I N D U S T R I A L A N D ENGINEERING CHEMISTRY
1146
Vol. 23, No. 10
Rate of Dissolution of a Granular Solid' K. M. Watson DEPARTMENT O F C H E M I C A L EWXNEERING, UNIVERSITY
OF WISCONSIN,
MADISON,WlS,
C
OSSIDERABLE simiBased o n t h e t r e a t m e n t of dissolution as a diffusional face. From Fick's law this Process, m a t h e m a t i c a l relationships a r e developed rate of diffusiuI, is proporlarity exists between the vaporization of a between t h e r a t e of dissolution of a g r a n u l a r solid a n d t i o n a l to the con,er,tration t h e various d e t e r m i n i n g factors. liquid and the dissolution of gradient across the film and a solid. This analogy has reA m e t h o d a n d a p p a r a t u s have been developed for t h e the area of t,he i n t e r f a c e . c e n t l y been e x t e n d e d by quantitative s t u d y of r a t e s of dissolution under widely Thus, Gapon ( 2 ) to yield quantit,avarying conditions. - ~ = D A d~c T(1); tive expressions for the rate T h e coefficients a n d f u n c t i o n s of t h e proposed e q u a tions have been evaluated by experimental studies of ofdissolutionofasolid surwhere e = time face. From this viewpoint t h e r a t e of dissolution of s o d i u m carbonate decaW' = w e i g h t of u n d i s solvrd solid solute the unit process of leaching or hydrate i n water. The general relationships derived a t timc 0 extraction may be treated as for t h i s typical system should be quantitatively appliD = diHu.;ion coefficient cable t o o t h e r a q u e o u s systems. similar to that of drying. In A = intcrfac:al area a t each process a material is retime H c = concentration of solute in solution moved from an inert carrier by dispersing it into a stream of fluid. In developing methods for correlation of the factors dex = distance from interface termining the rate a t which leaching or extraction proceeds, it Over not too ranges of concentration thrl diffusion seems profitable to adopt a treatment similar to that which has may be taken as constant and E;quation been developed for drying processes. Complete discussions written in partially integrated form: of these quantitative principles of drying operations may be found in the standard texts of chemical engineering (1, 7 ) . - -dW' = DA(ci - C ) (2) I n dealing with general extraction problems, the natures de L of the solvent, solute, and solid carrier are all of the greatest where ci = concentration of saturated solution at interface importance in determining the rate a t which extraction will L = effective thickness of stationary film of solution proceed. It is improbable that general methods can be developed for prediction of the effects of changes in these fac- This form of equation has been developed and discussed in tors, However, by thorough investigation of a few typical numerous published papers (2, 3, 4 , 5, 6). As the dissolution of a material proceeds in either an intersystems it should be possible to develop relationships between rate of extraction and such operating conditions as mittent or counterflow type of process, the concentration temperature, the initial state of subdivision of the solid, the of the solution increases and the surface area and weight of rate of flow of the solvent, and the concentration of the soh- undissolved solute diininish. The temperature ( I f the system tion formed. These relationships should, be more or less may also undergo change. As a result, the interfacial area A general in nature and applicable t o various systems of ma- of Equation 2 will vary as a function of rV', the weight of terials which are not too different from those from which undissolved solute. Both the diffusion coefficient D and the they were derived. With such relationships available, it film thickness L may vary as functions of the concentration will be possible to completely predict the behavior of a specific of the solution and the temperature. These functions may extraction system from only a minimum amount of direct be included in Equation 2. Since it is convenient to base all experimental data which is necessary to establish the effects calculations on a w i t weight of original solid charge, W will be used t'o designate the weight of undissolved solute present of the natures of the materials of the system. I n the complete absence of quantitative information re- a t any stage of the process, per unit weight of original solid garding the factors affecting extraction rates, it is desirable charge. Thus, to begin the colIection of such data by consideration of the dW - D J o (3) simplest case. This is represented by the leaching of a solid dFt - Lo f(W)j(t)j(c).(ci - C) containing only a single soluble substance, in which the quan- where W = weight of undissolved solute per unit weight of tity of insoluble material is very small in comparison to that original charge of the solute. Such a material mill behave as though it were D,,, A o ,Lo = initial values of D , A , and L,respectively. a t the a pure substance. The remainder of this paper will be debeginning of a dissolution corresponding to standard conditions of temperature and concenvoted to consideration of the dissolution of such a typical tration a t which conditions f( LV),J ( l ) . and f(c) granular substance, which contains only small quantities equal unity of insoluble materials. t = temperature of solution
--
Mechanism of Dissolution
If the Kernst theory of interfacial equilibrium is accepted, the surface of a dissolving solid may be considered as being in contact with a thin film of relatively stationary solution which is saturated with solute a t the interface. At the outer boundary of this film will be the average conditions of the main body of the solution. From this viewpoint the rate at which the solid dissolves is equal t o the rate at which solute diffuses through the film of stationary solution at the inter1
Received June 8,1931.
The term DoAo/Loof Equation 3 is determined by the relative rate of moyement of the solution b)ast the solid surfaces and by the initial conditions and natures of' the sulid charge and the solvent material. It is indepe~~detlt of temperature t or concentration C. The concentration, ci, of the saturated layer at the interface is fixed by the solubility of the solute and the temperature a t the interface. An experimental study of the interfacial temperatures of dissolving solids was reported by Watson and Kowalke (S), It was found that, even in the case
INDUSTRIAL A N D ENGINEERING CHEMISTRY
October, 1931
of a solute having a high heat of solution, the interfacial temperature differs but little from that of the surrounding solution. This interfacial temperature is analogous to the wet-bulb temperature of a liquid-gas system. However, the interfacial temperature fails to show the constmcy during adiabatic dissolution which characterizes the wet-bulb temperature during adia,batic vaporization.
tion of the behavior of another similar system may be made from only sufficient direct experimental data to evaluate the factor k' for this particular system. In this treatment it has been assumed that the effects of the different variables are independent of each other. This assumption is probably not entirely correct, but a more rigorous analysis would become very complicated.
Lo ai- ma/
Experimental Method
n
The functions and coefficient of Equation 6 may be evaluated by experimental studies on a thin layer of solid charge contained in a short chamber through which solvent may be passed a t a constant rate. In a short chamber, conditions rill be nearly uniform throughout, and it may be assumed that the mean concentration of the solution in the chamber is the arithmetic average of the concentration entering and lcnving. I t is also permissible to neglect diffcrences in the particle sizes of the undissolved solute a t the two ends of the chamber.
' /
. , n :
Figure 1- Cross Section of Experimental Dissolution Chamber
Because of the small difference between interfacial temperature and that of the surrounding solution, the following equation seems justified: ti
-c
=
k"(cc
- C)
1147
(4)
where cl = saturation concentration corresponding to temperature of main body of solution
Equation 4 is a good approximation only because of the small difference in temperature between the interface and the main body of solution. The approximation is best when the temperature-solubility relationship is linear. Combining (4) and (31,
The term D d o k " / L o will be termed the dissolution coefficient, K . Then.
In an intermittent or batch type of dissolution process, the dissolution coefficient will be constant throughout the process if the rate of movement of the solvent past the dissolving solid is constant. In a continuous type of process the coefficient will be constant as long as the natures and rates of feed of both the solvent and the solid charged are constant. However, the value of K will be a function of all these initial conditions which are considered to be constant throughout any given process. Thus,
APPARATUS-The details of the experimental dissolution chamber are shown in Figure 1. The solid charge is supported between two 100-mesh screens in a chamber 15.5 cm. in diameter and 2 cm. in length. The solvent may be introduced a t either end of the chamber. In order to insure uniform distribution of the solvent, a distribution plate is provided a t each end These consist of steel plates through each of which are forty uniformly spaced holes, made with a No. 60 drill. The pressure drops across these plates render the drop across the solid charge negligible, and satisfactorily uniform distribution is obtained. The complete experimental equipment is shown in Figure 2. By means of three-way cocks, solvent can be passed either upward or downward through the dissolution chamber A . The solvent is forced through the dissolution chamber by means of comprcssed-air pressure above the liquid surface in the solvent chamber D. The rate of solvent flow may be regulated by varying the pressure in chamber D and also by means of the needle valves a t the outlet of the dissolution chamber. An orifice meter is provided for control of this rate. The solvent chamber D may be refilled without interrupting the course of an experimental run by means of the auxiliary pressure chamber C. This chamber may be intermittently filled from reservoir B and emptied into chamber D. The temperature of the solvent may be regulated by means of electrical immersion heaters in chamber D and reservoir B. Thermometers are provided for measuring the temperature of the solvent entering and the solution leaving the dissolution chamber A .
...
Iwgr
where d
V k'
K = k'j(d)j( V ) (7) = average initial particle diameter of solid solute charge = velocity of flow of solvent past dissohing surfaces = factor dependent on natures of solvent ,and solute
The factor k' should be directly proportional to the coefficient of diffusion of the solute-solvent system and also dependent on the viscosity and density of the solvent and the shape of the solid particles. By integration of Elquation 6, the time required to reduce W , the weight of undissolved solute per unit weight of charge, to any desired value may be calculated. Before this integration can be performed, the various functions and coefficients must be evaluated for the particular system under consideration. It will be necessary to determine the value of k' of Equation 7 by direct experimentation on each particular system. However, the forms of the various functions should be similar for different systems of somewhat similar characteristics. If the general forms of these functions are determined for a typical system, complete predic-
rWO-W4V COCKS
(B TYpll'iwr ~---- _ ~ -- -
.
= -
_ ~- _ =~
Figure 2-Experimental
@ .4.ecDLc
COVT.(
VALVtS
Dissolution Apparatus
Operetion-In making an expcrimental run, the dissolution chamber was filled with a layer of solute charge 1.8 cm. in thickness. This charge was carefully settled by gentle shaking and leveled with a gage bar The chamber was then assembled into the apparatus and the reservoir chambers B and D filled with solvent a t the proper temperature. Water a t this same temperature was circulated through the water jacket surrounding the dissolution chamber.
I N D U S T R I A L A N D ENGINEERING C H E X I S T R Y
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When all preliminary preparations were complete, the dissolution chamber was quickly filled with solution which was saturated with solute a t the temperature of the run. This saturated starting solution was introduced through the outlet of the dissolution chamber, the air being displaced through air vents a t the top of the chamber. The flow of solvent was then started, the rate being regulated from the reading of the orifice meters. All of the solution discharged from the chamber during a run was collected in individually measured portions corresponding to definite time intervals. Ordinarily the total volume was separated into about fifteen fractions, each of which was measured and analyzed for solute content. The temperatures of the solvent entering and of the solution leaving the chamber were recorded a t the beginning of the collection of each fraction. The run was continued until dissolution was complete. From these data the average rate of dissolution during the period corresponding to each fraction of solution was calculated. The average amount of undissolved solute present in the chamber during each period was obtained by adding together the total quantities of solute collected in all subsequent periods. The average concentration difference, ct - c, during each period was obtained from the average temperature in the chamber and the solubility data of the system.
9
P P
r
' '
4 J0 i- Y7-L L 1 C.F
dhchwe
Figure 3-correction f i r Effect of Saturated Starting Solution o n S o h tion Concentrations
Vol. 23, No. 10
amount of solubility and thermochemical data available. The general relationships derived for this system should be applicable to other aqueous solutions. In all the experiments herein reported the direction of solvent flow was downward. The results of each experimental run were represented by a curve relating the dissolution rate R per unit concentration difference to the weight of undissolved solute JV per unit' weight of original charge. From Equation 7 ,
Since K , f(t), and j ( c ) are all constant throughout a run in the short experimental dissolution chamber, a single curve relating R and W is sufficient to evaluate f ( W ) . UNrTs-The proper choice of units for the expression of concentration c is debatable. For the integration of Equation 6 it would be desirable to express concentrations in terms of the weight of solute per unit weight of pure solvent. However, the concentration unit of Fick's law of diffusion, EFFECTO F S T A R T I N Gon which Equation 6 is based, is weight of solute per unit SoLuTioN-The data col- volume of solution. This unit results in the greatest conl e c t e d d u r i n g t h e first stancy of the diffusion coefficient D, indicating that it is part of each run was of concentration difference per unit volume that is the driving questionable value because force of diffusion. An additional argument in favor of exof the effect of the satu- pressing concentrations in terms of weight of solute per unit rated s t a r t i n g solution volume of solution lies in the fact that many analytical data originally present in the are obtained directly in these units, and that in industrial chamber. This solution practice solutions are generally measured volumetrically. t e n d e d to mix with the For these reasons, it has been judged desirable to express confirst solvent i n t r o d u c e d centrations in terms of the number of grams'of anhydrous and to increase the concen- Na2C03 per 100 cc. of solution. Following is a summary tration of the s o l u t i o n of the units employed: formed. E x p e r i m e n t s were conducted to deterc = Concentration, grams NanCOa per 100 cc. solution W = grams of undissolved anhydrous NazC03 per 1000 mine the magnitude of this grams of Na2C03.10H~0 charged effectas follows:
The dissolution chamber was charged with clean, uniformly sized gravel and then filled with concentrated aqueous sodium carbonate solution. Approximately 820 cc. of the solution were required to fill the chamber. This solution was then displaced by the introduction of pure water a t a constant rate of flow as in a dissolution run. These exDeriments were conducted with eravel of various sizes and witG various rates of water flow.- The direction of flow of the water was downward in all cases. It was found that the effect of the starting solution became negligible after 1600 cc. of solution were discharged from the chamber. Variations in the rate of flow of the water and in the particle size of the gravel had little effect on the extent to which the starting solution and the water intermixed.
I n the majority of the runs data were not recorded until after 1600 cc. of solution were discharged from the chamber. However, under conditions promoting rapid dissolution, a considerable portion of the solute would dissolve during this initial period. For use in these cases the curve of Figure 3 was plotted, expressing a correction to be subtracted from the observed concentrations of all portions of solution collected before 1600 cc. of solution had been discharged. This correction was expressed on the basis of a unit concentration difference between the starting solution and the solvent and was plotted against the total volume of solution discharged from the chamber. By use of this correction it was possible to obtain satisfactory data after only 1200 cc. of solution were discharged. All of the experimental work described in this paper was carried out with sodium carbonate decahydrate (NazCOa.10HzO) as the solute and water as the solvent. This system was selected because of the ease with which concentrations could be analytically determined and because of the large
8 = time. minutes
R = &am, NatCOa dissolved per minute per kg. of
NazCOa.lOHnO charged per unit concentration difference d = average initial particle diameter, cm. V = rate of solvent flow, liters per minute per sq. dm. of cross-sectional area
-
-
W pma/&
of or&ha/ charge
Figure 4-Effect of Particle-Size Distribution o n Nature of Dissolution-Rate Curve
EVALUATION OF f(Hr)-The form of the function relating the rates of dissolution to the fraction of solute undissolved will obviously be dependent on the shapes of the solid solute particles and on the particle-size distribution. In order to
I N D U S T R I A L A N D ENGINEERING CHEMISTRY
October, 1931
investigate the effect of particle-size distribution, several experimental runs were carried out in which this factor was varied. Charges were made up by mixing various proportions of uniformly sized, irregularly shaped particles as follows: Run 25-Uniformly sized, average diameter = 0.57 cm. Run 7 0 - 2 5 per cent, average diameter = 0.89 cm. 0.57 cm. 0 . 2 5 cm. 0.57 cm. 0.25 cm. Run 7 2 - 4 0 per cent, average diameter = 0 . 8 8 cm. 50 per cent, average diameter = 0.57 cm.
50 per cent, average diameter = 25 per cent, average diameter = Run 71-50 per cent, average diameter = 50 per cent, average diameter =
1149
making series of runs with different initial particle sizes and rates of solvent flow the effects of these factors on K may be determined. EFFECTOF INITIAL PARTICLE DIAMETER-TWOseries of runs were carried out in which the particle size of the original solute charge was varied. I n one series the rate of solvent flow was constant at 0.219 and in the other a t 0.547 liter per minute per sq. dni. Pure water a t 20" C. was the solvent, permitting use of Equation 10 for direct calculation of values of K. The results are shown graphically in Figure 5. The dotted curves of Figure 5 were plotted from the equation,
These runs were all conducted with pure water a t 20" C. as the-solvent, introduced a t a rate of 0.109 liter per minute
It is apparent that the coefficient of dissolution is approximately inversely proportional to the first power of initial particle diameter. The error of this relationship is probably little greater than that of the experimental data. This result is in agreement with that mathematically predicted by assuming that the only effect of change in particle size is a change in the interfacial area. EFFECTOF RATEOF SOLVENT FLOW-TWO series of runs were carried out to determine the effect of the rate of solvent flow V on the factor k S of Equation 11. In both series pure water a t 20" C. was used as the solvent. The solute charge had an initial average particle diameter of 0.25 cm. in the first series and 0.57 em. in the second. From these results values of ka were calculated from Equation 11 and plotted in Figure 6. The four points represented by circles in this figure are the average results of the series of runs made in the determination of the effect of particle size. These points should have more significance than those representing the results of a single run.
d- owrage pult,c/r &mtep - cm Figurc 5 -LffsC< of Illltidl F a i t i c k Slzt OILCoeffi* cient of Dissolution Temperature, 20° C . Rate solvent flow er sq. dm. per minute 61, 0.219 liter, 92, 0.547 liter
per sq. dm. The corresponding dissolution-rate curves are plotted in Figure 4. It will be noted that abrupt variations in particle size produce points of inflection in these curves, as would be expected. However, for mixtures in which the particle size does not vary over wide limits, or in which the variation is continuous, these curves may be represented by equations of the form, R = kz(W)^
(9)
Where the variation in particle size is not large it is found that the exponent n is equal to 0.7. The dotted curve of Figure 4 is plotted from Equation 9 with n = 0.7 and kz determined from the data of run 25. If the particles are assumed t o be of uniform size, the exposed surface area may be mathematically shown to be directly proportional to ( W ) l 3 provided each particle remains geometrically similar to itself as it dissolves. All other experiments were carried out with solute charges of uniformly sized particles. COEFFICIENT K-It is convenient to assign values of unity to f(c) and f(l) of Equation 8 to correspond to aero concentration and a temperature of 20" C., respectively. If this is done, numerical values of K may be obtained by carrying out dissolution experiments under these conditions. Then from Equations 8 and 9, K = - R W0.7
(10)
ifc=Oandt=2O0C.
Thus, one value of K can be obtained from each experimental run conducted with pure water a t 20" C. as the solvent. By
0.02
Figure 6-Effect
of Rate of Solvent Flow o n Coefficient of Dissolution Temperature, 20' C.
It will be noted from Figure 6 that the particle size of the charge has little apparent effect on the relationship between the dissolution coefficient and the rate of solvent flow. The form of the relationship is somewhat surprising. The coefficient of dissolution is increased by increased rate of solvent flow until a maximum is reached. Further increase in the rate of solvent flow does not increase the rate of dissolution.
INDUSTRIAL AND ENGINEERING CHEMISTRY
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The explanation of this behavior is not readily apparent.
It might be taken to indicate that a t high rates of solvent flow the thickness of the film of solution a t the rapidly dissolving solid surfaces is not diminished by increased rate of solvent flow. Another view might be that a t high rates of dissolution the Kernst theory of interfacial equilibrium no longer applies and that the rate of dissolution is limited by the rate a t which molecules or ions enter the solution from the solid surface. The portions of the curves of Figure 6 which lie below the maxima are satisfactorily represented by the following-empirical equation: k3 = 0.615
- O.OS(0.6 - V)'
Vol. 23, No. 10
were uncertain but indicated a decrease in f ( t ) with increased temperature.
08
p 06 0.4
(12)
The dotted lines of Figure 6 were plotted from this equation. Combining Equations 11 and 12, K =
0 GI5
- 0.0S(0.6 - V)' d
Figure 8-Evaluation
(13)
Equation 13 is applicable only where the rate of solvent flow I;is less than 0.6. This equation, with different proportionality factors, should be applicable to other aqueous systems.
0.0
3 \
COMPLETEEwATrox-Equation de
- K ( W)OJ(l
of j ( t )
6 may be written as:
- 0.015c)(ct
- c)
(15)
This equation should be applicable with fair approximation to other aqueous systems whose general charactcristics we not greatly different from that investigated. The coefficient K may be obtained from Equation 13 in which a proportionality factor must be empirically established for each system. Integration of the General Equation
06 04
az
Q
o
'
5
, /O '
,
I5
umuye concenhation (2J Figure ?-Evaluation of f ( c ) Temperature, 1 8 O C
Particle diameter, 0 40 cm
EVALUATION oFf(c)-In order to evaluate f ( c ) of Equation 6, two series of experimental runs were conducted using sodium carbonate solutions of various concentrations as the solvents. All experiments were a t 20" C., but two rates of solvent flow were used. Values of f ( c ) were calculated from Equations 6 and 13. The results are indicated graphically in Figure 7 . Considerable difficulty was experienced in obtaining consistent results, especially a t the higher concentrations. The only conclusion warranted by these data is that the rate of dissolution is somewhat diminished by increase in concentration. This effect may be mathematically expressed by the following equation: f(c) = 1.0
-
0.015~
Before Equation 15 can be integrated, it is necessary to express ct, the saturation concentration, as a function of c and then express c as a function of W . The integration may then be carried out graphically,. plotting the reciprocal of the right-hand side of the equation as ordinate against W . The area under this curve between two abscissas, W , and W2,will represent the time of dissolution required for a change from W , to W,. In either a continuous or intermittent process the concen-
(14)
This result is in qualitative agreement with that which would be expected from the increased viscosity and density accompanying increased concentration. If the velocities of flow were such that natural convection was important in determining film thicknesses, this result niight be quite different. EVALUATION OF f(t)-Several experiments were carried out in an attempt to evaluate f ( t ) of Equation 6. Pure water was used as the solvent a t temperatures ranging from 8" to 30" C. At the higher temperatures the rates of dissolution were high because of the large differences in concentration, and the results became very erratic. A less soluble solute would have been more satisfactory for investigation of this effect. The reliable results are shown graphically in Figure 8. These indicate that in the range from 8" to 23' C., f ( t ) is substantially constant. A t higher temperatures the data
Figure 9-Relationship
between c a n d ct in Adiabatic Dissolution of NanCOrlOHaO
tration c may be expressed as a function of W by means of a weight balance equating the loss of solute by the solid to
October, 1931
INDUSTRIAL A N D ENGINEERING CHEMISTRY
the gain by the solution. The general procediire is similar to that followed in the integration of general equations for drying operations (1, 7 ) . However, rigorous solution of the problem is complicated by the fact that the unit of concentration c is based on a unit volume of solution rather than on a unit quantity of pure solvent. It seems desirable for ordinary purposes to make the simplifying assumption that the volunie of solution does not change during a dissolution process; that is, the volume of the solution is :ilways equal to that of the pure solvent. The errors involved will not exceed 5 per cent for many systems. With this assumption the weight balance is readily established exactly as in dryer calculations. ISOTHERMAL PnocEssEs-If a dissolution process is conducted without appreciable change in temperature, the integration of Equation 15 is considerably simplified. I n this case ct is constant and equal to the saturation concentration a t the temperature of operation. ADIABATICPnocEssEs-In a process conducted under adiabatic conditions, the temperature of the solution undergoes continual change as its concentration increases. Watson and Kowalke (8) have demonstrated a method whereby the relationship between temperature and concentration in such processes may be represented by dissolution charts, similar in principle t o this humidity chart. From the dissolution chart of a system, a second chart may be prepared relating cf to c. Such a chart for the system of sodium carbonate decahydrate and water is shown in Figure 9. The dissolution of this material is accompanied by absorp-
1151
tion of heat and reduction in temperature. For example, if dissolution is started with pure water a t a temperature of 20” C., the initial value of cf will be 22 grams per 100 cc. As dissolution proceeds and the temperature is reduced, ct diminishes, the solution finally becoming saturated with a concentration of 9.5 grams per 100 cc. By means of a chart, such as Figure 9, a graphical relationship between c and ct is established which permits integration of Equation 15 to apply to an adiabatic process. Acknowledgment
This investigation was conducted under the supervision of 0. 1,. Kowalke, chairman of the Department of Chemical Engineering, to whom acknowledgment is due for his helpful suggestions duping the completion of the work. The author is also indebted to 0. A. Hougen for his suggestions and critical review of the manuscript. Literature Cited (1) Badger and McCabe, “Elements of Chemical Engineering,” McGrawHill, 1931. ( 2 ) Gapon, Z . Elehrrochem., 34, 803-5 (1028). (3) Lewis, J. IND. ENG.CHEM.,8,825-32 (1916). (4) Lidell, “Handbook of Chemical Engineering,” p. 344, McGraw-Hill, 1922. ( 5 ) Murphree, IND. EKG.CHEM.,16, 148 (1923). (6) Thorman, Chem. A p p . , 16, 185-6,209-11 (1929). (7) Walker, Lewis, and McAdams, “Principles of Chemical Engineering.” McGraw-Hill, 1927. ( 8 ) Watson and Kowalke, I N D . END. CHEM.,22, 370 (1930).
Metallic Constituents of Crude William B. Shirey 110 WILLARD SI., BERLIN,N. H .
Samples of petroleums from different localities are a n a l y s i s of 99.94 per cent, N SPITE of the fact that analyzed. There is found to be a loose quantitative and of the H a r d s t o f t , ash, petroleum is rock oil and ratio between the vanadium and nickel content in the giving a summation analysis closely associated with petroleum ashes. In so far as other mineral constituof 96.99 per cent. Ramsay the mineral world through ents of petroleum are concerned, little or no regularity (5) has recorded a number of geologic time if not in the is found. Analyses do not reveal common occurrence analyses of nickel in petroprocess of its f o r m a t i o n , of metals in sufficient amounts to make petroleum ash l e u m oils, a s p h a l t s a n d very l i t t l e is k n o w n conof interest as a source of rarer metals. Ditches. his main obiect becerning i t s mineral or ing to ’uphold the Sabatierm e t a l i i c constituents. Thomas (8) called attention to the importance of the problem Senderens (7) theory of the formation of petroleum by hyin 1924: “The mineral content of petroleum has hitherto drogenation of simple substances, such as carbon monoxide been largely overlooked, to such a degree, in fact, that one or carbon dioxide, nickel acting as a catalyst. Hackford (4) rarely, if ever, finds a complete analysis of the ash quoted, cites the multiplicity of elements present in the ash from Mexialthough the percentage of the ash is invariably determined can oil as indicating that this oil was derived from marine in analyses of crude oils.” More recently, Gurwitsch (3) has plants, though he maintains that oils of different regions have stated: “The composition of the ash of petroleum oil is a different origins. This research was undertaken to study the quantitative matter of the greatest interest, as throwing light on the probable origin of petroleum-whether the ash content of crude relations between the various metallic constituents of peoils stands in relationship to their general composition is a troleum ash and to determine the possible presence of metals which may have had a catalytic influence on the genesis of the question not yet investigated.” Thomas (8) cites two quantitative analyses and a number oil. It was also thought possible that certain rare metals of qualitative analyses of Persian, Hardstoft, Pennsylvania, might be found present in valuable quantities. Samples of petroleum coke were obtained from different Mexican, Baku, Egyptian, Canadian, Ohio, Patagonian, Japanese, and Chidersynde petroleums. The only quantita- petroleum fields of the United States and these were contive analyses cited are of the Persian ash, giving a summation verted to ash for the analyses.
I
Received June 2, 1931. Project 30 of the American Petroleum Institute Research. Financial assistance in this work was received from a research fund of the American Petroleum Institute donated by John D. Rockefeller. This fund is being administered by the institute with the cooperation of the Central Petroleum Committee of the National Research Council. Dr. Gerald Wendt was director of the project 1 2
Histories of Coke Samples
CRUDE-The crude oil, which is piped (1) CALIFORNIA from the San Joaquin Valley fields to the Union Oil Company refinery, is not run to coke in this plant, and the coke received had not been through any plant treatment. A large
