Acknowledgment, Literature Cited, Industrial and Engineering Chemistry

1202

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

Vol. 40, No. 7

ACKNOWLEDGMENT

The authors wish t o acknowledge the assistance of H.

G.

Dawson of the Firestone Research Laboratory for the analytical values of Table VI and to

H. H.

Miller of the Xylos Rubber Company for various reclaim evaluations and other data. Ap- preciation is expressed for the encouragement and assistance of F.

W.

Stavely and

R. F.

Dunbrook, and for the permission t o publish this manuscript by the managements of the Firestone Tire & Rubber Company and the Xylos Rubber Company.

LITERATURE CITED

Andrews, R. D., Tobolsky, A. V., and Hanson, E. E., J . Applied British Ministry of Supply, private communication (June 1943).

British Ministry of Supply, private communication (May 1946).

Carpenter, A. S., IND. ENG. CHEM., 39, 187 (1947).

Dasher, P., U. S. Patents 2,304,548, 2,304,549, 2,304,550, Essex, W. G., U. S. Patent 2,154,894 (1939).

Farmer, E. H., in “Advancesin Colloid Science,” Vol. 11, p. 303, New York. Interscience Publishers. 1946.

Phys., 17, 352-61 (1946),

2,304,551 (1942).

Farmer, E. H,, Trans. Faraday SOC., 42,228-36 (1946).

Garvey, B. S., U. S. Patent 2,193,624 (1940).

Gillman, H. H., Rubber Aoe (New York), 58, 709-14 (19461, Gumlich, W., U. S. Patent 2,280,484 (1942).

Gumlich, W., and Ecker, R., U. S. Patent 2,338,427 (1944).

Hughes, A. J., and Amphlett, P. H., Trans. I n s t . Rubber I n d . , 19, 165 (1944).

I. G. Farbenindustrie, A. G., Kautschuk-Zentrallaboratorium, Leverkusen, “Report on Reclaiming of Buna Vulcanizates with the Aid of Renacit” (Aug. 28, 1945).

Ioannue, J. P., U. S. Patent 2,069,151 (1937).

Jones, F. A., Owen, E. W. B., Tidmus, J. J., andFraser, E. E., Trans. I n s t . Rubber I n d . , 19, 190 (1944).

Kirby, W. G., and Steinle, L. E., U. 9. Patent 2,279,047 (1942).

Ibid., 2,359,122 (1944) ; 2,363,873 (1944) ; 2,372,584 (1945).

Miller, G. R., in “Chemistry and Technology of Rubber,” bi Davis, C. C. and Blake, J. T., pp. 720-38, New York, Rein- hold Publishing Gorp., 1937.

Lutz, G ~ n t m i - Z t g . , 25, 120-1 (1910).

Mooney, M., IND. ENG. CHEM., ANAL. ED., 6 , 147 (1934).

Neal, A. M., and Schaffer, J. R., Jr., U. 5. Patent 2,333,810 Oldham, E. W., Baker, L. M., and Craytor, M. W., IND. ENG.

Palmer, H. F., and Kilbourne, F. L., Jr., IND. ENG. CHEM., 32, Ritter, J. J., and Sharp, E. D., J. Am. Chem. SOL, 59, 2351 Sebrell, L. B., Canadian Patent 289,290 (1929) ; Chem. Zentr..

Shelton, J. R., and Winn, H., IND. ENG. CHEM., 39, 1133 (1947).

Simmons, H. E., War Production Board, Office of the Rubber Director, private communication, Feb. 23 and June 3, 1943.

Smith, G. E. P., Jr., “Antioxidant Effects in Natural and Syn- thetic Rubbers,” Symposium on Degradation and Aging of High Polymers, Polytechnic Institute of Brooklyn, Nov. 30.

1946.

(1943).

CHEM., ANAL. ED., 8 , 4 1 (1936).

512 (1940).

(1937).

103, I, 2392 (1932).

Smith, G. E. P., Jr., Ambelang, J. C., and Gottschalk, G. W., Spence, P., and Ferry, J. B., J. Am. Chem. SOC., 59, 1648 (1937).

Taylor, H. S., and Tobolsky, A. V., Ibid., 67, 2063 (1945).

Tobolsky, A. V., Prettyman. I. B.. and Dillon, J. H., J . Applied IND. ENG. CHEM., 38, 1166 (1946).

_ _

P hys .,-l5, 380 (1944).

(1946).

U. S. Rubber Co., British Patents 575,545, 575,546, 575,545 Waters, W. A., Trans. Faraday Soc., 42, 189 (1946),

Wolf, G. M., Deger, T. E., Cramer, H. I., and DeHilster, C. C..

Ziegler, K., and Ganicke, K., Ann., 551, 213 (1942).

IND. ENG. CHEM., 38, 1157 (1946).

RECEIVED June 10, 1947. Presented at the meeting of the Division of

Rubber Chemistry of the AMERICAN CHEMICAL SOCIETY, Cleveland, Ohio May 26 t o 28, 1947.

CITRIC ACID

Production by Submerged Fermentation with Aspergillus niger

PIKG SHU

AND

MARVIN J. JOHNSON

U n i v e r s i t y of Wisconsin, Madison, Wis.

Average yields of 72 grams of anhydrous citric acid per 100 grams of added sucrose were obtained by submerged culture of Aspergillus niger in shake flasks on a synthetic medium a t a n initial sucrose concentration of 140 grams per liter. The fermentation required 9 days. A 70%

yield was obtained i n 12 days at a sucrose concentration of 260 grams per liter. Data on the effect of changes i n composition of the medium are presented. The optimal conditions for shake flask fermentations include potas- sium dihydrogen phosphate above 1 gram per liter, mag- nesium sulfate heptahydrate above 0.25 gram per liter, iron concentration of 1 mg. per liter, 2.5 grams per liter of nnimonium nitrate, and an initial pH between 2.2 and 4.2.

ONSIDERABLE research effort has been expended on attempts t o develop a submerged fermentation process for citric acid production (16). Amelung (1) reported citric acid production from sucrose by aerating a submerged culture of Aspergillus japonicus. The yield of citric acid was very low.

According t o a recent patent of Szucs (fd), citric acid has been successfully produced in submerged cultures of Aspergillus niger.

Szucs’ preferred procedure involves transfer of preformed my- celium from a growth medium t o a fermentation medium, and

the use of oxygen or air-oxygen mixture for aeration. Similarly, Karow and Waksman ( 2 , 13) reported the production of citric acid in submerged cuItures of Aspergillus wentii. The maximum citric acid yield is obtained when oxygen is used for aeration, and after the desired growth is obtained the growth medium is replaced by a fermentation medium.

Using shake flask technique, Perquin (8) systematically studied the effect of variation of the environmental conditions (both gaseous and liquid phases) on the production of citric acid in submerged cultures of Aspergillus niger. He concluded that the presence of zinc sulfate, potassium chloride, and increased con- centration of magnesium sulfate in the liquid phase favored the production of citric acid. On the other hand, the presence of a high concentration of potassium dihydrogen phosphate i n the medium was unfavorable. The use of oxygen or oxygen-air mixture for aeration resulted in a higher citric acid yield. Under all conditions, only a small amount of citric acid was produced.

Karow and Waksman ( 2 ) demonstrated the requirement of manganese sulfate for maximum citric acid production by sub- merged culture of Aspergillus wentii. The substitution of urea for other nitrogenous salts proved satisfactory. They also found that the presence of magnesium sulfate and high concen- trations of potassium dihydrogen phosphate in replacement or fermentation medium were unfavorable for citric acid production.

July 1948

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

Studies on citric acid production by the surface culture method

(5-6, 8, 9) have shown the fermentation

to

be very sensitive t o changes i n trace metal and phosphate concentrations, nitrogen source, initial pH, and other factors. The optimum conditions vary with the strain of microorganism. No satisfactory condi- tions for a n efficient one step submerged fermentation for the production of citric acid have been reported.

I n the present study, submerged citric acid fermentations were carried out; in these citric acid was produced on the growth

medium. The effect of varia-

tions in environmental conditions on citric acid yield and on the chemical changes in the medium were investigated; large scale fermentations or fermentations of crude sugar were not at- tempted.

Air was used as an oxygen source.

METHODS

The organism used in the experiments was a colony isolated from culture 72-4 ( B ) , which in turn was a colony isolated from Asper illus niger ATCC 1015. The stock culture was carried on soil. h a n s f e r s were made from a soil stock culture through two successive sugar agar slants t o a n agar bottle plate. These plates had an agar surface of approximately 72 sq. cm. and contained 25 ml. of agar medium A (Table I). The inoculated bottle plates were incubated at 30 ^O C. Spores from 3- to 5-day old bottle plates were suspended in 50 ml. of sterile distilled water, and 1.5 ml.

of the suspension were used to inoculate 50 ml. of fermentation medium contained in a cotton-plugged 500-ml. Erlenmeyer flask.

These fermentation flasks were incubated at 25" C. on a shaker which moved the flasks in a horizontal circle 1 inch in diameter at a speed of 270 r.p.m. The composition of all fermentation media was that of medium

B,

Table

I,

except for components being systematically varied. At intervals of 5, 7, and 9 days, samples were taken. The figures given in the tables are for samples taken at 9 days, except where otherwise stated. Residual reducing sugar was determined by the method of Shaffer and Somogyi (10) and citric acid by the method of Perlman, Lardy, and Johnson ( 7 ) . In the use of this method, it was found t h a t 0.6 N ferrous sulfate solution was much superior to hydrogen peroxide for removal of excess permanganate. Reaction was more rapid, and a slight excess was not detrimental. Titratable acidity was expressed in terms of anhydrous citric acid. Evapo- ration was corrected by setting up a n uninoculated control flask.

All the determined values were calculated on the basis of the sugar concentration of the control flask. D r y weight was deter- mined on the washed mycelia after drying at 110' C. overnight.

TABLE

I.

COMPOSITION OF MEDIA

Medium A Medium B,

Constituents Wt.,/Liter' Wt. ,/Liter

Domino morose, g.

Bacto agar, g.

KHpPOi, g.

MgS04.7H10, g.

N H I N O ~ , g.

HCI, g.

140 I 0 20.0 1 . 0 0 . 2 5 2 . 5

..

0 . 4 8 3 . 8 2 . 2

< 1 . 0

1 4 0 . 0 2 : 5 0 . 2 5 2 . 5 t o p H 3.8

0.06 0 . 2 5 1 . 3

<1.0

0 Listed quantities of metals include amounts present as impurities in other constituents of the medium. Media were sterilized .at 120° C. for 15 minutes.

b The importance of low manganese concentrations in both the sporula- tion and fermentation media for submerged citrio acid production is demon- strated in work reported elsewhere (2 1 ) .

EXPERIMENTAL RESULTS

EFFECT OF VARIATION OF CONSTITUENTS OF THE MEDIUM.

Data shown in Table

I1

indicate that high yields on utilized sugar were obtained at sucrose concentrations of 145 and 264 grams per liter. At low concentrations, the yield was poor.

As shown in Table 111, levels of MgS04.7H2O below 0.5 gram per liter resulted in lower yields. Up t o a concentration of 2 grams per liter of medium, the conversion efficiency of the fer- mentation was not affected.

The compound used as

a

nitrogen source and its Concentration seem to be critical for citric acid production. Porges (9) reported

1203

TABLE

11.

EFFECT

OF SUCROSE CONCENTRATION O N CITRIC ACID PRODUCTION

Yield of Citric A & nn

-

___

- - .-

Sucrose Available Utilized Acidity Due Residual hlycelial Concn., sugar, sugar, t o Citric Acid, Sugar, Weight G./100 MI. % '% % of Total G./100 M1. G./100 MI.

TABLE

111. EFFECT ^OF MAGNESIUM SULFATE CONCENTRATION

O N CITRIC ACID PRODUCTION

Yield of Citric Acid on

M 80r.7HgO Available U6ilized Acidity Due Residual Mycelial 6oncn,, sugar, sugar, to Citric Acid, Sugar Weight G./Liter % % % of Total G./100 Ml. G./lOO MI.

that sodium nitrate is a better nitrogen source than ammonium nitrate. This conclusion was not confirmed i n preliminary ex- periments. The best nitrogen source appeared to be ammonium nitrate which was used in all subsequent experiments. The data of Table IV show that the optimum concentration of ammonium nitrate is in the neighborhood of 2.5 grams per liter.

At either side of the optimum concentration, a low acid yield and poor growth were observed. It appeared from preliminary ex- periments that the phosphate ion might function in some manner other than as a simple nutrient and buffer.

It

appears t o be related to the acid production rate inasmuch as the most rapid acid production was observed at phosphate concentrations above the optimum value for growth (Table V). As the p H of the medium drops rapidly to approximately 2 a t all phosphate con- centrations, the buffering action of phosphate cannot be re- sponsible for the observed effect.

It

has been well established that there is a n optimum con- centration of iron for maximum citric acid production (6). The optimum level as determined in the present study was approxi- mately 1 mg. per liter as shown in Table VI.

It

is evident from the table that mycelial weight varies directly with iron concen- tration. At low levels of iron, sugar utilization is poor because of

TABLE

IV. EFFECT O F AMMONIUM NITRATE CONCENTRATION

ON CITRIC ACID

PRODUCTION

Yield of Citric Acid on

NHiNOa Available Utilized Acidity Due Residual Mycelial Conqn., sugar, sugar, t o C i t m Acid, Sugar, Weight G./Liter % % % of Total G./100 MI. G./100 MI.

T A ~ L E

V. EFFECT OF

POTASSIUM

DIHYDROGEN PHOSPHATE CONCENTRATION ON CITRIC ACID PRODUCTION

Titratable Acidity Acidity Due Residual Mycelial KHzPOi c ~ ~ ~ ~ t o Citric Acid ~ ~ $ ~ Sugar a t ~ D ~Weight a t y s Concn., a t 9 t h Day, 9 t h Day, 9 t h Day, G./Liter 3 . 5 5 . 5 7 9 yo Total G./100 MI. G./100 MI.

1204

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

Vol. 40,

No.

7 concentrations permit,ted heavy growt,h with an accompanying to depend on the method of aeration employed.

TABLE VI. EFFECT O F I R O N CONCENTRATIOW ^{O N} CITRIC ACID decrease in yield, The optimum groR-th level may be expected PRODUCTION

The initial pH value of the medium influences the rate of acid Mg./Liter Addeda9 ^sugar, %

togiirfi$tt:f3

G , ~ & f ~ $ f l ,

G:T:ah&l.

and acid production are greatly ret'arded. I n contrast to t h e

3.0 13 29 6 3 6 . 4 2 . 7 results obtained in surface cultures

( 4 ) ,

a very broad pH optimum

4 . 0 19 34 62 5 . 0 2 . 6 is obtained.

0 . 8 77 77 94 0 . 0 1 . 8

0 . 4 77 86 98 1 . 2 1 . 6 EFFECT OF A 4ON ACID PRODUCTION. ~ ~ In this investiya- ~ ~ ~ ~ ~

tion, the only data on variation in air supply have been obtained

0 . 0 43 66 92 3 . 9 0 . 9

by comparison of fermentations in the rotary shaker with those done in a reciprocating shaker having a stroke length of 4 inches, acid yield was obtained in 8 days for those flasks on the rotary shaker, and in 11 days for those on the reciprocating shaker.

The yield of citric acid was the same for both methods of shaking.

After the initial growt,h phase, the rate of acid production re-

0 . 0 2 8 . 0 23 68 0 . 5 mained almost constant in both cases. The rat'e in the recipro-

0 . 0 2 0 . 8 23 71 0 . 3 cating shaker was approximately 65% of the rate in the rotary

0 . 0 2 0 . 0 2 8 8 3 0 . 2

0.10 8 . 0 2 8 39 0 . 8 shaker.

0 . 1 0 0 . 8 3 4 55 0 . 7 It

0 . 1 0 0 . 0 48 63 0 . 7

1 . 0 8 . 0 27 2 8 2 . 4 has been shown (Table 17111) that, a t high initial pH levels, t,he

1 . 0 0 . 8 65 65 1 . 7

1 . 0 0 . 0 48 60 1 . 1 fermentation period could be shortened without reduction in

yields, and (Table 11) that the yield on fermented sugar was not decreased up t o a sugar concentration of 2670. Therefore, 1 liter of basal medium B was prepared .rrith a sucrose concen- t,ration of 25Y0 and an initial pH of 4.5 and inoculated with 30 The inoculated medium was distributed in 50-ml. portions in 500-mi. Erlenmeyer

fernlentation flasks. bar-

vested and determinat,ions lTere made for p ~ , reducing sugar, total acidity, citric acid, and dry weight of mycelium (Figure 2).

The p~ of the medium dropped t,,, 2 before much growt,h had Yield of Citric

Acid on

1:on Available Utiliaed Acidity Due Residual Mycelial production (Table 1'111). At low initial pH value, both growth

a Basal medium contained 0.5 mg. of iron per liter as impurities.

TABLE

VII: EFFECT O F I R O N CONCENTRATION A T VARIOUS running a t 86 cycles per minute (Figure 1). Maximum citric KH2POa CONCENTRATIOSS~

Titratable Acid Calculated as Citric Acid on KHzPOI, Fe + + + added, available, utilized,

G./Liter AIg./Liter 70 %

~ i\Iycelial

~!Ff,$$~&l.

Variations in Basal Medium B

CHEMICAL CHANGES DURING COURSE OF FERMESTATIOK.

a Initial pH of medium was 2.8 and all determinations mere made on tenth day.

deficient growth. At high iron levels, the heavy growth obtained may depress yields because of the increased amount of sugar utilized as a growth substrate. and because of the decrease in available air caused by the high viscosity of the medium when heavy growth Occurs. That the effect of iron on Yield is due to it.s effect on growth is shown by the data O f Table VII. I n this experiment growth was controlled by making phosphate con- centrat.ion the limiting factor. At low phosphate concentrations the yield of acid calculated on sugar utilized was independent' of the iron concentration. At a high phosphate level, high iron

of a spore suspension from a bottle

intervals, duplicate flasks

I occurred.

The fermentation can be divided into two distinct phases, an initial gromth phase and an acid production phase. ~~~i~~ the period of initial growt,h, sugar Qras utilized mainly for mycelium production; only a little acid vias produced. Shortly after the beginning of acid production, mycelial growth st,opped and most, of the sugar utilized was convert,ed to citric acid. The rate of acid production remained const,ant, almost t o the end of the fermentation. Figure 2 shows that between the 140th and 240th hours, 6.7 grams of sucrose per 100 ml. were fermented. If all of the carbon in this sucrose were converted to citric acid, 7.5, grams of acid could be formed; actually 9.9 grams were formed.

I n addition, an appreciable amount of mycelial growth occurred.

Hence a nonreducing int,ermediate compound must be present in considerable quantities. The presence of a compound having

HOURS

Figure 1. Effect of Aeration on Citric Acid Production

TABLE VIII. EFFECT OF IXITIAL pH o x CITRIC h c ~ d PRODUCTION

.4cidity

Residual Mycrlial Initial Titratable Acid Calculated c i E c & d

sugar

a t weight at pH,of as % Citric Acid O n a t 9 t h Day, 9th Day, 9 t h r ) a y , Medium 3 . 5 5 , s 7 9 70 of Total G./100 MI. G./100 MI.

1 . 7 6 . 3 7 . 3 9 . 0

...

^{1 0 . 6 0 . 7}

2 . 2 0 : 3 27 51 63 101 1 . 8 1 . 4

2 . 8 14 45 60 67 94 0 . 7 1 . 5

3 . 3 16 48 64 70 98 0 . 0 1 . 7

3 . 7 20 45 62 71 98 0 . 0 1 . 2

4 . 2 28 64 71 71 98 0 . 0 1 . 6

4 . 9 3 2 59 67 65 96 0 . 0 1 . 8 Figure 2. Chemical Changes during

HOURS

Fermentation

July 1948

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

1205

reducing properties after hydrolysis has been reported (14) in a (7) Perlman, D., Lardy, H. A., and Johnson, M. J., IND. ENQ.

(8) Perquin, L. H. C., dissertation, Delft, 1938.

citric acid fermentation with glucose as the carbon source.

I n this series of fermentations with 26 grams of sucrose per (9) Parges, N,, Am, J , Botany, 19, 559 (1932).

liter, 70% citric acid on the basis of available Sucrose or 77% on the basis of sugar utilized, was obtained in a period of

17

days.

The average yield of seven fermentations on the control medium containing 140 grams of sucrose per liter has been 72%.

CHEM., ANAL. ED., 16,515 (1944).

(10) Shaffer, P. A., and Somogyi, M., J . Bid. Chem., 100, 695 (11) ^Shui p . ~ and Johnson, M.J.9 J . BaCt.3 541 161 (1947).

(12) S z ~ c s , J., U. S. Patent 2,353,771 (1944).

(13) Waksman, S. A , , and Karow, E. O., U. S. Patent 2,394,031 (1933).

(1946).

58,555 (1936).

(14) Wells, P. A., Moyer, A. J., and May, 0. E., J . Am. Chsm. Soc., (15) Wells, P. A., and Ward, G. E., IND. ENG-. CHEM., 31, 172 (1939).

LITERATURE CITED (1) Amelung, H., Chem.-Ztg., 54, 118 (1930).

( 2 ) Karom’, E* 0.8 and Waksman,

s. *.,

^{IND. ENG. CHEM., 399 821}

(1947).

(3) Loeseoke, H. W. von, Chem. Eng. News, 23, 1952 (1945).

(4) Perlman, D., M.S. thesis, Univ. of Wisconsin, 1943.

(5) Perlman, D., Dorrell, W. W., and Johnson, M. J., Arch. Bio- (6) Perlman, D., Kita, D. A., and Peterson, W. H., Ibid., 11, 123

RECEIVED May 9, 1947. Presented before the Division of Agricultural and Food Chemistry a t the 111th Meeting of t h e AMERICAN CHEMICAL SOCIETY, Atlantic City, N. J. Published with the approval of the Director, Wisconsin Agricultural Experiment Station. Supported in p a r t by a grant- in-aid from the Sugar Research Foundation, Ino., New York, N. Y . chem., 10, 131 (1946).

(1946).

Alpha- and Beta-Hydroxyls of Glycerol

in Preparation of Alkyd ^Resins

HENRY A. GOLDSMITH1

Standard Varnish Works, Staten Island, N . Y . HIS paper has been

T

prompted by certain general observations made during experimental work on modified glycerylphthal- a t e resins in which oils (or, more exactly, the mono- glycerides of these oils) were used in d a c e of fattv

Certain changes are observed in the behavior of fatty acid modified alkyds when monoglycerides (from fatty acids and glycerol or from trig1ycer;de oils and glycerol) are used i n place of fatty acids, or when the order of introduc- tion of the alkyd ingredients is modified. It is shown that the primary hy’droxyls of glycerof react more readily with phthalic carboxyl than with that of fatty acid, whereas the reverse occurs with the secondary hydroxyl. This ob- servation is used to interpret the differences between the

acid first, then adding phthalic anhydride ffatty a c i d - m o n o g l y c e r i d e method); or it may be made by reacting glycerol and oil, and heating the product with phthalic an- hydride (oil-monoglyceride method).

acids, or in- which

thk

two types of alkyds.

sequence of addition of the resin ingredients was

modified. The phenomena which accompanied such changes were sometimes favorable, sometimes unfavorable, from an in- dustrial point of view, but appeared to follow a certain definite pattern. An attempt will be made to point out the more striking of these regularities, and to give an explanation of them. Schei- ber (18) has recently summarized the methods of incorporating fatty acids, either as such or as triglycerides, into glycerylphthal- a t e resins. The two simplest and most direct methods of accomplishing the fatty acid modification of an alkyd are: with f a t t y acids; with monoglycerides which may be obtained by reacting glycerol with either f a t t y acids or with triglyceride oils.

Additional triglyceride oils can be incorporated into the alkyd by using either one of these methods, but t h a t will be considered only

as

a special case of the methods mentioned. The alkyds on which this paper was based were mainly those of the drying oil type prepared from phthalic anhydride, glycerol, and fatty acids or the corresponding oils. However, the conclusions which are presented apply to those alkyds in which’these ingredients have been partially replaced by other dicarboxylic acid anhydrides (maleic), other monocarboxylic acids (rosin), or even other polyhydric alcohols (hexitols, pentaerythritol).

REPLACEMENT OF FATTY ACIDS BY MONOGLYCERIDES When an alkyd is made from glycerol, phthalic anhydride, and f a t t y acids, it may be made by reacting glycerol with phthalic anhydride first, then adding fatty acid or reacting all ingredients together (fatty acid method); by reacting glycerol with fatty

1 Present address, 25 Minetta Lane, New York, N. Y.

A series of experimental alkyds, representing varia- tions of five basic for- mulas, was selected to describe these methods, as well as the differences which were observed between the fatty acid method and the two monoglyceride methods, and between their products.

One or several of the following phenomena were found to occur when the monoglyceride methods replaced the fatty acid method:

The rate of esterification slackened at somewhat higher acid values, despite the fact t h a t the initial acidity in the mono- glyceride methods was lower.

Bodying and gelation occurred a t somewhat higher acid values.

The resin, until just before it required reducing, remained somewhat softer and tackier. This was verified by placing a small sample (pill or bead) on a glass plate, allowing it t o cool completely, and pressing the thumb or thumbnail into it.

Conversion, under equal baking conditions, of a film of the re- duced resin was not as rapid and the baked film was somewhat softer or tackier.

The product tolerated more aliphatic hydrocarbon thinner.

The resin, though apparently bodied equally as far, had lower viscosity when reduced to the same concentration in the same solvents. This was probably a consequence of its greater solu- bility.

I n the examples which follow, not all the phenomena were observed every time. Also, the degree of difference between the fatty acid type and the monoglyceride type varied with the formula; they appeared to become less pronounced with increas- ing oil length. These differences do not necessarily make one or the other type more desirable. For instance, the greater toler-