INDUXTRIAL A N D ENGINEERING CHEMISTRY
August, 1924
With pulp no such difficulty occurs, because of the lower lignin content and more especially because of the different physical form which permits complete penetration. The use of a water jacket around the reaction bulb is desirable, because the reaction is markedly exothermic, and without the water jacket the bulb becomes distinctly warm. Irregular action of the chlorine and hydrochloric acid formed as a by-product is better controlled if a water jacket is used.
TRANSLATION OF RESULTS Theoretically, it is to be expected that the so-called chlorine number as determined by this method should yield valuable data as to the amount of bleach required for any given pulp. I t is quite true that chlorination followed by alkaline treatment will not in itself yield a white pulp. A comparatively small amount of nonligneous material remains to color the pulp very distinctly. These residues may be completely and quickly oxidized through the application of a small amount of hypochlorite. For example, an exceedingly hard pulp, after chlorination in the method described followed by an alkaline wash, will yield a fine, white fiber by the application of the equivalent of about 3 per cent dry bleach. The results as determined require the use of an arbitrary factor or constant to convert the chlorine number into percentage of dry bleaching powder or available chlorine. Under conditions prevailing in this mill, a factor of 5 seems to yield a satisfactory white color with the minimum amount of unexpended bleach. With a chlorine number of 4.1, for example, the equivalent of 20.5 per cent dry 33 per cent bleaching powder would be required. It is quite possible that the factor would have to be altered slightly for very widely differing pulps. I n bleaching a hard pulp there is evidently much more gas evolved than with a soft pulp bleached under similar conditions. If this gas is assumed to be carbon dioxide, as pointed out by Schwalbe and Wt:nzl,ll it would quite likely have an effect on the reaction characteristics. Furthermore, in bleaching hard pulps the bleach is necessarily not all expended in useful work. The yellow, water-soluble extractives or decomposition products will in themselves consume considerable bleach. These and other considerations make it, appear doubtful whether two widely different pulps may be experimentally or commercially bleached, even under identical conditions, with any assurance that a proportionality factor may be rigidly applied to them. CONCLUSIONS The foregoing method for the determination of the chlorine absorbed by unbleached sulfite pulps suggests a rapid means for the evaluation of the comparative bleach requirement of pulps. The results obtained are strictly comparative in themselves and can be translated into bleach equivalent terms by means of a factor which depends on the conditions under which the bleach liquor is utilized. Manipulative technic is no more difficult than with an Orsat apparatus, and can be easily mastered by an operator with little or no chemical training. No attempt has been made to correlate the results with those obtained by other methods, neither has the method been applied to other than sulfite pulps. The application of gas volumetric methods might be used to advantage in the critical study of ligneous fiber. ACKNOWLEDGMENT The writer is indebted to Claude A. Sorg for advice and to Max Eisenmenger for accumulating the data incidental to the development of the method. 11
Pagier-Fabr., 21, 288 (1923).
811
Met hyla tions' Hydrolysis of Dimethyl Sulfate By H. F. Lewis with O'Neal Mason and Russell Morgan CORNELL COLLEGE, MT.
VERNON,1.4.
The rates of hydrolysis of dimethyl sulfate at 95" C. have been determined in the presence of the following reagents: sulfuric, hydrochloric, and acetic acid; sodium and potassium hydroxides; and sodium chloride and sulfate, potassium chloride, and magnesium sulfate. I n the hydrolysis in the presence of water alone the concentration ratio of dimethyl sulfate to water has very great influence on the rate of hydrolysis, the rate of reaction in a mixture of molecular amounts of dimethyl sulfate and water being very rapid. The observation of Klemenc regarding the relatively greater influence of potassium hydroxide than sodium hydroxide has been substantiated at the temperature of 95 C. Salts are found to haw a very great depressing action on the rate of hydrolysis.
IMETHYL sulfate has become within the last few years a rather common methylating agent, both in the chemical industry and in the research laboratory. As ordinarily used, but one-half of the methyl groups goes into the methylation, the other half forming methyl hydrogen sulfate or its salts, or the dimethyl ether. In consideration of this fact, a study hds been undertaken to determine the conditions involved in methylation with this type of a reagent. An investigation of the hydrolysis of dimethyl sulfate under various conditions is described in this paper.
D
THEORETICAL I n the hydrolysis of dimethyl sulfate with water, the reaction may proceed with the methylation of water according to the following equations:
++
(CH3)aSOd HzO = CHsOH f CH3HSOp CHsHS04 HzO = CHsOH f HPSO~ CH30H f CH3HS04 = CHsOCHs f
(1) (2) (3)
At the same time, for each molecule of methanol formed there is an equivalent amount of hydrogen, as is also the case in Reaction 3. This is titrated and calculated back to dimethyl sulfate hydrolyzed, furnishing an index of the rate and extent of hydrolysis. A study has been made of the influence of: (1) Varying ratios of water and dimethyl sulfate on the hydrolysis of dimethyl sulfate, the temperature being 95' C. (2) Such acids as sulfuric, hydrochloric, and acetic. (3) Alkalies-as, for example, sodium and potassium hydroxides. (4) Salts, such as sodium and potassium chlorides and sodium and magnesium sulfates. METHODS INVOLVED I n each case the desired weight of dimethyl sulfate was introduced into a 500-cc., round-bottom flask, and in the hydrolysis with water enough water was added to make the total weight 100 grams. In the reactions with acids, alkalies, and salts, the weight of the particular reagent added was included in the 100 grams. The flask was connected with a bulb condenser, the temperature raised as rapidly as possible to 95" C., and kept a t that temperature for the desired time. At the completion of this period, the reaction was stopped with the addition of a large volume of cold distilled water. The sulfuric acid formed was titrated directly against standard 1
Received February 7, 1924,
INDUSTRIAL A N D ENGINEERING CHEMISTRY
812
sodium hydroxide in the usual manner. If the reaction was alkaline, the excess alkali was titrated back against standard sulfuric acid. Since the rate of hydrolysis a t room temperature is very small, and especially in the hydrolysis of methyl hydrogen sulfate, the titration value represents with some accuracy the hydrolysis conditions a t the conclusion of the experiment. The dimethyl sulfate used was redistilled a t 15 mm., the constant boiling fraction being collected and used. Its acidity at 0" C. was negligible.
In each case the percentage of sodium hydroxide is as stated, while the potassium hydroxide is present in the same molar ratios. TABLE111-PERCENTAGE
ALKALINEHYDROLYSIS O F DIMBTHYL SULFATE (Temperature looo C.) c TIMEO F HYDROLYSIS--Alkali 3 Minutes 15 Minutes 1 Hour 3 Hours 1% dimethyl suZfat6 50.9 51.9 55.2 64.0 1 % NaOH 36.8 53.9 80.5 85.1 :% KOH 58.1 60.9 88.4 90.8 20% NaOH 32.0 49.1 75.6 90.8 257, KOH 52.2 80.2 92.1 98.0 25% dimethyl sulfate
EXPERIMENTAL DATA HYDROLYSIS WITH WATER-In the following experiments the percentage of dimethyl sulfate varied all the way from 0.5 to 75.0 per cent. For each different concentration, a time-rate of hydrolysis curve was made. The results have been incorporated in Table I.
--
TABLEI-PERCENTAGE Dimethyl Sulfate 0.5 0.99 1.95 4.75 11.5 21.0 28.6 40.0 48.0 56.5 66.0 75.0
3 Minutes 49.9 50.9 53.0 56.8 66.1 60.4 61.8 64.6 88.0 89.0 95.9 96.0
HYDROLYSIS O F DIMETHYL SULFATE
WATER
WITH
2 Hours 56.9 59.0 66.1 74.6 87.9 92.1 96.0
3 Hours 81.8 64.0 72.3 78.9 93.2 96.1 96.5 94.0 94.2 94.0
..
..
.. ..
9?:8
TABLE11-PERCENTAGE HYDROLYSIS OF DIMETHYL SULFATE IN ACID
1 % HZSO, 1% HC1 1 7 C2H402 2 5 9 HZSO4 2 5 d CZH402
1 7 C2H402 25% HC1 257, CzH402
---
l%NaOH 1 9 KOH 52% NaOH 25% KOH
60.0 55.7 54.2 Insoluble Insoluble
75.1 71.2 64.1 Insoluble Insoluble
89.2 76.9 71.7 88.8 86.8
96.1 89.5 90.5 93.0 95.7
In the solutions of low concentrations of dimethyl sulfate, the greater hydrolytic influence of potassium hydroxide is noted. This checks the observations of Klemenq2 although his work was carried out at much lower temperatures, When a concentrated solution of the sulfate is being hydrolyzed with an amount of alkali less than molar, however, there is not a great deal of difference to be noted between the rates of hydrolysis of potassium and sodium hydroxides. HYDROLYSIS OF DIMETHYL SULFATE IN THE PRESENCE OF SALTS-From the results obtained in the alkaline hydrolyses, it became evident that the salts formed as the result of the hydrolysis had a direct influence on the rate of hydrolysis. Consequently, as a check the relative rates in the presence of salts and in aqueous solutions were determined. The salts used included sodium and potassium chlorides, sodium sulfate, and magnesium sulfate. The results have been incorporated in Table IV.
1
These results indicate that with a relatively low concentration of dimethyl sulfate in water the first group hydrolyzes with extreme ease, whereas the second group comes off slowly. With a relative increase in the concentration of dimethyl sulfate a remarkable increase in the rate of hydrolysis of dimethyl sulfate is noticed. HYDROLYSIS IN THE PRESENCE OF ACIDS-The results obtained on the rate of hydrolysis of dimethyl sulfate in the presence of such acids as sulfuric, hydrochloric, and acetic are given in Table 11.
Acid
Vol. 16, N o . 8
SOLUTION
(Temperature looo C.) TIMEO F HYDROLYSIS3 Minutes 15 Minutes 1 Hour 1%.- dimethvl - sulfate 50.9 51.9 55.2 39.0 49.6 64.2 26.2 33.2 53.0 48.9 55.6 60.0 44.9 49.5 54.2 22.1 31.6 46.7 25% . _dimethyl sulfate 75:l 60.0 89.2 54.1 67.9 87.1 39.5 68.6 73.4 42.2 57.7 67.8 48.9 55.3 58.1 37.0 50.1
..
TABLEIV-PERCENTAGE HYDROLYSISO F DIMETHYLSULFATE Dimethyl Sulfate Per cent 1 25
7
3 Hours
1
64.0 69.3 68.8 60.8 66.1
25
96.1 91.2 80.9
25
..
50:2 51.0
These data suggest that small amounts of acids in the presence of relatively small concentrations of dimethyl sulfate tend to slow up the hydrolysis in the early stages while ultimately the rate is more rapid than in water alone. Even larger quantities of sulfuric acid have little influence on the rate of hydrolysis under the above conditions. Any acid whatever in the presence of the higher relative concentration of dimethyl sulfate in water depresses the reaction, although small amounts of sulfuric acid have but little influence. The almost total absence of hydrolysis of the second group in the presence of large amounts of acetic acid should be noted. ALKALINE HYDROLYSIS-complete series of alkaline hydrolyses were run, using sodium and potassium hydroxides as the hydrolytic agents. The results of these experiments are given in Table 111.
2
1
IN
THE
PRESENCE OB CERTAIN SALTS (Temperature 95" C.) ----TIME OB HYDROLYSIS Salt 3 15 1 3 Per cent Hour Minutes Minutes Hours 50.9 51.9 55.2 64.0 23.5 1 NaCl 24.6 38.6 8.4 25 NaCl 8.5 10.3 9.i 75.0 60.0 89.0 96.0 1 NSCl 47.1 66.0 62.1 82.0 25 NaCl Not completely soluble 2 2 . 4 26.7 26.1 1 KCI 26.2 26.0 32.3 37.2 25 KC1 5.0 7.0 11.9 10.8 1 KCI 40.5 63.6 68.6 83.8 25 KCI Not completely soluble 1 3 . 6 29.1 46.2 26.1 1 NazSOi 23.9 35.6 37.0 25 NazSOa 19.1 18.8 20.9 21.8 1 MgSOa 45.7 41.0 48.6 50.0 25.5 25 MgSOa 26.2 29.5 41.0 55.5 1 MgSOa 65.5 84.6 25 MgSOd 37.5 36.0 53:l 79.8
-
-
The results bear out the indications of the alkaline hydrolyses. As might be expected, a small amount of salt has little influence on the hydrolysis of a large amount of dimethyl sulfate, while a large amount of salt has a surprising influence on a, small amount of dimethyl sulfate. Moreover, there is not a great deal of difference in the relative influence of sodium and potassium chlorides except in the series using both 25 per cent of methyl sulfate and 25 per cent of the salt. Sodium sulfate and chloride have about the same effect, while magnesium sulfate produces much less depression of the rates of hydrolysis than do the other three salts. ACKNOWLEDGMENT The authors are indebted to the National Aniline & Chemical Company for help in carrying on this research. 2
Monatsh., 38, 553 (1918).
