February, 1933
IXDUSTRIAL AND ENGINEERING
while disodium phosphate has merit as an emulsifying agent below p H 10.2, in the presence of soap, trisodium phosphate rather than disodium phosphate should be used.
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165
CHEMISTRY
24, 1051-7 (1932).
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RECEIVED August 2, 1932. Presented before the Division o€ Colloid
LITERATURE CITED
Chemistry a t the 84th Meeting of the American Chemical Society, Denver, Colo., August 22 t o 26. 1932. Publirrhed b y permission of The Provident Chemical Works, a subsidiary of The Swann Corporation. The experimental work was carried out b y Elbert L. Jung a n d t h e results prepared for publication b y Beatrice F. Grey
(1) Baker, IND.EBG.CHEV.,23, 1026-32 (1931). (2) Chapin, 0 2 1 &. Fat I n d . , 4, 15-21 (1927). (3) Fall, J. Phys. Chem., 31, 801-49 (1927). (4) Snell, ISD.EXG.C H E V, 24, 76-80 (1932).
Purification of Brine by Ammoniation w. c. HSIEH,E. 0. WILSON, Yenching University, Peiping, China, , ~ N DT. P. Hou, Pacific, Alkali Company, Tangku, China T T H E Pacific Alkali Company a t Tangku, near Tientsin, China, sodium carbonate is manufactured by the Solvay process from crude salt obtained by the solar evaporation of sea brine. The salt used contains a higher percentage of magnesium than the rock salt or natural brines that are largely used as raw materials for the manufacture of soda ash in other parts of the world. I n order to produce a product of sufficient purity and to avoid clogging the carbonating towers, it is essential that the magnesium be largely removed early in the process. This paper presents the results of a study of the factors influencing the precipitation of magnesium by ammoniation. Recovered gas containing ammonia and some carbon dioxide from the filters, carbonating towers, ammonia stills, etc., meets the crude brine and serves to introduce the required amount of ammonia into the brine, a t the same time precipitating the calcium, magnesium, and oxides of iron and aluminum. TElis process avoids the addition of any special precipitating agents, such as lime or soda ash, and under proper conditions efficiently removes the calcium and magnesium. The chief defect of the method is the coprecipitation of sodium carbonate and sodium chloride which results in a considerable loss of alkali. Further work on this phase of the problem is now in progress.
A
gas through the solution. To obtain the higher concentrations of ammonia, it was found necessary to cool the brine after a preliminary heating to 60-65" C. to cause coagulation. Samples were withdrawn through a rubber-tipped pipet, the rubber tip being covered with filter paper. Total ammonia was determined in the filtered samples by the Kjeldahl method, and magnesium by the gravimetric method, weighing as magnesium pyrophosphate. The results are shown in Figure 1 and the following table: EXPT. T O T A L37% Grams/Ziter 1 10.49 2 14.49 3 28.59 4 41.02
JIg Mg./lite? 511.9 328.9 160.7 128.8
EXPT. TOTALNH3 M g Grams/laler M g . / h t e r 5 65.30 114.0 6 81.36 111.5 7 88.78 109.9
The magnesium remaining in solution in the brine decreases as the concentration of total ammonia increases, the optimum concentration being between 20 and 40 grams per
EFFECTOF COKCENTRATJON OF ANMOKIA ON PRECIPITATION OF MAGNESIUM The sea salt, obtained by solar evaporation, is collected in large piles. On standing through the rainy season, a large amount of the more soluble magnesium compounds is leached out. For this experiment a sample of freshly harvested salt was used as representing the worst possible conditions. Analyses of samples of new and one-year-old salt are as follows: OLD SALT KE% SALT
% Cas04 MgSOi MgClz NaCl
1.17 0.12
g;:$;
OLD
72 1.I02
s!:g0; . 8 1
Insol. matter Moisture and combined HzO
SILT. % 0 58
s 4 L T ' NET5
% 0.64 5.34
10 43
A solution of the salt of specific gravity 1.2 was made, using distilled water. Insoluble impurities wire removed by filtration. Sufficlent ammonium carbonate was added to precipitate all of the calcium in the brine and leave an excess; then the magnesium was precipitated by bubbling dry ammonia gas through the solution. The temperature of the brine during ammoniation was kept between 60" and 65" C. by means of a water bath. The temperature and pressure of the gas were keot constant. No agitation of the brine was provided except that furnished b y t h e bubbling of the
Total NH3 in AmmoniatedBrinc,gram//iter
FIGURE 1. AMMONIA AND MAGNESIUM IN AMMONIATED BRINE
liter. It is probable that the precipitate formed is a basic carbonate, and the solubility is certainly influenced by the presence of sodium chloride as well as the ammonia.
EFFECT O F TEMPERATURE O S SETTLIKG RliTE O F CALCIUMASD MAGKESIUM PRECIPITATES Ammonia gas was bubbled through a solution of the brine, made as above and containing an excess of ammonium carbonate, until the concentration- of total ammonia was
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I N D U S T R I A L A N D E N G I K E E R I N G C H E R;I I S T R 1-
166
within the optimum range. Actually a concentration of 22.7 grams per liter was obtained. This ammoniated solution was poured into cylinders with stoppers, and placed in thermostats kept a t 30", 40", 50°, 60", and 70" C., respectively. The heights of the precipitates were measured every hour. The percentage of settling for each interval of time was calculated and plotted against time. As the critical I401
1
VOI.
23,
so. 2
The rate of flow was obtained by actually measuring the volume of the clear liquid flowing from the tenth bottle. The results are expressed in terms of the number of bottles required to produce a clear solution. Samples were withdrawn from the bottles and examined in Kesaler tubes. The rate of flow was adjusted by means of a leveling bottle placed between the absorber and settling bottle 1. The results are shown in Figure 3 The number of vats, shown as abscissa, refers to the number required to obtain a clear effluent a t the corresponding rate of flow. A straight-line relationship is obtained.
APJALYSISOF SCALE FRO11 AMMONIATION SYSTEM Two samples of scale were taken, one from the absorber main and one from the discharge pipe at the absorber bottom. The first sample was taken on June 15 and the second on July 15, 1931. The results of the analyses, in terms of the calculated compounds, are given in the following table: SAMPLE % . Insoluble mntter CaCOs hIgCO3
(NHdzSOa
NazSOh FeS Fez03 and AIzOs
NaC1
N a H C 0 3
L
'1
2
3
Hours
NazC03 NHaHCOs H 2 0 (by difference) Total
I
4
5
FIGURE 2. SETTLING RATESOF PRECIPITATES
PRECIPITATES 2.5hr. 3hr. 3.5hr.
H E I Q H T S OF
OC.
30 40 50 55 60 65 70
%4
92.5 91.6 91.5 90.1 88.4 88.0 43.5
% height
Uhr.
2hr.
%
%
91.2 90.5 89.5 90.5 89.5 88.5 89.5 86.0 81.4 76.0 74.0 44.0 14.5 4.85 height of ppt. total height of liquid
70
0.350 6.880 30.650
0.165 16.480 27.639
0.019
0.299
0.105 0.010 0,232 19.152 0.785 34.695
O:i)38 0.030 21.400 2.630 37.330 0.232 0.441 100.000
0 .' 438 13m05
MOLECULAR PROPORTIONS
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temperature was found to be between 50" and 60" C., this experiment was repeated for 55" C.; in this case a concentration of ammonia of 20.7 grams per liter was obtained. The results are shown in Figure 2 and the following table: TEMP. l h r .
SlhlPLE
70
--. 4hr.
%
%
%
%
88.9 88.6 87.0 82.5 52.0 13.8 3.9
87.9 87.0 85.6 77.0 33.4 5.3 3.4
86.9 85.5 84.5 67.0 12.8 4.4 3.4
85.4 84.0 82.0 51.0 4.9 3.9 3.4
'O0'
KUMBEROF SETTLING VATS REQUIREDvs. RATE OF
FLOW I n this experiment a large volume of saturated brine, containing a constant quantity of precipitate and ammonia, was needed. This was obtained from the bottom of an ammonia absorber a t the Pacific Alkali Company. The
Boftles R o u t e d
FIGURE3. NUMBEROF BOTTLES REQUIRED TO PRODUCE A CLEAR SOLUTION
temperature of the ammoniated brine varied from 62.5" to 66.0" C. Ten 5-liter bottles were connected in series and attached to the pipe leading from the ammonia absorber.
21.400
58.46
=
0 . 3 6 6 mole
NaiCOa
=
0 . 3 5 2 niole
hlgCOa
=
0 . 3 6 3 mole
yi,?:
--
= 0 . 3271; ini,le
34g2 F4$g
=
0.3276 nir~le
=
0.3:?77 niole
Thus both samples, collected a t different times and from different places in the ammoniation system, show the same molal ratio of sodium chloride, sodium carbonate, and magnesium carbonate-i. e., 1:l:l.
DISCUSSION OF RESULTS The results show that the efficiency of the precipitation of magnesium compounds in ammoniated crude brine is greatly influenced by the concentration of ammonia. The rate of settling of the resulting precipitate is a function of the temperature and the rate of flow of brine through the system. It is obvious that the concentration of magnesium is also important Experiments not recorded here have shown that higher concentrations of magnesium cause the formation of a thick colloidal precipitate which settles with difficulty. The occurrence of sodium chloride, sodium carbonate, and magnesium carbonate in molecular proportions is of considerable interest. The brine, entering the ammoniation system, soon becomes less than saturated, owing to the action of the ammonia and the condensation of water vapor carried by the gas. Samples of the brine from the ammoniation system will actually dissolve more sodium chloride if it is added. The formation of sodium carbonate is also unexpected a t this point as the concentration of carbon dioxide is not high enough to precipitate even the bicarbonate. These facts, together with the results of the analysis of the scale, led the authors to suspect that the sodium chloride, sodium carbonate, and magnesium carbonate were precipitated together as a triple salt. I n an attempt to verify this point, a complete study of the mutual solubilities of the three salts in distilled water was made a t 20" and 55" C. The results of this study showed that no triple salt was formed with the pure compounds a t these temperatures. The low solubility of the magnesium
February, 1933
INDUSTRIAL AND
ENGINEEHIXG CHEMISTRY
carbonate and the absence of ammonia and carbon dioxide in the case of the laboratory solubility experiments doubtless account for the difference. I n the plant the magnesium is present as chloride and sulfate, and is probably precipitated hst as a basic partially ammoniated carbonate, which changes over to the normal salt shown by the analysis. The formation of such a triple salt frcrm solutions of' magnesium chloride, sodium carbonate, and sodium chloride was claimed by de Schulten, but little information is available concerning 1 Mellor, J. W., "Comprehensive Treatise o n Inorganic and Theoretical Chemistry," Vol. 111, p. 367, Longmans, 1924.
167
its properties or exact method of formation. The loss of alkali due to the co-precipitation of sodium carbonate and sodium chloride amounts to about 4 and 2 tons, respectively, per hundred tons of soda ash produced. The purity of the final product is, however, very satisfactory, analyzing 99.04 per cent sodium carbonate. Experiments are now in progress with the object of finding a n economical method of removing the magnesium from the brine before it enters the ammoniation system. RECEIVED .4upup.t 27, 1932.
Photochemical 0.xidation of Cottonseed Oil GEORGER. GREENBANKAND GEORGEE. HOLM Bureau of Dairy Industry, 1 :. S. Department of *\griculture, Washington, D. C.
A
T h e relalire accelerating effect of light of filters ( 3 ) p r e p a r e d by filling Petri d i s h e s with solutions of that heat and light acdifferen[ of the visiblf specfrun upon the dyes or inorganic salts and sealcelerate the autoxidation aatoxidation of cottonseed oil is studied. The ing the space between the bases of fats and oils. However, there greatest accplerafi%' effect is nofed in the range and covers w i t h s e a l i n g wax. seem to be no available data on Thesefilterswerepermanentand of fhe oranae band; the blue range is fhe least t h e relative effects of various easily prepared. In making the bands of the spectrum upon the effeciipe. comparisons, it mas necessary p r o m o t i o n of these oxidative that the transmitted energy for c h a n g e s , notwithstanding the general impression that light transmitted by amher glass of each range of wave bands used should be equal. To accomplish this, a thermopile (described by Coblentz, I ) was placed various shades is the least effective in this respect. Because of the general practice of packing fat-containing in the position to be occupied by the fat container and the products in glass containers of various colors. a better knowl- light source adjusted in each case to give equal deflections edge of the relative accelerating effect of different spectral of a galvanometer. Table I1 gives the oxygen absorption per 100 grams of bands of light upon fat oxidation is of consideraLle practical fat when light from different sections of the spectrum was interest. studied. These results confirm the qualitative observations OXYGEN ABSORPTIOX CAT.4LYZED BY L I G H ~ and indicate that the orange band of the spectrum is decidedly more powerful as an accelerator of fat oxidation T h a t oxygen absorption by a fat is strongly accelerated than are the red, green, or blue bands. There also seems by light of the visible spectrum is indicated by tlie results of to be an indication in these results that yellow-orange light the following experiment. is more powerful in this respect than is orange-red light. One hundred prams of cottonseed oil were placed in a dosed tube with a small side tube t o R hich I\ as attached t graduated TABLE I. RELLTIVE C.4TlLYTIC EFFECT OF LIGHT OF J-ARTING gas buret containing oxygen The tube containing the fat was ISTEXSITY so arranged that it could be shaken continuouslv, thus producing LIGHT 01 ABSORBED BY PHOTOthorough mixing of the fat and ovvgen To askertain the effect INTEKSITT TIME 100 0 . Of OIL ACCELERATION of light of the visible spectrum, the beam of light from a proHours cc. X check jection lantern carrying a 500-matt hIa7dn lamp I\as directed None 8 0.2 1.0 Diffuse upon the tube. A filtw prepared from a solution of 17 grams 8 1.1 5.5 IntenPe 13.1 8 65.5 of copper sulfate in a liter of Yater R as used to sei een out the infra-red rays, and this filter was cooled xith a currmt of air. TABLE11. ABSORPTIOSOF OSTGES BY COTTONSEED OIL \VHESThe absorption of oxygen by the fat, when kept in the dark PLACED IS LIGHTOF VARIOCS BANDSOF VISIBLE SPECTRUM and when subjected to the diffuse light of a room and to the LIGHT TIME ABSORPTIOS OF TRlKSMITTED B.4sD OF EXPT. 0 2 PER 100 CC. strong artificial light described, waq determined. The 2. FIours cc . results are given in Table I. 4450-4950 Upper blue 8 2.60 UTHORS generally agree
OXYGEN
ABSORPTION iiCCELERATED BY LIGHTFRO\l PARTS OF SPECTRUM
T'SRIOL-S
Qualitative observations had been made from time to time which indicated that the light of the red m d of the spectrum was the most active as a fat-oxidation accelerator. T o ascertain the most effective wave bands as well as to determine their relative effects, the oxygen absorption by samples of cottonseed oil in different lights consisiing of wave bands covering a range of approximately 500 -4.each mas measured. The desired spectral band was obtained by the use of
5100-5660 5540-5940 6100-6650 6500-7250
Green 1-elloa Orange Red
S 8
8 8
1.65 5.00 9.20 1.10
RATE OF REDUCTION OF METHYLENE BLUE IN FATSBT DIFFERENT BASDSOF LIGHT The effect of various bands of visible light as accelerators was studied further by means of the methylene blue reduction method published by the authors ( d ) , wherein the time of reduction of a n alcoholic methylene blue-fat solution is determined. The time of reduction is a measure of the resistance of a fat to oxidation.
