(REACTIONS IN INERT FUSED SUBSTANCES)
Conversion of Barytes to Barium Carbonate HAROLD SIMMONS BOOTH AND ELISHA FREDERICK POLLARD' Western Reserve University, Cleveland 6, Ohio
1
Crude barium sulfate (barytes) is very soluble in fused sodium chloride. After insoluble impurities are separated by settling and decantation, the addition of sodium carbonate to the melt followed by slow cooling converts the barium sulfate to barium carbonate which may be separated by leaching out the other salts. This procedure has the advantage over the preparation of barium carbonate from barium sulfide of yielding a barium carbonate free from objectionable sulfur compounds.
M
OST chemical processes are based on reactions in water as the parent solvent. The possibility of industrial processes in which other parent solvents, such as liquid ammonia, anhydrous hydrogen fluoride, or anhydrous acetic acid are used only recently has received much attention. Practically no study has been made of reactions in inert fused melts which might act as inert or parent solvents. As barium sulfate is insoluble in water and other ordinary parent solvents, the possibility of its reactions in fused inert inorganic substances was considered. Barium sulfate is soluble in fused sodium chloride (4) and it is well known that sodium carbonate likewise is soluble in fused sodium chloride (6). It seemed reasonable to expect, therefore, that barium sulfate and sodium carbonate might react in a fused sodium chloride bath (as solvent) to yield barium carbonate and sodium sulfate. Furthermore, sodium chloride as a solvent would permit the preliminary separation from the barium sulfate of inert impurities (1,a) such as silica and iron oxide. A qualitative experiment showed that barium sulfate, sodium carbonate, and also barium carbonate and sodium sulfate were soluble in the fused salt. Furthermore, on adding an excess of sodium carbonate to the solution of barium sulfate in the fused sodium chloride it was found that, on cooling and leaching with water, the residue was chiefly barium carbonate (8). It was noted also that a considerable excess of sodium carbonate was necessary to complete the conversion of the barium sulfate to carbonate. The solubility of barium sulfate in fused sodium chloride at a temperature slightly above the melting point was found to be 9.09 to LO grams of sodium chloride and 2.306 grams of barium sulfate to 4.344 grams of potassium chloride. The conversion of barium sulfate to barium carbonate by fusion with excess sodium carbonate has long been known. I n the following experiments a study was made of the fusion method usingsodium chloride as an inert solvent (1, 3). Converting barytes to the carbonate by this method eliminated the carbon reduction process and the objections to the preparation of useful barium salts from the aqueous sulfide solution. Tammann (6) contends that the reaction BaSOc
+ Na2C03= BaC03 + NazS04
(1)
does not take place to any noticeable extent below 850" C., but the work described in this paper shows that at 840" C. the reaction does take place, in fused inert solvents. 1 Present address, Southern Regional Research Laboratory, U. S. Department of Agriculture, New Orleans, La.
EXPERIMENTAL
I n all experiments the various mixtures contained 2 grams of barium sulfate and various amounts of sodium carbonate based on the assumption that the reaction proceeded according to Equation 1. For some of the experiments 5 grams and in others 10 grams of sodium chloride were used. By thus varying the amount of salt the effect of dilution was ascertained. The mixtures were heated in covered platinum crucibles in a Hoskins electric crucible furnace provided with a thermoelectric pyrometer for temperature measurements. Determinations were run in which different equivalents of the calculated amount of sodium carbonate were used. The effect of dilution with fused sodium chloride on the per cent conversion of barium sulfate to the carbonate at a definite temperature above the melting point of the solvent was studied. Several determinations were carried out to ascertain the effect of variations in the rate of cooling on the per cent conversion. Additional determinations were also run with or without the fused inert solvent to iind the effect of temperature and amount of heating on the per cent conversion. GROUPI. The components, consisting of 2 grams of pure barium sulfate, 5 grams of sodium chloride, and a calculated amount of sodium carbonate were mixed intimately and the mass was heated in the furnace up to 840' C., then held at that temperature for 30 minutes and subsequently cooled by decreasing the current to that needed to maintain the furnace temperature of 700" C. When the temperature reached 700" C. the current was cut off and the melt allowed to cool to room temperature, Time of cooling from 840" to 700" C. was 1 hour; from 700" C. to room temperature, 1 hour and 10 minutes. Several mixtures were heated again to 840" C. in the same m y and after holding the temperature constant for 30 minutes, the current was cut off and the fused mass allowed to cool slowly to room temperature. Results are shown in Table I and Figure 1. When the same mixtures were heated to 1000" C., maintained at that temperature for 30 minutes, and then the current was cut off and the products were allowed to cool slowly as before, the per cent conversion of barium sulfate was the same. Time of reactions for 0.5, 1, and 1.5 hours at 840' and 1000" C. failed to alter the per cent conversion. GROUP 11. Another set of experiments, analogous to Group I except that 10 grams instead of 5 grams of sodium chloride were used, was run to determine the effect of dilution of sodium chloride on the conversion. Results are shown in Table 11. GROUP111. These determinations were carried out in the same manner as Group I except no inert solvent, such as sodium chloride, was used (Table 111, Figure 2). Only four mixtures were run because the analysis of the products gave the same percentage of barium sulfate decomposed as found previously by using sodium chloride. GROUPIV. I n this set of experiments the compositions of the samples used in the various fusions were analogous to those in Group I, but the cooling process was altered by quick quenching in water. The sample was heated in the furnace to 1000" C. and held a t this temperature for 30 minutes. It was poured immediately into an evaporating dish containing water (Table IV, Figure 3). GROUPV. This group of experiments was a repetition of those in Group IV, except that 10 grams instead of 5 grams of sodium chloride were used in all the fusions (Table v, Figure 4).
1983
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
1984
TABLE I.
NaCl, Grams 5
5
6
6
6
CONVERSION O F
10 10 10
LO
TO
BARIWCARBOXATE
(Conversion using fused sodium chloride as solvent) % con. Mole Ratio Cos-BaC03 Ba+ K 'BaSOd, NasC03, version ? a t r BaC03 ions recovered Grams BaSO< ions Grains 0.9206 3.77 3.1850 92.85 I 3.50 2 93.07 0.8918 3.37 1 3.00 2.7300 89.21 2 89,16 0,8236 3.04 1 2.50 2,2750 82.35 2 82.37 0.8080 2.83 1 2.00 1.8200 70.56 2 70.85 0.5347 2.81 53.56 1 1.50 2 1.3650 53.38 2.82 1 1.00 0.3543 0,9100 35.26 2 35.60 4.40 1 0.50 0.1136 0.4550 11.50 2 11.23
TABLE11. CoxmnsIov
NaC1, Grains 10
BanIms SULF.4TE A T 830" C.
OF
BARIUM SUI,FATCTO 840" C.
Vol. 40, No. IO
BanIuhr
CONVERSION OF BaSO4TO BcrCOg IN FUSED N a 61 M SOLVENT AT 840° e.
CARBOXATE AT
(Conversion in dilute solution of fused sodium chloride) Mole Ratio __ % C?nBaCOa B a + + xC03--_ K C03--BaiOa, IiaaCOs, version Ba' BaCOa ions ions recovered Grams BaSOr Grains 0.0488 3.69 1 3.50 3.1850 95.03 2 94.73 0.8195 8.06 1 2.50 2.2750 81.83 2 82.03 0.5379 2.79 53.65 1 1.50 2 1.3650 53,94 0.3478 2.88 33.07 1 1.00 0,9100 2 3 4 , BO 0.1124 4.45 11.21 1 0.50 2 0.4650 11.27 +
OF BARICM SULFATE TO B.xnIuii CARBOSATE AT TABLE 111. COZVERSIOS 840" c.
(Conversion without sodium cliloride as solvent)
2
3.1850
2
2,2750
2
1,3650
a
0.4530
93.23 93.01 81.95 81.80 53.72 64.05 10.74 11.02
CONVERSION OF Ba 904 WlTHOVf No CI AS SOLVENT AT 8 4 0 ° C.
I
3.50
0,0313
3.76
1
2.50
0.8187
3.06
1
1.50
0.5388
2.78
1
0.50
0.1088
4.68
ANALYTICAL METHOD EMPLOYED
The chilled products from the furnace n-ere ground in an agate mortar and washed into beakers with 150 t o 200 nil. of distilled water. Quick quenching was accomplished by pouring the fused rnelts Erom 1000 O C. into 200 mi. of distilled nater. Then the solutions mere digested on a steam bath at 80" C. for 1 hour. After digestion the solutions were filtered through neighed
