INDUSTRIAL AND ENGINEERING CHEMISTRY 1152 Biochemical Oxygen D e m a n d , P. P. 1'1. Reduction. % P r i m a r y Chemical Primary Raw waste effluent effluent effluent Over-all 76.8 484 11.6 1832 2076 35 78.2 84.5 921 601 199 1649 1384 255 16 780 603 192 36 75 1160 840 130 27.6 88.5 E65 396 269 40 8 . 6 TABLE 11. TREBTMENT O F R a t e Applied 12 Hr. E a c h Day. Millions of Gallons per Acre precipitation applied to a pilot plant trickling filter 6 feet deep by 4 feet in diameter. The pH of the applied waste varied from 4.8 to 5.0. The first four and the last four sets of figures each represent consecutive days. Type of Slaughter Hogs a t plant capacity Cattle a t plant capacity Cattle and hogs a t p!ant capacity C a t t l e and ho.3 a t plant capacicy C a t t l e below capacity Cattle and hogs below capacity EFFLUENT ON TRICKLING FILTER B.O.D. Applied per Acre-Foot/ D a y , Lb. B.o.D.* P.P.nI* Influent Vol. 40, No. 6 Effluent B.O.D. Removal, 73 CONCLUSION -1 process has been described which will produce a major reduction in the strength of meat packing wastes, while reclaiming a usable product. Unfortunately, the value of the product pays only a small part of the maintenance, operating, and fixed expenses. Attempts t o separate the fat from the protein in the final product have not been successful, and neither has separate reclamation of the fat been accomplished prior to precipitation. If the fat and protein could be recovered separately, a much brighter economic picture might be presented, as the protein, freed of fat, would be m-orth more, and the fat would have a value exceeding that of the present product. LITERATURE CITED (1) Halvorsen, H. O., Cade, A. R., and Fullen, W. J., Sewage W o r k s J . , 3, 4 8 8 (1931). (2) Mortenson, E. X,, Proc. of Second Industrial Waste Conference, P u r d u e Univ. Eng. Bull. 60, 28 ( 1 9 4 7 ) . (3) Banders, M. D., U. S,Patent 2,204,703 (June 18, 1 9 4 0 ) . (4) I b i d . , 2,277,718 (March 31, 1942). The effluent from this type of chemical precipitation can be successfully treated on a standard type trickling filter. Table I1 gives the results of application of the effluent from chemical RECEIVED April 12, 1947. Presented before the Division of Water, Sexape, and Sanitation Chemistry at t h e 111th 3Ieeting of t h e . h E R I c A X CHEMICAL SOCIETY, Atlantic City, S . J. D. R. TORGESON Paci$c Experiment Station, C . S . Bureau of Mines, Berkeley, Calif. T HE nork reported in this paper m s prompted by requests from industry for data needed in conducting heat-balance calculations for the process of calcining trona t o soda ash. Such calculations have been hampered mainly by lack of a suitable heat of formation value for trona. From heat of solution measurements involving trona (NazCO3.NaHCO3.2HZ0),sodium carbonate, and sodium bicarbonate, the heat of formation of trona from its constituent compounds now has been determined and the heat of calcination evaluated. MATERIALS Three samples of trona were employed: Sample A, natural trona, was selected massive crystals from Marston, Wyoming, furnished by Westvaco Chlorine Products Corporation through the courtesy of J. A. Robertson. The crystal surfaces were scraped clean before crushing to -60 mesh. Analysis shoRed this material to be highly pure. Titration with standard hydrochloric acid gave 99.94% of the theoretical value for trona; the ignition loss a t 290" C. was 99.87% of the theoretical value; no chloride was present; and the water-insoluble residue was only 0.05%. The latter consisted of hairlike stringers presumably of clay. Sample B, synthetic trona, was prepared as follows: To 1000 grams of hot water there were added slowly, while stirring, 150 grams of sodium carbonate, 60 grams of sodium bicarbonate, and 200 grams of sodium chloride. Heating and stirring were continued until the solution became clear; the final temperature was about 100' C. The solution then was cooled slowlv, over a period of 30 hours, to an end temperature of 35' C.. to permit formation of trona crystals. The crystals mere removed, drained, washed lightly with 95Yc ethanol, and dried for several hours a t room temperature in a stream of tank carbon dioxide; drying was completed after crushing to -60 mesh. This process yielded material containing sodium chloride and sodium carbonate as impurities which resulted from incomplete drainage of mother liquor and incomplete washing. Attempts a t more thorough washing were not too successful because almost invariably some sodium carbonate was leached from the trona itself; this left an indefinite product. I t was consideied better, therefore, to permit the sodium chloride and carbonate to remain and make correction for them in the heat of solution results. Analysis of sample B indicated 97.72% trona, 1.75% sodium chloride, and 0.5391, sodium carbonate monohydrate. Sample C also was synthetic trona. I t was prepared like sample B except that freeing of the crystals from mother liquor impurities was less complete. Analysis gave 95.66% trona, 2.37% sodium chloride, and 1 . 9 7 5 sodium carbonate monohydrate. Reagent grade sodium bicarbonate was treated n-ith tank carbon dioxide for several hours at room temperature. Titration with standard hydrochloric acid showed virtually 100% purity. Sodium carbonate m s prepared from reagent grade sodium bicarbonate by heating a t 290' C. to constant weight. This material was employed in the heat of solution measurements and also served as the basis for standardizing the hydrochloric acid used in titrating the trona and sodium bicarbonate samples. 1153 INDUSTRIAL AND ENGINEERING CHEMISTRY June 1948 EXAMPLE OF >IEASURE.MESTS AND CALCULATIONS T.~BLE I. Step X o . 1 2 3 4 COJfPOSITIOT O F SOLUTIOXs (Run S o . 2, Natural Trona) 24.80' C. 1814.9 gram.: Composition 6,000grains of trona dissolved in 1814.9 grams of water 2 . 8 1 4 grams of sodium carbonate dissolved in 1814.9 grams of water 2.230 grams of sodium bicarbonate dksolved in final solution of step 2 0 . 9 5 6 grain of \vater dissolved in finalsolution of step 3 Therniostat teniperature constant a t Wt. of water in Deirar (corrected t o vacuuiii) Vit. of trona in saniple bulb (corrected t o vacuum) T i n e in therilloarat before s t a r t oi run Resistance thrrinnmetrr current innintained at 11in. rrona, Trona, Trona, Sample A Sample B Sample C SasC03 SallCOI r- ----------Calories per mole 1 6215 6201 A218 - 5309 3750 2 6220 6211 6218 - 5283 3754 3 6222 6227 - p288 3756 Mean 6219 2 4 6200 & 10 6221 & 6 -2294 j=15 3753 j=4 Convention as to signs: evolved heat ir negati7-e: absorbed heat is positive. ZIE.ISURE3I ENTS A S D RESULTS Thc. ap!i:aratus employed \ m s that descrilied by dout,liarcl ( $ ), with mirior modifications by 170uny ( 6 ) . Purc ~ w t e r\vas the solrent in thc hclat, of solution nieasureiiieiitrj. The aiiiourit s oi niatcrials clissulved Jwre such t h a t the, final average coiiceiitration \v:ts that obtained from 6.000 grmih of trona in 1814.9 grams of n-ater (vacuuiii \\-eighiiigs). Solution steps for which heats n-ere nieaiui.ed aiid t h e coi,respoiidiiig solution coiiipositioiis are indicated in Tahlc I. It is iilivious that, the .solutioii rwultiiig iroiii comt)incd strps 2, 3, :tiid 4 i-: tht, sairir as that from step 1. M w s u r t d heat of solutiori r i w l t s UI'P sho\\-ri in Table 11. They arc expresed in defiricd calorirs (1 cal. = 4.1833 international joules) per molo ( 3 ) . ~Iolccular n-eights are iii accordance ivith the 1941 Iiitcriiatioiul .Itomic Keights \VeiyIiings n-ere corrected to viicuuiii h\- iiic'aiis of the follon-irig densitici:.: trona, 2.14 grams per e(..; sotlimii carhnatc~,2.53 grams p c cc.: ~ :in11sodiuiri bic,arhonate, 2.21 graiii.; pcr cc. The rcsults for trona nere c.orrccrc~t1for inipuritiel; as i'ollo~~s: s:tinplc A , $3 c:d. cori,ecrion for the iuwlulilc re5idue: siiiiiplt. B, net corrwtion of $70 csl. for sodium carbonate monohyclratcs and sodium chloride; saiiiple C, net correction of +233 cal. for sodium carbonate monohydrate and sodiuni chloride. Data for coi~rcctingsaiiiplcs B aiid C \VCI'P taken from Bichon.slr>- and Rosini (1), Sodium carbonate arid bicarbonate result,s required no correction for impurities. Step 4 of T:tble I also \ w s investigated experimentally. It \\-a< found that the lieat of dilution by water of the final solution of strp 3 \vas negligibly siiiall at thi.; concentration. It was equiwt o leqs t,han 1 cal, per mol(. of added lvater. t h c w i,<o1)taiiicd 1H2g8.:6 = -7760 = = 812 3183.2:; r3185.31) Brohe bulb of trona ) 311.5 8.5 9.3 3098 I 3094 3092 3091 Sollition period 3089 3089 ,3089 3088 17 3088 31 3088.44 Strniiy state estahlished 3088.64 3088.83 TYarining rate, Rz = 0.092 P v./min. 3089, on 8089 18 n t e r current on (3089.2ij 11~ 0.190319 I I m t input period for cali0 190316 0 . 1 9 0 ~ 1 ~ bration, 600.4 see. n . i9o,3ii 340'3. c,:i, 11v:iicr current off .im.31 S t i w i y state established 3409.11 10.5 ~ 12 14 18 20 22 24 27 29 31 33 35 3i ~ ~ 38 40 42 44 46 48 51 . - 3-i .>a :um. ijs -_ 3408 A8 .I, 3408.4: s4 Calibration Cnlculntion. 3409.03 p 1.. 3089,27 P v. 320.36 P v. Correction for h e a t interchange with tlierixiostat -n O D ~ 0 , 1 n . j x 10 2 Correcteil teniperature ri-e Average heating current Time of heating Re-iqtunre of lirster coil E n e r g y i n p u t !(0.190516)2 X 9 9 . 4 7 X 600.41 Heat capacity of calorimeter + (:::y) ~ 0 . 0 0 p 7.. 320.42 P v. 0.190516 amp. 600.4 see. 9 9 . 4 7 ohm 2167.7 joule 8 . 7 6 5 joule/@ V. Hear of Solucion Cnlculationr ance tliernionieter, e,m.f. tanFe thermouleter, e.1n.f. Tempizrature rise Correction for heat interchange with thermostat, using r , n i . f . V.Q. rime plot f o r solution yeriod, a' indicated bi,low Tit,,, Interval. Min. 7..5- 8 8- 9 9-10 10-11 11-12 12-14 14-16 16-29 Re5istance Therinometer, e.m.f., ~1 v. Warming Rate. v./min. P 0.057 0 ,O i O 0.088 0.090 0.0'31 0.092 0,002 n 093 Total correction -1.95 II v Corrcc tion. P , v. 0.029 0.076 0,088 0 , 090 0,091 0.184 0.184 1.209 1 .93 Corrected temperature rise Molecular weight of trona XIolal heat of solution 98.82 X 6 . 7 6 5 X 2 2 6 . 0 , i 4.1833 reiidue X Correction for O , O S % insoluble Final value, heat of solution of trona ( 3088.44 P v. 3183.31 P v. -96.8711 v. m-1 - 9 8 . 82 p v. 226.05 g r a m 6217 cal./mole. 3 cal. 6220 cal./mole NaCOa.SaHC03.2HxO LITERATURE CITED 20 cal. per moltLoftrona. To olitaiii t hci hmt of the tl(,c.ompoaition or calcining reaction, SazCOz.XaHC03.2II20 3184.971 TYaiiiiing rate, Ri = 0.073 3 1 8 > , 1 2 , p v.,/min. 7 , L7 HEATS OF FOR&IATION AND DECO>IPOSITION + SiaHCOa + 2Hz0(1) 3184.83 I 1- , I ( 8 i i t The precediiiy dat,a, properly coiiibincd, are suficieiir for awertaiiiing the heat of foriiintion of' trona from its constituent iwnipouiid,i. r1rr.c the mean valur for sample -1n-ill be adopted a9 the hcitt of solutioii of trona: the results for simples 13 :tnd C ax' lws C C A I , ~ niri hecause of the larger corrections for impuritici-. For t lie foi,iii:~tion r(Iactioi1, t!irrinnmetr.r. 3 ;. * 0.02 microamperes Keniarks liraistance e.m f . . ii 1 So. SazC03 1999.50 Log o i R u n Time. TABLE 11. HEATSOF SOLUTIO?;" Riiii 5.8106 grains I10 minutes =t Ta:COa f l/z COz f 5/2 (1j HzO(gj t lirrcl are iiecdixi the heat decomposition of sodium bicarbonat and t,hc IicTitt of vaporization of vatcxr. The former is A H ~ s . l s= 15,460 cal. per iiiole accordirig to Kellc~y(e), and the latter ih j.H?98.16 = 10,519.5 cal. pcr mole according to Wagman arid co-workers (.i). Thc. rcisultiiig hcat of t,he calcining reaction iq AH?yj.i~ = 14,260 * 100 cal. prr mole of trona. (s Bichows!q- aiid Rossini. " T h c r m o c h c m i ~ t r ~of~ Cticmics! Sub- s t m t e s , " pp. 138, 144,XeTT York, R e i n h o l d Pub. Corp.. 1936. ( 2 ) Kelley, C', S . B u r . Mines B i d . 384, 35 (1935). (3) Mueller aiid Rossiiii, Am. J . Phus., 12, 1 (1944). (4) Southard, Iz-D. ESG. CHEY.,3 2 , 1 4 2 (1940). ( 5 ) Waginan, Kilpatrick, Taylor, Pitzer, and R o s ~ i n i .J . Research SalZ. Bur. Standards, 34, 143 (1946). ( 0 ' Toung, J . Am. Chem. Soc., 67, 257 (1945). RECEIVED May 20, 1947. Published by permission of t h e Director, Bureau of Xlines, U. S. Departrnent of the Interior.
