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T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
one of sufficiently large crystal structure for convenient filtration and handling. With the xylene in use a t t h e time, however, satisfactory neutralization of the T N X could not be obtained owing t o t h e previously mentioned cementing together of the crystals on t h e treatment with hot water and consequent inclusion of acid. This was doubtless due t o the high content of isomeric compounds. STUDY O F R A W MATERIALS
I n order t o overcome this difficulty a study $as made of the rectification of solvent naphtha, and of t h e results obtained b y nitration of various ranges of the xylene fraction. Rectifications for this purpose were first carried out a t the Deepwater Point Works of the du Pont Company, and later a t the Frankford plant of the Barrett Company. The Barrett Company cobperated in all the later portions of this study, and the successful outcome of the work was in large measure due t o their assistance in settling this very vital phase of the problem. A comparison of the physical properties of xylenes from different portions of the range with the results obtained on nitration brought out the following points: I-The boiling range and specific gravity of t h e xylene do not offer a satisfactory control of t h e charact e r of the raw material, and the final value of t h e xylene for use in the manufacture of T N X can be established with satisfaction only by a nitration test carried out in a manner comparable with the plant method. 2-In general, T N X of the most satisfactory freezing point and in the best yields, is obtained from a xylene meeting the following boiling point specifications : Range, 1st drop to flask dry 3’ C. First drop, between 137.2O and 139.2’ C.
Vol.
12,
NO. 3
pounds from water-gas xylene b y sulfonation of t h e xylenes and separation of t h e unsulfonated residue, followed by nitration of mixtures of this material and coke-oven xylene, there was no effect shown on the freezing point of the resulting T N X , and no greater effect on yield was shown t h a n could be accounted for by the actual “paraffins” added. On t h e other hand, when water-gas xylenes of similar properties, but with varying “parafin” contents, were nitrated, there was a reduction in freezing point of T N X approximately proportional t o the “paraffin” content, and a reduction in yield greater t h a n could be explained on the ground of “paraffins” alone. These results apparently indicate t h a t “paraffins” are not responsible for the difference between cokeoven and water-gas xylene, and possibly indicate the presence of unidentified compounds in the watergas xylenes other t h a n “paraffins,” but appearing coincidentally with them. LARGE SCALE
OPERATIONS
As soon as progress had been made on the subject of specifications for t h e raw material, active operation was started in a semi-works plant constructed for the purpose, and i t was here demonstrated t h a t xylene of t h e type specified gave satisfaction on the larger scale operation. Final d a t a were also obtained in this work for the design of a large scale plant, and construction of this plant, with a potential capacity of 3,000,000 lbs. T N X per month, was a t once started. The first unit was completed August I , 1918, and operations were started a t once, and a t t h e time of the signing of the armistice two of the five units were in full production of a satisfactory product, with the other units nearing completion or in partial operation.
Flask dry, between 138 5O and 140.5’ C.
3-Xylenes taken from the p-xylene range will nitrate satisfactorily and give good freezing points, b u t yields will be low. +--Xylenes taken from the o-range, i. e., high in @-xylene, will give difficulty in nitration, with low yield and freezing point of product. 5-TNX samples having freezing points of 161.5 C. or better showed no tendency t o agglomeration of .crystals when treated with hot water. They could be neutralized without difficulty. I n addition t o t h e above points, i t was found t h a t t h e value of a xylene for the preparation of T N X depended in large measure upon the source of t h e xylene; for example, the coke-oven by-product xylene always gave a more satisfactory T N X t h a n xylene with a n identical boiling range from other sources, such as water-gas t a r , or drip oil. No satisfactory explanation has been found for this. Water-gas xylene and drip-oil xylene as a rule contain relatively high percentages of hydrocarbons (members of the paraffin a n d naphthene series, and usually designated“paraffins” for convenience) which resist sulfonation and nitration, and for a time these compounds were considered -responsible. However, on isolation of these com-
NOTES ON DOUBLE POLARIZATION METHODS FOR THE DETERMINATION OF SUCROSE AND A SUGGESTED NEW METHOD By Geo. W. Rolfe and L. F. Hoyt CAMBRIDGE, MASSACHUSETTS Received August 30, 1919
The well-known principles and methods of double polarization applied in t h e analysis of commercial sugar products need not be detailed here. The methods in use depend on the assumption t h a t t h e change in optical rotation of a sugar solution, which is the measure of the sucrose, is the result of t h e inversion of the sucrose only. One of t h e chief objections t o the original method of Clerget and Herafeld arises from the fact t h a t the direct reading is made on a practically neutral solution and t h e invert reading on a strongly acidulated one. Much work has been done in developing improved methods of procedure t o prevent or a t least mitigate the errors which are introduced under these conditions, especially in sugar estimations of low-grade products where the change in acidity causes changes in the optical rotation of the sugars, other t h a n sucrose, which are present. Those who are interested in these investigations may be I
Mar., 1920
T H E J O U R N A L OF 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
referred t o the voluminous and familiar papers of Pellet, Sidersky, Anderlik, and others. As the field has by no means been exhausted, even so far as t o develop methods which really meet many of the requirements of commercial analysis and general research, the present paper is published as suggestive of a new line of attack of the problem. I n making up the solutions two lots of commercial granulated sugar were used-one from the Standard Refinery of Boston, polarizing 99.95, and the other from the Revere Refinery, polarizing 99.99. The factors of inversion for these sugars were obtained by the Clerget method, modified by carrying out the inversion a t room temperature, and by the method of Herzfeld, likewise modified. Table I gives these factors (see also Table 11). TABLEI METHOD Clerget
SUGARUSED Std. Granulated Revere Granulated
TIME TEMPERATURE HRS. OC. FACTOR 22.0 23 144.56 22.0 28 144.17
Herzfeld
Std. Granulated Revere Granulated
21.5 21.5
AVERAGE 144.37 28 142.43 28 142.67
-
AVERAGE 142.56
I t is well known that the factor obtained by the invertase method of Hudson is much lower than t h a t obtained by the Clerget and similar procedures, and i t is also known t h a t this is caused by the fact t h a t the acid augments the invert reading. What does not seem t o be so well known, if it has been published a t all, is t h a t neutralized acid-inverted solutions give larger readings than the original acid solutions. Apparently neutralization does not affect the increase in rotation caused by the acid, but the reading is still further increased by the salts formed in neutralization as shown in Table 11. TABLEI1 (Method of Herzfeld) TSST 1 2
3
FACTOR FOR
ACID SOLUTION NEUTRALIZED SOWJTIONDIFFERENCE 143.30 0.87 142.43 0.70 143.39 142.69 0.75 143.41 142.66 AVERAGE 0.77
An invert-sugar solution, made by heating a N / 2 (saccharimetric) sucrose solution with 0.01 normal hydrochloric acid on a boiling water bath for 30 min., gave the factor 141.7,agreeing with t h a t given by Browne for a neutral solution, as was t o be expected, since the acidity was negligible. Adding hydrochloric acid in the proportion used in the Herzfeld method Addition of the increased the reading by -1.35. equivalent amount of sodium hydroxide t o produce a neutral solution, gave a further increase of -0.60. Some work was done with the modification of Anderlik, in which urea is used as a retardant of the inversion when the direct reading is made in the presence of the usual amount of hydrochloric acid. Our experience with this method on cane products was unsatisfactory, as the direct polarization changed rapidly and indeed was quite unmanageable when the This method, therefore, temperature approached 26 would be inapplicable in raw-sugar work in the tropics, however satisfactory it may be for low-grade beet
’.
2 jP’
products. Our tabulated results, which are not given here since the method has already been adversely criticized by Browne and others, show t h a t unless t h e direct polarization is completed in less t h a n 3 min. the error from inversion change is too great t o b e negligible. Glycocoll as a substitute for urea proved still more unsatisfactory. INVERSIONS
WITH
MONO-
AND TRICHLOROACETIC ACID
It seemed desirable t o find a substitute for hydrochloric acid which would invert so slowly a t ordinary temperatures as t o permit direct readings without error, and yet be sufficiently acid to effect complete inversion upon convenient heat treatment. Accordingly, the following investigations were made with mono- and trichloroacetic acids, which had the great advantage of giving no troublesome precipitate with the soluble lead salts which were left after clarifying. The affinity constant of trichloroacetic acid is given as 75.4 and t h a t of the monochloroacetic acid as 4.8, on the basis of HC1 = 100. TABLE111 DIRECTSACCHARIMETER READING WITH 0.5 G. TRICHLOROACETIC WITH0.5 G. MONOCHLOROACETIC. ACID ACID Time Time Min. Readinz Min. Readincr 19.2 5 3 50.00 50.00 6 50.00 19.3 5 50.00 8 50.00 50.00 19.4 10 50.00 19.6 10 50.00 15 19.3 15 50.00 50.00 20 20.4 20 49.90 50.00 30 20.6 49.75 50.00 30 45 20.9 40 49.70 49.85 60 21.4 60 49.55 49.80 25 hrs. 47.50 21.6 49.30 90 (13.0 g. of sucrose in 100 cc.)
TemF?ture
__
The first series of experiments (Table 111) was to determine the rates and factors of inversion a t ordinary temperatures of half (sugar) normal solutions. of sucrose, containing 0.5 g. of mono- and trichloroacetic acids, respectively. These two solutions were heated in stoppered flasks for 3 0 min. in a boiling water bath, and inverted smoothly without discoloration, giving. constants of 142.2 in both cases. OF ACETATES ON INVERSION FACTOR OF A N / 2 (SACCHARIMETRIC) SOLUTION O F SUCROSE INVERTED BY 3 0. OF MONOCHLOROACETIC ACID AT 100’ c. Sodium Acetate Time of per 100 Cc. Heating Average Value No. of G. Min. Inversion Factor Observations 141.02 10 30 None 141.00 5 30 0.0625 30 4 141.05 0.125 i4i. i o 1 30 0.325 141 .OO 5 30 0.500 140.32 4 30 0.625 141.06 3 60 0,625
TABLE IV-EFRECT
These inversions of pure sucrose solutions of commercial concentration promised a satisfactory method, but Tolman’s observations on citric acid inversions. have shown t h a t soluble acetates have a marked inhibitory effect. I t was calculated t h a t I cc. of lead acetate (sp. gr. 1.26)would leave soluble acetate equivalent to 0.125 g. of sodium acetate. A half (sugar) normal solution of sucrose was therefore made up with 0 . 5 g. of monochloroacetic acid and 0.625 g. of sodium acetate, the latter equivalent t o j cc. of lead acetate, which was considered a maximum for all ordinary commercial polarizations. I t was found t h a t acetate in this amount retarded inversion in the cold t o such an extent t h a t there was no change in the
T H E J O U R N A L OF 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
252
TABLEV-LAG r
A Reading
7
,
B Reading
11.50 12.20 13.00 13.15 13.50
Temp, Deg. 18.6 18.8 19.7 20.2 21.0
15 30
13.80 14.15
21.4 21.4
15 20
14.85 14.90
60
14.40
23.2
75
14.30 14.00
23.0
30 Hrs. 20
Time Min. 6 7 9 10 12.5
100
Time Min. 7
OF
POLARIZATION -
Time Min. 5 6
12
13.50 13.90 14.30 14.50 14.70
Temp. Deg. 19.8 19.8 20.0 20.3 20.8
8
9 10
OF
,
12,
No. 3
VARIOUS INVERTED SUGAR SOLUTIONS
C Reading
-
10 15
12.00 12.75 13.60 14.20 14.85
Temp. Deg. 19.4 19.5 20.0 20.4 20.8
21.3 21.6
20 30
14.95 14.85
21.2 21.7
14.80
22.0
15.35
22.0
15.85
20.0
100 Hrs. 18
16.10
20.0
8
Vol.
,
Time Min. 6 10 15 27 40 Hrs. 23
DReading
-
-E Time Min. 3 4 5 7 14
Reading
13.60 14.10 14.30 14.85 14.70
Temp. Deg. 22.1 22.4 22.4 22.6 23.6
12.70 13.25 13.55 14.05 14.35
Temp, Deg. 21.4 21.5 21.7 22.2 22.6
15.80
20.0
25 40 Hrs. 2.25
14.50 14.50
23.2 23.5
14.50
23.5
4 24
15.10 15.76
23.6 20.0
Hrs. 20 A-N/2 B-N/2 C-N/2
D-N/2 E-N/2
15.20 Sucrose solution inverted by 0.01 per cent HC1 at looo. Sucrose solution inverted by 0.01 normal HCI at 100". Sucrose solution inverted by 0.5 g. trichloroacetic acid at 100". Sucrose solution inverted by 3 g. monochloroacetic acid with 0.625 g. of NaCaHaOt. Sucrose solution inverted b y 3 8. monochloroacetic acid and 0.625 6. of NaCzHaOn.
direct reading for several hours, and even 30 min. treatment a t I O O O gave only 1 5 per cent inversion. The retarding influence of the soluble acetate could be overcome by increasing the amount of chloroacetic acid, but in the case of trichloroacetic acid this was not practicable because, if enough acid was used t o complete the inversion of a N / 2 solution, i t gave a reading of 49.90 after only 4 min. in the cold. Two grams of the trichloro-acid in the presence of 0.625 g. of soluble acetate caused an inversion of only 94.3 per cent in 30 min., 3 g. being necessary for complete inversion. With the soluble acetate omitted, 3 g. of trichloroacetic acid accelerated the inversion in the cold as shown. N / 2 solution, polarizing 50.00. At end of 5 min At end of 10 min.. At end of 25 rnin..
.......................... ........................ ........................
49.85 49.75 49.60
Furthermore, the trichloroacetic acid, decomposing in the water bath, frequently gave off so much chloroform vapor as t o burst the flasks. With monochloroacetic acid there is a slight depression of the polarization caused by the addition of the acid and acetate, as a similar N / z sugar solution a t the end of z min. gave a reading of 49.85 which remained constant through observations of a few minute intervals carried on for over an hour. A sample of Cuban second sugar, clarified with 2 cc. standard basic lead acetate solution per N / 2 weight and treated with 3 g. of monochloroacetic acid, gave a constant polarization for over an hour. T o test the effect of a n excess of lead acetate clarifier, a N / z sucrose solution t o which had been added I cc. of lead acetate clarifier, 0.5 g. of sodium acetate, and 3 g. of monochloroacetic acid, was found t o resist inversion for 30 min. in the cold but inverted smoothly in the boiling water bath in 30 min. with no signs of discoloration, the inversion factor being identical with t h a t of a lead-free solution similarly treated. Table I V shows the influence of varying amounts of sodium acetate on the inversion factor obtained with monochloroacetic acid. I t will be seen t h a t the inversion
is incomplete after 30 min. boiling in the presence of more t h a n 0.500 g. of soluble acetate. To test the effect of sodium chloride two inversions with monochloroacetic acid were made in t h e way described in the above series, one with 0.625 g. of acetate and 0.6 j g. of sodium chloride, the other with 0.65 g. of sodium chloride only. The factors obtained were 141.04and 141.08,respectively, showing t h a t a sodium chloride content up t o 5 per cent of the weight of sample does not affect the inversion. Whenever sugar solutions are inverted a t a high temperature with hydrochloric or monochloroacetic acid there is a noticeable lag in the polarization even after the solution has reached temperature equilibrium with t h a t of the saccharimeter, the constant reading being always (numerically) greater than the initial, This lag, usually lasting but a few minutes, has been repeatedly noticed in solutions treated by the Clerget and Herzfeld methods, and is greater the less the acid content. When N / I O O HC1 was used the initial polarizations were as much as two divisions lower numerically t h a n the final constant value. With chloroacetic acids the lag is smaller but i t lasts longer (Table V). The possible causes of this lag will not be discussed a t this time. The factor 141.0 has been adopted as correct for a monochloroacetic acid inversion, and is based on t h e series of inversions of pure sucrose shown in Table VI. The 6 0 min. inversions showed some decomposition, as indicated by the lower factor. If, however, low-grade products, requiring as much as 5 cc. of clarifier, are inverted, the time should be increased t o I hr., owing t o the retarding influence of the soluble acetates. This is made clear in Table IV. TABLEVI-DETERMINATIONOF INVERSION FACTORSBY CHLOROACETIC ACID METHOD 15 Min. 30 Min. 141.60 141.14 140.08 140.92 141.20 140.90 140.98 140.90 141.16 141.00
-
Av. 141.20
THE
MONO-
60 Min 140.30 140.38 140.40 140.20
-
......
140.97
140.32
T o compare this method with the invertase method of Hudson, accepted as the standard method for accurate results, a n invertase solution was prepared
Mar.,
1920
T H E J O U R N A L O F I N D U S T R I A L A N D E N G I N E E R I N G CH E M I S T R Y
from compressed yeast. Half-normal sugar solutions were inverted a t about 30’ C. with varying amounts of this solution. The results are given in Table VII. TABLE VII-INVERSION CONSTANTS BY INVERTASE METHODOF HUDSON TIMEOF INVERSION FACTORS FOR VOLUME OF INVERTASE SOLUTION USED Hrs. 21 45 70
5 cc. 140.46 141.54 141.70
7.5 cc. 141.54 141.34 141.72
10 cc. 141.68 141.72
Time permitted only comparative tests by t h e invertase, Herzfeld and monochloroacetic methods on two samples of Cuba seconds and one of refinery barrel sirup. I n the invertase tests the solutions were carefully “deleaded” according t o directions by Browne.1 I n the other tests the minimum amount of basic lead acetate t o clarify was used. Table VI11 shows the comparative results by the three methods, making i t clear t h a t the monochloroacetic acid method gives results much closer to those obtained by the standard invertase method than does the Herzfeld method. A-Comparison
SAMPLE METHOD
TABLE VI11 of Double Polarization Methods rnn- __
centraInvert tion Polarization Per Direct of ( A l l p e a d - Fac- cent Polar- Solu- ingsin.N/2 tor of Suization tion Solution) Used crose
Cuban Second -14.10 141.70 88.24 Sugar No. 1438 Invertase 88.01 N Monochloroacetic 44.44 N / 2 -13.51 141 .OO 88.45 -14.38 142.66 88.63 Herzfeld 89.01 N Cuban Second -11.18 141.70 84.08 Sugar No. 1323 Invertase 88.40 N Monochloroacetic 44.00 N/2 -11.26 141.00 84.36 N , 7 1 2 . 1 6 142.66 85.04 Herzfeld 88.23 Barrel SiruD from Am-. Sug. Rfy. Invertase 34.63 N -6.65 141.70 36.35 Monochloroacetic 17.39 N/2 -6.46 141.00 36.41 Herzfeld 35.02 N -6.93 142.66 36.85 B-Percentage Difference between Per cent of Sucrose b y Three Methods Monochloroacetic Herzfeld Herzfeld minus minus minus SAMPLE Invertase Invertase Monochloroacetic 0.18 0.2 1 0.39 Cuban Second h’o. 1438 0.28 0.96 0.68 Cuban Second hlo. 1323 0.44 Barrel Sirup 0.06 0.50
The effect of the monochloroacetic acid method on commercial glucose readings was briefly investigated. Many analysts do not realize t h a t commercial glucose is not a well-defined chemical compound but may vary considerably in composition and physical characteristics. The average glucose of to-day is considerably lower converted than t h a t of a few years ago so t h a t t h e Ventzke reading of I 7 5 for the (sucrose) normal weight under standard conditions of polarizing is too low. I n fact, the sample of glucose used in t h e present investigation showed a Ventzke reading of I 77.8 j. TABLE IX-EFFECT O F MONOCHLOROACETIC ACID O N COMMERCIAL GI,UCOSE READINGSIN DOUBLE POLARIZATION METHOD Readings TOTAL Readings with 3 g. DIFFERMonochlorowith TEST MADE no Acid acetic Acid DIFFERENCE ENCE (b) 88.10 (a b) = 0.60 1 .89 Before heating ( a ) 88.70 (c)86.81 (b-6) = 1.27 .... 88.09 After heating (b) 88.05 ( a - b) = 0 . 4 4 1.99 ( a ) 88.49 Before heating (c)86.85 (b-C) 1.50 .... After heating 88.50 (b) 87.98 ( a - b ) = 0.54 1.85 Before heating ( a ) 88.52 (c) 86.67 (b- 6 ) = 1.31 . .. After heating 88.53
-
5
.
AVERAGE1.88
Table I X shows the polarization effect of monochloroacetic acid, as used in t h e double polarization method described, on an approximately I O per cent solution of this glucose.2 “Handbook of Sugar Analysis,” p. 276. a Weber and McPherson’s investigations.
(lags), 312, 320.
J. A m . Chem. SOC.,11
253
SUMMARY
The following double polarization method is suggested as a result of these investigations. Dissolve the normal weight of sample in a IOO cc. flask, clarify with an appropriate amount of lead acetate, make up t o volume and filter (the usual procedure for commercial polarizations). Transfer 5 0 cc. of filtrate to a I O O cc. flask, add ~j cc. of a 20 per cent solution of monochloroacetic acid, make up t o volume with water, and polarize within I j min. after adding the acid. To invert, transfer about j o cc. of the solution t o a 5 0 cc. flask, stopper tightly by tying down the cork, and immerse flask in boiling water, maintaining active ebullition for 30 min., or for 6 0 min. for lowgrade products clarified -with a large amount of lead acetate. Remove flask, and cool quickly to room temperature. Allow to stand a t least 2 hrs. and polarize in a zoo mm. tube with thermometer.
s = -2 ( a - b ) t x 141 - 2 S = Per cent Sucrose a = Direct reading
IO0
b = Invert reading = Temperature
t
All solutions should be made and polarized as nearly as possible at 20’. The advantages of this method are: I-Direct and invert readings are made on a solution of unchanged acidity and sugar concentration. 11-Excess of basic lead acetate, equivalent t o one cc. in a half (sugar) normal solution, does not affect the inversion or produce troublesome precipitates. 111-It gives more accurate results than the Herzfeld method. IV-Inverted solutions of low-grade products are lighter in color than those inverted by t h e Herzfeld method, and therefore easier t o polarize. V-No error is introduced by making up t o volume after inversion. The chief disadvantage seems t o be the time required, but this is less than t h a t required by the invertase or the more rational modifications of the Clerget and Herzfeld methods in which t h e inversion is carried out a t room temperature, which requires a t least 2 2 hrs. The actual time required in manipulation is little, if any, more than t h a t taken by the usual methods.
T H E QUANTITIES OF PRESERVATIVES NECESSARY TO INHIBIT AND PREVENT ALCOHOLIC FERMENTATION AND THE GROWTH OF MOLDS’j2 By Margaret C. Perry and George D. Beal LABORATORY O F ORGANIC ANALYSIS,UNIVERSITY OB ILLINOIS, URBANA,
ILLINOIS
The practice of preserving perishable foodstuffs for longer or shorter periods is not new. The application of heat and cold are old family methods which 1 Abstracted from thesis submitted in partial fulfillment of the requirements for the degree of Master of Arts in Chemistry in the Graduate School of the University of Illinois. 3 Read a t the 58th Meeting of the American Chemical Society, Philadelphia, Pa., September 2 t o 6, 1919
