I N D U S T R I A L .45D EiVGIiC'EERING CHEMISTRY
August, 1930
003
Peanut-Hull Cellulose'" D. F. J. Lynch and Marshall J. Goss COLORA X D FARM WASTEDIVISION, BUREAUOF CHEMISTRY A N D SOILS,WASHINGTON, D. C.
An analytical study of peanut hulls was made to some hulls have been used as HE rapid growth of our determine a possible commercial use for this farm a roughage in cattle feed (19, cellulose i n d u s t r i e s , waste. The results agree with those of other investi21). Small quantities of hulls w i t h the consequent gators in that this waste would be an uneconomical are sold to be incorporated d e p l e t i n g demand on our source for pentosans. The comparatively high crudein fertilizers as a diluent (19) forests, h a s w a r r a n t e d a fiber content would indicate that the hulls might be and attempts have been made search for suitable raw mateused as a source for high-grade cellulose. The optito use peanut hulls in magrials to supplement the presmum conditions were determined for the production nesia plaster (%), slabs, tiles ent supply of wood pulp. The of cellulose from peanut hulls by the use of the soda (1.5), and fiber concrete. I n increase in the demand for method, the neutral sulfite method, and the sulfate the production of magnesia wood pulp, as estimated by method. Experiments indicate that the best results plaster, tiles, and fiber conthe U. S. Bureau of Census, are obtained with the neutral sulfite method, which crete the peanut hulls a r e is 5 per cent per annum. At gave yields of 40 to 42 per cent of unbleached pulp. A this rate of increase, in twenty substituted for sawdust and method is described for producing cellulose from this wood chips. The resultant years the annual demand for pulp which analyzes over 90 per cent alpha-cellulose. fiber concrete is reported by wood pulp will have reached There are collected annually at a few points in this the enormous amount of 15 the U. S. Bureau of Standcountry some 70,000 tons of peanut hulls available at a r d s to be weaker than the to 20 million cords of wood. a cost of $4 to $5 a ton, which might serve as a suppleUnder any program of reconcrete prepared with hardmental source for approximately 20,000 tons of alphaforestation yet advanced, it wood chips (18). Testsmade t o ascertain the possibility cellulose. will be impossible f o r o u r of substituting Deanut hulls forests to satisfv this demand. The depressioi in the agricultural industry since the World for cork board in refrigeration show the hulls?o* have 70 per War, together with the fact that cellulose comprises a con- cent of the insulating power of cork (21) and to have the siderable proportion of many agricultural wastes, has in- added disadvantage of absorbing water.3 Several years ago tensified this cellulose research. To warrant serious con- a useful and profitable outlet was found for ground peanut sideration, as a supplemental source for cellulose, a farm hulls in substituting them for middlings as a polishing medium waste should contain considerable cellulose and be available in tin-plate manufacture (20). While the peanut is growing in the soil some sand seems to be incorporated in the hull, in large volume at a low price. One agricultural waste which suggested itself, owing to its and the failure to remove this sand resulted in the scratching high crude-fiber content, is peanut hulls. Peanut hulls are of the tin plate. Today, therefore, this outlet for hulls is available in volume at the shelling plants. A recent report closed, and most of the hulls are burned as fuel under the issued by the Bureau of Agricultural Economics (6) states shelling plant boilers There exists some difficulty in handling the hulls and the fuel value is only about $2 a ton (?). that in the year 1927-28 there were produced in the Virginia-
T
Table I-Analysis INVESTIGATOR Ferris, Miss. Bgr. Expt. Sta., Bull. 130 Bull. Imperial Inst., 8 , 153 (1910) Fraps, Tex. Agr., Bull. 322 Reed, U. S. Dept. Agr., Bull. 1096 Farm Waste Division
Ha0 12.74 12.94 7.31-9.03 7.9 7.5-10.5
ASH 3.39 3.39 2.96-5.9 3.0 3 0-5 2
of Peanut Hulls
PROTEIN 7 22 7.20 5 64-7.87 6.8 5.9-7.0
Xort h Carolina section 102,549,580 pounds of Virginia shelled nuts; in the southeastern section, 39,998,794 pounds of shelled Virginia runners, and 133,890,362 pounds of shelled Spanish nuts; and in the Southwestern States, 33,214,654 pounds of Spanish nuts. As the kernel is estimated to be two-thirds of the weight of the Virginia peanut and 70 per cent of the weight of the Spanish variety, the peanut-shelling plants of the country, during the year 1926-27, had the problem of disposing of some 70,000 tons of peanut hulls. Independent estimates by experts in the shelling industry confirm the approximate accuracy of this figure. Numerous att,empts have been made to dispose of these hulls, with some success. Although the hulls conta'n little food value (.9), the crude fat content totaling only 3 to 4 per cent and the protein content averaging between 6 and 8 per cent, only 70 per cent of this protein being digestible, 1 Received April 19. 1930. Presented before the Division of Cellulose Chemistry a t the 77th Meeting of the American Chemical Society, Columbus, Ohio, April 29 to May 3, 1929. 2 One hundred seventy.eighth contribution from the Color and Farm U a s t e Division, E L ~ W of U Chemistry and Soils.
NITROGEN 1.77 1.17 ,.
o
.
g.ili:i2
FAT 2.68 2.68 1.11-2.83 2.9 2.1-2.8
NITROGEN-FREE EXTRACT CRUDEFIBER 19.42 67.29 19.42 67.42 15.95-21.9 54.03-67.55 17.1 62.3 16.0-19.3 59.0-66.1
Analytical
The incorporation of peanut hulls in some prepared cattle feeds focused the attention of the laboratories of the agricultural experimental stations upon this waste, and consequently niost of the reported work on peanut hulls originated in these laboratories. The low protein and fat content show that the hulls make a poor cattle food. Like many other wastes, peanut hulls contain a considerably high pentosan content, which is easily 1:yclrolyeed to xylose. -4s a source for this pentose, however, peanut hulls would have to compete with oat hulls and cottonseed hull bran. I n comparative experiments on peanut hulls and oat hulls, Fred, Peterson, and Anderson (8) obtained yields of 26.5 per cent of reducing sugars from oat. hulls and only 7.6 per cent from peanut hulls. These results, together with the high yields of 38 to 40 per cent reducing siigarp obtained from cottonseed hull bran by Jlarkley ( I d ) and Acree's determination showing that only one-half of the 17 per cent pentosan content of peanut hulls would yieldl 3
Tests made in this division.
Vol. 22, No. 8
I N D U S T U A L AND ENGl!NEERING CHEMISTRY
904
xylose (7), hold out little hope for the utilization of peanut hulls as a source for this sugar. The comparatively high cellulose content suggested that this waste might be a source of cellulose, but on the other hand the high ash might indicate trouble in the preparation of high-grade cellulose. With B view to utilizing peanut hulls as a source of cellnlose the following determinations were made.
0.3
8 . &E. 55
9.b10.1
0 47-0 56 3 0 -3.1 4 3
25.525.8 21.b21.55 0.5-0 6 3~2-3.3 4.6
Investigation of the ash showed that fine grains of silica accounted for a large part of the ash. Various methods of dusting, washing, shaking in tumbling sieves, and, in the case of ground hulls, air-separating devices were used to reduce t,he amount of ash. More consistent results were obtained by shaking the hulls in tumbling sieves. By this oper&oo the ash content of air& hulls was rdnced from 4.3 per cent to 1.65-1.9 per cent. Sixty per cent of this ash, which represents about 1.1 per cent of the airdry hulls, was found to be insoluble. As in the case of other farm wastes ($E?), peanut hulls are composed principally of cellulose, lignin, and pentosans. The isolation of the lignin was attempted by the Klason method, 72 per cent sulfuric acid being used, but the results were not in agreement. An adaptation of the Willstitter method, in which hydrochloric acid gas was bubbled through a suspension of finely ground bulls in a concentrated solution of hydrochloric acid, was then tried, and the several determinations agreed within 0.4 per cent.4 It was found impossible to identify pect.in in peanut hulls. I n the determination of the pentosan content the official A. 0. A. C. phloroglucinol method was followed ( 2 ) . The results obtained by this method may be high owing to furfural obtained from oxycelluloses, but good agreement was obtained in the several determinations run in this division, and these results were in fair agreement with those of other investigations (Table I).
By using t.he Jena glass Gooch crucible the residue can be stirred up well after each chlorinat.ion wit,h a glass rod and then thoroughly digested with warm sodium sulfite solution without removing it from the crucible. It was found impossible, however, to reduce the hulls to cellulose in the recommended five &minute periods of chlorination with subsequent digestions with 2 per cent sodium sulfite solution. It was generally found necessary to subject the hulls to ten such complete treatments to produce a high bleached, pure white cellulose residue. The determinations reported above represent the weighed residues of white cellulose obtained in this manner. Experimental
The actual production of peanut-hull pulp, with smallscale .apparatus, was next investigated. Some experiments were carried out witli nitric acid digestion as directed in the several patent specifications (IO),and yields comparable to those obtained by the older methods were not hard to produce. The pulp was easy to bleach, but evidently in all the experiments tried in this division t,he conditions of digestion were too drastic. Alpha-cellulose determinations run on
Table Ill-Camposltlon of PeanYt Hulls (Determinations made on s i f t 4 dry rLmpler oi various shipments) DBTBRXIN*TI"N
MINIMUX MAXIMUM Per L C I I P" C m l ,
Ash
1.6 1.95 16.5 19.4 Pent LIS 33.4 33.7 LigoiS 44.9 46.5 Cellulose. by diEerence 89.0 64.4 Crude fiber" PentoPana in Pulp* 13.5 16.9 Cellulose, total (Cr- and Bevau)*,6 47.2 51.0 Cellulase, total Weber and Welter)',i 43.5 45.0 The max(murn petcentages of crude 6ber and ceI!aluse were. of ~ W X K , found in those sampler showing lover percrnta~erof lignin and PentOaaus. b Consistently high. G Good check on same sample.
All the cellul~sedeterminations made by the Cross and Bevan chlorination method, in which the chlorination was carried out in a beaker, ran high. This is no doubt due to the difficulty of thoroughly chlorinating all the grains without at,tacking the cellulose. By using the adaptation recommended by Sieher and Walter (S8) but substituting a Jena glass Gooch crucible for t.he filter plate and fine muslin cloth recommended by those invest.igat,ors, lower and consistent results were obtained. The hulls were ground to pass through an XO-mesh sieve, and after extraction with an alcohol-benzene mixture (26) were chlorinated in the Jena crncible. 4 This determination w a ~ checked by Mar Phillips in his lignin investigations.
Fleure I-Typlcal
Peanut-Hull Flber.
X 50
bleached pulp obtained by this method gave results which averaged 63 to 68 per cent. Conditions and equipment p r e vented a thorough investigation of the application, to peanut hulls, of the acid sulfite method and Pomilio's chlorine p u l p ing method. Investigations, however, were carried out to ascertain the best conditions as to time, concentration of solutions, percentage of chemicals in relation to hulls, and temperature of digestion, using the soda method, the sulfate method, and the neutral sulfite or Keebra method. Table IV shows the minimum and maximum variances of the concentration of solution, time, and pressures which were used in all experiments. The results obtained with the various cooks are reported in this form in order to conserve space. For exampic, by the soda method, in which a 15 per cent sodium hydroxide solution was used, forty-eight cooks were made to determine wbet,her or not a good, bleachable pulp could be obtained. In these cooks t.he concentration of solution was 3, 5, and 7.5 per cent; time was 3, 4, 5, and 6 hours; pressure was 50, 75, 100, 125 pounds per square inch (3.5, 5.3, 7.0, and 8.8 kg. per sq. cm.). The
INDUSTRIAL -4ND ENGINEERING CHEMISTRY
August, 1930
T a b l e IV-Production CHEMICALS----
7--
NaOH
NazS
ACTIVE
NazCO3
%
ALKALI
%
of Cellulose from P e a n u t Hulls. CONCN. OF
SOLN.
%
TIME Hours
905
R e s u l t s O b t a i n e d with Various Cooks
PRESSURE Lbs./sq. t n .
RANGE
YIELDS
%
SODA METHOD
10 15 20 25 30 Parts
cb2 5 3-7 5 2 5-10 2 5-10 2 5-12 5
Parrs
Ports
3 3 3 1
1 1 1
3-6 3-6 3-6 3-6 3-6
50-1255 50-125 50-125 50-125 50-125
KO effect-unbleachable pulp Unbleachable-good pulp Unbleachable-good pulp Unbleachable-poor pulp Bleachable-poor pulp
0-45 47.5-38 46-35 45-33 41-27
Unbleachable-good pulp Unbleachable-good pulp No effect-bleachable pulp Unbleachable-good pulp Unbleachable-poor pulp Bleachable-poor pulp Bleachable-poor pulp
46-36 48.5-37 0-39 46-33 44-31 42-29 38-26
No effect-difficultly bleachable pulp Unbleachable-good pulp Unbleachable-good pulp Unbleachable-good pulp
0-46 49.5-41 49-39 48-38
S U L F A T E METHOD
10 10 10 2 2 2 2
1 1 1
20 15 10 15 20 25 30
2 5-7 5 2 5-7 5 0-2 5 2 5-7 5 2 5-7 5 2 5-10 2 5-12 5
3-6 3-6 3-6 3-6 3-6 3-6 3-6
50-125 75-125b 75-125 75-125 75-125 50-125 50-125
h E U T R A L S U L F I T E OR K E E B R A METHOD
NasSOa
% 2cb35 40 45 60 3.5 t o 8.8 kg. per s q . cm. b 5.3 to 8.8 kg. per sq. cm.
10-17 10-20 10-20 10-20
3-6 3-6
3-6 3-6
75-125 50-125 50-125 50-125
Q
pulps obtained covered a wide range, varying in effect from unbleachable to good bleachable pulps. It can be stated generally that with a quantity of the pulping agent sufficient to bring about any effect, an increase in either time or pressure improves the quality of the pulp until the optimum condition is reached. Passing this point the cellulose itself is attacked. The whole change is accompanied with a steady decrease in the yields of unbleached pulp. With identical conditions of time and pressure, an increase in the pulping agent moves this reaction in the same direction but a t a far greater rate. I n like manner an increment in pressure provides a greater effect than an increment in time. Little pulping effect was observed in 2-hour cooks, even with comparatively high percentages of chemicals. Variation in the concentration of the cooking liquor is limited because of the low density or fluffiness of dry peanut hulls. An amount of solution at least two and onehalf times the weight of the hulls must be used to prevent the charge from burning. Small-scale apparatus heated with steam was found impractical because of the high condensation due to the comparatively high surface radiation. With the sodium sulfite method yields of 42 per cent of unbleached pulp are readily duplicated. Sodium sulfite solutions, however, are not very effective in concentrations lower than 20 per cent, which necessitates the use of a considerable amount of sodium sulfite. This pulp is easily bleached. About 2 per cent lower yields of crude pulp are obtained with the soda method and with the sulfate method. Pulps obtained by these methods were harder to bleach. Pulps from all cooks should be removed as soon as practicable, as allowing the pulp to stand overnight, for example, in the cooking liquor increases the time and amount of water necessary to wash the pulp thoroughly, and makes the bleaching of the crude pulp more difficult. An amount of chlorine equal to about 20 per cent of the dry weight of the pulp is consumed in the bleaching with a loss of not more than 10 per cent of the pulp. Under the best conditions, therefore, yields of 36 to 38 per cent of white pulp are obtained. This bleached pulp will average 75 to 78 per cent alpha-cellulose (26). The pulp produced from peanut hulls is composed of fibers which are shown to be very dissimilar under the microscope, as seen by the accompanying microphotograph^.^ Figure 1 shows a typical fiber under a magnification of 50 X, while Figure 2 shows the larger variety of peanut-hull fiber under
the greater magnification of 130 X. The average length of the large fibers was found to measure 1.7 mm.8 I n 1917 the Forest Products Laboratory made some paper test sheets with equal parts of peanut-hull pulp and wood pulp, but according to tests carried out on these test sheets by the U. S. Bureau of Standards the paper was found to be weak (22). Experiments by the same laboratory to determine the suitability of peanut hulls for making paper board showed that with equal quantities by weight of disintegrated peanut hulls and old newspapers pulp board could be produced which was practically as good as many samples of chip board or wall board on the market. No attempt, however, has been made to utilize commercially any volume of these hulls in this manner ( S I ) . For utilization in the nitrocellulose or the rayon industry high alpha-cellulose with a low ash is demanded. It was found by experiment that the ash in peanut-hull pulp can be lowered by alternate treatments with very dilute acid and alkali at room temperature without detrimental effect on the cellulose. Pulp is added to a hydrochloric acid solution of not over 0.5 per cent HCl, in only such amounts as to make a 5 per cent pulp suspension. This suspension is stirred well, and the pulp is similarly treated with 0.25 per cent sodium hydroxide. After each acid and each alkali treatment the pulp must be washed free of acid and alkali with soft water. In this manner the ash can be brought below 0.3 per cent. The beta- and gamma-celluloses are removed by heating the pulp in a 5 to 7 per cent sodium hydroxide solution on a water bath or treating the pulp with a cold 8 to 9 per cent solution of sodium hydroxide. After this treatment the pulp is pressed to remove as much sodium hydroxide as possible. These alkali solutions are used in making up the cooking liquor. After pressing, the final traces of sodium hydroxide are washed out in cold soft water, and the pulp is dried at about 40' C. to a 5 to 7 per cent moisture content. I n this manner peanut-hull pulp averaging a t least 93 per cent alpha-cellulose, on the dry basis, can be prepared. Some attempts have been made to produce peanut-hull pulp to meet the specifications for nitration. It has been found that the pulp, as prepared, has too high a soda-soluble content and produces cuprammonium solutions of low viscosity. The samples tested contained 8 to 18 per cent sodasoluble material. Celluloses with more than 3 per cent of soda-soluble material are thought to produce on nitration
6 G.L.Keenan, microanalyst, Food, Drug, and Insecticide Administration, made these microphotographs.
6 Measurements made b y E. A. Read, senior microanalyst, Microchemical Unit, Food, Drug, and Insecticide Administration.
INDUSTRIAL A N D ENGINEERING C H E M I S T R Y
900
unstable nitrocellulose. Olsen (1 6), however, says that “samples of n.ood cellulose containing 10 per cent sodasoluble mat.erial and of cellulose from sugar cane and various straws containing about 20, per cent soda-soluble material have been nitrated and purified without difficulty to give stablc nitrocellulose.” According to these results it appears t.hat the stability of the nitrocellulose is not dependent on a low wda-mluble content in the cellulose. The main objection to a greater amount of soda-soluble material in a given cellulose than that specified was found by Olsen to be the reduction in the yield of nitrocellulose obtained. Cellulose containing 10 and 20 per cent soda-soluble matcrial were found to give, respcct,i\.ely, 6.2 and 18.7 per cent less nitro-
Val. 22, Ko. 8
cellulose materials. He says that the possible cellulose bases for rayon manufacture run the gamut of the vegetable kingdom. The governing condition secnis to be the extraction of the cellulose without breaking down the moleculc. Jackson aptly points out that if the rayon manufacturer is getting fairly good results at present, he cannot be blamed for being reluctant to make a change from one cellulose source t,o another, with thc ensuing costly r.hanges in machinery and process, unless a substantial advantage is to be gained thereby. If, however, there can he offered a steady bupply of cellulose other than cotton cellulose, in quantity, snd of absolute uniformity, Jackson sees such a change in the near future. As a source of cellulose supplemental t,o cotton linters and wood pulp, peanut hulls must meet t.hc competitioa of other waste products such as corn st.alks (12, 24, ,W, 90, %72j,Aax straw (4), esparto (3, ZS), bagasse (B),banana-stalk waste (23), cacoa waste (27j, Alpina nuts (fl), and Kaoliang stalk (34). The tropical wastes, however, appear to offer little competit,ion owing to t.he distance from the present celloIOSC market. With the other sources of cellulose peanut hulls seem to compare favorably. Itommcl (24) reports t,hat cornstalks, with an average 15-mile haul, cost $8 a ton and lhat straw costs from $7.50 to $14 a ton. Peanut hulls, with a cellulose content equal to or greatcr than that of otlier wastes, are already collected at the peanut-shelling plants and are being burned under the plant boilers. Since the fuel value is only $2 a ton ( I ? ) , these hiills can certainly he supplied at the few peanut-shelling centcrs in this country at a price of from $4 to $5 a ton. Conclusion
Figure 2-Larpe
Peanut-1Iull Fiber.
X 130
cellulose than the amount obtained with the staiidard celluloso. Olsen also statcs that “in much of the use to which nitrocellulose is piit ai1 ash content higher than 0.8 per cent, would probably be of no significance.” Improvement has been made in producing peanut-hull-pulp cnprammonium solutions of higher viscosity than formerly. $Ithough the viscosity is still below specification, it is iiot conceded that peanut-hull pulp cannot be prepared to meet this spceification of the nitrators. Today, however, most of the nitrators arc using purified second-cut cotton linters, which is the purest cellulose known to this division. Sulfite wood pulp prepared for usc in the viscose rayon process is not nearly so pure as this special cott.on linter pulp. The specifications for viscose pulp are not so strillgent as those for nitrocellulose. Further dryins is necessary as visrose pulp must contain not iiiore than 4.5 pcr cent moisture. A much lonw ash is also required. Retween 0.3 to 0.4 per cent ash is specified, but a pulp wit,h an ash uf less than 0.3 per ccnt. is desired ( I ) . A pulp which contains 87 per cent alpha-cellulose is acceptable, homver (17 ). Commercial visacse wood pulp contains bet.ween 87 and 90 per cent alpha cellulose, but according to the soda-soluble test this pulp contains between 14 and 20 per cent soda-soluble material. Samplcs of peanut-hull pulp compare very favorably with this viscose pulp. With the exception of the sulfit,e wood pulp, used in the viscose process, the various cellulose industries have looked to cotton and cottoii linters for their raw material. Jacka n (111, however, scfs the displacement of cotton with other
Expcriinental work shows that peanut hulls contain a large quantity of cellulose which can be extracted from the liulls by the conimon soda, the sulfate, or the neutral sulfitr method. The conditions of time, pressure, and conceiitration of chemicals necawry for thc produetion of good quality pulp are not so drastic as to affect the pulp inat,eriaily. Although this pulp cont.ains a comparatively high ash, this ash can he sirnply and inexpensively lowered to 0.3 per cent, and froin this pulp a high alphacellulose, averaging 03 per cent, can be produced. There arc collected at. a few p i n t s in this country somc 70,000 tons of peanut hulls available a t a cost of $4 to $5 a ton which might serve as a supplemental source for approximately 20,000 tons of alpha-cellulose. Acknowledgment Grateful acknowledgment is here made to L. It. Jones, of the Soubhern Oil and Feed Blills, fetersburg, T’a., for much valuable trade information and the samples of hulls received from hiin in the course of this nork. Literature Cited A m , Dyestiu? R i p l r . , 16, X I 3 (19171. Assocn. OITicial Agr Chem., Slrihodi, 1920, p . 96. Eelrni, Foio/orsrhund. 6, 98 (19271. Bray nnd Peterson, I N D ENC.Cnzx., 19. 371 (1027). Bull. Ini~mioiInsi.. 26, 122 (19271. l i n r . Am. Econ.. Pcunul CCrc. 601, 4 (March 13. ISLPj. (7) EmIry, IN”. ENC. CLIPIS., New3 Ed., 6, 3 (November 10, 18281. !S) Pied, Peterson. and Anderson. 1x0. BNO. Cs*bz., 16. 186 11913) (1) (2) (31 (41 (51 (6)
(111 Jackson. Tcxlilr World. ‘IS, No. 8, 21 (1928). (12) Kirkpatrick, Chem. M r l . Enp., 36. 401 !1928). (131 L e v i , A M congress0 naz. chim. Dura opDlicolo, l92S, 270:
2270 (1928,. (141 Mrrrkiey, J. A m . SOL.A r m . , 20, 1102 ( 1 9 2 8 ) . (15) Memcth. British Patent 184.910 (August 31, 19221. (16) oisen, I N O . BBO. ceer., ai , 356 (192s).
C. .I.. 23.
August, 1930
I S D U S T R I A L AND EIVGINEERI9G CHEMISTRY
P a p e r T r a d e J . , 83, 43 (December 23, 1926). P e a n u f J . , 8, No. 1, 39 (1928). P e a n u t P r o m o t e r , 1, No. 8, 52 (1918). Ibid., 1, No. 8, 49 (1918); 3, No. 5, 20 (1920). Ibid., 2, KO.15, 28 (1919). Ibid., 2, No. 1, 141 (1919). Redgrdve, P a p e r M a k e r s Monlhly, 64, 391 (1926). Rommel, ISD. Exc. CHEX., 20, 716 (1928). (2.5) Schorger. “Chemistry of Cellulose and Wood,” p. 512 (1926).
(17) (18) (19) (20) (21) (22) (23) (24)
907
(26) Schorger, I b i d . , p. 539. (27) Shaw a n d Bicking, Bur. Standards, T e c h . Paper 340, 323 (1927). (28) Sieber a n d Walter, Papier-Fabr., 11, 1179 (1913). (29) Spirindelli, Notia. c h i m . ind., 1, 412 (1926). (30) Sweeney, U. S. Patent 1,639,152 (August 16, 1927). (31) U. S. Dept. Agr., Bull. 1401, 76 (1926). (32) Webber, IHD. EKG.CHEM., 21, 270 (1929). (33) Yamamoto, U. S. Patent 1,436,747 (November 28, 1922)). (34) Yamamoto, Cellulose I n d . Tokyo, 4, 53 (1928).
Colloids in Granulated Sugar‘ C . F. Bardorf S T . LAWREXCE SUGAR
REFISEEIES,?.fONTREAL,
T
HE question of colloids (highly dispersed cane wax) in granulated sugar was brought to the attention of the author by the claim of certain soft-drink manufactcrers that some granulated sugars tend to coagulate the flavoring extract used in the preparation of aerated Leverages. This coagulation becomes apparent in one of two ways-the bottled product loses its brilliancy or some of the extract forms a flocculent collar on the surface of the liquid. It is the contention of these manufacturers that some quality in the granulated sugar is the primal cause of this phenomenon. Strange to say, granulated sugars of superior quality, from a refiner’s point of view, have proved more troublesome in this respect than those of admittedly inferior quality. For the purpose of rapid comparison, granulated sugars were subjected to three tests: (1) by observation of the brilliancy and color of the crystals under a daylight lamp, ( 2 ) by observation of a 50 per cent solution in a white glass tube (Nessler, 3/4 X 18 inches; depth of liquid, 12 inches), and (3) by a percolation test. The percolation test is made in a 1 X 4 inch glass tube. The tube is filled with the sugar to be examined and slightly tapped to settle the grains, and then 5 to 10 ml. of cold distilled water are dripped slowly on the sugar. As the water percolates through the crystals. it carries with it any coloring matter and also much of the colloidal wax. When the water has penetrated about 2 inches ( 5 cm.) of the crystals, a ring IS formed in the tube at the bottom of the descending column of water. This ring may be light yellow, or brownish, and when colloids are present to an appreciable extent, mill have a decidedly gray tinge. From the character and intensjty of the ring a fair estirnate can be made of the relative quality of the sugars under examination. Though admittedly crude, this method does enable the refiner to establish the variation in the so-called standard granulated sugars. Experimental With the cooperation of an aerated beverage manufacturer ten samples of granulated sugar were tested by preparing simpleasirups from the sugars and then adding an emulsified preparation which had previously been known to separate from the finished beverage. The usual trade bottles were filled with properly diluted extract and sirup and set aside for observation. After 2, 3, or 4 days a record was made of the condition of the beverage with respect to the absence or presence of coagulated or flocculated extract. Remarkable differences were to be observed; some bottles showed distinct rings of closely packed coagulated material while others exhibited loose flocculations. 1
Received April 23, 1930
Presented before t h e Division of Sugar
Chemistry a t t h e 79th Meeting of the American Chemical Society, Atldnta,
Ga , April 7 t o 11, 1930.
CAKADA
In the accompanying table the quality of the sugars is indicated in accordance with the three tests and degree of flocculation. Percentage of ash is also given. The sugars are classed as a,b, and c, according to their relative merits, in each column. Under flocculation, a indicates little or no flocculation; b, intermediate; and c, the maximum. TEST SAMPLE
TEST
1
2
a b b b
7 8
a a b b b b
c
c
9 10
a
1 2 3
4
5 6
a a
a
a
b a b
TEST 3
a a
b b b b c a a b
FLOCCLTJRBIXTY ASH Per cent a 0.0030 a 0.0076 b C C
c a a a b
0:00i0
0.0136 0.0164 0.0104 0.0020 0.0050 0,0074
LATIOX C
b b a a
C
a b a c
A critical examination of the table throws little light on the cause of flocculation. Since sugar of inferior qualityfor example, samples 4 and &proved satisfactory, samples 1 and 2 were found unsatisfactory. Again, the average percentage of ash of sugars classed as a, under flocculation column, is 0.010, while classes b and c contain, respectively, 0.005 and 0.009 per cent of ash. It was ascertained that sugars 1, 2 , G, and 10 had been refined from Katal raws; 4 and 5 from Cuban’s, and 8 and 9 from British R e s t Indian raws. It is further to be noted that a second lot of sugar No. 7 was subjected to another experiment and test and fell into the c class under turbidity, but nevertheless maintained its status as a in flxculation column. Conclusion
It would appear, then, that so far as this preliminary investigation has gone no conclusive data have been found to suggest the cause of flocculation produced by certain granulated sugars in beverages of this kind. General excellence of a sugar does not guarantee non-flocculent tendencies in the products. Indeed, from the observation of samples 1, 2 , 8, and 9 perfectly satisfactory beverage products would be expected. But since all granulated sugars ( S o . 2 excepted) refined from Satal raws fall into the c class as regards floc production, it is to be inferred that the colloid dispersion in this sugar has some adverse influence. That the nature of the dispersions, rather than the quantity of colloids present in the granulated sugar, is a determining factor is suggested by the fact that sugars 4 and 5 gave the most turbid solutions of the ten lots examined, and strange to say, produced no flocculation. Finally, samples 1, 2, 3, and 9 are to be regarded as very fine examples of standard granulated and are fully up t o the best comxercial products of their class.
