conception. Many of these emulsoids, when carefully freed from electrolytes, show only t h e faintest traces of optical discontinuity. The facts point t o their solutions being crystalloid in point of “dispersity,” while their behavior t o acids, alkalies, and salts is best explained in terms of definite chemical reactions. Their outstanding physical property, of forming very viscous solutions readily passing t o elastic gels, is explicable by t h e formation of tenuous networks, of molecular and submolecular mesh, woven perhaps b y the idiochemical affinity of Graham. The t r u e colloids do, however, pass b y easy transitions into t h e pseudo-colloids, for which t h e behavior is less dependent upon t h e chemical character of t h e molecules t h a n on dispersity of mass. Although emulsoids might be supposed more kin t o emulsions t h a n suspensoids, yet an emulsion is a good model of a suspensoid. Hence, all in all, I think we may say t h a t t h e development of colloid chemistry has been perfectly paradoxical. Like t h e completely irregular Brownian movement, which has formed a focus of certain aspects of colloid science, i t is impossible t o fix even approximately a tangent at any point of t h e trajectory of any particular development of t h e science. And this atmosphere of unlimited possibilities lends a fascination t o what a t first seems a repellent medley of empiricism and speculation. COLLOIDALIZING FUELS
I n considering t h e problem of stabilizing a suspension of coal or other carbonaceous matter in oil we can best start from a mathematical law for the fall of bodies in a viscous medium, i. e., one offering resistance t o shearing. Stokes’ law states t h a t t h e steady velocity of fall of a spherical body is given b y t h e formula
v = 27’(S where r = S = S‘ = g = Y
- s’)g gv
radius of particle specific gravity of sphere specific gravity of fluid acceleration per unit mass (gravity) = absolute viscosity of fluid
G I N E E RI A- G C N E M I S T R Y
39
The pulverized coal first tried was a. semi-anthracite of sp. gr. 1.467; t h e specific gravity of t h e oil was 200 0.8997(,~), its absolute viscosity 6. The radius of t h e coal particles could be taken as a first approximation as one-half the aperture of t h e screen they passed through, or one-quarter of the reciprocal of the mesh number. From these conditions we should have had: Mesh t o Which Coal Was Pulverized
50 100 200 400
2r Cm. 0.0127 0,00635 0.00317 0.00158
-------Rate Calculated In. per Day 96 24 6 1.5
of Fall-------
Actual Inappreciable in 7 days
........ ............ I
.
.
.
Appreciable in 4 weeks
The coal used was between I O O and 2 0 0 mesh fineness, and there was about 3 0 per cent by weight present. The wide deviation from Stokes’ law was in the right direction and so far promising. It could be tentatively explained: I-By nonspherical form of the particles. As platelets or spicules they would not fall straight. 2-By increased inner friction or mutual impedance in the concentrated suspension. However, “clumping” would accelerate settling. 3-By some kind of combination, e g , capillary adsorption, with the oil
The oil first used was moreover a nondescript material, very viscous-though not so viscous as Mexican fuel oil. It so happened t h a t t h e first supplies of oil now brought for trial were either Texas Oil Company’s Naval Fuel oils, of relatively low viscosity (around 20’ Engler) or Standard Oil Company’s Naval Fuel oils, of even lower viscosity. We soon found ,that fuel oil is a very variable material. It is well known t h a t mineral oils vary greatly in chemical composition. While Pennsylvania oils, of so-called paraffin base, do contain considerable proportions of saturated openchain hydrocarbons, together with lower members of t h e cyclic olefines, t h e midcontinental American oils have more of the cyclic olefines, also asphaltic hydrocarbons (rnalthenes, carbenes, etc.) and “free” carbon. More important for present considerations is their great variation in physical properties. Fuel oil is a residual product, left b y removal of t h e lighter fractions suitable for gasoline, kerosene, etc., and now still further diminished b y various cracking processes. The oil refiner grades his oils chiefly b y gravity. Expressed in terms of t h e Baume scale, they show pretty wide variation, yet in terms of specific gravity i t is not so considerable. For t h e problem of stably dispersing coal or carbon in oil, t h e variation of gravity, from 0.85 t o 0 . 9 6 , is not so formidable as t h e range of viscosity. This can and does vary from I t o 30,000, in terms of specific viscosity of water. Again, this viscosity varies greatly with temperature. I n our first work, as stated, we encountered the thin end of t h e wedge with oil of about z o o Engler. It was not found possible t o prepare stable composites with this oil untreated, even with coal pulverized so t h a t 99 per cent passed 2 0 0 mesh. To discuss t h e actual stages of treatment as t h e problem presented itself would take too much time and space. It was evident1that i t was necessary:
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Vol. 1 3 ,
No. E
x
2
n
b'
E
g.
I-To find working standards for the minimum and maximum viscosity permissible of the oil base.
3-To find protective colloids adequately stabilizing the comb posite within permissible viscosity limits.
2-To approach the practicable viscosity minima of stable composites t o specification maxima for atomizable fuels.
There are other factors, t o be touched u p o n , b u t these three are dominant. Yet they are very closely,
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1921
T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
interwoven, and interdependent. First, they have t o be considered in regard t o temperature. The viscosity of fuel oils sinks rapidly with rising temperat u r e , as shown in the diagrams (Fig. I). This has t o be considered in relation t o flash point. It has been found1 t h a t for effective atomization by mechanical burners t h e viscosity should be reduced, b y preheating, t o about 8’ Engler. Greater reduction gives no marked advantage. T o secure this, t h e temperature t o which the oil may be heated must not be higher t h a n its flash point. 30
y20
u
z
Lu
>
c
a v
2 10
41
of mixtures-whether for viscosities or fluiditiest h a t this has t o be done by “trial and error” methods i n the main.’ But, technically, it has been adequately solved, and a great amount of valuable d a t a secured. Commercially, i t is subject t o local a n d temporal conditions of availability. S T A B I L I Z A T I O N A N D P R O T E C T I V E COLLOIDS
As already stated, the problem of stabilizing suspensions of carbon in oil is not solely one of getting viscosity in t h e oil medium. While heavy paraffins and cyclic olefines give viscosity-and have also much protective value as semicolloids themselvesthey are too valuable, as lubricants, t o be very available in fuel oil. The more viscous residuals available for increasing viscosity are asphaltic materials, containing large amounts of “free carbon,” in colloidal suspension, but tending itself t o clot a n d settle out. There are two ways of stabilizing this, of which the first we need consider is the use of protective colloids. Protective colloids in aqueous systems are well known, e . g., gum arabic, gelatin, glue, etc. They are classed first name as emulsoids, or lyophile colloids-the from the idea t h a t they form a submicroscopic liquid dispersed phase, the second from their affinity for t h e solvent. It is the second conception which is t h e
TEMPERATUQE FAHRENHEIT FIG. 2-BLENDED
OIL CURVES
We have then one terminal pair of values t o be worked t o : Viscosity, 80” E . ; Temperature, flash point British naval specifications for the flash point were: not lower t h a n 1 7 5 ” F. closed cup, or 200’ F. open cup; U S. A. specifications: 15o’F. closed cup, or 175’ F. open cup. Considering then, for the original purpose, t h a t a close approximation t o naval standards was desirable, i t had t o be aimed t o make the terminal pair of values of t h e viscosity-temperature curve of the composite fuels 8 ” Engler a t 150’ F. There is, however, evidently a certain latitude, in t h a t with higher flash points a higher preheating temperature for t h e same viscosity is permissible. Again, the viscosity depends upon t h e pressure of injection. While blending a t first was mainly a problem of thickening thin oils t o suitable mi?zimum viscosity t o permit of practicable amounts of t h e “stabilizer” .or “fixateur” being used, i t later became rather a question of suitable maximum viscosity, so t h a t too thick a fuel did not result. It might be thought t h a t this latter condition simplifies t h e stabilizing problem, i n so far as stability depends upon viscosity. This is partly t r u e , ’ b u t not entirely. I n very viscous fuel oils, such as Mexican Panuco, etc., there is a strong tendency for “free carbon” and suspended carbon t o clot. So t h a t there also the role of “protective colloids” as also of peptizers and deflocculators is very important. Before passing t o these aspects, let me point out in conclusion of this section t h a t “blending” meant adjusting the oil base t o a standard viscositytemperature curve (Fig. 2). So great are t h e varieties of these curves with differe n t materials, and so large the deviation from any law 1
E. H. Peabody, “Oil Fuel,” Trans Internat. Eng. Cong., 1916.
PERCENTAGE FIG. %-CURVES SHOWING VISCOSITY OF FIXATED OIL IN RELATION TO CONCENTRATION AND STATEOF PROTECTIVE COLLOID
more important. Substances forming emulsoid colloids in nonaqueous media are also known. Many 1 See the recent and valuable paper by W. H. Herschel, “Saybolt Viscosity of Blends,” Bureau of Standards, Technologic Paper 164 (1920).
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soaps, particularly of t h e alkaline earth metals, such as lime soaps, form emulsoid colloids with mineral oils. It is a group of these which furnished t h e fixateur, or protective colloid used t o stabilize suspended carbon in colloidal fuel.’ Like emulsoid colloids in water, t h e preparations of these soaps in oil show a very rapid increase in t h e viscosity with increasing concentration of colloid (Fig. 3). This viscosity-concentration curve is very important i n judging t h e adequacy of dispersion of t h e colloid,
0
on t h e one hand, and t h e measure of its protective action on t h e other. With t h e particular t y p e of emulsoids we have t o deal with, the steepness of this curve depends markedly on t h e mode of preparation. It appears t h a t every gradation exists between t h e markedly emulsoid condition and suspensoid dispersion, in which t h e system is much less stable. QUANTITY O F FIXATEUR AND V I S C O S I T Y
The amount of fixateur which could be used was approximately fixed by conditions of cost, and varied from 0 . 5 t o 1.5 per cent. Although t h e immediate effect is t o thicken t h e oil, i, e., increase its viscosity, i t is t o be remarked t h a t increase of viscosity alone is not t h e sole condition conferring stability of suspension of carbon or pulverized coal, coke, etc. Oils thickened by other means, e. g., by vaseline, t o t h e same viscosity, gave much lower stabilities. It was repeatedly found t h a t viscosity, while a n important factor, was not t h e only one. This is already known t o be t h e case for t h e protective action of emulsoids on suspensoid colloids, and evidently extends t o suspensions. PLASTIC I N N E R FRICTION
O n t h e whole, i t is probable t h a t t h e immediate condition for protective action is strong adsorption of t h e colloid t o suspensoid or suspension. But this does not entirely account for t h e mechanism of protection. I believe we may account for this by t h e tendency of these colloids t o form heat reversible gels. Such gels-not coagula-may be imagined as very tenuous web-work or loams, t h e mesh or walls 1 T h e Suhmarine Defense Association, a war organization, dissolved and terminated its existence a t the close of hostilities. During the war it sponsored the new fuel. All patents, trade-marks, copyright and other rights in the fuel are in Mr. Lindon W. Bates’ name and are vested in a company. Release 01 patents since September 1920 has allowed explicit statement of the fixateur t o he made.
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of which are very probably submolecular i n dimensions; or, if we like, t h e whole mass of colloid forms one ’“molecule” uniformly dispersed through and partially dissolving t h e solvent. By partially, I mean t h a t p a r t only of t h e “molecule” of t h e emulsoid is consolute with t h e solvent or dispergent, while t h e other part of i t is insoluble, and its atoms tend t o unite, forming a semirigid framework. Such a system would have t h e following properties, which are observed i n jellies: I-Offer little resistance, unless very concentrated, to diffusion of solute. 2-Offer little resistance t o powerful shearing stress, or movement of heavy bodies. 3-offer great resistance t o very small shearing stress, or movement of very small masses. T h a t is, such systems would behave as $Rids for internal diffusion of solutes, and for shearing stress of appreciable magnitudes, b u t approach t h e behavior of elastic solids for internal movements of small magnitude. Internal friction of this t y p e has been termed “plastic,” and is illustrated diagrammatically in Fig. 4. Differential resistance of t h e kind noted is characteristic of t h e plasmas or body fluids of organisms, and i t is such a plasma which is required for.colloida1 fuel. Hence, i t has really more t h a n one coefficient of inner friction, and t h e gross viscosity is not a complete exponent of its inner state. PEPTIZATION A S D COLLOIDAL FUELS
I have said t h a t there is a second method of improving t h e stability of suspensoids and suspensions of carbon in oils, other t h a n t h e use of emulsoids or protectives. This consists in peptization. The t w o methods are probably connected. Protective action probably means strong adsorption, and adsorption leads t o peptization. But i t may not go so far. Peptization for stabilizing graphite was employed b y Acheson, who used tannic acid as a deflocculator. It was found in t h e present work t h a t “free carbon” in residual oils, such as pressure still oil and Mexican oils, could be peptized and stabilized by addition of certain by-products and distillates.’ This occurred with a lowering of t h e t o t a l viscosity, due t o t h e prevention of clumping, Next, a still more remarkable peptizing action of this t y p e has been observed. This was discovered as follows: We had found t h a t t h e peptizing of “free carbon” in petroleum residuals could be extended t o t h e problem of stabilizing dehydrated coal t a r s i n mineral oil. Further, reasoning b y analogy with Pickering’s emulsions, in which a finely divided solid was found t o stabilize a n emulsion of two immiscible liquids (oil and water), a n attempt was made t o stabilize coal t a r i n oil by further addition of pulverized coal. This attempt was largely SUCcessful, a stability extending into weeks being secured. We further added small amounts of peptizing substances t o these composites. On measuring t h e viscositytemperature curve of these, i t was observed t h a t when maintained some time a t relatively high temperatures t h e viscosity, instead of diminishing, actually increased. This thickening action was observed in detail. Dilution with xylene and microscopic examination, with 1
S o t a b l y creosote and naphthalene containing oils from tar.
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1921
T I I E J O U K X A L O F I i V D i i S T R I A L A N D ENGI,VEERIAVC C I i E Y I S T K Y
counting chamber, showed that the number of very small t o ultramicroscopic particles was greatly increased, these showing livcly Brownian movement. Peptization or partial solution of coals b y such means is t o be expected. The investigations of Bone, Wheeler and others‘ have shown t h a t in genera! w c may regard coal as composed of three principal fractions, u , 8, and y. Of thesc the u-portion is composed of compounds iiisolublc in pyridine; the &portion is soluble in pyrirline but insoluble in chloroform; while the y-,
or resinic portion, is soluble both in pyridine and chloroform. It is well known that the oils distilled from resinous bodies such as amber, copals. rosin, rubber, etc., are solvents for these substances themselves, the solutions, however, being generally incompietc (peptization). The microscopic examination of coals’ tends t o show t h a t with certain exceptions coal is far from being a physically or mcclianically homogeneous materia!, resultant of pyrogenic metamorphosis. To quote Wheeler and Stapes:* We conclude that coal is a conglomcrate of morphological orgntiired plant tissues, natmal plant substances devoid of morphological organization (such. for instance, as rcsins) togciliw with the degradation product.; of a. porlioii of the plant tissues :and cell conteuts comminuted, rnoiphologicnlly disorganized, or present in the form of varying members of the iilmili group. From this i t will he seen that the efficiency of pcptization by tars and distillates is likely to vary con.. siderably from one coal t o another, and again t o some extent with diflcrent particles of the same pnlverized coal. I n practice, this is found t o be the case. Actually, howevcr, cannel, bituminous thracite coal have been found pep mctlioils. Sach peptization does not, alone, neccssarily produce complete stabilization in the oil-tar medium. Generally it is easy t o sccnre 3 t o 4 wks. of hoinogencity. After this the composite gradually separates into an oily supernatant top lnycr over a more viscous mass. This lower layer, however, is usually quite easily remixed, and only very slowly, if a t ail, tends t o pass t o a dense, solid mass. Usually the. lower stratum forms a more or less mobile jelly, * 21. C. Stope. and R . V. Wheeler, rnonojrilph on the “Constitution of Coal,” Depwirnent of Scienti6c and IadiisLrid Reseiich oi Gt. Britain, I.ondon, 1918. 2 LOC/ Cent
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1146.i
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