Total Solids in Natural Brines GEORGEZINZALIANAND JAMESR. WITHROW, Ohio State University, Columbus, Ohio ANY workers omit detotal solids determination conIgnition at 750" C. appears to be the most retermination of t o t a l ditions. liable method for determining total solids in natusolids in brines because This work indicated: ral brines containing mixtures of magnesium, it is obviously a difficult detercalcium, and sodium chlorides as major con1. Ignition to constant weight mination of questionable reliaa t 750" C. was the most satisfacstituents, as well as being most certain as to combility. It is rather obvious, for tory, quickest, and most reliable instance, that the heat applied is position o j final ignited residue. Necessary method for total solids determinalikely to decompose some salts tion. corrections must be made according to the formula 2. Low temperatures such as present or fail to dehydrate them. proposed in this paper. 100" t o 150"C. required considerSweeney and Withrow (5) state able time for evaporation, and the Although heating a 25-cc. portion of the natut h a t ''brines r i c h in c a l c i u m a c c u r a c y of t h e results varied ral brine to constant weight at 150" C. gives chloride r e q u i r e a rather high largely depending on the relative amounts of the constituents. temperature, above 160" C., to fairly satisfactory results, the time required to 3. Magnesium chloridehexahyexpel the water completely. At reach constant weight and the necessary breaking drate decomposed practically at. this temperature m a g ne si u m all t e m p e r a t u r e s above 95" C. up of the residue to ensure maximum evaporation and calcium salts lose a part of (much below the temperature of of the enclosed water makes this determination complete dehydration) the rate and their acid constituents," whereas extent of decompositiondepending too tedious and subject to errors. Efremov holds (1) that "direct upon the temperature and length evaporation is likely to cause Since magnesium chloride solutions have a of heating. trouble owing to hydrolysis and 4. Magnesium chloride did not tendency to decompose at low temperatures (above lose all its chlorine a t 750" C., as hygroscopicity. Add 2.0 to 2.5 95" C.) results obtainable by heating mixtures analysis of the ignited residue intimes as much anhydrous Nar dicated the presence of some reof the various pure salts to constant weight at COS dissolved in hot w a t e r , sidual chlorine. 150' C. were not suflciently reliable. Results evaporate to dryness, heat a t 5. Calcium chloride a parently does not readily dehygate, 105" C. for one hour and then a t at 105" and 120" C. were sometimes as much as retaining 2 to 3 per cent water af150" C. for 5 to 6 hours." 12 per cent in error. ter being subjected t o heating at Phalen, who appears to have 150' C. for 40 to 50 hours. It done the most work on brines decomposed only s l i g h t l y at (4), reports that for total dissolved salts ''a convenient 750" C. (less than 0.5 per cent). Sodium chloride dry or in solution does not. show loss due volume of the dilute solution was evaporated to dryness in a to 6.decomposition or volatilization when dried at 750" C. in a weighed platinum dish and the residue was heated to constant muffle furnace. weight a t 105" C., cooled, and weighed. This estimate is not 7. Mixed solutions of these salts show greater loss due to reported but was used as a check on the analysis." Mellor volatilization and decomposition when ignited at 750" C. than in his discussions of properties of magnesium chloride (2) do the salts alone. states that "the hydrated salt cannot be dehydrated without EXPERIMENTAL PROCEDURE a loss of hydrogen chloride by simple heating, that according to F. P. Dunnington and F. W. Smither, all but one mole of SOLUTIONS.Stock solutions of the pure salts of magnesium the water of crystallization can be expelled a t 98" without chloride (hexahydrate), anhydrous calcium chloride, and decomposition, and the principal loss of hydrogen chloride sodium chloride, c. P., were prepared by weighing 20 grams occurs during the expulsion of the residual water." Mellor of each salt and dissolving each in 500 cc. of distilled water. furfher states (3) regarding properties of calcium chloride that SAMPLES. Different concentrations of these solutions were according to Bunsen, "even after the salt has been melted a t a subjected to the same heating conditions to see if dilution of white heat, it retains enough water to develop hydrogen when the solution would have any effect on the final result. melted with iron," and according to A. Weber, "the salt ANALYSIS.Twenty-five cubic centimeters of each of these dehydrated a t 200' C. is anhydrous." stock solutions were diluted to 1000 cc., and 25 cc. of these The literature is conflicting regarding decomposition of diluted solutions were then used for titrating with 0.1 N silver magnesium and calcium chlorides. Numerous temperatures nitrate solution using potassium chromate indicator (chlorine(98" to 157" C.) are reported a t which magnhkium chloride free). The chlorine content of each solution was used as a hexahydrate begins to decompose. basis in calculating the purity of the salts. Filtration of the I n any event we should have more precise information, calcium chloride solution was found to be necessary, as a since the value of this determination cannot be neglected as it certain amount of insoluble matter remained in the solution serves the double purpose first of giving the engineer (manu- when preparing stock solution. facturer) figures which could be used in calculating fuel reHEATING. Three different samples were used for each quirements for evaporation, and second, of serving as a check concentration or mixture of the salts, marked 1 , 2 , 3 . Sample on the analysis. Therefore, in this investigation pure salts 1 was ignited a t 750" C. to constant weight after an initial (c. P.) corresponding to the major constituents of the total drying a t 105" C. to prevent loss by spattering. Sample 2 solids in natural brines, such as sodium, calcium, and mag- was placed in an oven a t 105" C. and heated to constant nesium chlorides, were used. weight, and sample 3 was dried a t 120" C. to constant weight, First, the salts in solution were subjected -to heating a t cooled, and weighed. Samples 2 and 3 were then both placed various temperatures separately, then mixtures of these in an oven a t 150" C., allowed to reach constant weight, again solutions were also subjected to the same heating conditions cooled and weighed, and finally ignited a t 750" C. in a muffle to learn precisely what their behavior was under the customary furnace. 210
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
April 15, 1932
211
Since the loss of chlorine appeared obvious at the temperatures employed and reached a maximum decomposition at 750" C., the original weight of the sample was calculated UNDER HEATING STABILITYOF VARIOUSSALT SOLUTIONS (column D) as magnesium oxide instead of magnesium chloride CONDITIONS (column B). When the weight of the dry residue was divided Tables I through V show the study of the behavior of salt by the weight of the original sample, it gave as per cent resolutions under heating conditions. Because of limited covered 102.6 per cent a t 750" C. The results a t all the other space, data on several of the systems studied, such as pure temperatures should of course give correspondingly higher calcium chloride and pure sodium chloride, have been omitted. values with this method of calculation. MAGNESIUM CHLORIDE.The data of Table I show disThe column marked "Error" gave excellent support to the tinctly that all solutions of magnesium chloride, regardless of conclusions in that the variations in per cent error were much concentration, decompose, the extent of decomposition greater for 150' than they were for 750" C. I n the latter case the error was small and not affected by concentration or duradepending upon the temperature and length of heating. Assuming, however, that magnesium chloride solutions tion of evaporation. dehydrate without decomposition and calculate as such, the The final conclusion was that magnesium chloride solutions recoveyy at 105" C. (100 per cent concentration) is 131.6 per did not dehydrate uniformly at low temperatures. A temperacent (column C), the recovery a t 120" is 124.9, at 150",103.1, ture of a t least 700" C. should be employed for more uniform and a t 750" C. only 43.5 per cent. The recovery as per cent of results. High dilutions appeared to be the severest test for original sample a t 150" C. at this concentration appears to be studying evaporation conditions and influence. Therefore, the best, but not at all concordant, as indicated by the results dilute solutions were used in all subsequent work. and per cent error a t different concentrations. The results MAGNESIUM AND CALCIUM CHLORIDES.The data of Table obtained at 750" C. (calculated as magnesium chloride) were I1show that with increase in temperature of drying for any convery consistent, with the sole exception of 2.5 per cent con- centration of magnesium and calcium chlorides,there was a corcentration, which was 42.8 per cent These 750" C. results responding decrease in per cent recovery approaching the true were closer to the facts as shown by both recovery and per value a t 150" C. only. However, as the concentration of cent error, and conclusively prove the instability of magnesium chloride decreased in the mixture, the per cent magnesium chloride at this temperature. recovered at 750" C. rose from 72.5 to 96.2. This was Analysis of the residues at 150" and 750" C. showed that calculated under the assumption that magnesium chloride loss of chlorine was greatest at 750" C., where there was a did not decompose a t 750" C. If calculated on the basis of chlorine content of approximately 0.005 gram, present 100 per cent decomposition into MgO, then the per cent probably as MgOClz or MgO.MgClz. recovered as of original weight of sample (column E) was
This stepwise drying of samples 2 and 3 was for comparison with direct ignition on the rate and extent of decomposition.
TABLEI. MAGNESIUM CHLORIDE (HEXAHYDRATE) SYSTEM CONCENTRA-TEMP. T I O N OF
MgCh
% 100 (solid)
50
25
10
2.5
c
WT. AFTER DRYINQ DRYING 1 2 3 c. Gram Grams Grams 1.541 105 120 1.461 150 1.23 1.184 750 0.509 0,509 0.509 105 1,498 120 1.416 150 1.22 1.104 750 0.502 0.513 0.509 1.504 105 1.439 120 1.343 1.123 150 750 0.507 0.509 0.510 105 1.558 120 1.471 1.48 1.126 150 750 0,512 0.509 0.510 1.521 105 1.460 120 1.334 150 750 0.500 0.508 0.490 OF
A. Residue av. Grams 1.541 1.461 1.207 0.509 1.498 1.416 1.165 0.508 1.504 1.439 1.233 0.508 1.558 1.471 1.301 0.510 1.521 1.460 1.334 0.502
B. Original sample Grams 1.1711 1.1711 1.1711 1.1711 1.1711 1.1711 1.1711 1.1711 1.1711 1.1711 1.1711 1.1711 1.1711 1.1711 1.1711 1.1711 1.1711 1.1711 1.1711 1.1711
--.
7 ERROR TOTAL SOLIDS D A750' C. Residue D. Original E. MgO B - *15o0 XI00 in original sample as MgO recovered B % Gram % % % 131.6 0.496 124.9 0.496 103.1 0.496 - 3.8 43.5 0.496 102.5 -2.6 128.2 0.496 120.5 0.496 99.6 0.496 5.7 43.4 0.496 102.5 -2.4 128.7 0.496 123.0 0.496 105.2 0.496 - 5.3 43.4 0.496 102.5 -2.4 133.1 0.496 125.7 0.496 111.2 0.496 -11.1 43.6 0.496 102.9 -2.8 129.9 0.496 124.3 0,496 114.0 0.496 -13.7 42.8 0.496 101.1 -1.2
-
TABLE11. MAGNESIUM CHLORIDE-CALCIUM CHLORIDESYSTEM SALTIN 25 cc. OF SOLN. MgClz CaClz Gram Grams 0.264 0.473 (50%) (50%)
0,211 (25%)
1.134 (75%)
0.105 (10%)
1.710 (90%)
0.0529 (5%)
1.795 (95%)
0.0264 (2.5%)
1.845 (97.5%)
TEMP. OF
WT.AFTBR DRYING
DRYINQ
1
c.
Urams
105 120 150 750 105 120 150 750 105 120 150 750 105 120 150 750 105 120 150 750
2 Grams 0.928
0.527
0.757 0.544 1.610
1.171
1.516 1.165 1.937
1.716
1.834 1.696 2.015
1.760
1.874 1.780 2.060
1.799
1.890 1.806
3 Grams
0.923 0.746 0.533 1.573 1.365 1.184 1.923 1.862 1.698 1.825 1.827 1.740 1.946 1.905 1.781
A. Resi, due av. Grams 0.928 0.923 0.751 0.534 1.610 1.573 1.440 1.173 1.937 1.923 1.848 1.697 2.015 1.825 1.850 1.760 2.060 1.945 1.897 1.795
-
TOTAL SOLIDS B. Origi- C. Resi- D. Original due in nal sample as E. Re- - B sample Grams 0.737 0.737 0.737 0.737 1.345 1.345 1.345 1.345 1.815 1.815 1.815 1.815 1.847 1.847 1.847 1.847 1.871 1.871 1.871 1.871
+
original MgO CaClz covery Grams % % 126.1 0.585 125.3 0.585 101.9 0.685 72.5 0.585 91.2 1.223 119.8 1.223 117.0 1.223 107.0 1.223 87.2 96.1 106.7 1.755 106.0 1.755 101.9 1.755 93.5 1.755 96.6 1.812 108.9 98.8 1.812 100.1 1.812 95.3 1.812 97.2 111.7 1.856 1.856 104.7 1.856 102.0 1.856 96.2 97.8
x %
-ERROR D A750' 100
x 100 %
-1.9 8.7 -7.6 4.1 -1.8
3.3
-0.6 2.8 -1.4
3.3
212
ANALYTICAL EDITION
TABLE111.
MAGNESIUM CHLORIDE-SODIUM
Vol. 4, No. 2
CHLORIDE
SYSTEM
TOTAL SOLID8 SALTIN 25 cc. OF SOLN. MgClz NaCl Gram Gram 0.527 (50%)
0.999 (50%)
0.132 (25%)
0.750 (75%)
0.053 (10%)
0.900 (90%)
0.026 (5%)
0.960 (95%)
0.013 (2.5%)
0.975 (97.5%)
TEMP. OF
DRYINQ a
c.
105 120 150 750 105 120 150 750 105 120 150 750 105 120 150 750 105 120 150 760
4.
B.
WT. AFTER DRY IN^ 1 2 3 Grams Grams Grams
Residue av. Grams
Original sample Grams
1.656
1.666 1.637 1.521 1.174 0.928 0.912 0.858 0.785 0.975 0.972 0.943 0.905 0.994 0.990 0.979 0.956 1.004 0.995 0.990 0.980
1.526 1.526 1.526 1.526 0.882 0.882 0.882 0.882 0.953 0.953 0.953 0.953 0.976 0.976 0.976 0.976 0.988 0.988 0.988 0.988
1.145
1.485 1.191 0.928
0.769
0.860 0 0.975
0.899
0.941 0.910 0.994
0.966
0.980 0 1.004
0
0.995 0.985
1.637 1.558 1.187 0.912 0.856 0.801 0.972 0.946 0 0.990 0.978 0.957 0.995 0.986 0.975
7
---
R e s u e Orsnal E. Re- B in sample as NaCl covery original MgO 7% Grams 7% ,-
+
108.6 107.2 99.7 77.0 105.1 103.6 97.3 88.3 102.4 102.1 99.0 95.0 101.8 101.4 100.3 96.0 101.1 100.7 100.1 97.9
1.222 1.222 1.222 1.222 0.806 0.806 0.806 0.806 0.922 0.922 0.922 0.922 0.961 0.961 0.961 0.961 0.981 0.981 0.981 0.981
Also0
x
ERROR-100
D
x
-
100
%
% 0.32
96.2
3.94 2.72
97.4
2.6
98.3 -0.37
99.6
0.62
-0.24
99.8
0.12
TABLEIV. CALCIUM CHLORIDE-SODIUM CHLORIDESYSTEM SALTI N
25 cc.
CaClz Cram
OF
0.473 (50%)
Sam.
NaCl Gram
TEMP. OF WT. AFTER DRYINQ DRYIN~ 1 2 3 C. Grams Grams Crams
0.600 (50%)
105 120 150 0.968
0.236 (25%)
0.750 (75%)
750 105 120 150
0.900 (90%)
750 106 120 150
0.983
0.095 (10%)
1.001 0.968 1.008
0.992
0.950 (95%)
750 105 120 150
1.008 0.982 1.009
750 750
1.003 0.998
1.006 0.984 0
0.047 (5%) 0.024 (2.6%) 0
K
1.002 0.985 0.952 1.014
0.975 (97.5%) = 0.02 (when CaClz content is between 25-50 ) 3 0.01 (when CaCla content is between 10-202) 0.00 (when CaCh content is less than 10%)
0.992 0.992 0,936 1.001 0.994 0.945 1.016 1.012 0.984 1.116 1.017 0.995 0
4. Res1due av. Grams 1.002 0.992 0.989 0.952 1.014 1.001 0.998 0.966 1,008 1.016 1.010 0.986 1.009 1.116 1.011 0,994 0.998
TOTAL SOLIDS B. C. ResiD. OrigiOriginal due in nal sample E. Resample original as K n oovery Gram % %
7
0.973 0.973 0.973 0.973 0.986 0.986 0.986 0.986
103.0 102.0 101.6 98.0 102.6 101.6 101.2 98.1
0.954 0.954 0.954 0.954 0.966 0.966 0.966 0.966
100.0
0.999
.4 .7 99.9
0.997 0.997 0.999
99.7 99.9
ERROR
BB
100 D
%
- A7m0 x100 %
-1.6 99.9
0.28 -1.2
-1.4
0.00
0.30 0.0
-
higher, though much below its true value. The maximum was 97.8 per cent for a mixture containing 2.5 per cent of magnesium chloride and 97.5 per cent of calcium chloride. This loss of 2.2 per cent was apparently due to volatilization of the salts. It was not determined whether or not this loss was due to volatilization of the calcium or magnesium salt or both. It was obvious that high concentrations of magnesium chloride in the mixture had profound influence in bringing about greater decomposition and volatilization losses of calcium chloride, amounting to about 8 per cent when a 50-50 mixture of magnesium and calcium chlorides in solution was dried and heated to 750" C. This loss decreased with decreasing quantities of- magnesium chloride (91.2 to 97.8 per cent recovery), The results at 105" and 120" C. were very irregular, whereas a t 150" C. practically all concentrations gave fairly concordant results close to correct values, suggesting that this temperature was apparently the best one for drying. This neglected the fact, however, that both salts lost chlorine a t this low temperature (hydrochloric acid odor and also titration for total chlorides showed the loss) although, on the basis of weight of original sample and final dry residue (apparently dry), there should be no loss of chlorine, since the dry residue weighed more than the original sample-i. e., the salt alone, without the water which was added for the purposes of these investigations. The per cent error a t 150" C. was too irregular for satisfactory factorial treatment.
Therefore, the final conclusionmust be that, when a mixture of salts in solution is dried at low temperatures such as used in this work, there is a tendency for the salt mixture to retain a part of the water added as a hydrate, while decomposition also takes place. Since in some of the cases studied check results were obtained, this was probably due to the fact that the amount of decomposition and amount of water retained by the salts approximately balanced each other, making these results seem satisfactory to casual observation. Even though the results at 750" C. with mixtures are low, they are reliable and consistently connected inversely with magnesium content, showing a rational basis for factorial calculation. MAGNESIUM AND SODIUMCHLORIDES. Table 111 shows characteristics similar to those of Table 11-namely, the behavior of mixed salt solutions differed from the behavior of individual salt solutions under the same evaporation conditions. With this mixture both 105' and 120" C. gave high results directly proportional to the magnesium content which could be treated factorially. The 150" and 750" C. treated results are inversely proportional to the magnesium content. The per cent error a t 150" C. was entirely too erratic for factorial treatment, but the error a t 750" C. gave a good curve dependent upon the magnesium content. The table shows, a t high concentrations of magnesium chloride in the sodium chloride solution (50-50 mixture), a per cent recovery of 108.5 for 105", 107.2 for 102", 99.7 for 150", and 77.0 per cent for 750" C., assuming that magnesium
April 15, 1932
213
INDUSTRIAL AND ENGINEERING CHEMISTRY TABLEV. MAQNESIUM CHLORIDE-CALCIUM CHLORIDE AND SODIUM CHLORIDE SYSTEM
-
TOTALSoLIns 7 ERROR A. B. C. Resi- D. Origiduein nalsample E. Re- - B Original Residue WT. AFTER DRYINQ x 100* D x 100 SALTI N 25 cc. OF SOLUTION covery B as Ka sample original av. 2 3 DRYINQ 1 MgCln CaClz NaCl Gram Gram Gram C. Gram Grams Gram Grams Gram '% Gram % % % 0.132 0.236 0.50 ,105 0.991 0,991 0.868 114.1 0.788 125.8 0.909 0.909 0,868 104.7 0.788 115.1 (25%) (25%) (50%) 0.885 0.880 0.883 0.868 101.9 0.788 112.0 -1.58 0.0 750 0.788 0,793 0.782 0.788 0.868 90.8 0.788 100.0 0.053 0.189 0.70 105 0.976 0.976 0.942 103.6 0.909 107.5 0.970 0.970 0.942 103.0 0.909 106.8 (10%) (20%) (70%) 0.957 0.953 0.955 0.942 101.5 0.909 105.1 -1.38 750 0,907 0.911 0.805 0.908 0.942 96.5 0.909 100.1 0.11 0.026 0.142 0.80 105 1.013 1.013 0.968 104.2 0.952 105.0 0.989 0.989 0.968 102.1 0.952 103.9 (5%) (15%) (80%) 120 0.987 0.983 0.985 0.968 101.8 0.952 103.4 -1.70 150 1.05 0 0 0.942 0.968 97.4 0.952 99.0 750 0.942 0.013 0.095 0.878 750 0.975 0 0 0.975 0.986 98.9 0.978 99.8 0.37 (2.5%) (10%) (87.5) Magnesium chloride in original sample calculated as MgO; for values of R Bee footnote, Table IV, for CaClz corrections.
TEMP. OF
;ig
chloride did not decompose. On this assumption the 150" C. gave the best results with a per cent error ranging from 2.72 to -0.37 per cent. If we assume, however, that magnesium chloride decomposed into magnesium oxide and calculate the per cent recovery a t 750" C. only (because it was obvious that those a t low temperatures gave untrue values), this recovery ranged between 96.2 and 99.8 per cent for a 50-50 mixture of magnesium and sodium chlorides down to 2.5 of magnesium chloride and 97.5 per cent of sodium chloride, again demonstrating that the presence of magnesium meant loss of the other chlorides. The per cent recovery in the case of magnesium-sodium chloride mixtures, however, was higher as compared with the magnesium-calcium chloride system. The influence of high concentrations of magnesium chloride in the mixtures in bringing about decomposition of the salts which otherwise would not decompose under the same heating conditions is probably not new (no reference was found), but is of great interecst and may be useful in cases where at least two such salts are involved in a mixture. CALCIUMAND SODIUMCHLORIDES. I n Table IV the results a t 105" C. were high, varying directly as the calcium chloride content. Those at 120" C. were very irregular, and those at 150" C. were high and independent of the calcium chloride content though close to the facts. A factor could be used on the error. The results at 750" C., also assuming no decomposition, were low and smoothly, though inversely, proportional to the calcium chloride content.
recovery, thus indicating that the loss of 2 per cent at a 50-50 mixture was due to volatilization and not decomposition. MAGNESIUM-CALCIUM AND SODIUM CHLORIDES.Table V represents data obtained on mixtures of all the three salts in solution. Column C, as heretofore, represents the recovery of the sample as residue after drying at various temperatures. With the assumption that magnesium chloride does not decompose, the per cent recovery a t the various temperatures was high and decreased as the concentration of magnesium chloride decreased, except in the case of 150" C. when the results were not so high but were erratic. At 750" C. just the opposite takes place, in that the recovery increased from 90.8 to 98.9 per cent. It is known, and also was found, that magnesium chloride decomposes a t 750" C. and that there is approximately 2 per cent loss of calcium chloride also at high concentrations of this salt in the mixture (Table IV), hence upon recalculating (magnesium chloride as magnesium oxide and using the factor indicated in the note), a recovery of 100 per cent at 750" C. (column E) was obtained as per cent residue with practically all mixtures of the three salts in solution. The column "Error" also proved this. The column for 150" C. is very tempting in the smoothness of its results. A factor should work well for calculating results, but the 750" C. is a definitive procedure so far as chemical ending is concerned. GENERAL DISCUSSION
1. The behavior of the salt mixtures under heating conditions was different from those of the individual salts in soluSAMPLES OF NATURAL tion. TABLEVI. ANALYSIS OF TYPICAL BRINES 2. Evidently the temperature used by Sweeney and (Showing applioation of recommended method) Withrow gave apparently excellently concordant and correctDetermination ............................ 1 2 3 appearing results for some brine compositions. However, Specific gravity at 62' F.. . . . . . . . . . . . . . . . . . . . 1.194 Specific gravity a t 88' F . . ...................... 1 :Zi5 1:Zi8 the chemical inconsistency found in these results makes this Deposit on aeration.. ....................... 0.03 0.01 0.01 temperature inadvisable, as it inevitably will result in gross S i l h , gram ................................ 0.01 0.04 0.01 Iron and alumina, gram., . . . . . . . . . . . . . . . . . . . 0.02 0.23 0.02 error with some brine compositions. Calcium chloride, grams . . . . . . . . 9.90 11.43 11.27 Calcium sulfate, gram. . . . . . . . . . 0.05 0.03 0.07 3. Phalen used 105" C. for determining total solids, thus Magnesium chloride, grams.. . . . 2.17 1.76 3.32 neglecting completely the facts that complete dehydration Magnesium bromide, gram. . . . . . . . . . . . . . . . . . 0.17 0.09 0.21 10.40 13.17 11.30 Sodium chloride, grams of calcium chloride does not take place at 105" C. and that 0.27 0.27 0.43 Potassium chloride, gra magnesium chloride decomposes at a temperature of 95" C., 23.02 27.03 26.64 26.70 23.07 26.88 making possible errors, as shown in this work, of as high as 23.24 27.50 26.60 29.55 25.60 30.37 12 per cent. Any apparently useful results at 105" C. must have been a balancing of errors. 4. Summarizing the information gained through these 'The results obtained by heating different concentrations of investigations the following formula has been deduced for the calcium and sodium chlorides in a solution show also that calculation of total solids in natural brines: there was a loss of 2 per cent of residue recovery a t 750" C. for a 50-50 mixture, th% recovery increasing with decrease in TS = R 0.577 X MgC12 K X CaCh percentage of calcium chloride in the mixture approaching the where TS = solids true value 100 per cent. When analyzed for total chlorides, R = residue (weight) at 750" C. the residues gave a figure which, when calculated back to the o. 577 = MgCli - MgO correspopdingehlorides, resulted in a 100 per cent (practically) MgClz
+
+
A N A. L Y T I C A L E D I T I O N
214
K
0.02 for brines containing CaC& = 25 to 50% of sodium chloride content = 0.01 for brines containing CaCly = 10 to 20% of sodium chloride content = 0.00 for brines containing CaCla = less than 10% of sodium chloride content =
To illustrate the application of this formula and method of calculation, the following examples, with data taken from Table VI, column 1, are given (slide rule used for all calculations) :
+
+
TS = R 0.577 X MgClz K X CaCl2 Total solids by ignition (750' (2.).. . . . . . . = R = 21.62 0.577 X 2.17.. ..................... 1.252 0.198 0.02 x 9.90 ........................ Total solids calculated. . . . . . . . . . . . . . . . 23.07 Total solids by summation of analytical data. ............................ 23.02
Vol. 4, No. 2
Error = 23.02 -23.07 0.21% 23.02 loo= Total solids at 150" C. (assuming no decomposition) = 23.24 = Error = 23.02 -23 24 0.95% 23.02 Total solids at 105" C. (assuming no decomposition) = 25.60 23.02 -25.60 = Error = 11.6% 23.02 LITERATURE CITED (1) Efremov, J.Russian Phys.-Chem. SOC.,51,399-416 (1919). (2) Mellor, "A Comprehensive Treatise on Inorganic and Theoretical Chemistry," Vol. 111,p. 699, Longmans, 1923. (3) Mellor, Ibid., Vol. IV, p. 23. (4) Phalen, U. S. Geol. Survey, Bull. 669, 212 (1917). (5) Sweeney and Withrow, J. IND. ENG.CHEM.,9, 671 (1917).
RECEIVED March 23, 1931. Presented before the Division of Industrial and Engineering Chemistry a t the 81st Meeting of the American Chemical Society, Indianapolis, Ind., March 30 to April 3, 1931.
Determination of Iodine in Soils A New Method J. S. MCHARGUE, D. W. YOUNG,AND W. R. ROY,Kentucky Agricultural Experiment Station, Lexington, K y . during the burning. It can be demonstrated that most limestones contain iodine, as tests for its presence can be obtained by leaching 1000 grams of finely pulverized stone with distilled water, evaporating the filtrate to dryness, extracting the residue with alcohol, evaporating the alcoholic extract to dryness, and testing this residue for iodine by the carbon disulfide method. Apparently the iodine compound is volatilized when the stone is heated intensely, and should be recoverable from the gaseous products. Accordingly, an electric combustion-tube furnace was obtained for the purpose of burning as much as 100 grams of limestone or soil in a partially closed combustion tube and aspirating the volatile matter through a 5 per cent solution of potassium carbonate contained in a series of wash bottles. Figure 1shows the apparatus ready for use: 1 is an electric combustion-tube furnace having a 50-mm. hole through the center; 2, a quartz combustion tube, inside diameter 40 mm., EXPERIMENTAL PROCEDURE outside diameter 50 mm.; 3, a sillimanite combustion boat, Tests made on the water extract from 100 grams of burned 250 by 32 by 20 mm.; 4, a rheostat; and 5, gas wash bottles lime showed that no iodine was present. This fact led containing a 5 per cent solution of potasslum carbonate. to the inference that the limestone from which the lime was Three bottles are used. The combustion tube is inserted in burned either did not contain iodine or it had been volatilized the hole in the furnace. From 25 to 100 grams of soil or small pieces of rock are weighed into the combustion boat. The amount of material depends on whether the iodine content is high or low. Some limestone contains enough iodine to permit a determination to be m a d e on 25 g r a m s b y t h i s m e t h o d . ........................................................... Other rather pure limestone requires 100 grams, whereas sandstone rocks require 100 grams of material, and soils 25 to 50 grams. The small end of the quartz combustion tube is connected with three gas wash bottles. The large end of the tube is loosely stoppered by inserting an alundum crucible of the proper size. The wash bottles are connected by means of rubber tubing. A rubber stopper on the end of a bent glass tube connects the small end of the c o m b u s t i o n tube with the first wash FIGURE1. FURNACE READYFOR USE bottle. The last wash bottle is attached to a
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INCE iodine occurs in very minute quantities in nature, an accurate method for its determination in rocks and soils is highly desirable because no iodine survey is complete without a fairly definite knowledge of the amount of iodine contained in the rocks and soils of the region studied. One of the principal difficulties encountered in an investigation to ascertain whether or not any region of country is adequately supplied with iodine has been the lack of a satisfactory method for the determination of the element in rocks and soils, which, after all, are the principal sources of iodine for plants and animals on land. The methods used heretofore for the determination of iodine in rocks and soils have consisted in fusing a relatively small quantity of either of these materials with potassium hydroxide or the extraction with dilute acids. The methods are tedious, cumbersome, and probably subject to considerable errors.
