December, 1929
INDUSTRIAL A,YD ENGINEERIXG CHEMISTRY
1273
The Plasticity of Paint’ F. H. Rhodes and Joseph H. Wells CORNELL UNIVERSITY, ITHACA, N.Y.
The yield point of a paint increases with the concentration by volume of pigment in the paint. In paints containing equal concentrations by volume of pigment the yield point varies inversely with the average particle size. This relationship is qualitative only and is affected by the specific character of t h e pigment. Lithopone offers a n exception to this general rule, possibly because of its tendency to form relatively large and stable aggregates. The mobility of a paint decreases with increase in concentration of pigment. With paints containing zinc oxide, lithopone, or basic sulfate white lead the yield values increase with increase in acid number of the oil. With Dutch process white lead or electrolytic white lead a n increase in acidity of the oil causes first a n increase and then a decrease in yield value. Paints containing Titanox show a continuous decrease in yield value with increase in acidity of the oil. In almost every case the mobility of the paint increases with a n increase in t h e acidity of the oil, although with paints made with zinc oxide an increase in acid number from 2.9 to 6.1 lowered the mobility. This effect was probably due to the formation of zinc soaps.
All the pigments studied adsorb free fatty acid from linseed oil, although to markedly different extents. With all the pigments studied, the oil absorption decreases when the acid number of the oil is increased from 0.185 to 2.89. The decrease is greatest with zinc oxide and least with Titanox. Further increase in acid number to 6.07 causes further decrease in oil absorption with zinc oxide, lithopone, basic sulfate white lead, and Titanox, no further change with electrolytic white lead, and a n increase in the oil absorption of Dutch process white lead. There is a general qualitative relationship between the effects of acidity on oil absorption and on yield point, an increase in yield point being usually associated with a decrease in oil absorption. The extent to which the plastic characteristics of a paint are altered by the addition of a given amount of thinner depend to some extent upon the specific character of t h e thinner. Turpentine produces relatively less change in the plastic characteristics than does either petroleum thinner or xylene.
T IS commonly recognized that the plastic characteristics
ever, that the form of the size-distribution curve for the pigment also affects the plasticity (14). The various substances that are used as pigments in paints differ markedly in the ease with which they may be wetted by the vehicle and in the extent to which they may adsorb linseed oil or other components of the vehicle. Pigments that are not readily wetted tend to flocculate to a greater extent and therefore tend to give paints of higher yield points and slightly lower mobilities ( 2 , 15). In some instances the wetting of the pigment by the vehicle is decreased by the presence of a film of gas or moisture on the surface of the particles ( 9 ) . I n some cases the addition of a deflocculating agent has a very marked effect upon the plastic properties of the paint. For example, the addition of even a small amount of oleic acid greatly reduces the yield value of a suspension of lithopone in mineral oil. Traces of deflocculating agent may also affect the rate of settling and the oil absorption of the pigment. The various thinners used in paints may act to some extent as flocculating or deflocculating agents and may therefore have a specific effect upon the plastic characteristics (16). This specific effect may vary with the nature of the pigment present and with the composition of the vehicle. The effects of various foreign substances upon the consistency of paint have not been very thoroughly studied. I n some cases the addition of a small amount of water increases the yield value and decreases the mobility (6). Soaps which tend to give “false body” to the vehicle have a similar effect.
I
of a paint are important in determining the ease with which the paint may be applied and the manner in which the paint will “work up” under the brush. With any given paint the plastic characteristics will depend upon several factors, of which the following are the most Important: (1) the concentration by volume of pigment in the paint; ( 2 ) the fineness of the pigment; (3) the form of the sizedistribution curve for the pigment; (4) the extent to which the pigment is flocculated in the paint; ( 5 ) the shape of the particles; (6) the ease and extent to which the pigment is wetted by the vehicle; (7) the viscosity of the vehicle; and (8) the presence in the paint of certain substances, such as soap or water, which may cause “false body.” In general, an increase in the concentration by volume of pigment in the paint raises the yield point and reduces the mobility (11). At the higher concentrations of pigment the relationship between yield value and concentration of pigment is a linear one; a t lower concentrations the curve representing this relationship is flexed. According to some investigators, the mobility decreases linearly with increase in concentration of the pigment and becomes zero a t the concentration which corresponds to the cubical close packing of the particles ( 4 , 6,9). An increase of fineness of the pigment, other conditions remaining constant, causes an increase in the yield point of the paint (12, IS). Bingham and Jacques (6) observed that continued grinding reduced both the yield point, and the mobility of lithopone paint. I n this case, however, it is possible that the reduction of the particle size during grinding was a comparatively unimportant factor and that the changes in the plastic characteristics were due largely to changes in the degree arid manner in which the pigment is wetted by the vehicle. In most of the investigations dealing with the effect of particle size upon the plastic characteristics of paints the pigments which have been used have been of comparatively uniform particle size. There is some indication, how1
Received June 15, 1929.
EXPERIMENTAL PROCEDURE
Materials I n the preparation of the paints pure refined linseed oil from Xorth American seed was used. When analyzed by the methods recommended by the A. C. S. Committee on Analysis of Commercial Fats and Oils ( I ) , it showed the following characteristics:
INDUSTRIAL A S D ENGINEERI,!rG CHEMISTRY
1274 Saponification Acid number number Unsaponifiable matter Iodine value SDecific aravitv a t 1.5 5' C. -~
193 0 0 185
1.33 192.4 0 932
The pigments used were lithopone, zinc oxide (French process), basic carbonate white lead (Dutch process), basic carbonate white lead (electrolytic), basic sulfate white lead, and Titanox. The average particle size of each pigment, as determined by the method described by Green ( I O ) , was as follows: AVERAGE DIAMETER
PIGMENT
hlicrvns Dutch white lead Titanox Zinc oxide Lithopone Basic sulfate white lead Electrolytic white lead
1 92 0 812 0 62 0 614 1 014 0 997
The thinners used were pure xylene, pure gum turpentine, and a petroleum naphtha. The petroleum naphtha had a specific gravity of 0.7802 a t 15.5" C., and distilled completely between 157.5" and 205.0' C. The paints were prepared by grinding together weighed amounts of pigment and oil. The pigment was ground in a mortar with a small amount of oil until a smooth paste was obtained; then the rest of the oil was added and the grinding was continued until a smooth and unif o r m p a i n t was produced. The paint was passed through a 200mesh sieve and was then placed under vacuum for several hours and stirred a t intervals to eliminate bubbles of air. This standing under vacuum also a i d e d i n s e c u r i n g thorough wetting of the pigment by H the vehicle. In those cases in which thinner was used the thinner was a d d e d a f t e r the air bubbles had been eliminated.
E
'
Determination of Plasticity
The apparatus used to measure t h e p l a s t i c i t y of the paint was similar to that described by Bingham and Green (S, 6). The conD struction is shown in Figure 1. The p l a s t o m e t e r itself consisted of a brass cylinder, A , to contain the paint, provided with a capillary outlet tube through which the paint could be extruded under pressure. The cylinder was a brass cup proC vided with a brass cover held tightly in place by screws. The joint between cup and cover was made tight by a rubber gasket. The cover was provided with a central tube through which was inserted a stirrer, D,for stirring the paint in the cup. This central tube also served as an inlet for the compressed gas for forcing the paint through the efflux tube. The efflux tube, B , was a short Figure I-Apparatus for Determination of Plasticity l e n g t h of c a p i l l a r y Pyrex glass of Paint tubing with the ends c a r e f u l l y ground normal to the axis. It was held firmly in place by a brass stuffing box packed with cotton twiiie. To the lower end of the efflux tube was attached a glass receiver, C, which
Vol. 21, KO.12
opened to the atmosphere. The entire apparatus was placed in a thermostat, the temperature of which was kept at 30" * 0.1' c. The principal difference betwen this plastometer and that described by Bingham and Green is that in this apparatus provision is made for stirring the paint very slowly during the determination of outflow time. This stirring was found to be of advantage because it prevented the settling of the pigment which takes place when working with thin paints and channeling which may occur when working with thick paints. Furthermore, the time required for the paint to reach the temperature of the thermostat is decreased by stirring. The pressure required to force the paint through the efflux tube was obtained by admitting nitrogen under pressure to the space above the paint in the cylinder of the plastometer. Kitrogen was used for this purpose instead of air, becausp nitrogen is practically insoluble in paint. The nitrogen TVZZ supplied from a cylinder provided with a regulating needle valve. A balancing reservoir was connected into the line between the nitrogen tank and the plastometer in order to adsorb any slight rariations in pressure. The preswre on the paint within the plastometer was registered on an open mercury manometer. The differential pressure through the efflux tube was equal, therefore, to the sum of the pressure indication by this manometer and the hydrostatic pressure of the paint within the apparatus. I n any measurement of plasticity it is necessary to know accurately the dimensions of the capillary used. The capillary used in this work was 6.23 cm. long and the averagc radius of the bore, as determined by weighing the amount of mercury required to fill it, was 0.249 em. Examination under the microscope, using an accurately calibrated micrometer eyepiece, gave results which agreed very closely with the above value. The capillary was so nearly circular in cross section that the average radius could be considered the true effective radius. The procedure followed in determining the plasticity of a given sample of paint was essentially similar to that described by Bingham and Green. EXPERIMENTAL RESULTS
Effect of Concentration of Pigment
The first series of experiments was made to determine the relationships between the concentration of pigment and the yield point and mobility of the paint. The results are shown graphically by Figures 2 to 5 . In the graphs representing the relationships between concentration of pigment and yield value, the yield values are expressed in terms of the minimum pressure (in centimeters of mercury) required to start flow through the capillary efflux tube of the plastometer used in the experiments. These values can be converted into absolute units by multiplying by the factor 8L/(nR4Dg),in which L is the length of the capillary in centimeters (6.25), R is the radius of the capillary in centimeters (0.0249), D is the density of mercury (13.6), and 9 is the gravity constant (920.4). The numerical value of this correlation constant for the capillary used was 3104. The mobilities are expressed in terms of the slopes of the graphs obtained when the rates of flow, in cubic centimeters per minute, are plotted against the corresponding pressures in centimeters of mercury. I n every case the yield value increased with the concentration of pigment in the paint. In paints containing only relatively small amounts of pigment the rate of change in yield point with change in concentration of pigment was small; when the concentration exceeded a certain critical
December, 1929
Figure 2
Figure 5
ISDUSTRIAL A N D ENGINEERIXG CHEMIXTR Y
Figure 4
Figure 3
Figure 6
value the yield point increased rapidly and almost linearly. I n the graphs obtained by plotting yield points against concentrations by volume of pigment, the critical concentrations and the slopes of the graphs above these critical points depended upon the fineness of the pigment. With the finer pigments the break came a t a lower concentration and the slope above the critical point was greater. Marked exceptions to this generalization occurred in the cases of lithopone and Dutch process white lead. Lithopone, Tyhich is very fine, behaved like a pigment of large average particle size. The anomalous results obtained with this pigment were probably due to the fact that lithopone in suspension in linseed oil forms rather large and comparatively stable agglomerates. The Dutch process white lead was much less uniform in particle size than any of the other pigments. It is possible that this lack of uniformity may have been responsible for the unexpectedly high yield values of the Dutch lead paints. I n each case an increase in the concentration by volume of pigment in the paint decreased the mobility. The graphs representing the relationships between concentration and mobility are approximately linear a t the lower concentrations, but are noticeably flexed a t the higher concentrations. There
1275
Figure 7
does not appear to be any general relationship b e h e e n particle size and mobility. Effect of Acid Number of Oil on Plasticity of Paint
A small amount of the free fatty acids from linseed oil was prepared by saponifying a portion of the raw oil by means of alcoholic potash, distilling off the alcohol, liberating the free acids by the addition of dilute hydrochloric acid, washing the separated acids thoroughly with water, and drying by gentle heating under high vacuum. The acids thus prepared were clear yellow and showed an acid number of 202.35 and an iodine value (Wijs) of 197.3. By mixing various amounts of this free fatty acid with the original linseed oil, which had an acid number of 0.185, oiIs with acid numbers of 2.59, 2.89, and 6.07 were prepared. All of these oils showed the same viscosity, as determined with the Bingham viscometer, so that any observed effect of the acidity of the oil upon the plastic characteristics of the paint cannot be due to change of viscosity of the oil with acidity. With each oil and each pigment a series of paints of different Concentrations was prepared and the plasticity of each paint was measured. The results are suinniarized in Table I.
Table I-Effect3f:Acid ACID No.
oporL
PIGMENT
70by
wl.
Number of Oil a n d Kind of P i g m e n t on Plasticity of Paints
YIELD MOBIL- ACID N O . VALUE
ITY
2.89
6.07
1.4 2.4 6.3 13.2 14.5 19.9 2.0 7.4 15.0 25.1
0.0415 0,024 0,017 0.013 0.013 0.011 0.055 0.036 0.017 0.007
19.85 29.97 34.94 39.29
5.0 9.0 13.8 17.4
0,021 0,016 0.014 0.013
2 59 6.07
0.6 1.4 3.1 5.5 10.9 3 0 4 5 10 3 3.6 6.8 14.4
0.03 0.018 0.009 0.007 0,007 0 036 0 025 0 0175 0.037 0.026 0.0185
0.185
2.59
6.07
2.89
6.07
MOBILITY
49.88 60.04 69.16 50.01 59.60 70.20
0.5 1.2 3.25 2.0 4.0 8.2
0,032 0.019 0.008 0.032 0.0212 0.01
50.45 60.00 65.20 68.70
2.9 5.6 7.4 9.0
0.032 0.022 0.016 0.0115
49.93 59.80 70.4 75.0 39.24 50.12 60.03 70.51 74.98 49.50 59.98 64.8 71.17
1.3 1.7 7.0 10.5 1.99 2.4 6.0 10.5 12.7 1.4 2.1 3.2 9.4
0.034 0.0225 0.012 0.0065
....
0.034 0.023 0.012 0.0072 0.034 0,025 0.0205 0.013
ELECTROLYTIC WHITE LEAD
0.185
50.01 57.3 70.4
2.8 4.5 13.4
0.0296 0.0200 0.0065
2.89
49.80 60.30 68.70 50 00 60 3 70 1
4.8 17.0 4 5 7 S 18 3
0.029 0.0185 0.011 0 0296 0 0200 0 0100
6 07
8.0
TITANOX
0.185
BASIC SULFATE WHITE LEAD
0,185
YIELD VALUE
Yo by w l . Cm.Hg
20.01 30.26 34.27 39.9s 41.87 44.79 19.85 29.75 38.91 49.25
40.26 50.49 59.85 64.67 68.12 39 83 49 80 58 60 40.00 49.85 59.91
PIGMENT
DUTCH PROCESS WHITE LEAD
LITHOPO~E
D.185
OFOIL
Cm. Hg
ZINC O X I D E
0.185
VOl. 21, xo. 12
I N D U S T R I A L A N D ENGINEERING CHEMISTRY
1276
2.89
6.07
30.17 40.08 44.78 50.27 55.05 60.45 34.62 45.00 55.20 62.5 35.45 45.00 54.30
0.8 2.0 3.3 6.0 10.0 15.7 0.2 0.5 1.0 1.8 0.8 2.0 4.0
0.043 0,0345 0.03 0.0255
due to the formation of soaps of zinc by interaction between the pigment and the free acid. It is well known that such soaps do tend to thicken linseed oil and to give - it “false bodv.” Adsorption of Free Fatty Acids from Linseed Oil by Paint Pigments
Mixtures were prepared containing known amounts of pigment and of linseed oil of known initial acid number. Each such mixture was allowed to stand for 24 hours and was then centrifuged. The acid number of the clear oil was determined. The difference between the initial and the final acid number of the oil was, of course, proportional to the amount of acid adsorbed on the surface of the pigment. From data obtained in the determination of the particle size of the pigment the specific surface of the pigment (expressed in terms of square meters per gram) was calculated. From the specific surface of the pigment and the data obtained in the experiment on adsorption the amount of free acid adsorbed per unit of area of the pigment was determined. The distribution of an adsorbable material between a solution and an adsorbing surface is defined by the general equation: X / M , = KCn
0.021
0.0165 0.0375 0.02s
0.0175 0,011 0.039 0,029 0.019
The addition of free fatty acids to the paints containing zinc oxide caused an increase in yield point. This effect was most pronounced with those paints which contained a relatively low concentration of pigment. In many respects the effect of the addition of free acid upon the plastic characteristics of these paints was similar to that which might be expected from an increase in the fineness of the pigment, It is known that zinc oxide is flocculated to some extent when suspended in linseed oil. The addition of the free acid causes some deflocculation and thus acts to reduce the effective particle size. Quite similar effects were observed with paints containing lithopone and basic sulfate white lead. With the Dutch process white lead rather unexpected results were obtained. When the acid number of the oil was increased from 0.185 to 2.59, the normal and expected increase in yield value was observed, but further increase in acid number to 6.07 caused a decrease in yield value. Electrolytic white lead gave similar results. With Titanox the first mall increase in acid number lowered the yield value, b u t with further addition of acid the yield value again increased markedly. Of all the pigments studied, Titanox was t h e only one that was acidic instead of basic in character. It is possible that the first small addition of acid to the paints made wikh Titanox may have had a flocculating instead of a deflocculating action. I n general, an increase in the acid number of the oil caused an increase in the mobility of the paint. I n the case of the paints made with zinc oxide, however, this was not true. With these paints an increase in the acid number of the oil from 0.185 to 2.89 decreased the mobility, but further increase in acid number made the paints very markedly less mobile, Paints made with an oil of an acid number of 6.07 had lower mobilities than those made with almost neutral oil. This effect was especially pronounced in those paints that contained a low concentration of pigment. It is possible that this effect of high acidity may be
or log X / M , = log K
+ n log C
in which X is the amount of material adsorbed, M . is the total area of the adsorbing surface, C is the concentration of the adsorbable material in the solution in equilibrium with the adsorbent, K and n are constants, In these particular experiments the unit quantity of free fatty acid in terms of which both X and C were expressed was the amount required-to increase the acid number of one gram of oil by one unit. The unit of superficial area of pigment was one square meter. The results obtained in the experiments on adsorption are shown in Figure 6. In each instance the results agreed satisfactorily with those that should be obtained for a typical adsorption reaction. In general, the amount of free acid adsorbed per unit surface in equilibrium with a solution of given concentration of free acid increased with increase in the basic character of the pigment. The only exception to this generalization was electrolytic white lead, which showed less adsorptive power than did the basic sulfate white lead. Effect of Acidity of Oil on Oil Absorption of Pigments
Since the different pigments adsorb free fatty acids to markedly different extents, the acidity of the oil should affect the ease with which it will wet the pigment and should, therefore, influence the oil absorption of the pigment. The relationship between oil absorption and acidity of the oil has been discussed to some extent by Calbeck ( 7 ) , but only a few experimental results are given. I n the work of the present writers the oil absorption was determined by the following method: To 20 grams of the dry pigment in a beaker the oil was added dropwise from a buret. The beaker was shaken with a circular motion, so that as soon as a drop of oil struck the pigment it was covered with the dry powder. As the addition of the oil was continued, the small balls of wetted pigment coalesced to form larger lumps, which finally collected in a few large balls. The last few drops of acid were added very slowly. The volume of oil required to wet and take up all of the dry pigment was taken as the oil absorption number of the pigment. In each case oil absorption number was expressed as the number of cubic centimeters of oil required for 20 grams of pigment.
December, 1929
IYDUSTRIAL A N D ENGINEERING CHEMISTRY
The results are shown in Figure 7. In every case an increase in acid number from 0.185 to 2.89 lowered the oil absorption. The decrease was greatest in the case of zinc oxide and least with Titanox. Further increase in acidity to 6.07 further decreased the oil absorption with zinc oxide, lithopone, basic lead sulfate, and Titanox, but did not further change the value for electrolytic white lead and actually increased the oil absorption of Dutch process white lead. There seems to be a more or less general qualitative relationship between the effects of acidity on oil absorption and on yield point, an increase in yield point being usually associated with a decrease in oil absorption. The most marked exception is in the case of Titanox. With this pigment both the yield point and the oil absorption decreased with increase in acidity, although the effect on yield point was much more pronounced than that on oil absorption. The acidity of the oil influenced, not only the amount of oil required to wet the pigment, but also the character of the paste obtained when the pigment was completely wetted. Usually the nearly neutral oil gave a paste which was somewhat friable and sandy, while the oil containing free acid gave smoother and creamier pastes. I n the case of zinc oxide the addition of 22 drops of neutral oil in excess of that required to wet the pigment thinned the paste only slightly, while the same excess of oil of high acidity gave a thin paint. Effect of Nature of Thinner on Plastic Characteristics of a Paint Paints were prepared from zinc oxide, lithopone, and Dutch process white lead. In each case the vehicle used was linseed oil with an acid number of 0.185, the amount being just sufficient to give a rather thick paint. From each such base paint thinned paints were prepared by the addition of known amounts of pure gum turpentine, petroleum thinner, or xylene. The plastic characteristics of each base paint and of the three thinned paints prepared from it were measured. The results are shown in Table 11.
1277
T a b l e 11-Effect of Various T h i n n e r s o n Plasticity of P a i n t s C o n t a i n i n g Different P i g m e n t s
THINNER
h’one Turpentine Petroleum thinner
Xylene
DUTCHPROCSSS WHITELEAD Pn1h-1~
1 1 118i 1 Yield point
Mobility
Cm. H g 9.5
0.105
LITHoPoNE
ZLNC OXIDE^
PAINT b
~
Yield point
hfobility
Cm. Hg.
0.18
27.5 13.7
0.085 0.25
0.22 0.24
12.0 12.0
0.33 0.34
1
Yield point
Mobility
Cm. Hg 26.4
0.055
17.5
0.18
14.6
0.22
14.6
0.23
Base paint made with 210 grams of pigment and 70 grams of oil. Thinners added in the ratio of 3.33 grams to 100 grams of the base paint. b Base paint made with 100 grams of pigment and 99.67 grams of oil. Thinnrrs added in the ratio of 8 9 grams to 100 grams of the base paint, c Base paint made with 130 grams of pigment and 80.25 grams of oil.. Thinners added in the ratio of 8 grams t o 100 grams of the base paint. a
In every case the effect of turpentine in lowering the yield point and in increasing the mobility was much less pronounced than that of either the petroleum thinner or the xylene. T h e lower efficiency of turpentine as a thinner is probably related to its tendency to cause agglomeration of the pigment. Literature Cited A. C. S. Committee on Analysis of Commercial Fats and Oils, IND. ENG.CHEM.,18, 1346 (1926). Bartell and Osterhof, I b i d . , 19, 1277 (1927). Bingham, “Fluidity and Plasticity,” p. 77. Bingham, Bruce, and Wolbach, J . Franklin Insi., 195, 303 (1923). Bingham and Green, Proc. A m . Soc. Testing Materials, 19, 641 (1919). Bingham and Jacques, IND.ENG.CHEM.,16, 1033 (1923). Calbeck, Chem. Met. Eng., 31, 377 (1924). Dours ana Raaschon, Z . angew. Chem., 38, 381 (1925). Gardner, Paint Mfrs. Assocn: U. S., Tech. Circ. ZOO, 279 (1924). Green, “Photomicrographic Method for Determination of Particle Size of Paint and Rubber Pigments,” S e w Jersey Zinc Co., Research Bulletin. Green, Proc. A m . S O C .Tesling Materials, 20, 4R1 (1920). Green, IND.EN&CHEM.,15, 122 (1922). Green and Haslam, Ibid., 17,726 (1925); 19, 53 (1927). Ingalls, Paint Mfrs. Assocn. U.S., Tech. Circ. 135, 1 (1921). Sulman, Bull. Inst. Mining Met., 182 (1919). Walker and Thompson, Proc. A m . SOC.Testing Materials, 22, 464 (1922).
Some Unusual Alcoholic Fermentations’ John R. Eoff, Jr.,t Howland Buttler, and William Melchior S r . L O U I S . &lo.
H E quantities of alcohol that can be produced in fruit juices and other suitable solutions by yeast, fermentation vary with the composition of the solution, the nature of the yeast, and the environment. In the normal commercial manufacture of wines it is a rare fermentation that will produce more than 16 per cent alcohol by volume, even if sufficient sugar were present in the must. Several years ago in California wines that contained more than 18 per cent alcohol by volume were made solely by fermentation, but in order to obtain such high concentration special treatment was necessary, such as repeated additions of sugar or concentrated grape must while the fermentation progressed. KOauthentic information has come to the writers’ attention of a case where more than 18 per cent alcohol by volume has been produced by the unmolested fermentation of a must containing originally sufficient sugar for the purpose-i. e., normal fermentation. In a former employment the senior author made many
T
2
Calif.
Received October 10, 1928 Resubmitted h-ovember 11, 1929. Present address, Fruit Industries, Inc , 8 5 Second St., San Francisco,
unsuccessful attempts to ferment 18 per cent alcoholic wines in the normal way. He secured yeasts from many parts of the world and tried many different must compositions without avail. Correspondence with oenological and fermentation experts a t home and abroad brought the unanimous opinion that no yeast could produce normally as high as 18 per cent alcohol in wine, for it would cease to function before this alcoholic strength was reached. Eoff worked solely with pasteurized grape musts at this time and, as will be shown later, the probable cause of his failure was his inability to obtain fresh must. In the summer of 1925 the writers were interested in the development of some non-intoxicating beverages to which were added small amounts of different fermented fruit. juices to obtain flavor. Among the fruit juices tried was fermented pineapple juice. A few fresh pineapples were secured and ground without peeling in a hand meat grinder. To 1 gallon of crushed pineapple were added 2.5 gallons of 35 per cent cane-sugar solution and a small quantity of active Tokay yeast, the whole being placed in a glass jar. After standing at room temperature for 24 hours, vigorous
