THE JOURNAL OF INDUSTRIAL A N D ENGINEERING CHEMISTRY
924
VoI. 13, KO. 10
Dry Substance in Molasses, Sirups and Juices by the Spencer Electric O ~ n l By George P. Meade CENTRALCONTROLLABORATORY, CUBAN-AMERICAN SUGARCo., CARDENAS, CUBA
The design of the Spencer electric oven and its use for drying granular and fibrous substances, such as raw sugar, press-cake, bagasse, cotton, etc., have been described by Dr. G. L. Spencer.2 Essentially, the oven is a device by means of which a large volume of heated air is drawn through the substance to be dried. The heating element is a coil of resistance wire connected in series with a sliding rheostat so that the temperature of the air may be controlled. The air is drawn over the heated coil, and through a capsule containing the sample, by a vacuum pump or steam ejector. The oven is made in two sizes, the smaller size being used in the experiments here described. The capsule is a metal cylinder, 3 cm. in diameter x 4 cm. high, fitted with a bottom of metal filter cloth to permit the air to pass freely. To make the oven available for drying solutions, Dr. Spencer suggested that the liquid might be absorbed on asbestos, somewhat after the Babcock method of drying rnilke3 Accordingly, experiments were carried out based on the ‘following method: The capsule is filled with freshly ignited, fluffy asbestos, loosely packed, and the whole weighed. The capsule holds about 6 g. of asbestos. The liquid to be dried is run on the asbestos, drop by drop, in an amount not to exceed 4 cc., and the capsule, plus sample, is again weighed. The air current of the oven is then turned on and the oven heated to 110” C.,after which the capsule is placed in the oven, the temperature is again brought to llOo, and maintained a t that point throughout the heating period, while the full current of air is drawn through the sample. At the end of the period the electric current and the air are both shut off, and the capsule is removed to a desiccator, cooled, and weighed. AU of the work here reported was done with one capsule only in the oven a t a time, with the other holes well stoppered, This was found necessary for accurate work, as the laboratory air-pump did not give a sufficiently large volume of air for two capsules a t once. Furthermore, with two capsules in the oven a t a time, one sample frequently dried faster than the other, owing probably to the fact that the asbestos was less closely packed in one capsule than in the other. TABLEI-DRY SUBSTANCE DETERMINED IN KNOWNSOLUTIONS OF REFINED SUGAR IN WATER
..
-.
Weimht _-oi_ nf
Per cent Sugar Sample Dried Taken Grams
23.71 23.71 24.35 31.02 35.02 44.42 44.42
-
-
The solution described in Table I1 was made up to simulate to some extent a raw cane juice. The results are like those for the thinner pure sugar solutions. I n order to see the effect of the temperature of 110’ on an easily decomposable substance such as levulose, various solutions of invert sugar and salt were made by inverting known weights of refined sugar with hydrochloric acid, and neutralizing the acid with standard sodium hydroxide. The percentage of combined solids was calculated from the weight of invert sugar plus the weight of salt formed by the acid and alkali, divided by the weight of the solution. TABLE111-SOLUTIONSCONTAINING KNOWNWEIGHTOF INVERT SUGAR AND SODIUMCHLORIDE Per cent Solids Weight of Taken (Invert Sample Dried -Per cent Solids FoundGrams Sugar f NaC1) After 10 Min. After 15 Min. After 20 Min.
25.38 25.38 29.61 29.61 33.73 33.73
23.68 23.71 24.33 31.20 3.5.15 44.71 44.67
Sample
h70. 1 1 2 2
31.15 35.06 44.57 44.65
.... ....
The results of tests on aqueous solutions of refined sugar are given in Table I. It is seen that in all cases with pure sugar solutions more than 99 per cent of the water is driven off in 10 min., and with the thinner solutions it is all driven off in that time. Practically constant weight is reached in all eases after 15 min.
8 “ (
Per cent Solids Taken
14.09 14.09
;0;5.00)
Weight of Sample Dried Grams
2.9370 3.4234
)
15.78 15.75 20.29 20.33
15.76 15.75 20.28 20.32
-Per cent Solids FoundAfter 10 Min. After 15 Min.
....
Weight of from 20Dilute Solution Per cent Solids (Dil. Sol.) Min. PeSamDle Dried 10 Min. 15 Min. 20 Min. riod) REMARKS
3.5390 3.6126 3.0910 4.1123
M5
D5
14.13 14.11
1 Presented before the Section of Sugar Chemistry and Technology a t the 61st Meeting of the American Chemical Society, Rochester, N. Y., April 26 to 29,1921. 2 THIS JOURNAL, 1s (l921),70. 8 U S. Department of Agriculture, Blrlletin 46 (Revised Ed., 1899),5L.
15.76 20.28 20.32
Per cent Water in lasses Orig.(Calc. Mo-
+105.345]
14.15 14.11
3.2747 3.5554 3.7282 3.2931
TABLE V-RAW SUGAR FACTORY FINALMOLASSES (Dilution 1: 1 except where noted)
TABLE11-SOLUTIONSOF RAWSUGAR IN WATER (15 g. of raw sugar containing 1.02 per cent moisture dissolved in distilled water and made to 100 cc. weighed 105.346 g. = 14.09 per cent solids)
[
25.39 25.49 29.63 29.69 33.74 33.69
TABLEIV-RAW CANEJUICE Weight of I Per cent Solids Found--r Sample Dried Grams After 10 Min. After 15 Min. After 20 Min.
....
31.11 35.02 44.57 44.54
25.46 25.52 29.72 29.72 33.77 33.71
The results of tests with raw cane juice are given in Table IV. It is evident from these tests that 10 min. is sufficient to dry juices, and such thin solutions as are of low viscosity. The agreement between duplicates in many other juice tests not listed has been found to be practically as good as those reported above.
-
.... .... 24.33
25.60 25.72 29.95 29.97 33.90 33.79
Invert sugar and salt solutions (Table 111) give much the same class of results as are obtained with pure sugar solutions. Only a fraction of a per cent of water remains after 10 min ’ heating. The agreement, after 20 min.’ heating, between the known solids and the solids found, is invariably very close, indicating that no destruction of levulose takes place in that length of time. No discoloration was apparent in any of the samples.
Per cent Solids Found After 10 min. After 15 min. After 20 min.
6.2245 4.8285 3.1712 3.2310 2.7948 6.0437 5.9998
3.1720 3.2294 3.7995 3.6584 3.1855 3.3592
D4
39.98 39.93 39.90 19.94
.... ....
4.1115 4.0854 3.4766 3.5666
40.23 40.22
3.0920 3.0300
40.65 40.50
3.2058 3.4467 2.4570 3.3774
40.14 40.38
.... ....
....
39.68 39.68 39.81 19.89 ’
.... .... 40.06 40.05
.. . . .. . . .. .... ., .... .. .,
....
39.59 39.52 39.67 19.82
20.82 20.96 20.66 20.72 Dilution 1 : 3
39.59 39.60 39.93 39.91
20.82 Tests made i n 20.80 factory lab. 20.14 N o change in 20.18 wt. op heat-
39.88 39.83 39.80 39.71 39.66 39.72
2.7900 3.3932 3.2876
40.64 40.50
40.38 40.24
40.26 40.20 40.11
4.1094
20.32
20.16
20.06
min. ing J more 20.24 Tests made in 20.34 lab. of factory of origin
20.48 Extra heating 20.58 periods show. 20.68 ed continued 20.56 loss,not checking in the various duplicates 19.48 Duplicates fail19.60 ed to check 19.78 after 30 min. heating 19.76 Dilution 1 :3
Oct., 1921
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 CHEMISTRY
Materials high in solids, such as molasses, sirups, and honey, must be diluted wit,h an equal weight of water so that the asbestos will absorb the liquid. I n the case of molasses, this dilution offers no added manipulation in raw sugar factory practice, since the “double dilution” method is routine procedure for molasses densities by the Brix hydrometer. A portion of this solution may be conveniently used for the moisture determination in the Spencer oven. In the runs recorded in Table V, dilution of 1 : 3 was tried in two cases, as noted, to see whether the more dilute solution would dry more rapidly. The work with molasses shows the same general trend as the results with known solutions, in that nearly all of the water is driven off in the first 10 min. The moisture in the original molasses, calculated from the solids obtained after 20 min.’ drying, shows good agreement between duplicates, considering that the variations are multiplied on account of the dilution employed. Nothing is gained by using a 1 : 3 dilution. I n those cases where samples were subjected to extra heating beyond 20 rnin., the results were erratic. Based on the work with known solutions, together with the work on the molasses, the conclusion seems safe that 20 rnin.’ heating with the air a t 110”C . is the correct period to employ for this class of material. Heating to constant weight should not be attempted.
925
TABLEVI-STRAINED HONEY (Diluted 1 : 1 by weight) Weight Dilute Solution Dried 3.6362 4.8078 4.0930
-Per cent Solids (Dil. 16 Min. 10 Min. 36.90 37.03 36.89 37.02 37.01 37.14
Sol.)20 Min. 36.89 36.88 36.99
Per cent Moisture Original (Calc. from 20-Min. Period) 26.22 26.24 26.02
I n three tests on honey recorded in Table VI constant weight was reached in 15 min. The original honey was thin, probably diluted by the seller, which accounts for the relatively high percentage of moisture.
SUMMARY By absorbing the liquid on asbestos, after the manner of the Babcock method of drying milk, the Spencer electric oven may be used for determining dry substa6ce in solutions. Known solutions of sugar, and of invert sugar and salt, are dried to practically constant weight in 20 min., the agreement between solids taken and solids found being to 1 part in 300, or better. Thin solutions of low viscosity, such as cane juice, are fully dried in 10 min. Molasses, sirups, and honey must, be diluted 1 : 1 by weight with water before drying. The heating period for these materials should be 20 min. a t 110” C., and no attempt should be made to reach constant weight by extra heating periods. For work of this character a very strong current of air through the oven is required.
The Determination of Reducing Sugars in Lead-Preserved Cane Juices I By Joseph B. Harris CENTRALCONTROL LABORATORY, CUBAN-AMBRICAN SUGARCo., CARDENAS, CUBA
The percentage of glucose or reducing sugars in cane-sugar factory products is used for the calculation of “glucose ratios” and “glucose balances” for the purpose of knowing whethey sucrose is being inverted, or glucose being destroyed, a t any stage of the process. For this purpose the best comparative figure is that obtained by making the determination on the material without the use of lead, thus showing all copper reducing substances, and leaving no question as to an indeterminate amount of reducing substance precipitated or changed by the lead. Since the figure is used or-ly for the comparison of relative amounts of reducing substance in the various stages of the process, the question as to the presence of reducing substances, not reducing sugars, is of no interest. I n this paper the term “reducing sugars” or “glucose” is used to mean all copper-reducing substances present in the material. The determination of the reducing sugars without the use of lead on the heavier materials, such as sirup, molasses, or sugars, is very simple, since the composite samples can be kept for a reasonable length of time, but for compositing juice samples a preservative is necessary. Dry basic lead acetate, in the proportion of 20 g. per liter of juice, has been found the most effectivepreservative, so that for comparative purposes the problem of determining the reducing sugars in the juice becomes that of seeking a reagent for deleading that will overcome the effect of the lead and give the same result as would have been obtained had the juice been analyzed without the use of lead. The present investigation was taken up for the purpose of &ding such an agent for the lead-preserved juice, which would give results comparable to those of the sirups, molasses, and sugars on which the reducing sugars have been determined 1 Presented before the Section of Sugar Chemistry and Technology at the 61st Meeting of the American Chemical Society, Rochester, N. Y., April 26 to 29, 1921
without lead for several years.’
EXPERIMENTAL PART A number of samples of raw cane juice were divided in two portions, the amount of copper reduced being determined on one untreated portion, after filtering without lead, using kieselguhr only to aid filtration. For the purposes of the investigation this gives the true amount of reducing sugars. At the same time 20 g. of dry basic lead acetate per liter were added to the other portion, which was shaken thoroughly and left standing for 24 hrs. The leaded portion was then reshaken, and 100-cc. portions of the leaded juice, roughly measured in a graduated cylinder, were treated with the following reagents: 0 75 g. dry sodium oxalate 1 Og sodiumchloride 1 . 5 g sodium bicarbonate 0 . 5 g. pulverized crystals of oxalic acid 0 . 2 to 0 . 3 cc. phosphoric acid-85 per cent, C. P. 0 . 2 t o 0 . 3 cc. acetic ac id-99.5 per cent, C. P. No deleading agent
After treatment with the reagents the juice was filtered, and the amount of copper reduced was determined on the filtrate. Copper reduction was carried out by the Meissl and Hiller method: 50 cc. of the solution for analysis (containing 10 to 15 g. of juice) and 50 cc. of mixed Fehling solution were heated to the boiling point in a beaker on an electric hot plate in 4 min., and maintained a t gentle ebullition for exactly 2 min. The boiling point was determined by a thermometer in the liquid. At the end of the boiling period, 100 cc. of cold, recently boiled, distilled water were added, the solution filtered through an alundum crucible. The cuprous oxide was burned to cupric oxide and weighed as cupric oxide. The results are given in the following tables: 1
Meade and Harris, THISJOURNAL, 8 (1918), 604.
