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t o arrive at t h e refining value of a slow filtering sugar. The third item t o be taken into account as affecting the value of a raw sugar is its readiness t o yield u p its color on filtration through boneblack or on subjection t o any other decolorizing process. After all, refining sugar is principally decolorizing it, and any system of standardization or valuation of raws which ignores this important feature is lacking in one of t h e essential details. Sugars may be of a wide range of shades and from many causes, as t h e variety of cane, burnt cane, caramelization during manufacture, over-liming, working back molasses and second or third product sugars, contamination by iron salts, and so on. Some of these coloring matters are more easily absorbed t h a n others and their absorption b y different agents varies widely. For instance, t h e natural color of cane juice is only slightly absorbed by boneblack, while Norit absorbs it quite freely; and this latter agent takes u p 9 5 parts of color due t o t h e action of lime on invert sugar as easily as it absorbs 2 3 parts of color due t o caramel. These and other considerations render a n empirical test desirable, based on general common practice. Such a determination of t h e decolorability of a raw sugar b y boneblack, for instance, may be arrived a t by dissolving I O g. of raw sugar in 30 cc. of water, adding 0 . 2 j g. of Filtercel and 2 g. of t h e best boneblack ground finer t h a n 60 mesh, bringing all gently t o a boil, and filtering through paper. A similar test, made as the first is, but without boneblack, affords t h e basis of comparison. After reading the colors of t h e filtrates either against a tintometer standard or by comparing the depths of columns t o give equal colors, one may readily calculate t h e amount of color absorbed b y the boneblack. I t will be foyrrd t h a t a fair average sugar will yield about 7 5 per cent of its color in this test, and any greater amount yielded means a proportional economy in char work required, while a smaller absorption designates a larger amount of char work t h a t will be required. One can easily calculate the amount t o be added t o or deducted from the basic price of a sugar t o arrive a t its value in respect t o filterability. Thus a sugar giving up only 6 0 per cent of color instead of 7 j per cent should have l s / a ~ of the normal char filtering expense deducted from the basic price t o recompense for the extra expense t h a t will be entailed in its char filtration. Other factors might be taken into account, as t h e amount of ash in t h e raw sugar, but as under present conditions it is of less importance how much melassigenic ash there is t h a n how much time and labor will have t o be expended in refining t h e sugar, these factors may, for t h e present, be disregarded. The extra refining expenses enumerated in t h e above examples are very small, i t is true, and would occur in relatively few cases, b u t with upward of $600,000 worth of raw sugar entering t h e port of New York alone, daily, even small decimals add up t o large aggregates and are certainly worth taking into account. Just now there is so ready a market for all raw sugar
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t h a t competition in its sale is slight, b u t when t h e present stress is over and Europe resumes her large production there will be a great surplus, with corresponding competition t o sell. Then the purchaser will pick and choose what suits him best, and i t is t h e part of caution for the raw-sugar maker t o consider what class of sugars will be most desired and t o manage his manufacture accordingly. It is in t h e hope of assisting in this very particular discrimination t h a t these suggestions are presented. YONKERS, NEWYORK
ON THE PREPARATION OF AN ACTIVE DECOLORIZING CARBON FROM KELP1 By F. W. ZERBAN AND
E. C. PREELAND
Dr. J . W. Turrentine, in charge of the United States Experimental Kelp Potash Plant a t Summerland, California, has for several years been engaged in working out methods for the commercial utilization of t h e giant kelps of t h e Pacific Coast. During the course of his investigations it occurred t o him t h a t t h e char obtained in the manufacturing process used might perhaps be converted into a decolorizing carbon. It appears, however. t h a t this question was not taken up actively, until one of t h e authors of this article conceived t h e same idea, while engaged in a study on carbons t h a t might be used in t h e cane sugar industry. At his request, Dr. Turrentine sent him some dried kelp t o experiment with. I n .the first test t h e kelp, after thorough drying and grinding, was carbonized in an iron retort provided with an outlet for gases, until no more fumes were given off. The char was then transferred t o a closed iron receptacle and heated for 2 hrs. t o a bright red heat. It was then cooled, boiled out with hydrochloric acid, washed with water, and dried. Upon examination it was found t h a t the resulting carbon reduced t h e color of a molasses test solution t o about one-third of t h a t obtained b y using a n equal quantity of our standard carbon, Norit. A sample of kelp char, also received from Dr. Turrentine, when treated in a similar manner as t h e dried kelp, produced only a very poor carbon. We therefore decided t o investigate this matter more thoroughly, a n d at our request Dr. Turrentine very kindly furnished us an ample supply of raw material for our further experiments, and we wish t o express t o him our thanks for this courtesy, as well as for t h e great interest he has taken in t h e progress of our work. The material received consisted of three different samples. The first, A, was kelp (Macrocystis p y r i f e r a ) dried in a rotary kiln; t h e second, B, was “incinerated” kelp, prepared as described below; and t h e third, C, was a sample made b y subjecting kelp t o destructive distillation. The last sample was kindly sent t o us through Dr. Spencer, who was investigating t h e destructive distillation of kelp at t h e Forest Products Laboratory, Madison, Wisconsin. None of t h e three samples had been leached with water. 1 Presented before the Division of Industrial Chemists and Chemical Engineers at the 56th Meeting of the American Chemical Society, Cleveland, September 10 t o 13, 1918.
Oct., 1918
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
Upon investigation it was found t h a t there are three factors which have an important effect on the properties of the final product sought. First of these is the particular point in the process a t which the soluble salts a n d other ash constituents are removed. The second is t h e method by which the material is carbonized. We used two different ways with Sample A. I n one experiment it was charred in an open iron saucepan over a gas ring burner, until fumes ceased t o come off and t h e material was thoroughly carbonized. I n other tests the process was conducted in a half gallon, heavy iron retort with a descending iron condensing tube about in. in diameter and 3 f t . long. ‘This was heated over a gas ring burner. Sample B, which was a char, had been prepared by feeding dried kelp into a revolving “incinerator,” setting it on fire, and after i t had been heated sufficiently, cooling it rapidly by quenching. Sample C was only partly carbonized, having undergone destructive distillation at a temperature not exceeding 314’ C. The third factor is the temperature t o which the char, obtained b y carbonization, is heated in a closed receptacle. We effected this final heating in a n iron cylinder made from a nipple of 2-in. pipe, closed a t both ends by screwed-on iron caps. This cylinder was placed in a muffle furnace commonly used for making ash determinations in sugar products, and which produces a maximum heat of about 800’ t o gooo
c.
The three factors mentioned will be taken up in detail in this paper. The decolorizing effect on sugar products of the various carbons made was determined b y the following method: 5 g. of the carbon under examination are added t o zoo cc. of a 3 per cent solution of a stock sample of low-grade molasses. The solution is brought just t o the boiling point and a t once filtered through a folded filter. The decolorized solution is then compared colorimetrically with one obtained under t h e same conditions, b u t using 5 g. of Norit instead of the carbon. The color of the solution obtained b y means of Norit is used as a standard a n d is called “I.,’ Carbons more effective than Norit will give figures below “I)) and those less effective The reciprocals of the figures figures above “I”. give a direct measure of t h e effectiveness of the carbon as compared with Xorit. E F F E C T O F LEACHING
A part of each sample, A, B, and C, was boiled out several times with water, thoroughly drained, and again dried. Parallel experiments were then made with both leached and unleached material. The following table gives the tests and their results: COLOROR SOLUTION DECOLORIZSD WITH CARBONFROM Leached Not leached before before TREATMENT heating heating A, charred in retort, heated t o bright red heat in closed iron cylinder, boiled out with water. 5.00 2.86 A, charred, heated t o bright red heat, boiled out with acid, then water.. T.. . . . . . . . . . . . . . . . . . . . 2.78 1.25 B heated t o bright red heat boiled out with water. 2.56 1.37 B: heated t o bright red heat, boiled out with acid, then water 1.47 0.34 3.33 C , heated t o bright red heat, boiled out with water. 3.57 C , heated t o bright red heat, boiled out with acid, then water ................................. 1.85 1.37
.....
.................................
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The table shows t h a t t h e better carbon is always obtained from the unleached material, and, in fact, the only carbon t h a t is better than Norit, and considerably so, was prepared from material t h a t was not treated with any solvent until after it had been brought t o red heat. We may conclude from this t h a t if our object is t o make an active carbon, none of the mineral matter must be removed before heating the material t o red heat. E F F E C T O F METHOD O F CARBONIZATION
The way in which the kelp is carbonized is almost of as great importance as t h e question of leaching. The different methods of charring have already been Clescribed above. It is very difficult t o carbonize t h e kelp in the iron retort always under the same conditions on account of varying gas pressure and because the condensing tube often gets more or less clogged with tarry products, thus preventing the free escape of the fumes. The effect of these factors which were not under control is strikingly shown in the figures below. TREATMENT COLOR A, carbonized in an open saucepan, then heated t o bright red 0.28 heat in closed cylinder, boiled out with acid, then water.. A, carbonized in iron retort, then heated t o bright red heat, boiled 0.3 1 out with acid, then water.. Same, other experiment.. .................................. 0.50 Same, other experiment., 0.75 Same, other experiment., .................................. 1.25 B heated t o bright red heat boiled out with acid then water.. . 0.34 C: heated t o bright red heat: boiled out with acid: then water.. 1.37 C, first completely carbonized in open saucepan, heated t o bright red heat, boiled out with acid, then w a t e r . , ................ 1.70
.... ............................... ..................................
.
These experiments show t h a t the best results are obtained when the raw material is carbonized quickly a t a comparatively high temperature and in such a way t h a t the fumes can freely escape. Carbonization alone, howevei , is not sufficient t o make an active decolorizing carbon, as is shown by the fact t h a t Sample B itself, without first being heated t o red hest, produced a color of 3.70 when extracted with water, and of I . 56 when extracted with acid and then washed with water. Sample C gave 3.85 and I. 7 2 , respectively. EFFECT
OF
TEMPERATURE
TO
WHICH
THE
MATERIAL
IS HEATED AFTER CARBONIZATION
Three series of experiments were made this question, two (I t o 4 and j t o 8) with tained b y carbonizing Sample A in the iron low temperature, and another with Sample ceived (9 to 11). No. 1
2 3 4
5 6
7 8 9
10 11
t o test char obretort a t B as re-
TREATMENT A, carbonized in iron retort, heated t o full red heat, boiled out with water.. .................................... A, carbonized, heated t o medium red heat, boiled out with water . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A, carbonized, heated t o low red heat, boiled out with water. A, carbonized, heated t o barely red heat, boiled out with water.. . . ith . . .acid, .... A, carbonize then water ......................................... A, carbonized, heated t o medium red heat, boiled out with acid then water.. ................................... A, carAonized, heated t o low red heat, boiled out with acid, then water.. . . . . . . . . . . . . . . ..... t with A, carbonized, heated t o bare1 acid, then water.. .................................... B, heated t o full red heat, boiled out with acid, then water 0 . 3 4 and 0.30 average .............................. B, heated t o mLdium red heat, boiled out with acid, then water .................................. h B, heated t o low red heat, boiled out with ac water... ...........................................
COLOR 2.86
3.23 3.57 4.17 1.25 1.52 1.47 1.72 0.32 0.682 1 .4.3
8x4
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We find t h a t within the temperatures a t which tests were made t h e best carbon is obtained by heating t o the highest temperature, full red heat. It is possible a n d even probable t h a t still better carbons might be prepared by heating t o even higher temperatures, b u t this would hardly be of practical interest. One experiment was made in which a quantity of B was heated in a clay crucible in a Fletcher furnace, b u t observation showed t h a t the temperature was not a n y higher t h a n we could obtain with the iron cylinder in t h e muffle furnace. The resulting carbon, after washing with acid and water, produced a color of 0 . 3 6 , which is very close t o the 0 . 3 2 shown in the above table for the muffle heated carbon. Another experiment was carried out in order t o see whether a good carbon could not be made in one operation. The iron cylinder described above was filled with dried kelp, and one of the caps was only screwed on loosely, so t h a t the fumes might escape, without giving t h e air free access t o t h e char. After heating t o full red heat the carbon was boiled o u t with acid, and washed with water. I t produced a color of 0 . 7 5 , a n d was therefore much less effective than the carbon produced in two operations. We have also found t h a t i t is not necessary t o extract t h e carbon directly with hydrochloric acid. T h e water-soluble salts can first be removed with this solvent, and the greater p a r t of t h e remaining ash is then dissolved with hydrochloric acid, after which the acid is again washed out with water. Summarizing briefly, our tests have shown t h a t a carbon which has a much greater decolorizing power than Norit can be prepared in the laboratory by quickly carbonizing dried Pacific Coast kelp in such a way t h a t the fumes can freely escape. After they cease t o come off, the char is transferred t o a closed iron receptacle and heated for 2 hrs. or so to red heat. Instead of charring dried kelp, “incinerated” kelp may be used directly. The carbon is then boiled out either with dilute hydrochloric acid, or first with water a n d then acid. This is again washed out with water, and the carbon dried. I t remains to be seen whether t h e process can be worked successfully a n d economically on a large scale, a n d whether the price t o be gotten for the finished product will warrant its manufacture. The most logical place to work out t h e first problem is the United States Experimental Kelp Potash Plant in California, and we hope t h a t t h e Bureau of Soils may be willing and able t o take u p this project. The great decolorizing power of the kelp carbon is probably due t o two factors. We had found before t h a t active decolorizing carbons can be prepared from cellulose materials by first impregnating them with either infusible substances like lime, alumina, silica, or else with such substances as chlorides, etc., which are volatile a t the temperature a t which the carbon is made. I n all these cases t h e carbon must be heated t o red heat t o get good results, and the impregnating substances must then be removed with proper solvents. I n the particular case of potassium chloride as impregnating substance t h e carbon obtained was
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rather poor, and the potassium chloride content of t h e kelp alone would not explain the decolorizing power of the kelp carbon. There is also too little infusible ash t o account for. it. However, a distinguishing feature of kelp is its high nitrogen coptent, a n d i t seems reasonable t o suppose t h a t this is largely responsible for t h e great effect of kelp carbon. T h e great decolorizing power of carbons made from highly nitrogenous materials, like blood charcoal, or the carbon made from the residues of the manufacture of ferrocyanide a n d from similar materials has long been well known. We noticed t h a t in every case where we obtained a good carbon from kelp, Prussian blue was formed when the carbon coming from t h e muffle was extracted with hydrochloric acid. It imparted t o t h e wash waters a deep blue color, being dissolved in colloidal form. The r6le played b y t h e nitrogen is not known definitely, b u t the effect of its presence is quite plain. SUMMARY
It is shown in this paper t h a t under proper conditions a decolorizing carbon much more effective t h a n Norit can be prepared from Pacific Coast kelp. T h e f?ctors affecting the decolorizing power of the carbon are discussed, and a method for making the most effective carbon is described. LOUIRIANA SUGAREXPERIMENT STATION N E W ORLEANS.LOUISIANA
THE ROLE OF OXIDASES AND OF IRON I N THE COLOR CHANGES OF SUGAR CANE JUICE‘ By F. W. ZERBAN
If the methods now being used in t h e manufacture of white sugar directly from t h e cane are t o be placed on a strictly scientific basis, it will be necessary t o gain a more accurate knowledge of the coloring matters which have t o be removed or the formation of which has t o be avoided. A great deal of work has already been done in this direction, but much more still remains t o be done. Any such investigation must first take into consideration t h e coloring matter found in the cane itself and in the raw juice obtained from it by applying pressure or diffusion. Previous investigators have found t h a t t h e cane contains chlorophyll, saccharetin, and, in. the case of dark-colored canes, also anthocyanin. Neither t h e chlorophyll nor t h e saccharetin dissolve in t h e juice upon milling, but pass into i t mechanically with t h e finely divided bagasse. They therefore do not affect t h e color of the juice itself, except in t h e form of solid suspended particles, and do not make their presence felt until the juice is treated with lime, a n excess of which causes t h e saccharetin t o t u r n yellow. Anthocyanin, however, is quite soluble in t h e raw juice, a n d this is the reason why dark-colored canes give a darker juice than light-colored ones. But all these facts do not explain the dark color of raw juice from light-colored canes. C. A. Browne2 1 Presented before the Division of Agricultural and Food Chemistry at the 56th Meeting of the American Chemical Society, Cleveland, S e g tember 10 to 13, 1918. 2 Louisiana Bulletin, 7 5 , 249; 91, 17.
