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I part of the salt equals 0.04427 part Cr. If X equal the amount of ferrous ammonium sulfate used, I cc. of t h e permanganate equal T g. of ferrous ammonium sulfate used, a n d assume y cc. of permanganate were used in titrating A grams of the sample, then the per cent of chromium is found by the following equation: Per cent Chromium = ( X - T y ) 4.427/A
MANGANESE
Evaporate I O O cc. of the “stock” solution almost t o dryness, take u p with concentrated nitric acid, and evaporate t o about half the bulk. Precipitate the manganese with 5 g. potassium chlorate, and evaporate t o small volume, adding potassium chlorate a second time. Dilute the solution with water, filter through a thin layer of asbestos on a Gooch filter, and wash thoroughly with water. Transfer the precipitate and asbestos t o a beaker, a d d ferrous ammonium sulfate from the burette until the precipitate is dissolved, dissolve with ferrous ammonium sulfate, the precipit a t e clinging t o the sides of the crucible, and wash the crucible thoroughly with hot water. Titrate the excess of ferrous ammonium sulfate with permanganate. Metallic iron times 0.3918 = Mn. The per cent of manganese may be found by the following equation, where X is t h e number of grams of ferrous ammonium sulfate used, y the iron equivalent per cc. of the permanganate solution, T the cc. of permanganate used, 14.25 t h e per cent of iron in ferrous ammonium sulfate, a n d A the grams of the substance used. Per cent Manganese = (0.1425X - T y ) 49.18/A ZINC’
STANDARDIZATION OF THE POTASSIUM F E R R O C Y A N D E
-Weigh about 0.2 g. of pure zinc into a flask and dissolve in hydrochloric acid. When the zinc is dissolved, dilute with about 50 cc. of water, neutralize with ammonium hydroxide a n d after making slightly alkaline acidify with hydrochloric acid, adding a slight excess. Dilute t o about 2 5 0 cc., heat t o 7-80’ C., and titrate with potassium ferrocyanide solution as follows: place about one-third of the zinc solution in a 400-500 cc. beaker and titrate with potassium ferrocyanide until a drop, when removed and tested on a porcelain color plate with the uranium solution, shows a brown tinge; add another third of t h e zinc solution and continue the titration until the end-point is passed; then a d d the last portion and finish the titration very carefully. The reaction is sharper if several drops are taken for the end-point. A correction should be made for the amount of ferrocyanide required t o produce the color when no zinc is present. The equivalent per cc. of t h e ferrocyanide is thus obtained. THE DETERMINATION-Evaporate the filtrate from the iron-chromium precipitation almost t o dryness, take up with concentrated nitric acid, evaporate t o about half bulk, add 2-3 g. of potassium chlorate, boil for a few minutes, dilute and filter through a Gooch filter. Neutralize the filtrate containing zinc and 1 Adapted from Fahlberg’s method, E. Prost, 2. anal. Chem., 460 1896); Chem. News, 76, 6.
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nickel with ammonium hydroxide, heat to boiling, and add 2 0 t o 30 cc. of a I per cent solution of dimethylglyoxime. Allow the precipitate to settle and filter through a Gooch. Neutralize the filtrate with hydrochloric acid, a d d a slight excess, and heat the solution t o jo-80’ C. Conduct the titration as described under the standardization of potassium ferrocyanide. CARBON
The carbon may be determined by direct combustion in a current of oxygen, and by the apparatus described by Blair, “ T h e Chemical Analysis of Iron and Steel,” 7th Ed., 1912,p. 134. The writer is indebted t o Dr. C. S. Palmer for his kindly advice and helpful suggestions during t h e progress of this work. MELLON INSTITUTE os INDUSTRIAL RESEARCH UNIVERSITY OF PITTSBURGH
A SIMPLIFIED INVERSION PROCESS FOR THE DETERMINATlON OF SUCROSE BY DOUBLE POLARIZATION’ By HERBERT S. WALKER Received November 4, 1916
Probably the greatest drawback t o the use of “true sucrose” determinations in sugar factory control work has been the necessity for such extreme care in the regulation of time and temperature required b y the Herzfeld-Clerget inversion process. So sensitive t o faulty manipulation is the method ordinarily used t h a t a n inexperienced chemist may get even less accurate results by double polarization than by simply assuming the direct polarization t o represent “true sucrose.’’ T o avoid any decomposition of fructose during inversion, Tolman* suggested inverting a t ordinary laboratory temperatures. This method has never been largely adopted in cane sugar factories, owing to the fact t h a t a t least I O hrs. are required for t h e complete inversion of t h e half-normal weight of pure sucrose in 50 cc., and probably a considerably longer time would be needed where organic impurities are present, as in the case of waste molasses. Steuerwalda has also proposed inverting in the cold, and shortens the time required t o 2 or 3 hrs. by using three times the usual quantity of acid (30 cc. of a mixture of equal parts concentrated HC1 and water). The convenience of using a diluted acid will be appreciated by anyone who has had t o measure many successive portions of concentrated HC1 with the same pipette. Steuerwald’s method, however, as pointed out by Pellet4 when dealing with impure cane or beet products, accentuates the error inherent in the Herzfeld-Clerget process in t h a t optically active substances other t h a n sucrose may, in a strongly acid medium, have quite different rotation from t h a t indicated i n a neutral or slightly acid solution used for direct polarization. I Presented a t the Annual Meeting of t h e Hawaiian Chemists’ Association, October 12, 1916. 2 U. S. Bur. Chem., Bull. 73, 69. 8 Archief, 1913, 831. 4 I. S. J.. 1916, 83.
May, 1917
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
The writer has for some time held t h e idea t h a t for rapid work in a sugar factory a compromise between these methods might be advantageously employed, heating t h e sugar solution before adding acid t o some definite temperature and letting i t cool down slowly in air during a time sufficient for t h e inversion t o become completed. The only attention required would be t o control the temperature of solution a t t h e moment of adding t h e acid. Since t h e preliminary heating would be in neutral solution t h e time requked t o raise t o a definite temperature would be immaterial. Aside from its convenience of manipulation, such a method should, theoretically, possess the advantage over t h e Herzfeld procedure of being less subject t o error due t o destruction of fructose, since t h e maximum temperature of t h e solution would. coincide with t h e minimum amount of invert sugar present a n d a t t h e time of nearly complete inversion t h e temperature should have dropped t o such a point t h a t there would no longer be any danger from this source. I n working out this method, I j min. n-as chosen as a convenient time for the duration of inversion. T o avoid if possible any great change in t h e inversion constant, t h e same concentrations of sugar and acid were used as in t h e Herzfeld method. E X P E R I M E N T I-Approximately 130 g. "Crystal Domino" sugar were dissolved in 500 cc. solution, giving a direct polarization of 99.66. Fifty cc. portions of this solution were pipetted into 100-cc. flasks, 2 5 cc. water added, t h e flasks heated in a water bath t o certain different temperatures, I O cc. of a mixture of equal volumes concentrated HC1 and water added, t h e whole allowed t o stand I j min. in air, then cooled down t o room temperature in water, made u p t o I O O cc. and polarized. A parallel test was made at the same time, using t h e Herzfeld procedure. The results appear in Table I. The percentages of sucrose were calculated, using t h e same direct polarization and t h e constant, 144.66 - o.st, for all. All tests b y t h e new method yielded lower results than b y t h e Herzfeld. E X P E R I Y E S T 2-To determine whether this was due t o incomplete inversion in I j min. or t o too high or too low initial temperatures, a similar experiment was carried out at lower temperatures, letting t h e solutions stand in air for 30 min. after adding acid. With initial temperatures between 7 2 and 64' t h e results obtained are fairly constant among themselves and agree well with those obtained b y the Herzfeld method. E X P E R I M E N T 3-With a lower initial temperature t h a n 56' inversion is not complete in 30 min. EXPERIMENT 4-Here t h e time of inversion was cut t o 15 min. The surprising fact brought out b y these tests is t h e comparatively great latitude of t h e method. While t h e Herzfeld procedure requires a rigid adherence t o 69' and a definite time of heating, this method, with initial temperatures anywhere between 59 and 7 0 ° , yields concordant results which agree with those obtained b y the Herzfeld method as closely as t h e latter do with each other. It also appears t h a t 1 5 min. is a n ample time for inversion a n d t h a t standing 1 5
49 1
TABLEI-SUCROSE DETERMINATIONS ON "CRYSTAL DOMINO"SUGAR Results by Herzfeld and Author's Methods with Differences from Herzfeld Method Direct InverMETHOD Expt. Polar- sion HBRZPELD -NEW Acid added at No. ization (Min.) METHOD 75O' 73O 71OC. 1 99.66 15 77O 99.65 99.71 99.83 99.81 99.93" . -0.12 4 . 2 8 -0.22 -0.10 Difference 70' 68' 64' C. 72' 2 99.61 30 99.91 99.86 Av. 99.89 99.86 99.81 9 9 . 9 0 99.89 0.00 +O.OI .... Difference -0.03 -0.08 48' C. 60 56' 520 64' 9 9 . 50 30 99.89 99.80 3 97.10 Av. 99.85 99.92 99.91 9 9 . 8 3 99.22 -2.75 Difference +0.07 + O . 06 -0.02 -0.63 4 99.62 15 99.89 99.99 70° 67' 65' 63" 59' C. Av. 99.94 99.93 100.03 100.03 100.00 99.93 Difference -0.01 + 0 . 0 9 4-0.09 $ 0 . 0 6 -0.01
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.... ....
. .. .. .. .. ..
min. longer has no effect on results. With a laboratory temperature of 26' t h e solutions were found t o drop from 7 0 t o 46' and from 60 t o 41' on standing in air for 30 min., so i t is extremely improbable t h a t any further destruction of fructose would take place, even if t h e inverted solutions were allowed t o stand several hours longer. Having obtained such satisfactory results from pure sugar, several experiments were next made t o see if t h e method would work equally well on molasses. -4 large sample of molasses was clarified according t o t h e method of t h e Hawaiian Chemists' Association and inverted b y the Herzfeld and b y t h e new method. Results of the tests are given i n Table 11. TABLE11-sUCROSE DETERMINATIONS O N MOLASSES Results by Herzfeld and Author's Methods with Differences from Herzfeld Method Direct InverExpt. Polar- sion HERZPELD7 NEW METHOD No. ization (Min.) METHOD Acid Added at 71' 69OC. 75' 73' 7io 5 2 i . 9 0 15 33.28 32.82 33.05 34.16 34.69 34.17 -1.41 -1.87 -1.64 -0.53 Difference -0.52 61' 59' 57'C. 65' 63' 6 27.66 30 67' 34.33 34.29 34.10 34.09 34.04 33.16 34.51 -0.22 -0.41 -0.42 -0.47 -1.35 Diference -0.18 7 27.60 30 5.5 cc. 5 cc. (I c 5 acid a$ded) (No y i d added) 67 69 67OC. 69 HC1 HC1 33.30 33.10 34.41 34.30 34.45 34.52 8 27.44 30 34.33 34.34 72' 70' 68' 66' 64OC. Av. 34.34 34.32 34.39 34.34 34.39 34.37 Difference -0.02 +0.05 0.00 +0.05 +0.03 9 2 7 . 4 0 30 34.51 34.58 70' 64' 60" 58' 56'C. Av. 34.54 34.59 34.59 34.61 34.41 34.01 +0.05 $0.05 +0.07 -0.13 -0.53 Diffeyencc 10 27.58 15 34.54 34.50 70' 67' 65' 63' 60°C. 34.61 34.61 34.63 34.59 34.43 Av. 34.52 +0.09 +0.09 4-0.11 +0.07 -0.09 Diferencc
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EXPERIMENT 5 - 7 I . j O g. waste molasses were dissolved in water, clarified with 80 cc. basic lead acetate, made u p t o 500 cc. and filtered. For direct polarization 50 cc. filtrate were treated with I cc. saturated aluminum sulfate solution, made t o 5 5 cc., filtered and polarized. Reading X 2 = direct polarization: 7 5 cc. of t h e first filtrate were inverted, cooled, made t o roo cc., decolorized with a slight excess of zinc dust, filtered and polarized in a 400 mm. tube. Reading X 4/3 x I O / I I = Invert polarization. Factor = 142. E X P E R I M E N T 6-Since all these results were much lower t h a n those obtained b y t h e Herzfeld method, 30 min. standing and a lower initial temperature were next tried. While a n improvement over t h e preceding test, these results were still rather low and irregular. EXPERIMENT 7-It was thought t h a t t h e excess of basic lead acetate in solution might have had a destructive effect on t h e fructose already present i n t h e molasses during t h e heating prior t o adding acid. T o determine if this were the case, this experiment was performed in pairs, one of each pair being manipulated
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as before, t h e other treated with I cc. of I : I HC1 (this being approximately the amount of acid necessary t o neutralize the alkalinity due to basic lead ace, tate) before heating. It is quite evident t h a t a serious loss occurs if solutions of molasses clarified with excess of basic lead acetate are heated before adding acid, while if the alkalinity be neutralized prior t o heating all irregularities seem t o disappear. Further tests were made t o determine the permissible limit of initial temperature. I n all the following experiments the solutions to be inverted were first neutralized with I cc. of I : I HC1. EXPERIMENTS 8 A N D g showed initial temperatures between 70 a n d 60’ t o yield satisfactory results on 30 min. standing. EXPERIMENT A O -I final test was made t o cover the above range with a n inversion period of only 15 min. T h e safe limit of initial temperatures for waste molasses thus appears t o lie between 7 0 and 63’ for a I 5-min. inversion period. MODIFIED INVERSION METKOD
The modified inversion method proposed, based on t h e above experimental evidence, is as follows: Place 50 cc. or 7 5 cc. of the solution used for direct polarization in a 100-cc. flask (in case 50 cc. are used a d d 2 5 cc. water) and heat in a water bath t o 65’ C. Remove from bath, add I O cc. of a mixture of equal volumes HC1 (sp. gr. 1.188) and water, allow t o cool down spontaneously in air for 1 5 min. or as much longer as may be convenient, then cool in water t o room temperature, make up to IOO cc. and polarize as usual. In the case of low-grade products which have been clarified with a large excess of basic lead acetate, i t is imperative t h a t t h e excess alkalinity be neutralized before heating, this being best accomplished by the addition of I cc. (or z cc. in exceptional cases where a large excess of dry lead acetate has been used) of t h e dilute acid used for inversion. When a considerable number of determinations are t o be made a t the same time, the writer uses for a water b a t h a flat bottomed iron pan accommodating a dozen or more flasks and containing only enough water t o be above t h e surface of t h e liquid in t h e flasks. T h e whole is heated t o about 7 0 ° , the flame turned out and when a thermometer in one of t h e flasks indicates 67’ t h e flasks are taken out one a t a time, acid added and set aside for inversion. From a scientific standpoint this inversion process may be criticized on account of the fact that, due to variations in laboratory temperature and in thickness of flasks, marked variations in the rate of cooling, a n d hence in the speed of inversion, may occur. Practically no difference outside the experimental error could be detected, even when the temperatures a t which acid was added varied as much as IO’. It may be also t h a t t h e constant required for this method will be found on careful investigation t o vary slightly from t h a t now used in the Herzfeld method, which is itself under suspicion. I n the above work no attempt has been made a t much greater accuracy t h a n what
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might be expected in a well equipped factory laboratory, and within these limits the method has been found fully as accurate as t h a t of Herzfeld, and much more convenient, DEPARTMENT OF SUGAR TECHNOLOGY COLLEGE OB HAWAII.HONOLULU
THE CHEMICAL CHANGES WHICH ARE CAUSED BY DEFECATION OF SORGHUM JUICE FOR SYRUP MANUFACTURE By ARTHURK. ANDERSON Received November 4, 1916
The manufacture of sorghum syrup consists of three distinct processes: ( I ) The extraction of the juice from the cane; ( 2 ) the purification of the crude juice, which is the process commonly called defecation; a n d (3) evaporation. T h e quality of syrup produced depends t o a large extent on the purity of the juice which is evaporated, which in turn is dependent upon the efficiency of the method used in defecation. Since defecation is the most important process in sorghum syrup manufacture, it was found desirable, in connection with the work on sorghum which is being done a t the Minnesota Experiment Station, to undertake the study reported in this paper. I n the past there have been many different methods used in defecation.’ Those which have survived a n d which are found in use a t the present time in Minnesota are of two types. A t the larger factories what is known as the lime process is employed, while a t the smaller mills heat alone is used. The factory method may be briefly described as follows: The juice from the press is pumped t o a “defecator,” which is a square tank of about joo gallons capacity. Near the bottom of the t a n k are steam coils which are used t o heat the juice during defecation. When the defecator is full, if lime is t o be added, i t is added as milk of lime and stirred in well. The heat is then turned on and t h e juice heated t o the ‘(cracking point.” T h e heat is then turned off a n d the juice allowed to subside for about I 5 min. During the defecation the impurities either rise t o the top, forming a scum, or settle t o the bottom of the defecator. After subsiding, the clear juice is drawn off and evaporated. I n some of the smaller mills the processes of defecation and evaporation are carried on together. I n these places open pan evaporators are employed a n d the green juice is run directly into t h e evaporator. The impurities are skimmed off as they rise. AS a rule no lime is used a t such mills. A third method, known as the “phosphate” method, has been proposed, and while not yet in actual use in Minnesota mills, it seemed so promising t h a t it was decided t o include it among those t o be investigated. I n this method the filled defecator is heated for 30 min. with calcium acid phosphate and then treated with lime. T h e tri-calcium phosphate which precipitates out has a clearing effect on the juice. The purpose of t h e preliminary heating with the calcium 1
Harvey W. Wiley, “Record of Experiments with Sorghum in 1892,”
U. S. Dept. Agr., Bur. of Chern., Bull. 87 (1893). 8C-95.
