August 1949
INDUSTRIAL AND ENGINEERING CHEMISTRY NOMEXCLATURE
b = specific gas constant, 0.25504 (lb./sq. in.)(cu. fk/lb.)/
(1) Batuecas, J . chim. p h y s . , 31,165 (1934).
12. P = pressure, lb./sq. in. abs. p" = residual vapor pressure, Ib./sq. in.
(2)
II
p,'l = reference vapor pressure, Ib./sq. in. abs. 459.69) T = absolute temperature, R = (' F. specific volume, cu. ft./lb. 17 residual volume, @ T I P ) - V , cu. ft./lb. II
+
v =
Z
=
1737
LITERATURE CITED
compressibility factor, PV/b?'
Gilliland and Scheeline, IND. EKG.CHEM.,32,48(1940).
( 3 ) Powell and Giauque, J . Am. Chem. Soc., 61, 2366 (1939). (4) Roper, J . Phys. Chem.,44, 835 (1940). (5) Sage and Lacey, Trans. Am. Inst. Mining M e t . Enyrs., 136, 136 (1940).
Seibert and Burrell, J . Am. Chem. Soc., 37, 2683 (1918). (7) Vaughan and Graves, IKD. ENG.CHEIII., 32,1252 (1940). (8) Wiiikler and Maass, Can. J . Research, 9, 610 (1933). (6)
RECEIVED August 2, 1948.
ANTIFOULING PAINTS Role of Pigment Particle Size in the Performance of Toxic Paints ALLEN L. ALEXANDER, J. B. BALLENTINEl, AND M. 0. YEITER2 Naval Research Laboratory, Washington, D . C . T h e current study describes a method for classifying a standard pigment sample into fractions of measured particle size. Classified fractions were incorporated into a standard antifouling matrix and two slightly varied vehicles. The paints were studied carefully to determine characteristics resulting from variations in particle size with a view- of establishing the precise effect of particle size on performance. Viscositj characteristics imparted by the fine particles did not appear to be so severe as supposed heretofore, although paints containing high percentages of small particles may be expected to exhibit
higher viscosities in the normal pattern. Only initial leaching rate values appear to be enhanced by predominantly small particles of toxic pigment. The steady state leaching rate remains unaffected in a given matrix regardless of particle size. I n antifouling paints prepared from rosin and its derivative larger pigments seem to reinforce the physical stability of the film much more effectively than extremely small particles; however, when organic tougheners are added for the purpose of strengthening the film the influence of pigment particle size becomes less significant as a stabilizer of film integrity.
A
dieted by oil absorption values. They display also decided thixotropic properties after periods of storage. On the ot,her hand, cuprous oxide of pyrochemical origin is characterized by high apparent density, low oil absorption, and a rather dull red color. It imparts low consist'ency to the paints in which i t is incorporated. This pigment produces paints of a fairly standard consistency with much less after-bodying in storage. Each of these phenomena may be associated inimediately with pigment particle size. Because the much more finely divided electrolytic product displays more erratic physical properties in paints it is a further purpose of this research to study the influence of particle size on some of the physical properties of paints prepared from cuprous oxide of controlled particle size and apparent, surface area.
S A RESULTof researches reported in recent gears, successful antifouling paints may be designed with the assurance that effective suppression of marine growth may be maintained for periods up to several years. A significant contribution was made by Ketchum and associates ( 6 ) with the demonstration that for paints containing metallic copper or its compounds as the toxic, ~ copper per square the rate of dissolution must exceed 1 0 of centimeter of paint surface per day to prevent the attachment and growth of fouling organisms. Subsequently a number of mechanisms for maintaining this rate were investigated. Ferry and Carritt (.2) made an exhaustive study of the solubilit,y and rate of solution of cuprous oxide (the most commonly used copper ingredient))and Ferry and Riley ( 3 )reported on the solubilities of various antifouling toxics in sea water. Such data are valuable in the design of antifouling coatings intended t o maintain adequate b u t nonexcessive leaching rates. Matrix solubility has been demonstrated by Ketchuni, Ferry, and Burns ( 5 ) to be a crit,ical factor in controlling the rate of release of toxic to sea water, while the role of film permeability as described by Young and Schneider ( Y ) and discussed further by Alexander and Benemclis ( 1 ) cannot be disregarded in the formulation of efficient' antifouling paints. Particle size or total surface area of toxic pigment obviously bears a direct relationship t o leaching rate along with each of the factors mentioned above and it is a purpose of this paper to discuss the effect of particle size on antifouling efficiency as demonstrated by leaching rate measurements and marine exposure of paints containing pigments of predetermined range of particle size. Experience in the manufacture of paint a t the Mare Island Kava1 Shipyard ( 7 ) has indicated cuprous oxide of electrolytic origin to be of relatively low apparent density and high oil absorption, arid to possess a highly brilliant yellow color attributable to its fine particle size. Paints prepared from it follow somewhat erratic patterns of consistency (on the high side) as pre1 2
Present address, University of Xorth Carolina, Chapel Hill, N. C. Present address, Rohrn & Haas Company, Philadelphia, Pa.
PARTICLE CLASSIFICATION AND MEASUREMENT
The classification or even the nieasurement of true particle size is rarely a n absolute process and owing t o the volume of material involved in a study of this nature, absolut,e methods free of numerous assumptions are not' often applicable. The results obtained are dependent' in a large degree on the physical principle3 involved and the validity of the assumptions made. I n the case of cuprous oxide the aut,hors are dealing with part,icles irregular in shape which can be classified and measured only by imaginary conversion to spheres which are assumed to be equivalent in some property to the particles. Thus, in sieving, the particles are assumed to be the largest sphere that would pass a given aperture and sedimentation assumes the particles to be spheres of identical material possessing the same falling velocity in a fluid (4).When thesedimentation process is reversed and the particle is balanced or rises in an upward flowing column of liquid or gas, it is termed elutriat'ion. Separation of particles of subsieve size into fractions may be effected by means of a series of cylindro-conical forms of succes-
1738
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
sivcly increasing diameter of n-hich the Roller particle size analyzer ( 8 ) is tvoical. As a result of increasing diameter of successive cylinders the gas velocity decreases in each stage, the coarse particles remaining in the first vessel and relatively finer particles remaining in succeeding vessels. Air elutriation appeared t o offer the most practical met,liod of separating the particles into graded fractions wit,li fairly close size limits, and is the only method presently available for classifying subsieve particles without wetting. T h e disadvantages of air elutriation are the length of time involved, particularly for fine particles, and there may be considerable overlapping of size between consecut,ive fractions because of varying air vclocities across the section of the elutriation tube. I n order to expedite the classification process a preliminary separation n-as made in an air elutriation tube shown in Figure 1in nhich the upn-ard velocity of the air was controlled outside of the tube. The sample of cuprous oxide was placed in a beaker which served as R sample container for the glass cylindrical tube t o which i t mas connected by a rubber gasket,. Air under constant, pressure u-as inFiWre Air Elutriation Tube jected through a tube leading to a n inverted glass funnel over the top of which a perforated glass disk vias sealed. Through the four perforations pieces of small copper tubing extended as indicated touching the surface of the sample. During operation the beaker mas vigorously shaken by means of a flexible wire attachment t o an off-center connection with an electric motor. The samples were collected in a porous extraction thimble a t the top of t,he column. By carefully regulating the air pressure entering the column approximate particle size of each sample was controlled. The final separation was made in the Roller analyzer, Figure 2. Particle size was determined for each fraction bv eaaminat'ion under a microscope \\.ith a 97x, 1.8mni. oil immersion objective Y.A. 1.25, and a lox eyepiece. A graduat,ed s c a l e w a s inserted in the eyepiece and calibrated with a stage microrneter. I .mproved vision !vas obtained through the use of a E u s c o p e which projected the field of view upon a silvered screen where it was observed through a stereoscopetype eyepiece. The assembled a p p a r a t u s is shown in Figure 3 . . Sanip1,es for microscopic inspection were prepared b y shaking a small amount of thoroughly mixed pigment from a glass rod upon a slide; t o t,his 3 or 4 drops Figure 2. Roller Analyzer " A
I
Vol. 41, No. 8
of a mixture of n-et ting agent, gelatin, and gum arabic in aqueous solution were added. Uniform dispersion m-as effected by means of a small artist's brush using a circular motion.- After drying, the slide was niacle perinanent by covering n-it11 a t'hin coat of acrylate lacquer. T h e act,ual number of particles falling between each unit of the scale was counted with the aid of a multiple laboratory counter. Microscopical measurement affords the unique feat'ure that particles arc measured individually instead of being g r o ~ p e d and estimated statistically, although to eiipure a reprc count the number of particles inrolved is necessarily la1 elutriation process was repeated follomcl by frequent microscopic examination until definitely classified fractions of cuprous oxide were obtained for incorporat,ioii int~oexperiiiient,al psint. Particle size distribution data on the pigment TVCTC obtained by establishing definite size limits bi:twccn which each particle must, fall and assuming that all particles n-ithin eack range possessed a diamekr equal to the upper limits. For example, in the range 0 t o 0.88,~ t,he assumption vias iiiadc that each particlc was 0 . 3 8 ~in dianieter while each of thoie falling bet\veen 0.88 to 1 . 7 5 , ~ir-ere described by the value 1 . 7 5 ~ . hssuming further the particles to be iiid each to be a sphere, thc n-eight)of a particl(: he calculated as follon-s:
Where 6.26 = density of cuprous oxide in g.,)nil. 0.5235~2~ = volume of particle of 0' dianicter ( l / i , 2 r d 3 ) 1 >: = p 3/cni.3
By actual count the percentage of part'icles from each classified
group falling betu-een eshblished size limits was estimated. This furnished the basis for calculating the total surface area for any given weight of material whose particle size distribution had been determined. The calculation follows: 100 X 10" X .rrd2 - area in square
6.26 X 0.5236d3
100 X lox2X r d L : 1 x 1012 6.26 X 0.5236d3
=
,u
of 100 grama of material of d diameter
squaie nieteis ol 100 grains of inxterial of d diameter
= -95.948
d
From the two equations data for particle weight and surface area were calculaled as shown in Table I. The sample selected for classification was taken from a routine procurement of pyrochemical cuprous oxide described by S a v y
Figure 3.
Apparatus for Determining Particle Size
August 1949
TABLE I. CALCULATION OF PARTICLE WEIGHT AND SURFACE AREA
Fraction No.
l'/z 2 3 4 20 40 50
TABLE 11. SURFACE AREA Fraction 1 2 3
Size Limits, 0-5 0-10 0-20 0-80 5-10 10-20 20-80
f 6 7
'
Surface Area per 100 G . Pigment, Sq. M. 108.7 54.82 37.82 27.33 18.23 13.67 2.74 1.37 1.10
Particle Xt., G. X lo-" 0.223 1.757 5.308 14.053 47.429 112.425 14,063.1 112,425.0 219,580.0
Diameter ( d ) , p 0.88 1.75 2.53 3.50 6.25 7.00 35.00 70.00 87.50
vs 1
OF
3 50
i"--7I i
;I 300
* I N I T I A L - 1293CPl 8 WEEKS-I327Cp.
Surface Area/100 G., Sq. M. 37.69 22.10 6.88 2.33 11.30 6.82 2.72
fi
AVERAGE-1225cp.
KEY
0 SURFACE
0.88 1.25 2.63 3.60 5.25 7.00 8.75
38.60 46.00 11.25 2.50 1.75
43.66 33.00 11.80
...
2i:Oo 26.26
..,
2.00 0.70 ...
...
... . . I
... ., ,
6.00 3.00
... ...
...
...
AREA
Sq MoIcrS/100
Classified Fractions 0-20 0-80 5-10 10-20 % Distribution 18.33 4.55 13.00 1.76 31.83 76.09 7.00 ... 10.93 15.42 0.50 0.44 14.78 19.76 9.50 1.76 6.75 7.91 27.00 1.32 4.50 2.37 25.50 2.20 2.89 1.78 12.50 9.25 ... ... ... ... ... 0.60 , 2.20 ... 1.38 ... 0.88 ... ... ... , 0.40 ... ...
..
..
.
I
20-80
., ... ,
,..
...
...
... ... ,..
5.92 12.13
.
...
0.30
specification 52C4. By the air elutriation process it was separated into seven fractions falling between the limits designated in Table 11, which also lists the surface area of 100 grams of pigment calculated as above. T o illustrate the effectiveness of the separation the percentage of particles of each diameter in several classified groups is shown i n Table 111. PAIhT PREPARATION AND PROPERTIES
The matrices of two typical antifouling formulations were selected for studying the classified fractions of cuprous oxidenamely, S a v y specification 52P61 along with a n experimental variation given in Table IV. Previous experience indicated t h a t fine particles of cuprous oxide dispersed in matrices of this type exhibit a tendency to be removed by reacting with components of t h e vehicles presumably to form copper soaps. I n order to reduce this tendency a quantity of 52P61 vehicle was pigmented with cuprous oxide and after 4 weeks of standing the pigment was removed by filtration through an analytical grade of diatomaceous silica. This "reacted" vehicle formed a third medium in which the classified particles were studied.
Viscosity, 52P61 Vehicle
stant rate for 15 minutes. Grinding of the primary pigment was avoided to minimize any change in particle size after classification. Particle size of the dispersed pigment in the paint was determined from diluted samples spread on slides and examined under the microscope as described above. VISCOSITY. Because of the difficulty in obtaining sufficicnt quantity of classified pigments, paints for viscosity studies were confined t o the two vehicles 52P61 and 52P61X. After grinding, half-pint containers were filled with the paints and the temperature of the paint was maintained constant until viscosity was measured by means of a Stormer viscometer a t intervals of 1, 2, 4, and 8 weeks. Initial, final, and average viscosity values for the two series of paints are plotted in Figures 4 and 5. I n some instances average viscosity is highest because of high values obtained for second and fourth weeks. For comparison, similar figures are given for a very finely divided electrolytic cuprous oxide. I n Figure 4 the fairly smooth curves follow rather closely the wellrecognized viscometric properties of paints of this nature. T h e extremely high initial and continued viscosity of the electrolytic product should be noted. There are occasional wide variations from each curve which represent an unusual behavior b u t each is rather a n exception to the general pattern. The paints derived from 52P61X displayed a somewhat more erratic behavior in their viscosity characteristics as indicated in Figure 5 . Initial values were constant, following a straight line relationship with surface area. T h e final values, after 8 weeks of storage, while not conforming t o a n exact pattern, do produce a general trend with
0
All vehicles were ground on a laboratory 3-1-011 mill at a tight adjustment with the specified amount of diatomaceous silica. T h e classified cuprous oxide was stirred in and agitated at a con-
i
TABLE IV. PAINT FORMULATIONS Rosin, W.W.
52P61X, G. 211.0 106.0 14.0 176.0
'ii.0
422.0 1000,0 a
gram)
SIZE DISTRIBUTION O F DRYPlQMENTS
0-10
L(
8 WEEKS
0
d AVERAGE
Figure 4. PARTlCLE
0-5
4o:OO
400
DRYPIGMENTS
~~
TABLE 111. PaAcle Diameter,
1739
INDUSTRIAL AND ENGINEERING CHEMISTRY
AVERLGE.K44CP,
'52P61a,G . 224.0 112.0
...
66.0 75.0 75.0 448.0 1000.0
I
I
10
5
1
I5
I
20
S U R F A C E bREA-SQ M E T E R S / 1 0 0
I
25
I
30
GRAMS
Same quantities used for 52P61 reacted.
Figure 5.
Viscosity, 52P61X Vehicle
I
35
INDUSTRIAL A N D E N G I N E E R I N G CHEMISTRY
1740 60
I
Vol. 41, No. 8
I
a
70
-
I
I
I
I
I
I
I
I
40
0
I
STATE
STEADY
I
I
1
~
1
0
/ V
30-
20-
e// -
o--o-
-
W
4
m
f
0
IO
20
SURFACE A R E A
Figure 7 . Ahoce.
Belou,.
-so
METERS/IOO
0
INITIAL R A T E
0
STEADY S T A T E
25
PHYSICAL
CChGlTlON
SURFACE
AREA
60
30
35
GRAMS
Leaching Rates 52P61 vehicle
5ZP61 reacted vehicle
markedly increased viscosity with surface area. The average figures for the entire 8-weeli period are considerably higher than for the 52P61 vehicle and do not folloiv any readily described pattern. -4gain it may be noted that the clcctrolytic cuprous oxide produced a paint of high initial and continuing viscosity although somewhat belon- that of 52P61. Froin these data i t may be coiicluded that fur a matrix containing principally rosin a i d its derivatives, viscometric properties may be expected t o l o l l o ~the normal pattern of increasing directly with total surface area of pigment. In the case of the electrolytic cuprous oxide it might be assumed that the true surface area is many times in e apparent area, thus accounting for the wide difference values. I t does appear sigiiificant, hon-ever, that the after-bodyiiig previously reported (7') does not always follow as evinced by a rather steady viscosity over the 8-week period. The additicn of a toughener in the form of PlioliCe (52P(iIX),
even in relatively small amounts: appears to introduce a marked effect upori viscosity. This propt does riot manifest itself imrnediately as the initial viscosity ve is exactly in the normal pattern. On standing, however, .the general level of all T is raised Tvhile displaying veri- poor correlation vc-ith apparent surface area. Again the values for the elect,rolytic product are higher and more or less constant. The addition of a toughener such as Pliolite may not be expected to add to the package stability of t h e paiiits> although it tend?: t o raise the general level of viscosity throughout the range with thc csception of initial values. LEACFIISGRATE ~IE.4STRi;JIEh-P. h i n t s for leidiiiig ratt: ineasurenierit, were forwarded to the \$700ds Hole Occanographic Institutioii, wlio lrindly furnished thc data of Figures 6 arid i as deteriiiined by the soaking method described by Ketchum et a/. ( 6 ) . Leaching rates were determined for paints prepared from three vehicles and each of the classified pigments. h s might he expected from this general t,ype of' formulation, the leaching rate of each T V ~ Ssufliciently above the established niiriimuni (107 per sq. cm. per 2 1 hours) to ensure adequate antifouling performance of the paints throughout the ppriods studied. The initial rate increases rapidly with apparent surface area of pigment: vhereas the effect o n steady rate is markedly less. The curves of Figures 6 and i (above) are almost identical which indicates that the addition of a tougheiier such as Pliolite, while obviously influencing viscosity arid storag ahiliry, producm no significant changes in the rates at n-hich copper may be leached from the paint. Certainly any influence exerted by this minor change in vehicle conipositioii is masked completely by the variations resulting iroin increased surface area of pigment. The dovc-nward displaceiiient of the initial rate curve of Figure i (below) implies that' the "reacted" vehicle must display somexvhat different properties during the early periods of exposure to sea water. I t could he presumed that the leaching rate might be much higher if, as \vas previously suggested, an Liunreacted" vehicle tends to remove significant quantities of thc smaller particles. Since this is not borne out' by the dat,a, t,hr lowered value? may be ascribed to t'he prcvious formation of highly insoluble co2per resinate requiring additional time before a constant rate of matrix solution is attained. That such a condition is finally reached is attested by the fact that the steady state curves from each veliic~leare alniost identical. From the leaching rate data it, may be concluded that pwticle size 01' apparept, surface area is not critical in achieving and maintaining a definite leaching rate, whereas a finely divided pigment greatly increases the initial leaching rate. I t might be helpful, therefore, in the design of certain types of paints Ti-hich normally shoxy a tendency to foul during early exposure, to include minimum quantities of finely divided pigments t o ensure adequate
August
1949
INDUSTRIAL AND ENGINEERING CHEMISTRY
initial protection. The fact that wide variance in pigment size influences performance only in the initial stages suggests that eventually a dissolution rate is attained, involving matrix, pigment, and sea Jvater and i n which particle size is of no consideration. This cmforms to the theory of Ketchum et al. (6) for soluble matrix paints.
\*/
9oc
'
1
/KEY
,
sqW22,50BRE:tmt
14
16
272
0
P H Y S I C A L CONDl
I
I
801
0'
FOULING
I
,lo;
I
I
8 IO 12 EXPOSURE T I M E I N M O N T H S
VEHICLE
52P6l 18
Figure 9. Resistance to Exposure
EXPOSVRE RESrs~an-CE.Inasmuch as final appraisal of any paint system must await exposure to actual enviroiirnent~alcondition, pariels were prepared from each paint a i d exposed for periods up to 18 months a t Miami Beach, Fla. The panels were inspected monthly and the per cent surface area free from fouling noted. Similar data were recorded describing the over-all physical condition of the pa,int films iri terms of their general iiitrgrity. Da.ta from typical exposures, plotted in Figures 8, 9, and 10, were selected as representative ext,remes in pigment particle size dispersed in two vehicles. Similar dat,a were obtained for each classified pigment fraction. Inspection of Figure 8 discloses that in combinat,ion wit,h vehicle 52P61 small particle size is not conducive t o long range performance. The fouling protection was maintained initially with the small particles but ultimate failure resulted much earlier. This is in accord x i t h behavior predicted from the leaching rate study. The physical condition of the films containing small particles deteriorated
l?41
much more rapidly than when composed of larger masses. Adequate performance resulted from the formulations of all but the finest particles with the prolonged effect being inost pronounced for those containing a minimum of extra fine particles (Figure 9). With reference to all fouling data present,ed herein, it should be pointed out that, on successive months a paint may appear to improve as a result of the disappearance of a number of attached organism noted a t an earlier inspection. Usually in such cases the organisms counted during earlier inspection were loosely attached owing to the inherent properties of the paint,. When a formulation comes back it is considered efficient until such time as it remains below 80% for two consecutive months. By reference to Figure 10 i t mag be concluded that the addition of the tougheiier Pliolite detracts from the effective life of t,he paint. Leaching rate determinations were not carried t o a point where this behavior could be predicted. On the ot'her hand, t'he presence of the Pliolite obviously reinforces t,he matrices containing small pigment particles to a degree that enhances their physical performance to an acceptable value. Again 1.00% protection from fouling was obtained during the initial months with the small particle pigment which further substantiates the prediction made from the leaching rate values. SUMMARY
For the types of matrices investigated, the role of pigment particle size is not so critical as might be supposed. This present investigation does not take into account, however, insoluble matrix paints whose efficiency depends on continuous contact of pigment particles. For rosin-type vehicles, free of ot,her reinforcing materials, larger pigment particles obviously perform as reinforcing agents for maintaining improved film integrity while supplying an adequat,e source of toxic. Such improvement is not detectable in paints reinforced with less soluble iFgredients such as Pliolite, in which case smaller particles seem to reinforce physical stability of the film although its active life is not extended beyond t,hat afforded by t,he larger particles. The addition of relatively small amounts of other matrix ingredients affects storage stability more radically than do abrupt changes in particle size, although viscosity changes do follow a normal pattern for s ~ u i a t i o nin pigment surface area. Small particle size provides for high initial leaching rates but the steady state rate is independent of t'ot'al surface area of pigment within the limits studied.
30
ACKNOWLEDGMENT
f
Y .e
The authors wish to express their appreciation to Ciarles Weiss and A. C. Frue for conducting the exposure t,est and t,o members of the staff of the Woods Hole Oceanographic Institution for the leaching rate determinations. 7 - 0 1I
0
0
F O U L IKN E GY PHYSICAL CONDITION
6o
SURFACE
LITERATURE CITED
fiREA
(1)
Alexander, A. L., axid Benemelis, R. L., IND. ENG.CHEY.,41, 1532 (1949).
Ferry, J. D., and Carritt, D. E . , I b i d . , 38, 612 (1946). Ferry, J. D., and Riley, G. A , , I b i d . , 699 (1946) Heywood, Harold, presented before tho Institution of Chemical Engineers and Society of Chemical Industries, February 1947. (5) Ketchum, B. H., Ferry, J. D., and Burns, A. E . , Jr., IND. ENG. CHEM.,38, 931 (1946). ( 0 ) Ketchum, B. H., Yerry, J. D., Redfield, A . C., and Burns, A . E., Jr., Ibid., 37, 456-60 (1945). (7) Mare Island Naval Shipyard, Paint Lab., private oonimunica(2) (3) (4)
Or/
-! FOULING
O
\
PHYSICAL C O N D I T I O N SURFACE
AREfi
VEHICLE
52P6lX
1
4
6
50 2
I
EXPOSURE
Figure 10.
I
8
IO TIME
I
12
, 14
IN M O N T H S
Resistance to Exposure
\d \
16
I
tion. (8) Roller, P. S., IND. ENG.CHEM.,ANAL.ED.,3, 212-16 (1931). (9) Young, G. IT., and Schneider, W . K., IRD.ERG.CHEM.,35, 43C (1943).
I6
RECEIVEDNovember 3, 1948. Presented before the Dirision of Paint, Varnish, and Plastics Chemistry a t the 113th Meeting of the A 4 3 ~ E R I C . % ~ C H E h f I C A L SOCIETY, Chicago, 111.
