ANALYTICAL' EDITION
42
nearly to dryness. In doing so, it was found that free selenium tends ,to separate out in a colloidal form difficult to filter, and also tends to give a color to the solution. I n addition, the iron and vanadium present must be eliminated or corrected for. A few colorimetric determinations of titanium were attempted in various zirconium selenite filtrates, using 50-cc. Nessler tubes for comparison with standards. With 4.0 mg. of titanium originally present, the estimated amount of titanium in three determinations was between 3.5 and 5.0 mg., but the time spent in the determinations makes the method impracticable for ordinary use. It would be preferable to determine the titanium independently on an
Vol. 5, No. 1
aliquot portion of the solution prior to the precipitation of zirconium selenite. LITERATURE CITED (1) Beans, I€. T., and Mossman, D. R.,J. Am. Chem. Soc., 54. 1905 (1932). (2) Blair, A. A., Ibid., 30, 1229 (1908). (3) Brown, J., and Madden, H. T., Ibid., 42, 36 (1920). (4) , . , Lundell, G. E. F.. a n d Knowles, H. B., IND.ENQ.C H E M .14, 1136 (1922). (5) Simpson, S. G., and Schumb, W. C., J. Am. Chem. Soc., 53, 921 (1931). (6) Smith, M. M., and James, C., Ibid., 42, 1764 (1920).
RECEIVED August 6, 1932
Determination of Small Amounts of Invert Sugar in the Presence of Sucrose Revised Procedures A. H. EDWARDS AND S. J. OSBORN, Great Western Sugar Company, Denver, Colo.
T
The analysis of beet sugar factory products more attention than it has refactory p r o d u c t s i n d v e d on the Part of sugar involves the determination of small amounts of chemists, although their method volves the determination invert sugar in the presence of relatively large has been adopted by the Assoof small amounts of invert sugar in the presence of relatively large W?RXUU% Of Sucrose. With the exception of ciation of Official Agricultural amounts of sucrose, Present the Herzfeld method, which is directly applicable Chemists (1) for the determionly to the analysis of raw sugar and to which nation of reducing sugars in methods do not have tables that plants. The Quisumbing and there are certain objections, present are suitably worked out for raThomas tables, however, are tios of sucrose and invert sugar are nod well adapted to the determination of not sufficiently comprehensive in the variety of products encountered, and the reduction invert sugar in beet sugar factory products, to cover the ratios of sucrose and invert sugar usually enprocedure is open to various obincluding molasses. jections. The Herzfeld method Preliminary investigations covered various countered in beet p r o d u c t s . (5, 9)1 which has internsdetails and in particular conjrmed the necessity many These features, authors devised i n v e s t i ga anew ted tional usage, is applicable only of improvement in the usual methods of preparing heating procedure for the reto raw sugar and cannot be Fehling solutions. A Procedure WPlicable LO used for molasses without serious duction, and were the first to all beet sugar factory products is described, and insist on the preparation of error. Analysts also complain of the difficulty of securing two methods of carrying out the copper reductions Fehling solutions by a method are recommended, ~ d and ~ ~which insures ~ exact proportions. t ~ check results by the Herzfeld P r e l i m i n a r y to adapting the which is a t t r i b u t e d tageS Of the [WO methods are discussed, and Quisumbing and Thomas method by Pick (12) to local overheating of the solution caused by ComPlete tables for the use Of both d h o d s are to the purpose in question, the influence of some details of prothe a p p l i c a t i o n of i n t e n s e given. heat. cedure was investigated. I n order to make the methods applicable to all beet sugar INVESTIGATIONS factory products of widely varying concentration and purity, One thing which had to be decided was the amount of dry the following simple procedure is employed: The calculated amount of the test sample is weighed out which will yield substance which should be used for the determination. It exactly a desired and definite amount of dry substance (5 or was found difficult to filter and wash the precipitate from a 2.5 grams) in the 50 ml. of solution used to reduce the Fehling molasses solution containing 10 grams of dry substance (in solution. This calculation is abridged by the use of tables, 50 ml.), even when the amount of invert sugar present was and, in place of true dry substance, refractometer or Brix low. A test solution containing 5 grams of dry substance values may be used if desired. By constructing copper gave sufficient material for accurate results, was easy to tables, in which the reducing effect of various amounts of handle, and yielded a precipitate of good color. Good results sucrose (5,2.5, and 1.5grams) is taken into account, the invert were also obtained with 2.5 grams of dry substance, but the value may be obtained lrom knowledge of the approximate accidental error increases with decreasing concentration. purity of the product under examination. The invert values The authors therefore recommend the use ordinarily of 5 in the copper tables are expressed as percentages on dry grams of dry substance, and of 2.5 grams when the percentage substance, which is often the basis desired in recording data of invert sugar is fairly high-i. e., above 1.5 per cent. Some or comparing the amount of invert sugar in a series of different typical results obtained with different amounts of dry substance are shown in Table I. The percentage of invert products. The Quisumbing and Thomas ( I S ) investigation deserves sugar found tends to increase slightly with decreasing conHE analysis of beet sugar
INDUSTRIAL AND ENGINEERING CHEMISTRY
January 15, 1933
centration of the test solution. The lower results at the higher concentration are evidently due to the depressing action of the greater concentration of impurities. For this reason it is desirable to avoid high concentrations in the analysis of impure products. A question which cannot yet be definitely answered is the absolute accuracy within small limits of the values found in the analysis of an impure product like molasses. It is unnecessary to reopen the question of lead clarification, because sugar chemists are agreed that, except possibly for products of high purity, the solution should first be clarified with neutral lead acetate and the excess of lead should be removed by a suitable reagent. TABLEI. INVERT SUGAR FOUND IN MOLASSES 10 grama dry substance
INVERT SUGAR IN: 5 grams dry substance
Sample 1
0:60 0.65 0.62 0.60 Av. 0.61
recommended by Cook and McAllep (8). The use of sodium oxalate alone is unsatisfactory for beet products. The phosphate is a good precipitant for the lead, and the use of the oxalate insures the removal of calcium. Ten milliliters of the solution are sufficient for deleading 100 ml. of molasses solution when 5 to 15 ml. of lead solution have been used for clarification. Table IV shows that a considerable excess of the deleading reagent does not affect the amount of copper reduced within the limit of experimental error. On the other hand, the amount of copper reduced is seriously lowered if the excess of lead is not removed. The data in these two respects are in agreement with those of Cook and McAllep (7) on cane molasses. OF REAGENTS ON COPPER R E D U C ~FROM D TABLEIV. EFFECT FEHLING SOLUTION
2.5 rams dry s&stance
%
%
0.60 0.59 0.65 0.67 0.60 0.62
0.71 0.66 0.59 0.62 0.57
%
43
c
REAGH~NT Neutral lead acetate Oxalate-phosphate
0 ml. reagent
COPPERREDUCED 1 ml. 2 ml. 6 ml. reagent reagent reagent
10 ml. reagent
MQ.
Mg.
Mg.
Ma.
No.
60.0 50.0
48.6 50.6
44.4 51.0
38.7 50.4
30.6 51.8
Considerable work was done with the use of a more dilute Fehling solution, with the idea that the influence of sucrose is 1:i2 1.13 proportional to the amount of copper present, and that, 1.16 1.18 1.21 1.17 therefore, as a great deal of the copper would be rapidly Av. 1.16 1.20 reduced by the invert sugar present, the amount left to react I n this procedure, the use of 10 ml. of neutral lead acetate with the sucrose would be smaller. This procedure was tried solution (55' Brix) was found to be necessary for the clarifica- with both the Quisumbing and Thomas and the Herzfeld tion of 22 grams of molasses dry substance. The use of only methods. The idea was given up on account of the fact that 5 ml. gave incomplete clarification, as evidenced by darker both methods yielded a fine, muddy brown precipitate of a solutions and high values for invert sugar, as shown in Table very unsatisfactory character. The use of Fehling solutions prepared in inexact proportions 11. I n these tests a molasses solution containing 5 grams of dry substance in 50 ml. of test solution was clarified with or from reagents of doubtful purity is a prolific source of error various amounts of neutral lead acetate and deleaded with in all invert sugar methods. The solutions are also subject 10 ml. of 5 per cent solution of ammonium dihydrogen phos- to deterioration on long standing and should be well protected from contamination. Quisumbing and Thomas (14) have phate and sodium oxalate. prescribed a definite procedure for the preparation of Fehling SUGARFOUND IN MOLASSES TABLE 11. INVERT solutions which should eliminate any uncertainty as to their exact composition, particularly with regard to the purity and -INVERT SUGAR, USINQ: 5 ml. 10 ml. 15 ml. exact concentration of the sodium hydroxide in the alkaline lead acetate lead acetate lead acetate tartrate solution. They have also modified the concentra% % % 0.62 0.55 0.58 tions of these solutions on the basis of their work. The 0.66 0.61 0.59 Quisumbing and Thomas modifications of Fehling solution 0.64 0.60 0.57 0.95 0.84 0.88 have been employed in the methods described in this paper. Av. of 4 samples 0.718 0.650 0.655 Erratic results obtained with some Fehling solutions are 0.57 0.42 exemplified in Table V. I n the first series the old solution B 0.54 0.43 Av. of 6 samples 0.66 0.58 was plainly at fault. Solution 1 was carefully prepared from C.P. chemicals. The average amount of copper obtained Solutions of neutral lead acetate prepared from c. P. chemi- with this solution, 19.3 mg., is in good agreement with the cals were found to have a pH value of about 6.2. No differ- value of 18.0 mg. in Table IX for zero invert in the presence of ence in results was found between lead acetate of 6.0 and 7.0 3 grams of sucrose. Solution 2 gave low results, the cause of pH, respectively. (See Table 111.) It therefore seems un- which was not determined. Solution 3 gave high results necessary to readjust the pH of this solution. caused by impure Rochelle salt. Solution 4 gave high and erratic results, which were found to be due to the presence of TABLE111. INVERT SUGARFOUND IN MOLASSESCLARIFIED suspended copper in the bottom of the bottle of copper sulfate WITH NEUTRAL LEADACETATE solution. INVERT SCGAR. Usrlra LEADACETATEOF: Sample 2
'
6.0 pH
Sample 1 Sample 2 Sample 3
0.63
1.21 1.26 1.28 1.26 1.25
1.19
% 0.40 0.39
--
7.0 pH % 0.39
0.40
0.38
0.38
0.40 0.38 0.39
0.41 0.40 0.39
0.56 0.55
0.56 0.55 0.55 0.448
0.55
hv. 0.444
For a deleading agent a solution containing 5 per cent each of sodium oxalate and ammonium dihydrogen phosphate has been adopted, similar to the oxalate-phosphate mixture
TABLEV. VARIATIONIN AMOUNTOF COPPERREDUCED FRON FEHLINQ SOLUTION DUETO IMPURITIES IN REAGENTS (Fehling solution with 3 grama sugar) NEWSOLUTIONSOLDSOLUTION A NEW SOLUTION A A AND B NEWSOLUTION B OLDSOLUTION B Ma. MR. Mu.
OLDSOLUTIONS A ANDFB MO.
SOLUTION 1
SOLUTION 2
SOLUTION 3
Mu.
Mg.
Mu.
Ma.
19.5 18.8 19.5 Av. 19.3
13.0 13.0 13.0 13.0
26.0 25.4 25.0 25.1
30.4 23.6 28.2 27.4
SOLUTION 4
44
ANALYTICAL EDITION
The statement is made by Quisumbing and Thomas ( I S ) that after 30 minutes' heating at 80" C. the reducing action of glucose on Fehling solution is practically completed. This caused the authors to do work with sucrose alone, invert sugar alone, and mixtures of invert sugar and sucrose to
r(
Vol. 5, No. 1
contamination with impurities, and doubtfulness of the composition of the precipitate in the first case, but because it is exceedingly difficult to prepare asbestos mats which will not lose weight as the result of the action of hot Fehling solution. The subsequent use of acid to reclaim the asbestos tends to reactivate its solubility in alkali. New asbestos requires prolonged treatment with acid and alkali. Asbestos mats tested under such blank conditions will at times exhibit an important and disturbing loss in weight. Considerable time is required to prepare and test out an asbestos mat for a gravimetric method, and even then one cannot be absolutely certain of its subsequent behavior. Methods of titrating directly in the solution without filtering out the reduced copper can hardly be recommended, at least when the determination is made on impure products. For the determination of the reduced copper the authors decidedly prefer the Low volumetric thiosulfate method (8, l o ) , from the standpoints of both accuracy and convenience. The electrolytic method if properly conducted (10) is probably equally accurate, but electrolytic apparatus is not commonly available in sugar laboratories. These two methods are certainly in most favor among metallurgical chemists who demand a high order of accuracy and whose opinion should be given some weight. I n the thiosulfate method the introduction of a layer of glass beads is advantageous in facilitating the two evaporations to expel the red fumes and the excess of bromine.
FIGURE1. AMOUNTOF COPPERREDUCEDFROM FEHLING SOLUTION BY SUCROSE AND INVERT SUGAR FOR VARIOUS HEATING PERIODS
determine their rate of reduction of Fehling solution at 80" C. The results are shown in Figure 1. Curve C indicates that the rate of reduction of invert sugar is slow for the period of 20 to 60 minutes. The reducing action of 3 grams of sucrose (Curve D) is rapid and continues a t a uniform rate for 2 hours. Results for a longer time were not obtained. A mixture of invert sugar and sucrose also showed a rapid rate of reduction (Curves A and B). Figure 2 shows that the amount of copper reduced by 3 grams of sucrose during a period of 30 minutes is considerably influenced by the temperature, the rate of reduction increasing with increasing temperature. I n the development of the method a period of 30 minutes' heating a t 80" C. was employed, as recommended by Quisumbing and Thomas. These authors attempted to eliminate the reducing effect of sucrose by working a t a low concentration (less than 400 mg. of sucrose). This procedure is objectionable for the purpose in question because experimental error is so much magnified a t such low concentrations. Although in the adaptation of the Quisumbing and Thomas method the blank correction for sucrose is considerable, the method has many advantages. A well-prepared asbestos mat in a Gooch crucible is the best filtering medium. The use of paper is unsatisfactory because of slow filtration and the fact that copper tends to pass through the filter. The Jena glass filter No. 1-G 4 was found to retain all the copper but required more time than the asbestos filter. Weighing the copper directly as CuO, CUZO, or Cu is unsatisfactory, not only because of the danger of
Tmnw4.m
mnN0 tali.
C
FIGURE2. EFFECTOF TEMPERATURE ON AMOUNTOF COPPERREDUCED FROM FEHLING SOLUTION BY ~O-MINUTE HEATINGMETHOD
The necessity of frequent preparation of the starch indicator can be avoided by the use of the de Koninck starch solution ( I I ) , which is described below under "Reagents." QUISUMBING AND THOMAS METHOD Quisumbing and Thomas carried out the reduction by immersing a beaker covered with a watch glass in a water bath. A beaker is an extremely inconvenient vessel to use in this manner and does not permit the surface of the solution to be well protected from the air during the heating period. A slight modification has therefore been made, employing a 250-ml. Pyrex Erlenmeyer flask, covered with a small watch glass, which can conveniently be clamped in place and be well submerged in the bath. With the standard conditions selected and the details of procedure decided, points for a series of curves as shown in Figure 3 were determined and from these curves Tables VIII,
January 15, 1933
INDUSTRIAL AND ENGINEERING CHEMISTRY
45
IX, and X were calculated. The relationship, within the Examples of such parallel tests will be found in Tables I, 111, concentrations covered, is perfectly linear and the copper and V. Other advantages of the method are (a) the amount values can be expressed by a straight-line formula. The of solution to filter (100 ml.) is small, (b) a granular red points in the curves were carefully determined, each one being precipitate is obtained which has settled to the bottom of the an average of a number of determinations made on several flask at the end of the heating period and therefore permits independently prepared solutions. The invert sugar solu- rapid filtration and washing by decantation, (c) the time and tions used were prepared from sucrose of high purity by temperature of heating are definite, and (d) on account of the inverting with hydrochloric acid for 24 hours a t room tempera- physical properties and settling of the precipitate, products ture (8, 4). containing relatively high percentages of invert sugar can To compare the copper values with those of Quisumbing be easily handled. and Thomas, values in the presence of 2 grams of sucrose have TWO-MINUTE HEATING METHOD been calculated by interpolation between the determined values for 1.5 and 3 grams, respectively, to compare with the The basic idea of this method was suggested by an obQuisumbing and Thomas values in the presence of 2 grams of servation of Bruhns ( 6 ) , who states that the reducing power sucrose, the highest amount used by them. The authors’ of invert sugar is practically exhausted when the mixture of copper value for zero invert sugar in the bresence of 2 grams sugar and Fehling solution begins to boil, and that sucrose of-sucrose thus obtained is 160 mg., which is considerably higher than the value of 9.3 mg. in Quisumbing and Thomas’ Table VI11 (IS). There is, however, a peculiar relationship in this table. If the Quisumbing and Thomas copper values for various amounts of invert sugar in the presence of 2 grams of sucrose are plotted, they form practically a straight line for all points except that representing zero invert sugar, where there is a sharp break in the curve between 10 and 0 mg. of invert sugar. This deviation does not appear consistent and is not upheld by results of the authors. The Quisumbing and Thomas copper value for zero invert sugar obtained by linear extrapolation of the straight line representing their other values is about 20 mg., which is in fair agreement with the authors’ value of 16.0 mg. for the same conditions. The highest amount of invert sugar employed in this work was 80 mg., which yielded 162.2 mg. copper in the presence of 1.5 grams of sucrose (value for 3.20 per cent invert sugar on dry substance in Table X), and 167.6 mg. copper in the presence of 3 grams of sucrose (value for 1.60 per cent invert sugar on dry substance in Table IX). By interpolation the authors’ copper value for 80 mg. of invert sugar in the presence FIGURE3. PERCENTAGE OF INVERT SUGARCALCULATED FROM AMOUNT OF of 2 grams of sucrose would be 164.0 mg., as comREDUCED COPPER( QUISUMBINGAND THOMAS PROCEDURE) uared with the Quisumbine and Thomas value causes only slight reduction when the solution is heated bf 170.9 for the- same colditions. When it is considered that the manipulation has been rapidly to the boiling point. It therefore seemed that if the slightly modified, the differences indicated do not appear reduction were made by heating rapidly to the boiling point, serious, provided that the comparison for zero invert sugar is the reducing effect of the invert sugar would be so largely made with the Quisumbing and Thomas extrapolated value. utilized that it could be used as an accurate measure of the The amount of copper reduced by sucrose alone in this invert sugar, while a t the same time the objectionable reducmethod is large-viz-., 18.0 mg. for 3 grams of sucrose and ing effect of the sucrose in other methods would be avoided. 25.0 mg. for 5 grams. This is in the nature of a correction for These expectations were borne out. The curves in Figure 4 show that, after boiling commences, a blank determination, and it is objectionable on general principles to use a method in which the blank correction is the copper reduced by invert sugar increases very slowly with continued boiling, while the copper reduced in the presence of so great. Close temperature control is necessary in this method. sucrose increases fairly rapidly, and the data therefore conA difference of even one degree in the average temperature firm the general nature of Bruhns’ observation. will, according to Figure 2, cause a variation of 2 to 3 mg. in The procedure accordingly selected for this method was to the amount of copper reduced. While the use of a thermo- heat the solution to the boiling point in a period of 2 minutes, statically controlled, agitated water bath would therefore and then to cool by the immediate addition of cold water. seem most desirable, all the authors’ work has been done with Under these standard conditions points for a series of curves the use of an ordinary water bath, heated by steam introduced as shown in Figure 5 were determined, and from these Tables through a perforated coil and controlled manually by a 0.25- XI, XII, and XI11 were calculated. These curves also show inch needle valve. This arrangement permits of sufficiently a linear relationship. An inexpensive electric heater, such as the Gilmer, is close temperature control for the order of accuracy of such a method. conveni6nt and can be easily adjusted for the purpose, and is I n spite of these disadvantages the Quisumbing and a great improvement over the old gas burner because it Thomas method gives results that can be closely duplicated. avoids the direct application of a hot flame.
ANALYTICAL EDITION
46
Vol. 5, No. 1
2-minute heating method for very small amounts of invert sugar or like its simplicity when a quick determination is required. On the other hand, they prefer the Quisumbing and Thomas method for larger amounts of invert sugar on account of the greater ease of filtering and washing the precipitate. A detailed description of the recommended procedure follows. The Fehling solutions used in both methods are the Quisumbing and Thomas modifications,
The values for zero per cent invert sugar in the presence of sucrose are extremely small-via., 2.8 mg. for 3 grams of sucrose and 3.8 mg. for 5 grams. This indicates that the question of local overheating to which Pick (12) alludes cannot be serious in this method.
REAGENTS NEUTRALLEAD ACETATESOLUTION.Transfer 422.5 grams of c. P. neutral (not basic) lead acetate (Pb(CHsC00)2.-
3Hz0) to a 1000-ml. flask, fill the flask about three-fourths On Cnlp I
O t BOIlIq
0
I
40
l i t Sugar I P1X.d
60
60
R i i b Tha rehiin So1utlm.
PI
I
110
until the lead acetate is comdetelv dissolved. Fill to the mark with water, cool to 20" 6,mlke up to the mark again with water, and mix. The solution should have a density of approximately 55" Brix. OXALATE-PHOSPHATE SOLUTION.Dissolve 5 grams of c. P . sodium oxalate and 5 grams of c. P. ammonium dihydrogen phosphate in water and make up to 100 ml. FEELINQSOLUTION A. Dissolve 42 grams of c. P. crystallized copper sulfate in boiling water, dilute to a volume of 500 ml. a t 20" C., mix, and filter. Determine the amount of copper in solution by a standard method, such as the titration of 10 ml, according to the volumetric thiosulfate method. Dilute the copper sulfate solution so that 10 ml. contain exactly 210 mg. of copper, or so that 41.2 grams of CuSO4.5H20 are present in 500 ml. of the solution. I
FIGURE4. EFFECTOF BOILINGON REDUCING POWER OF INVERTSUGAROR MIXTUREOF INVERTSUGARAND SUCROSE
I n the description of the method below, a tolerance of 10 seconds in the heating period is given. This allows for ordinary variations in adjusting the heater and in judging the exact end point. The curves in Figure 4 show that this tolerance is without serious influence. The heating was controlled within closer limits than this in establishing the curves on Figure 5. The basic data for this method were determined at an altitude of 3930 feet where the boiling point of water is about 96' C. It cannot be definitely stated how much variation might be found at sea level or other altitudes, although the fact that a tolerance of *10 seconds is permitted in the method would indicate that this feature is probably of negligible importance. It wouId have a more decided influence-in the Herzfeld method, in which the temperature of the solution is maintained at the boiling point for a protracted period of time. The primary advantage of this method is the small correction for the reducing effect of sucrose. Other advantages are the simplicity of the procedure and the short length of time required. The solution does not boil over, as sometimes happens in the Herzfeld method. The single disadvantage is the fact that the precipitate is finely divided and difficult to filter, in which respects it resembles but is no worse than the precipitate obtained in the Herzfeld method. More than ordinary care has to be taken in the preparation of asbestos mats which wiIl retain all the precipitated copper.
COMPARISON OF THE Two METHODS The authors have no absolute preference between the two methods described. Both give reproducible results. Chemists who have worked with both methods generally prefer the
I
[
3
40
3
FIGURE5. PERCENTAGE OF INVERT SUGARCALCULATED FROM AMOUNTOF REDUCEDCOPPER(TWO-MINUTE HEATING PROCEDURE) FEHLING SOLUTION B. Prepare a saturated solution of c. P. sodium hydroxide by dissolving 100 grams in 95 to 100 ml. of water in a Pyrex flask, and let stand for several days until the insoluble carbonates and other impurities have settled out. Then siphon off the clear solution (or filter through asbestos in a Gooch crucible if necessary), and determine its alkalinity by titrating with standard acid. Dissolve 173 grams of c. P. sodium potassium tartrate (Rochelle salt) in water in a 500ml. flask and add the calculated amount of the sodium hydroxide solution which will contain exactly 65 grams of
January 15, 1933 TABLEVI.
INDUSTRIAL AND ENGINEERING CHEMISTRY DE-
TABLEVII. WEIQHTOF MATERIALFOR INVERT SUGARDE-
(To yield 5 grams of dry substance) BRIXOR BRIX OR BRIX OR DRYSUBDRYSUBDRYSUBSTANCE GRAMS STANCE GRAMS STANCE GRAMS 55.0 40.0 70.0 31.4 85.0 25.9 55.5 39.6 70.5 31.2 85.5 25.7 39.3 56.0 71.0 31.0 86.0 25.6 56.5 38.9 71.6 30.8 86.5 25.4 57.0 38.6 72.0 30.6 87 .O 25.3 38.3 57.5 87.5 72.5 30.3 25.1
(To yield 2.5 grams of dry substanrre) BRIXOR BRIXOR BRIXOR BRIXOR DRYSUBDRYSUBDRYSUBDRYSUBSTANCE G R A M S O STANCE GRAMS STANCE GRAMS STANCE GRAMS 40.0 27.5 55.0 20.0 70.0 15.7 85.0 12.9 40.5 27.2 55.5 19.8 70.5 15.6 85.5 12.9 41.0 26.8 19.6 56.0 71.0 15.5 86.0 12.8 41.5 26.5 19.5 56.5 71.5 86.5 15.4 12.7 42.0 26.2 19.3 57.0 72.0 15.3 87.0 12.6 42.5 25.9 57.5 19.1 72.5 15.2 87.5 12.6
!J\'EIQHT
BRIX OR DRYSUBSTANCE G R A M S a
MATERIALFOR INVERT SUQAR TERMINATION
47
OF
TERMINATION
40.0 40.5 41.0 41.5 42.0 42.5
55.0 54.3 53.7 53 0
43.0 43.5 44.0 44.5 45.0 45.5
51.2 50.6 50.0 49.4 48.9 48.4
58.0 58.5 59.0 59.5 60.0 60 5
37.9 37.6 37.3 37.0 36.7 36.4
73.0 73.5 74.0 74.5 75.0 75.5
30.1 29.9 29.7 29.5 29.3 29.1
88.0 88.5 89.0 89.5 90.0 90.5
25.0 24.9 24.7 24.6 24.4 24.3
43.0 43.5 44.0 44.5 45.0 45.5
25.6 25.3 25.0 24.7 24.4 24.2
58.0 58.5 59.0 59.5 60.0 60.5
19.0 18.8 18.6 18.5 18.3 18.2
78.0 73.5 74.0 74.5 75.0 75.5
15.1 15.0 14.9 14.8 14.7 14.6
88.0 88.5 89.0 89.5 90.0 90.5
46.0 46.5 47.0 47.5 48.0 48.5
47.8 47.3 46.8 46.3 45.8 45.4
61.0 61.5 62.0 62.5 63.0 63.5
36.1 35.8 35.5 35.2 34.9 34.6
76.0 76.5 77.0 77.5 78.0 78.5
28.9 28.8 28.6 28.4 28.2 28.0
91.0 91.5 92.0 92.5 93.0 93.5
24.2 24.0 23.9 23.8 23.7 23.5
46.0 46.5 47.0 47.5 48.0 48.5
23.9 23.7 23.4 23.2 22.9 22.7
61.0 61.5 62.0 62.5 63.0 63.5
18.0 17.9 17.7 17.6 17.5 17.3
76.0 76.5 77.0 77.5 78.0 78.5
14.5 14.4 14.3 14.2 14.1 14.0
91.0 91.5 92.0 92.5 93.0 93.5
12.1 12.0 12.0 11.9 11.8 11.8
49.0 49.5 50.0 50.5 51.0 51.5
44.9 44.4 44.0 43.6 43.1 42.7
64.0 64.5 65.0 65.5 66.0 66.5
34.4 34.1 33.8 33.6 33.3 33.1
79.0 79.5 80.0 80.5 81.0 81.5
27.8 27.7 27.5 27.3 27.2 27.0
94.0 94.5 95.0 95.5 96.0 96.5
23.4 23.3 23.2 23.0 22.9 22.8
49.0 49.5 50.0 50.5 51.0 51.5
22.4 22.2 22.0 21.8 21.6 21.4
64.0 64.5 65.0 65.5 66.5
17.2 17.1 16.9 16.8 16.7 16.5
79.0 79.5 80.0 80.5 81.0 81.5
13.9 13.8 13.8 13.7 13.6 13.5
94.0 94.5 95.0 95.5 96 .O 96.5
11.7 11.6 11.6 11.5 11.5 11.4
52.0 52.5 53.0 53.5 54.0 54.5
42.3 41.9 41.5 41.1 40.7 40.4
67.0 67.5 68.0 68.5 69.0 69.5
32.8 32.6 32.4 32.1 31.9 31.7
82.0 82.5 83.0 83.5 84.0 84.5
26.8 26.7 26.5 26.3 26.2 26.0
97.0 97.5 98.0 98.5 99.0 99.5 100.0
22.7 22.6 22.4 22.3 22.2 22.1 22.0
52.0 52.5 58.0 53.5 54.0 54.5
21.2 21.0 20.8 20.6 20.4 20.2
67.0 67.5 68.0 68.5 69.0 69.5
16.4 16.3 16.2 16.1 15.9 15.8
82.0 82.5 83.0 83.5 84.0 84.5
13.4 13.3 13.3 13.2 13.1 13.0
97.0 97.5 98.0 98.5 99.0 99.5 100.0
11.3 11.3 11.2 11.2 11.1 11.1 11.0
a
52.4
51.8
Grams =
2200 Brix or dry substance'
NaOH, then complete the volume to 500 ml. with water. It is essential that the sodium hydroxide solution be prepared as described and that all reagents be of high purity, because the purity of the reagents and the concentration of the alkali have such a decided influence on the reaction. DE KONINCK STARCH SOLUTION.Grind 2 grams of potato starch to a paste with cold water, and add to a liter of boiling water. Boil 2 or 3 minutes, and then add 8 ml. of a 10 per cent solution of potassium iodide saturated with mercuric iodide. Allow the solution to cool, pour into a tall glass cylinder, and decant the clear liquid after it has stood a day or two. Use 10 ml. as an indicator in iodometric titrations, This solution will keep almost indefinitely.
Grams =
M~THOD I (QUISUMBINQ AND THOMAS).Heat in a water bath at exactly 80" C. for exactly 30 minutes. The flask must be clamped in place so that the level of the liquid is submerged
1100
12.2
12.2
Brix or dry eubatanoe'
TABLE VIII. PERCENTAQE OF INVERT SUQARBY QUISUMBINQ AND THOMAS METHOD (5 grams dry substance, 5 grams sucrose-for
sugar and thick juice)
INVERT^
INVERT
SUQAR O N DRY
SUQAR O N DRY
COPPER SUBSTANCE COPPER SUBSTANCE Mo. % Mg. % 0.00 25.0
DETERMINATION Weigh out the number of grams of material represented by the fraction 2200/per cent dry substance, which can conveniently be obtained from Table VI. This yields 5 grams of dry substance in the final determination and is the amount to be used when possible. If the amount of copper found is beyond the limit of the copper table, the determination should be repeated on 2.5 grams of dry substance, using the number of grams of material equal to 1100/per cent dry substance as given by Table VII. The determination may also be made on 2,5 grams of dry substance in the case of dilute solutions, such as thin juice, which do not fall within the range of the volumetric procedure for 5 grams of dry substance. Dissolve in hot water, rinse into a 200-ml. flask, cool, add 10 ml. of neutral lead acetate solution, make up to the mark with water, shake well, and filter. To 100 ml. of the filtrate add 10 ml. of the oxalate-phosphate solution, shake, and filter. Measure with a pipet 25 ml. each of the Fehling solutions A and B into a 250-ml. Erlenmeyer flask, add 50 ml. of the clarified, deleaded test solution, and heat by one of the two procedures specified below.
66.0
12.5 12.4 12.4 12.3
a
INVERT SUQAR
DRY COPPER SUBSTANCE Mo. % ON
26.8 28.7 30.5 32.3 34.1
0.02 0.04 0.06 0.08 0.10
81.6 83.5 85.3 87.1 88.9
0.62 0.64 0.66 0.68 0.70
136.4 138.3 140.1 141.9 143.7
1.22 1.24 1.26 1.28 1.30
36.0 37.8 39.6 41.4 43.3
0.12 0.14 0.16 0.18 0.20
90.8 92.6 94.4 96.2 98.1
0.72 0.74 0.76 0.78 0.80
145.6 147.4 149.2 151.0 152.9
1.32 1.34 1.36 1.38 1.40
45.1 46.9 48.7 50.6 52.4
0.22 0.24 0.26 0.28 0.30
99.9 101.7 103.5 105.4 107.2
0.82 0.84 0.86 0.88 0.90
154.7 156.5 158.3 160.2 162.0
1.42 1.44 1.46 1.48 1.50
54.2 56.1 57.9 59.7 61.5
0.32 0.34 0.36 0.38 0.40
109.0 110.9 112.7 114.6 116.3
0.92 0.94 0.96 0.98 1.00
163.8 165.7 167.5 169.3 171.1
1.52 1.54 1.56 1.58 1.60
63.4 65.2 67.0 68.8 70.7
0.42 0.44 0.46 0.48 0.50
118.2 120.0 121.8 123.6 126.5
1.02 1.04 1.06 1.08 1.10
72.5 74.3 76.1 78.0 79.8
0.62 0.54 0.56 0.58 0.60
127.3 1.12 129.1 1.14 130.9 1.16 132.8 1.18 134.6 1.20 CU 25.0# % Invert sugar = Mg. 91.333
-
about 2 inches below the level of the water in the bath. A ring stand and clamp make a convenient arrangement for holding the flask in place during the heating period. The neck of the Erlenmeyer flask must be covered with a watch glass throughout the heating period to prevent unnecessary access of air to the solution. METHODI1 (TWO-MINUTEHEATINQ).Place the flask on an electric heater, adjusted with a rheostat so that the 100 ml. of solution will come to B full boil in exactly 2 minutes, within a tolerance of * 10 seconds. (Preliminary adjustment of the rheostat may be made with the use of 100 ml. of water in a
ANALYTICAL EDITION
48
Vol. 3, No. 1
OF INVERT SUGAR BY QUISUMBING TABLEX. PERCENTAGE AND THOMAS METHOD
TABLEIX. PERCENTAGE OF INVERT SUGAR BY QUISUMBING AND THOMAS METHOD
' (2.5grams dry substance, 1.5 grams sucrose) (5 grams dry substance, 3 grams sucrose-for molasses) INVERT INVERT INVERT" INVBRT~ INVERT INVERT INVERT SUQAR SUQAR SUQAR SUGAR SUGAR SUGAR SUQAR ON DRY ON DRY ON DRY ON DRY ON DRY ON DRY O N DRY SUBSUBSUBSUBCOPPERSUBSTANCE COPPER SUBSTANCE COPPBRSUBSTANCE COPPER STANCE COPPFlR STANCE COPPER STANCE COPPERSTANCE % Me. % Mo. M O . Me. MO % MO % % % 18.0 0.00 15.0 0.00 0.56 120.9 1.10 0.02 70.4 19.9 0.58 122.7 1.12 0.04 72.2 21.7 15.9 0.82 0.02 52.7 89.5 1.62 126.3 2.42 1.14 0.60 124.6 0.06 74.1 23.6 16.8 0.04 53.6 90.4 1.64 127.2 2.44 0.84 1.16 0.62 126.5 25.5 0.08 76.0 17.8 0.06 91.4 1.66 138.2 2.46 0.86 54.6 1.18 0.64 128.3 0.10 77.8 27.4 18.7 0.08 55.5 92.3 1.68 129.1 2.48 0.88 19.6 0.10 93.2 1.70 0.90 56.4 130.0 2.50 0.66 130.2 1.20 0.12 79.7 29.2 0.68 132.1 1.22 0.14 81.6 31.1 20.5 0.12 0.92 94.1 1.72 130.9 57.3 2.52 0.70 133 9 1.24 0.16 83.5 32.9 21.4 58.2 2.54 0.14 0.94 1.74 131.8 95.0 1.26 0.72 135.8 0.18 85.3 34.8 22.4 0.96 59.2 2.56 0.16 96.0 1.76 132.8 1.28 0.74 137.7 0.20 87.2 36.7 23.3 0.98 60.1 2.58 0.18 96.9 1.78 133.7 24.2 1.00 61.0 2.60 0.20 97.8 1.80 134.6 0.76 139.6 1.30 0.22 89.1 38.6 1.32 0.78 141.4 0.24 90.9 40.4 25.1 1.02 1.82 0.22 61.9 98.7 135.5 2.62 0.80 143.3 1.34 0.26 92.8 42.3 26.0 0.24 99.6 136.4 2.64 1.04 1.84 62.8 0.82 145.2 1.36 0.28 94.7 44.2 27.0 0.26 63.8 100.6 137.4 2.66 1.06 1.86 0.84 147.0 1.38 46.1 0.30 96.5 27.9 0.28 101.5 138.3 1.08 1.88 64.7 2.68 28.8 0.30 65.6 102.4 139.2 2.70 1.10 1.90 0.86 148.9 1.40 47.9 0.32 98.4 0.88 150.8 1.42 49.8 0.34 100.3 29.7 1.92 0.32 66.5 1.12 103.3 140.1 2.72 0.90 152.6 1.44 0.36 102.2 51.6 30.6 0.34 67.4 1.14 104.2 141.0 2.74 1.94 0.92 154.5 1.46 0.38 104.0 53.5 31.6 1.96 0.36 1.16 105.2 142.0 2.76 68.4 0.94 156.4 1.48 55.4 0.40 105.9 32.5 0.38 69.3 1.18 106.1 142.9 2.78 1.98 33.4 2.00 0.40 70.2 107.0 143.8 2.80 1.20 1.50 0.96 158.3 57.3 0.42 107.8 1.52 0.98 160.1 59.1 0.44 109.6 34.3 2.02 107.9 144.7 2.82 0.42 71.1 1.22 1.54 1.00 162.0 0.46 111.5 61.0 35.2 108.8 145.6 2.84 2.04 0.44 72.0 1.24 1.56 1.02 163.9 62.9 0.48 113.4 109.8 146.6 2.86 36.2 2.06 0.46 73.0 1.26 1.04 165.7 1.58 0.50 115.2 64.8 110.7 147.5 2.88 37.1 2.08 0.48 73.9 1.28 2.90 38.0 0.50 1.30 111.6 148.4 2.10 74.8 1.06 167.6 1.60 0.52 117.1 66.6 0.54 119.0 1.08 68.5 2.92 38.9 112.5 2.12 149.3 0.52 75.7 1.32 Mg. CU - 18.0. 2.94 39.8 113.4 2.14 150.2 0.54 1.34 76.6 a % Invert sugar = 114.4 2.16 151.2 2.96 0.56 1.36 40.8 77.6 93.5 41.7 2.18 152.1 2.98 115.3 0.58 1.38 78.5 42.6 3.00 2.20 153.0 116.2 0.60 79.4 1.40
.
OF INVERT SGGAR BY TWO-MINUTE TABLEXI. PERCENTAGE HEATINQ METHOD
(5 grams dry substance, 5 grams suorose-for sugar and thick juice) INVERT INVERT INVERT^ SUQAR SUGAR SUGAR ON DRY ON DRY ON DRY C O P P E R SUBSTANCE COPPDR SUB~TANCB COPPER SUBSTANCE % Mo. Me. Mo % % 0.00 3.8 1.22 115.6 60.7 0.62 0.02 5.6 1.24 117.6 62.6 0.64 0.04 7.5 1.26 119.5 64.4 0.66 0.06 9.3 1.28 121.3 0.68 66.2 0.08 11.1 1.30 123.1 0.70 68.1 0.10 13.0
.
14.8 16.7 18.5 20.3 22.2
0.12 0.14 0.16 0.18 0.20
69.9 71.7 73.6 75.4 77.2
0.72 0.74 0.76 0.78 0.80
125.0 126.8 128.6 130.5 132.3
1.32 1.34 1.36 1.38 1.40
24.0 25.8 27.7 29.5 31.3
0.22 0.24 0.26 0.28 0.30
79.1 80.9 82.7 84.6 86.4
0.82 0.84 0.86 0.88 0.90
134.2 136.0 137.8 139.7 141.5
1.42 1.44 1.46 1.48 1.50
33.2 35.0 36.8 38.7 40.5
0.32 0.34 0.36 0.38 0.40
88.3 90.1 91.9 93.8 95.6
0.92 0.94 0.96 0.98 1.00
143.3 145.2 147.0 148.8 150.7
1.52 1.54 1.56 1.58 1.60
42.4 44.2 46.0 47.9 49.7
0.42 0.44 0.46 0.48 0.50
97.4 99.3 101.1 102.9 104.8
1.02 1.04 1.06 1.08 1.10
152.5 154.4 156.2 158.0 159.9
1.62 1.64 1.66 1.68 1.70
1.12 1.14 1.16 1.18 1.20
161.7 163.5 165.4 167.2 169.0
1.72 1.74 1.76 1.78 1.80
106.6 108.5 110.3 112.1 114.0 Mg. CU - 3.8, a % Invert sugar = 91,80 51.5 63.4 55.2 57.0 58.9
0.52 0.54 0.56 0.58 0.60
250-ml. Erlenmeyer flask.) As soon as the solution comes to a full boil, remove the flask from the heater, and cool by the immediate addition of 100 ml. of water of room temperature. After the heating by Method I or I1 has been completed, filter the solution immediately or after allowing it to stand only long enough for the cop er precipitate to settle, employing a Gooch crucible with an asgestos mat about 8 mm. thick. More rapid filtration and better washing can be accomplished if the liquid
43.5 44.4 45.4 46.3 47.2
0.62 0.64 0.66 0.68 0.70
80.3 81.2 82.2 83.1 84.0
48.1 49.0 50.0 50.9 51.8
0.72 0.74 0.76 0.78 0.80
84.9 85.8 86.7 87.7 88.6 Mg.
a
% Invert sugar
-
I
117.1 118.0 119.0 119.9 120.8
2.22 2.24 2.26 2.28 2.30
153.9 154.9 155.8 156.7 157.6
3.02 3.04 3.06 3.08 3.10
121.7 1.52 122.6 1.54 123.6 1.56 124.5 1.58 125.4 1.60 CU - 15.0. 46.0
2.32 2.34 2.36 2.38 2.40
158.5 159.4 160.4 161.3 162.2
3.12 3.14 3.16 3.18 3.20
1.42 1.44 1.46 1.48 1.50
is carefully decanted from the copper precipitate, which is then washed well by decantation, and finally the contents of the flask are washed into the crucible and the washing is completed. It is unnecessary to police the flask if the same flask is used for the determination of the copper by the volumetric thiosulfate method. DETERNIXATION OF REDUCED COPPER Determine by a standard method, preferably the volumetric thiosulfate method. USE OF COPPERTABLES METHOD I (QUISUMBING AND THOMAS). If the determination is made on 5 grams of dry substance, obtain the percentage of invert sugar from Table VI11 or IX. Use Table VI11 for sugar or juices of high purity. Use Table IX for molasses of approximately 60 purity. Values for products of intermediate purity between sugar and molasses can be obtained most accurately by interpolation between Tables VI11 and IX. If the determination is made on 2.5 grams of dry substance, use Table X, which is intended for molasses, but can be used without serious error for products of higher purity. METHOD I1 (TWO-MINUTE HEATING).The use of Tables XI, XII, and XI11 is similar to that of Tables VIII, IX, and X, respectively. In the case of products of abnormally high invert sugar content, of which 2.5 grams of dry substance should be used,
January 15, 1933
INDUSTRIAL AND ENGINEERING
CHEMISTRY
49
TABLEXII. PERCENTAQE OF INVERT SUQAR BY TWO-MINUTE TABLE XIII. PERCENTAQE OF INVERT SUQAR BY TWO-MINUTE HEATINQ METHOD HEATINQ METHOD (5 grams dry substance, 3 grams sucrose-for molasses) INVERT INVERT= INVERT SUQAR SUQAR SUQAR O N DRY O N DRY O N DRY COPPER SUBSTANCE COPPER SUBSTANCE COPPER SUBSTANCE Mo % Mg % Me. % 2.8 0.00
.
.
%
Mg.
0.00
%
Mg.
1.9
%
MQ.
11.9
0.02 0.04 0.06 0.08 0.10
59.1 60.9 62.7 64.5 66.3
0.62 0.64 0.66 0.68 0.70
113.5 115.3 117.1 119.0 120.8
1.22 1.24 1.26 1.28 1.30
3.7 5.5 7.3 9.1 10.9
0.04 0.08 0.12 0.16 0.20
57.7 59.5 61.3 63.1 64.9
1.24 1.28 1.32 1.36 1.40
111.8 113.6 115.4 117.2 119.0
2.44 2.48 2.52 2.56 2.60
13.7 15.5 17 3 19 1 21.0
0.12 0.14 0.16 0.18 0.20
68.1 70.0 71.8 73.6 76.4
0.72 0.74 0.76 0.78 0.80
122.6 124.4 126.2 128.0 129.9
1.32 1.34 1.36 1.38 1.40
12.7 14.5 16.3 18.1 19.9
0.24 0.28 0.32 0.36 0.40
66.7 68.5 70.3 72.1 73 9
1.44 1.48 1.52 1.56 1.60
120.8 122.6 124.4 126.2 128.0
2.64 2.68 2.72 2.76 2.80
22.8 24.6 26.4 28.2 30.0
0.22 0.24 0.26 0.28 0.30
77.2 79.0 80.8 82.7 84.5
0.82 0.84 0.86 0.88 0.90
131.7 133.5 135.3 137.1 138.9
1.42 1.44 1.46 1.48 1.50
21.7 23.5 35.3 27.1 28.9
0.44 0.48 0.52 0.66 0.60
75.7 77.6 79.4 81.2 83.0
1.64 1.68 1.72 1.76 1.80
129.8 131.6 133.4 135.2 137.0
2.84 2.88 2.92 2.96 3.00
31.8 33.7 35 5 37.3 39.1
0.32 0.34 0.36 0.38 0.40
86.3 88.1 89.9 91.7 93.6
0.92 0.94 0.96 0.98 1.00
140.7 142.6 144.4 146.2 148.0
1.52 1.54 1.66 1.58 1.60
30.7 32.5 34.3 36.1 37.9
0.64 0.68 0.72 0.76 0.80
84.8 86.6 88.4 90.2 92.0
1.84 1.88 1.92 1.96 2.00
138.8 140.6 142.4 144.2 146.0
3.04 3.08 3.12 3.16 3.20
40.9 42.7 44.6 46.4 48.2
0.42 0.44 0.46 0.48 0.50
95.4 97.2 99.0 100.8 102.6
1.02 1.04 1.06 1.08 1.10
149.8 151.6 153.4 155.3 157.1
1.62 1.64 1.66 1.68 1.70
39.7 41.5 43.3 45.1 46.9
0.84 0.88 0.92 0.96 1.00
93.8 95.6 97.4 99.2 101.0
2.04 2.08 2.12 2.16 2.20
147.8 149.6 151.4 153.2 155.0
3.24 3.28 3.32 3.36 3.40
50.0 51.8 53.6 55.4 57.3
0.52 0.54 0.56 0.58 0.60
1.12 1.14 1.16 1.18 1.20
158.9 160.7 162.5 164.3 166.2
1.72 1.74 1.76 1.78 1.80
48.7 50.6 52.3 54.1 55.9
1.04 1.08 1.12 1.16 1.20
102.8 104.6 106.4 108.2 110.0
2.24 2.28 2.32 2.36 2.40
166.8 158.6 160.4 162.2 164.0
3.44 3.48 3.52 3.56 3.60
4.6 6.4 8.2
10.1
a
(2.5 grams dry substance, 1.5 grams sucrose) INVERT INVERT SUQAR SUGAR SUQAR O N DRY O N DRY ON DRY COPPER SUBSTANCE COPPER SUBSTANCE COPPER SUBSTANCE INVERT“
104.4 106.3 108.1 109.9 111.7 Mg.Cu 2.8. % Invert sugar = 90.75
-
Tables X and XI11 can be considerably extrapolated with reasonable accuracy by means of the formulas a t the bottom of the tables. This must not be carried to too great an extreme-i. e., to the region where the amount of invert sugar present is sufficient to reduce the Fehling solution completely. Care must be taken not to confuse the use of the various tables. BLANKDETERMINATIONS Before making any invert sugar determinations with new solutions, or with old solutions that have stood for any length of time, conduct one or more blank determinations as follows: Weigh out 12 grams of sugar of high purity, free from reducing sugars, dissolve in water, and make up to a volume of 200 ml. Make an invert sugar determination with 50 ml. of this solution (3 grams of sucrose) according to the standard procedure. The amount of copper obtained should, according to the tables, be 18.0 mg. for the Quisumbing and Thomas heating method, or 2.8 mg. for the 2-minute heating method. If the amount obtained differs from the theoretical value by more than 3 or 4 mg., there has been some fault in the technic or in the preparation or condition of the reagents, which it should be possible to correct. CONCLUSIONS Present methods for the determination of small amounts of invert sugar in the presence of sucrose are not readily adaptable to products of varying concentration and purity and are open to various objections. As a result of investigations, a procedure applicable to all beet sugar factory products is described and two methods of carrying out the copper reduction are recommended. The following conclusions are drawn: The amount of the test solution used for the reduction of 50 ml. of Fehling solution should contain 5 grams of dry substance; it is not
a
% Invert sugar = Mg. 45.03 Cu - ’”*
practical to reduce the strength of the Fehling solution; the solution should be clarified with neutral lead acetate and is best deleaded by a solution of sodium oxalate and ammonium dihydrogen phosphate; and the Fehling solutions must be prepared from reagents of high purity and the concentrations must be carefully controlled.
ACKNOWLEDGMENT The authors’ thanks are due to R, J. Brown for helpful suggestions advanced during the development of the methods. LITERATURE CITED (1) Assoc. Official Agr. Chem., Official a n d Tentative Methods, p. 112 (1930). (2) Ibid., p. 377. (3) Ibid... a. _ 380. (4j Browne, “Handbook of Sugar Analysis,” p. 390, C h a p m a n & Hall, 1912. (5) Ibid., p. 428. (6) Bruhns, Centr. Zuckerind., 37, 1268 (1929). (7) Cook and McAllep, Facts About Sugar, 23, 783, 806 (1928). (8) Ibid., p. 807. (9) Herzfeld, 2. Ver. Deut. Zuckerind., 35, 985 (1885). (10) Low, “Technical Methods of Ore Analysis,” p. 78, Wiley, 1922. (11) Lunge, translated by Keane, “Technical Methods of Chemical Analysis,” Vol. 1, p. 114, Gurney & Jackson, London, 1908. (12) Pick, Z. Zuckerind. lechoslovak. Rep., 49, 223-4 (1925). (13) Quisumbing a n d Thomas, J. Am. Chem. Soc., 43, 1503 (1921). (14) Ibid., pp. 1509, 1520. RBCEIVED August 30, 1932. Presented before the Division of Sugar Chemistry at the 84th Meeting of the American Chemical Society, Denver, Colo., August 22 t o 26, 1932.
JAPANESE IMPORT AND EXPORT LICENSESYSTEM FOR SULFATE OF AMMONIAABOLISHED. The licensing regulations, promulgated in Japan on December 8, 1931, t o govern the importation and ex ortation of sulfate of ammonia, and enforced on imports with effect from January 15, 1932, were canceled on December 6, according to a cablegram received in the Department of Com-
merce.
