Partial Acetylation of Cotton Cellulose bv Ketene J
CARL HAMALAINEN AND J. DAVID REID Southern Regional Research Laboratory, New Orleans, La.
Linters and cotton sewing thread have been acetylated with ketene. Treatment involves preswelling with water, removal of excess water by extraction, suspension of the cotton in an inert solvent (preferably ether) containing a catalyst (preferably perchloric acid), and treatment with ketene as prepared by pyrolysis of acetone. Samples containing u p to 17% acetyl retained their fibrous structure with only slight degradation. The ketene acetylation was accompanied by an objectionable polymerization of ketene which produced a yellow to dark brown coloration of the sample. The color could be removed by hot alcohol. Although the emphasis was on the reaction of water-activated, solvent-dehydrated cellulose with ketene, some experiments were tried i n which the cotton was swollen with acetic acid before introduction of ketene. dcetylation was probably due to the acetic anhydride formed.
T
HE partial acetylation of cotton yarn or cloth, carried out by treatment with acetlc acid-acetic anhydride mixtures, gives a product which is very resistant to microbiological attack, as ha5 been shown in a number of cases (2, 12). It was desired, in the present work, t o investigate the use of ketene as the reagent in obtaining a similar partially acetylated product. The manufacture of cellulose acetate by direct addition of ketene has been patented by Nightingale (8, Qj and the preparation of mixed esters using ketene and acids by Graves ( 3 ) . Starches have been acetylated in this manner by Talley and Smith (11) who also discuss some of the previous work on acetylation of carbohydrates with ketene. The patent literature (6, 8, 9) gives the impression that acetylation of cellulose is easily accomplished by ketene. On the other hand, Rice et al. (IO) state that ketene does not appear to have any action on cellulose, The authors have found that although this is true with unactivated natural cellulose, it is possible to obtain satisfactory acetylation by preswelling of the material. Ketene is low in cost, being used commercially ( 6 ) for the regeneration of acetic acid to acetic anhydride in the production of cellulose acetate. I n the present investigation, preliminary experiments were made using commercially purified, low-viscosity linters and were followed by experiments on cotton sewing thread. Ketene was prepared by pyrolysis of acetone using an apparatus similar t o t h a t used in the pyrolysis of turpentine for the production of isoprene on the recommendation of L. A. Goldblatt Who has prepared ketene in this manner ( 1 ) . The ketene gas, diluted with the other products of pyrolysis, principally methane, was passed through organic solvents containing the cellulose in suspension. Liquids in which cellulose acetate mas not soluble were preferable in order to retain the fibrous structure of the product. Most experiments, therefore, were carried out in benzene or ether, a t temperatures varying from 2 " to 80" C. The higher temperatures increased the rate and degree of acetylation, but degradation of the cellulose and production of colored polymers of ketene were also increased. I n some cases the cotton was pretreated with acetic acid before introduction of ketene. In these cases ketene probably formed acetic anhydride before acetylating
the cotton. This phase of the work was not studied further because acetic anhydride acetylation of cotton has already been studied extensively by other workers. EXPERIMEXTA L
APPARATUSFOR !LCETYLATION. An 18- to 20-inch length of KO.27 Chrome1 C wire was made into a helical coil approximately 3.5 inches in length for use as the pyrolyzing coil. This was heated to a bright cherry red with about 10 amperes of alternating current controlled with a variable transformer. The coil was submerged in acetone in a 1-liter, 3-necked flask, which in turn rested in a cold water bath to reduce the amount of refluxing acetone and also to reduce fire hazard if the flask were accidentally broken. An efficient condenser with at least a T 3 4 / 4 5 joint was necessary t o prevent flooding by the condensed acetone-one of the type in which the cooling liquid runs through an inner coil was found satisfactory. With care not to condense the ketene, a short condenser, cooled by solid carbon dioxide, was used to remove practically all of the remaining acetone. The gas was then passed through a flowmeter, the acetylation vessel, a second flowmeter, and finally a wet test gas meter. The usual rate of flow desired was 0.3 mole of ketene per hour which was found to correspond t o a gas flow rate of 0.3 liter per minute as measured by the wet test gas meter.. Unfortunately, the rates of pyrolysis and side reactions varied during each run, probably due t o changes in the surface characteristics of the wire, variations in heating, etc. The proportion of methane and other gaseous products to ketene probably varied also. The ketene was nearly all absorbed in the reaction vessel which consisted of a 500-ml. gas washing bottle (Pyrex No. 31750) with a fritted disk bottom. The gases were passed through the bottom disk into the liquid in which the cotton was placed. A condenser, cooled with ice water, was placed above the reaction flask to return vapors of the liquid used. This type of gas washing bottle is also adaptable for filtering and washing the sample upon completion of the reaction. Great care must be observed in the handling and disposal of ketene since it is very poisonous and irritating ( I S ) . All experiments were conducted in a well-ventilated hood. TYPICAL Ruu. Five grams of air-dry purified cotton linters were swollen by soaking in water overnight, under vacuum, which helped penetration by expelling entrapped air. Wa'ter was removed by pressing and extracting twice with 95% ethyl alcohol. The alcohol was squeezed out and part of the residual alcohol removed b washing with ethyl ether. Finally, the material was extractez7 hours with ether in a Soxhlet apparatus, using metallic sodium in the boiling flask to destroy the residual water and the remaining alcohol. The dry, swollen cellulose was suspended in the reaction vessel in 150 nil. of dry ether containing 0.05 ml. of 6070 perchloric acid. Ketene was passed through the ether a t a rate of approximately 0.3 mole per hour. Temperature varied from 21 t o 26 C. The reaction was allowed to proceed for approximately 0.5 hour until 10 liters of by-product gas had passed through the flask as measured on a wet test gas meter. When about 3 liters of gas had passed through, the linters were observed to swell slightly, and a light yellow color formed, presumably from polymerization of the ketene. This color usually darkened somewhat as the reaction proceeded. Expericnce showed t h a t this yellowing generally indicated acetylation of the activated cellulose. After disconnecting the reaction vessel, the linters were filtered in the vessel and washed once with alcohol which removed most of the color. They were then soaked in a beaker of alcohol overnight, the alcohol was brought to a boil, and filteiad hot. Practically all of the polymerized ketene was soluble in boiling alcohol. The sample was then boiled in several changes of water and dried for analysis. Acetyl values were obtained from duplicate portions of each sample by the modified Eberstadt method ( 7 ) . The acetyl content varied from 16 to 1S70. Uniformity of treatment
1018
O
INDUSTRIAL AND ENGINEERING CHEMISTRY
May 1949
OF VARIOUS TREATMENTS ON KETENEACETYLATION OF TABLE I. EFFECT PURIFIED LINTERS
Run No. 104 114 123 266 337 102 110 120 267 281
Sample Weight, G. 2 2 2 5 5 2 2 2 5 5
Pretreatment a
b 0
d e
a b 0
d f
Diluent 100 ml. ether 100 ml. ether 100 ml. ether 150 ml. ether 150 ml. ether 100 ml. benzene 100 ml. benzene 100 ml. benzene 150 ml. benzene 150 ml. benzene
Catalyst, 60% HClOr, M1. 0.05 0.06 0.0: 0.05 0.05 0.05 0.05 f
Approx. Temp., OC. 35 35 35 25 25 80 80 80 25-56 25-56
Vol. Gas, L. fi
6 6 10 10 6 6 6 10 10
Air-dry linters soaked in 50 ml. of ether several hours prior t o ketene treatment. Linters preswollen in water. extracted with alcohol then ether. Linters preswollen in water: water removed by aaehtropic distillation with benzene. d Linters soaked several hours in 100 ml. glacial acetic acid Containing 0.25 ml. of 60% HC104; pressed to abqut ZO070 wet pickup prior t o ketene treatment. e Linters preswollen in water. extracted with alcohol. traces of alcohol and water removed by extraction with ether in Soxhlet appakatus with metallic sodiim in the extraction flask. Linters preswollen in water; extracted with alcohol then ether; soaked in 100 ml. ether containing 0.25 ml. of 60% HClOl for several hours prior t o ketene treatment.
was checked by dyeing with Celliton Fast Blue which dyes cellulose acetate but not untreated cotton. Approximately 450 runs were conducted on cotton linters and sewing thread and selected runs are used,here for illustration. RESULTS
'
I n Table I are summarized the EFFECT OF PRETREATMENT. results of some typical runs showing chiefly the effect of pretreatment. Run 104 was made on air-dry linters presoaked in ether and shows practically no acetylation. Run 114, in which the linters were first swollen in water and then pretreated successively with alcohol and ether, showed satisfactory acetylation. This technique is similar t o that suggested for rapid acetylation of cellulose (4). If the water is removed by azeotropic distillation with benzene as in run 123, the susceptibility of the cellulose t o acetylation is greatly reduced. I n run 266 the cellulose was preswollen in glacial acetic acid before treatment. Presumably acetic anhydride is formed which then acetylates the cellulose. I n a continuous partial acetylation process, ketene gas might be used to regenerate the acetic anhydride used. I n run 337 extreme care was exercised in removing traces of alcohol and water from the cellulose prior to treatment. It gave results similar to run 114 in which probably traces of water and alcohol remained; but since a large excess of ketene was used, amounts consumed by these agents would be negligible. Benzene at its reflux temperature was used as the diluent in runs 102, 110, and 120, The results in these runs again show the necessity of activating the linters by swelling prior t o ketene treatment. Run 267, preswollen in glacial acetic acid containing the catalyst, showed extremely high acetylation in benzene when treated with ketene at the temperature range of 25' t o 56' C. Run 281, preswollen in water, followed by extraction with alcohol and ether t o effect the removal of the water, and then by soaking in ether containing the catalyst before the introduction of ketene, also showed considerable acetylation. EFFECTOF DIFFERENT CATALYSTS AND CATALYST CONCENTRATIONS. I n Table I1 is shown the effect of different catalysts upon the acetylation reaction of ketene on activated linters of low viscosity. The catalyst concentration selected for this series was 5% of the weight of cellulose, which was considered to be in a range high enough for most catalysts t o show their effect upon the reaction. Only 2 of the 12 compounds had any appreciable effect in catalyzing the reaction-sulfuric acid and perchloric acid, the latter having slightly greater activity than the former. As may be seen from 'I1, O*OZ5 to ml. Of 60% perchloric acid for 5 grams of cotton in 150 ml. of ether as diluent gave approximately optimum results as judged by acetyl content and the appearance of the sample.
EFFECTOF TEXPERATURE AND DILUThe data given in Table IV show the effect of temperature and nature of the diluent upon the acetylation reaction on water-activated linters. The samples obtained a t the higher temperatures were considerably degraded. Sample 398 run in benzene at 60" t o 70" C. had lost much of its fibrous character. Ether is probably the best diluent of the three resulting in the least coloring and degradative effects. EFFECT OF ALCOHOLAND WATER. Anomalous results obtained in some runs were due t o the presence of water and alcohol in the ether used. This was believed t o be a result of the catalytic effect of ether peroxide impurities in the ether, but neither the addition of concentrated ether peroxides nor t h e a d d i t i o n of b e n z o y l p e r o x i d e ENT.
Time of Reaction, Acetyl, Min. 70 1.6 35 16.8 40 3.7 15 12.9 27 16.8 32 2.0 33 29.4 36 9.6 19 36.3 35 26.6 29
a b c
1019
affected the acetylation. Apparently the ketene reacted almost exclusively with the alcohol or water before reacting with the cellulose, little acetylation taking place, as would be expected, when the alcohol and water were present in sufficient amounts t o react with the major part of the ketene. EFFECTOF REACTIONTIMEAND KETENE CONCENTRATIOS. I n Figure 1 are shown the results of treating 5-gram samples of linters of low viscosity with three different concentrations of ketene. The linters were preswollen in water, washed with alcohol and ether, extracted with ether in a Soxhlet extractor over sodium metal, and suspended in ether containing 0.05 ml. of 60% perchloric acid. An ether solution of definite ketene content was immediately added t o give a total volume of 150 ml. with a ketene content as indicated in the figure. The reaction was allowed t o proceed for varying lengths of time a t a room temperature of approximately 25" C. I t is apparent that acetylation occurs rapidly. If the ketene concentration is sufficiently high' the acetylation is accomplished within the first
TABLE11. EFFECTOF DIFFERENTCATALYSTSON KETENE ACETYLATION OF ACTIVATED LINTERS
Run No.0 371 372 373 374 375 376 377 378 379 380 381 382
Catalystb 60% perchloric acid Zinc chloridec Sulfuric acid Phosphoric acid Benzenesulfonic acid p-Toluenesulfonic acid Potassium acetate" Magnesium perchlorate Aluminum ohloride Sodium bisulfate0 Triethylamine Benzoyl peroxide
Acetyl, % 18.8 6.4 16.1 7.3 7.6 7.5 2.0 6.1 3.8 2.7 4.9 1.7
b A catalyst concentration of 5%-of the weight of cellulose was used. 6
Remained in Buspension in the diluent.
TABLE I11
EFFECT OF CONCENTRATION OF PERCHLORIC ACID' OF A~~~~~~~ L~~~~~
eATALYST 'IN K~~~~~ A~~~~~~~~~
R u n N0.a Catalyst, 60% HClOd, M1. Acetyl, % 259 None 2.2 260 0,005 7.5 261 0.010 10.8 262 0.025 14.3 0.05 16.7 263 0.10 17.5 264 a Sam les consisted of 5 grams of low-viscosity linters preswollen in water: e x t r a c t e f w i t h alcohol and ether t o remove water. then suspended in 150 ml. of ether containing the catalyst, Ten liters of &s were pawed through a t room temperature (250 c.), in approximately one-half hour.
INDUSTRIAL AND ENGINEERING CHEMISTRY
1020
18
I
n 1
I
16 14 12
s ' to
>-
L
- 8 4c
6
4 2
-
A h
c)
I
80
60
90
/
0 0
U I
120
REACTION TIME, MINUTES Effect of Reaction Time and Concentration of Ketene i n Ether upon Acetylation of Activated Cellulose
Figure 1.
A , 8.21 P a m of ketene per 5 grams of low-viscosity linters; B , 1.05 grams of ketene per 5 grams of low-viscosity linters; C, 1.22 grams of ketene per 5 grams of sewing thread; D , 1.7 grams of ketene per 5 grams of low-viscosity linters
Vol. 41, No. 5
ketene treatment. Ten liters of gas ~verepassed through in each case in approximately 0.5 hour. Although much of the ether was swept through the system. a considerable amount remained on the fibers as evidenced by the condensation and dripping of solvent from the condenser locatrd above the reaction vessel Thus the effect corresponded to treatment with a concentrated ether solution of ketene rather than gaseous krtene. The presence of catalyst resulted in a product having 22 SyOacetyl. E-IoTTever, it was spotty due to localized areas of ketene polymer formation and was quite brittle and powdery indicating a high degree of degradation possibly owing to the high temperature of treatment. The sample treated with ketene with no catalyst preqent contained only 3.6% acetyl. ACETYL.4TIoX OF SEWINGTHREAD.After establishing the conditions for the acetylation of purified cotton linters with ketene, partial acetylation of natural cotton sewng thread was attempted. The results are similar to those obtained with purified linters and are shown in Table V and Figure 1. Run 370 on unswollen natural cotton gave 0.470 acetyl content indicating negligible reactivity. Runs 365 through 369 shon varistion in acetyl content and breaking strength with change in conditions. Up t o 17% acetyl content may be obtained with loss of about 12'3, in breaking strength. An acetylation of 39% r a s obtained by preswelling thread Tvith glacial acetic acid and treating with 10 liters of ketene-bearing gas using benzene as the djluent. However, the breaking strength was reduced to 1 pound, about 10yo of the original strength. Mercerized thread gave higher acetyl content with less degradation, probably because of the swelling action of the alkali which aided the penetration of the ketene allowing more rapid and uniform reaction. Thew was little difference between the reactivity of the thread mercerized under tension and that mercerized without tension Runs 424 through 430 show that activated natural sewing thread can be acetylated by a n ether solution of ketene within the first few minutes of reaction. However, the losses in stiength were high, ranging up t o 3snp. SL \II14KY
few minutes of reaction time. Based on the acetyl content of the linters, only 17y0 of the ketene reacted a t the lowest concentration, 57.6% a t the intermediate, and 6l.5Y0 a t the highest concentration of ketene. This indicates that the reaction is more efficient as the ratio of ketene to cellulose increases. The curves in the figure coireapond to straight lines on a semilogarithmic plot. EFFECT OF GASEOUSKETEKS. Two samples of water-activated, alcohol-extracted linters were extracted with ether in a Soxhlet extractor with metallic sodium in the extraction flask. One sample was further pretreated by soaking in 150 nil. of ether containing 0.05 ml. of 607' perchloric acid. Both were pressed free of excess ether (to about 200% wet pickup) then placed in the reaction vessels and immersed in a boiling water bath for the
Linters and cotton sewing thread have been acetylated with ketene. Treatment involves preswelling with water, removal of excess water by extraction, suspension of the cotton in an inert
TABLE
No.a
Run
Pietreatmrnt
365 306 3F7
b b h c
368 3G0
42.5 426
OF TEMPERATITRE AXII XATUREOF DILUENT TABLE IV. EFFECT O N KETENEACETYLATION OF BCTIV.4TED LIKTERS
427 425 429 430
h E T Y L A T 1 O N O F SEWING
Vol. Gas, L. 3 6
Y 3 6 10
11 20
29
I f
30
i
BO
G
00
i f
..
THREAD
Time of Loss in Rreaking Strength Reaction, -4cety1, Over T h a t of Control Samples, 7' Min. %
11 18 20 GO 1 5 13
E
d
370 424
v.
4.6 17.2 17.4 9.2 15.9 0.4 8'2 8.8
10.0 10.1 11.7 0.8
15.1 1.9
sampies consisted of approximately 6 grams of sewing throad. b Sewing thread prerioudy mercerized under tension: extracted with alcohol, then ether in a Soxhlet extractor with mctallic sodium in t h e extraotion flask; suspended in 150 ml. ether containing 0.05 ml. of 60% I-IClOi aq cataiyst. Treated with ketene a t room temperature of approximately
384
16.1
2.50
397 39.3
17.2
Run X 0 . a 391 302 393 395
Diluent, 150 1\11.
Temperatnre Rangeb,
C. .4cetyl, % ' 12.5 12.1
21.0 Benzene a Samples consisted of 5 gra:ns of low-viscosity linters presirollen in water, extracted with a!cohol; extracted w i t h ether in a Soxhlet extractor with k e t d l i c sodium in the exLraction flask: then suspanded in 150 ml. of the diluent containing 0.05 ,ml. of 60% HC104. Ten liters of gas w e r e passed through in each case, In about, one-half hour. b Temperatiires y e r e maintained by an ice bath, warm water bath, and hot water bath, respectively. Measurement of t h e temperature was made from a short stem thermometer suspended in the mass of linters during the course of t h e reaction.
a .411
c.
Sample previously mercerized without tension then treated as in b. K O pretreatment: suspended in 150 ml. ether containing 0.05 ral. of 6 0 4 TlClOc as catalyst; then treated with ketene gas a t room temperature. ;'Samples were natural sewing thread preswollen in water' extracted with alcohol, then ether in a Soxhlet extraotor with metallic ~ o b l n min t h e extraction fla5k; then trrated with 150 ml. ether containing 0.05 ml. of 60% HCIOI as t h e cata.iyst. N o ketene added. f Samples prehreated as in e, then treated with 150 ml. s t h w containing 0.05 ml. HClOn as catalyst and 1.22 grams ketene in solution a t room temperatura. (I N o pretreatment: natural sewing thread treated with 150 ml. ether containing n.O.5 mi. of HClOI as catalyst a n d 1.22 grams ketene in .solution at room temperature. c d
May 1949
INDUSTRIAL AND ENGINEERING CHEMISTRY
solvent (preferably ether) containing a catalyst (preferably perchloric acid), and treatment with ketene as prepared by pyrolysis of acetone. Samples containing up t o 17% acetyl retained their fibrous structure with only slight degradation. The ketene acetylation was accompanied by a n objectionable polymerization of ketene which produced a yellow to dark brown coloration of the sample. The color could be removed by hot alcohol. Although the emphasis was on the reaction of water-activated, solvent-dehydrated cellulose with ketene, some experiments were tried in which the cotton was swollen with acetic acid before the introduction of the ketene. The acetylation was probably due t o the acetic anhydride formed. LITERATURE CITED
(1) Davis, B. L., Goldblatt, L. A., and Palkin, S., IND. ENG.CHEM..
38, 53 (1946).
mulsion
1021
(2) Goldthwait, C. F., MoLaren, J., and Voorhies, S. T . , Jr., Textile WorEd, 96, No. 2, 115 (1946). (3) Graves, G. De W., U. S. Patent 1,990,483 (Feb. 12, 1935). (4) Heuser, E., “Cellulose Chemistry,” p. 248, New York, John Wiley & Sons, 1944. (5) Ketoid Company, Brit. Patent 237,575 (July 22, 1924). (6) Middleton, E. B., U. S. Patent 1,685,220 (Sept. 25, 1928). (7) Murray, T . F., Jr., Staud, C. J., and Gray, H. Le B., IND.ENG. CHEM.,ANAL.ED.,^, 269 (1931). (8) Nightingale, D. A , , Brit. Patent 237,591 (Oct. 29, 1925). (9) Nightingale, D. A,, U. S. Patent 1,604,471 (Oct. 26, 1926). (10) Rice, F. O., Greenberg, J., Waters, C. E., and Vollrath, R. E., J . Am. Chem. Soc., 56, 1760 (1934). (11) Talley, E. A., and Smith, L. T., J. 0 ~ gChem., . 10, 141 (1945). (12) Wolcott, B., U. S. Patent 1,474,574 (Dee. 10, 1921). (13) Wooster, H. A., Lushbaugh, C. C., and Redemann, C. E., J.Ind. Hug. Toxicol., 29,56-7 (1947). RECEIVEDJuly 10, 194% Presented before Meeting-in-Miniature of the Louisiana Section, BMERICAN CHEXICAL SOCIETY, S e w Orleans; La., May 14 t o 15, 1948.
olyrnerization of Methyl etone with Butadiene CHARLES W. GOULD AND G. E. HULSE Hercules Powder Company, Wilmington 99, Del.
v .
I he emulsion copolymerization of methyl isopropenyl ketone with butadiene has been investigated to determine the effects of emulsifier, modifier, temperature, ratio of monomers, and pH on the rate of reaction and viscosity of the copolymer. It was found that the reaction could be carried out using a wide variety of emulsifiers and a pH ranging at least from 3 to 10. Mercaptan modifiers had the usual effect on the molecular weight and were necessary to produce a soluble, plastic polymer. The polymerization rate was proportional to the per cent ketone in the monomer mixture and was increased about threefold by raising the reaction temperature from 40” to 50” C. In comparing the copolymerization with that of styrene and butadiene, the chief points of contrast are: the much faster rate (about four times that of a comparable styrenebutadiene copolymerization) and the formation of polymers which have a very high Mooney viscosity (170), yet are completely soluble, even at conversions of 80% or more.
U
KSATURATED ketones such as methyl isopropenyl ketone have been copolymerized with butadiene by a number of investigators (3-6, 7 , IO). However, little has been published concerning the effect of systematic variation of reaction conditions on the rate of copolymerization and the properties of the polymers. It was to be expected that substitution of a n acetyl group for a phenyl group side chain in a vinyl-butadiene copolymer would give a polymer considerably different from, a n d with some advantage over, GR-s. The greater electronegativity and hydrogen bonding ability of the carbonyl group should lead to a definite difference in intermolecular forces, which should be reflected in the physical properties. I n addition, the smaller size of the acetyl group probably permits closer packing of the molecular chains. A further difference exists in the substitution of a methyl group for hydrogen on the alpha carbon of the vinyl group. This eliminates from the polymer the tertiary carbon atom, which is particularly subject to dehydrogenation by a free radical, thus initiating a chain branching reaction,
Because preliminary experiments indicated that the copolymer had attractive properties and the ketone monomer can be prepared from readily available raw materials ( I , l l ) ,i t w m of interest to investigate the copolymerization further. Accordingly, experiments have been made t o determine the effects of emulsifying agent, modifier, temperature, ratio of monomers, and p H on the rate of reaction and the viscosity of the polymer. EXPER1:MENTAL
The general procedure was similar to t h a t described by Fryling (6). The polymerizations were carried out in ordinary %ounce carbonated beverage bottles, closed with a crown cap. The standard recipe used in this work, unless otherwise noted, was as follows: Emulsifying agent Potassium persulfate Double-distilledwater to make Monomers, butadiene methyl isopropenyl ketone Modifier, primary mercaptan
+
2.50 grama 0.15 gram 90.0 ml. 50.0 grams 0.25 gram
Most of the work reported here was done with Duponol C emulsifier in a buffered system, usually at p H 5 . In this case, the following reagents were added: 0.5432 N sodium hydroxide
Potassium acid phthalate
3.96 ml. 0.92 gram
DESCRIPTION OF REAGENTS. It was found t h a t more consistent and higher conversions could be obtained if the usual laboratory distilled water was redistilled in a glass apparatus before use. Similarly, better results were obtained when the buffer solutions were freshly prepared each time, and the methyl isopropenyl ketone monomer was fractionated t o give a product with a refractive index, n%o, in the range 1.4233 t o 1.4237. As determined in this laboratory, the refractive index, nk0,of pure methyl isopropenyl ketone is 1.4233; Morgan (11)has reported a value of 1-4220.
The emulsifying agents suchas Duponol C (Du Pont), Triton K60 @ohm and Haas), and f a t t y amine acetate (Armour) were used as received. The inorganic reagents such as potassium persulfate
-
