TITANIUM SULFATE SOLUTIONS - Industrial & Engineering

TITANIUM SULFATE SOLUTIONS Refractive Index and Viscosity Measurements ARTHUR W. HIXSON AND JOSEPH D. STETKEWICZ] Columbia University, New York, N. Y

Measurements of refractive index, dispersion, and viscosity were made on titanium sulfate solutions of acidities (ratios of sulfur trioxide to titanium dioxide) ranging from 1.001 to 3.004 and concentrations ranging from 0.5 to 26 per cent titanium dioxide. No definite break was found in the curves which might indicate complex or compound formation at any definite concentration or composition, but the viscosity measurements did produce evidence of complex formation. Refractivities were found to be additive. The course of a hydrolysis by boiling was followed by refractive index measurements and by analyses, and commercial use of refractive index in conjunction with density is suggested.

NE of the most spectacular developments in modern

0

chemical technology has been the rapid growth of the use of titanium pigments in the protective coating industries. Practically all processes for the manufacture of titanium paint pigments depend upon the hydrolysis of properly formed titanium sulfate solutions. Although the titanium sulfate solution is the basis of all pigments and processes, very little is known about its structure. It is generally agreed by those familiar with this field of chemistry that substantial improvements in the manufacture of these pigments will undoubtedly result from a more complete knowledge of the structure. Various methods are employed in obtaining titanium dioxide from its minerals, the most important being the treatment of the ores with sulfuric acid and subsequent hydrolysis. The type of precipitate resulting from hydrolysis is dependent upon the conditions under which this operation is performed. Hixson and Plechner (7) investigated the thermal hydrolysis of titanium sulfate solutions of various titanium dioxide concentrations and acidities (ratios of sulfur trioxide to titanium dioxide) and determined the maximum yields of titanium dioxide. Parravano and Caglioti ( I S ) showed that the rate of hydrolysis can be increased by the addition of precipitating nuclei and that the structure of the precipitate is in some cases dependent upon the kind of nuclei added. Work and Tuwiner (19) found that a pigment with greater hiding power could be prepared from solutions of higher concentration and lower acidity. Work and Ligorio (18) produced a pigment of high hiding power from sulfate solutions with acidity of less than 1.00, and studied the effect of addition agents and coprecipitation on the yield of titanium dioxide. The type of compound formed by the hydrolysis is dependent upon the condition and composition of the solution. Exactly what does exist in these solutions is not fully understood. It is yet to be ascertained whether or not complexes are formed in solutions of titanium sulfate. The precipitate which forms contains some sulfate, and even calcination does not entirely eliminate this sulfate, which has led to the belief that the precipitate is in reality a basic sulfate ( I S ) . Blumenfeld (3) states that the precise chemical linkage between the sulfuric acid and titanium in sulfate solutions is not com1

Present address, Bucknell University, Lewisburg, Penna.

pletely understood, and reports a marked increase in the rate of hydrolysis if carried out in the presence of colloidal titanium oxide. Weiss and Landecker (16) found that titanic acid is quite soluble in a sulfuric acid solution of hydrogen peroxide, and that the solution is a true solution ultramicroscopically. Jander and Jahr ( 8 ) had investigated the hydrolysis of inorganic salts, including zirconyl chlorate and nitrate, and the chemistry of their high-molecular products of hydrolysis. They found that most of the salts yield a number of products of hydrolysis and that their solutions contain several isopolybases in contact with one another. I n contrast to the behavior of salts of weak polybasic acids, the hydrolysis and aggregation of salts of weak polyacid bases is affected by the anion combined with the base or its product of hydrolysis. The course of the hydrolysis for salts of rather basic hydroxides depends upon the concentration to a greater extent than for salts of weak acids. The alleged definite intermediate products are assigned formulas of the Werner type. The aging of freshly formed gels of the hydrous oxides is believed to be due to chemical transformations which are essentially identical with those assumed to take place in solution. Contrary to the opinion of Jander and Jahr, however, other investigators believe that the aging of gels is physical rather than chemical. Investigations by Wintgen and Lins (17) on titanium dioxide hydrosols prepared by dialyzing titanium tetrachloride solutions showed that the appearance of the sols (clear or cloudy) could not be correlated either with the chlorine content or the specific conductivity, and quite different looking sols were obtained under supposedly identical conditions of preparation. For the determination of the structure of the colloid particles, the specific conductivity of the ultrafiltrates was determined, but no definite relation to these values with the type of preparation of the sol could be found. On the basis of the electromagnetic theory of light, Lorenz and Lorentz (5) showed that

%-herer = specific refractivity n = refractive index d = density 1009

1010

INDUSTRIAL AND ENGINEERING CHEMISTRY

VOL. 32, NO. 7

of sulfuric acid present in the solutiors was determined by titration with standard 0.25 N sodium hydroxide, using methyl AC l.6 orange as an indicator. PREPARATION OF SOLUTIONS. 1.5 1.5 The solutions investigated were prepared from commercial titanium tetrachloride ob9 $ I.+ I# tained from the Titanium Alloy Manufacturing Com?3 pany. The crude tetrachloG E f.3 65 ride was first distilled, and thz fraction boiling between 135 9 and 138’ C. was collected and l.2 A 2 redistilled. The product thus obtained was yellow, owing to the presence of free chlorine. 1. I /. / The last traces of chlorine were removed by refluxing over sodium amalgam for several 1.0 /.0 0 8 /d 2f 32 10 +8 hours before the final distillax 77.0, tion. The purified tetraXSO, chloride was diluted with water, and the titanium dioxide FIGURE 1. RELATIONBETWEEN TITANIUM DIOXIDEAND SULFUR TRIOXID~ CONTENTS AND was precipitated by boiling. DENSITYOF TITANYLSULFATE SOLUTIONS The D r e c i Di t a t e d t i t a n i um dioxiae was dissolved by the addition of concentrated sulfuric acid; after the solution was adjusted to 10 per cent titanium If the specific refraction be multiplied by the molecular weight dioxide and 40 per cent acid, it was boiled to precipitate titanyl of the substance, a value termed “molecular refractivity” is sulfate. To the titanyl sulfate was added an equal amount of obtained. Molecular refractivity affords a means of comparwater, and the resulting solution was concentrated by evaporaing the refractive power of various substances, since it has tion under reduced pressure a t 60’ C. to produce a thick, clear, sirupy mass, with the following composition: titanium dioxide, been shown that the molecular refraction of a compound is an 26.34 per cent; sulfur trioxide, 26.37 per cent; acidity (ratio additive property; i. e., i t is equal to the sum of the refractive of sulfur trioxide to titanium dioxide), 1.001. A slight turbidity constants of its components. Bruhl (4) and others carried out was observed before concentration under vacuum, but the experiments to determine the refractive constants of the elesolution was clear after concentration. This action was also observed by Mecklenburg (11). ments and common groups, and found that the refractive By adding varying amounts of concentrated sulfuric acid to effect is somewhat dependent upon the valency and mode of this solution, the ratio of sulfur trioxide to titanium dioxide was linkage. Gladstone and Hibbert (6) showed that the influvaried from 1.001 to 3.004 as follows: ence of the solution on the salt is complex. Briihl found that Series Ratio Series Ratio there is better correlation between the calculated and experiA 1.001 E 2.775 mental additivity in refractive power than in dispersion and B 1.259 F 2.936 C 1.591 G 3.004 that constitution has a greater effect on the dispersive power D 2.069 H H&Oi than on refractivity. After the measurements were made on the first solution of each Various investigators (2,16)showed that the additive charseries, 10 cc. of water were added and the mixture was shaken acter of viscosity becomes apparent when correct methods of well. The tests were then repeated on this diluted solution. Successive dilutions were made in the same way. The acidity comparing the quantitative measurements are used, and that ratio was thus maintained constant for each series. Meaaurei t is possible t o reconstruct the viscosity of the molecule from ments of refractive index and viscosity were also made on a series the viscosity effects of its component parts. The main porof pure sulfuric acid solutions (series H) for the purpose of caltion of the work of these investigators had been carried out on culating the additive refractivity. Refractive index and dispersion measurements were made nonelectrolytes. I n considering solutions of electrolytes in with a Pulfrich refractometer. The light source was a helium ionizing media, however, it is evident that besides association tube, and readings were taken for the red line (6678 A.), the yelor combination with the solvent, the effect of ionization must low line (5876 $), and the green line (5016 A.). All values were be taken into account. It was found that fluidity and concalculated according to the formula ductivity increase with dilution and that the conductivityn = 1/N2 - sin2 i and fluidity-concentration curves have the same form. If (2) where ?t = refractive index of solution combination takes place between two substances when N = refractive index of prism mixed, the viscosity of the mixture differs widely from that i = angle observed on refractometer calculated from the viscosities of the pure substances. KaFor the instrument used, N (yellow) is 1.62100; N (red) is nitz (IO)investigated mixtures of salts in aqueous solution and 1.61526; and N (green) is 1.63070. in many cases found distinct evidence of the formation of Viscosity measurements were made at 25’ C. with a Fenske complex salts, the viscosity of the mixtures being greater than modification of the Ostwald type of viscometer. Density was that calculated. determined by the use of a 10-cc. specific-gravity bottle with a thermometer ground stopper. In view of the above findings a n investigation was undertaken t o determine whether any constitutional or structural Refractive Index Measurements changes could be discerned in the solutions of titanium dioxide The refractive index of the solutions decreased slightly with in sulfuric acid. time. Therefore this property had to be determined within one month after preparation in order to obtain comparable Analyses and Tests data. This decrease may be due to hydrolysis, agglomeration, The method outlined bg Thornton ( 1 4 ) was used for the gravior dehydration of the colloidal titanium dioxide. Hydrolysis metric determination of titanium dioxide. Most of the titanium seems to be the more likely explanation, since titanium dioxide dioxide determinations, however, were carried out volumetrically precipitates on standing. All solutions examined gave a as described by Jarmus and Willets (9) since their method rereadily discernible Tyndall cone. quires much less time than that of Thornton. The total amount 1.7


JULY, 1940

1011

Table I shows the composition and density of the various series of solutions A500 investigated. I n Figure 1 (left) where the density is 447s plotted against the titanium dioxide content, the effect 1.4of raising the acidity is a n i n c r e a s e i n t h e density, which is to be expected from 6425 the high density of the acid. The deviation from a 1.I W straight line, however, seems to point to compound or complex formation as the hJ7.9 concentration increases. In order to compare the densi*350 ties of the solutions with sulfuric acid alone, the 6325 0 4 8 I.? 16 PO 24 28 density was plotted against the sulfur trioxide content x 71’4 %SO, (Figure 1, right). Here i t FIGCRE 2. RELATION BETWEEN REFRACTIVE INDEXAND TITANIUM DIOXIDEAND SULFUR TRIi s e v i d e n t t h a t as t h e OXIDE CONTENTS O F TITANYL SULFATE SOLUTIONS acidity decreases, the deviation from a straight-line Table I1 gives the values obtained for the refractive index function increases; this points to a greater degree of complex of the solutions. The values under nz are those for the yellow formation in the more basic solutions, due probably to the line of the helium source of light, nlfor the red line, and n8for greater degree of hydrolysis. the green line. I n solutions 1A and 2 8 the red and green lines were in the opposite positions relative to the yellow line AXD DENSITY OF SOLCTIONS TABLEI. COMPOSITION from that normally observed. This was due to the difference S o h . % Ti02 % SO3 d25 S o h . % Ti02 % Sc)s dz5 in the relative dispersive power of the prism and the liquid. A Series, S O d T i 0 2 1.001 E Series, SOs/TiOz = 2.775 Only a few mixtures or compounds exhibit this property, one 6678 1A 2 6 , 34 2 6 , 39 ,7002 1E 15, 15 41, 82 2A 25.42 25.47 1.6524 2E 12.91 35 74 1.5378 being a benzene-toluene mixture. The values for n3 - n1 (the 3A 21.97 22.01 1.5318 3E 10.82 30.05 1.4333 specific dispersion) are also recorded. Figure 2 shows the 44 20.69 20.73 1.4857 4E 9.414 26.18 1.3629 5A 6A 18.51 16.42 1 16,44 8.55 1.4161 1,3576 6E 5E 6,897 8.278 22.95 19,20 1,2490 1.8080 values far the refractive index, n2, plotted against titanium 7A 14.77 14.79 1,3077 7E 5.738 15.91 1.2005 dioxide and sulfur trioxide content. The values for the re8A 12.95 12.97 1.2625 8E 4.754 13.21 1.1620 9A 11.45 11.47 1,2228 9E 4.022 11.15 1.1337 fractive index for the red and green lines produce similar 10A 10.08 10.09 1,1900 10E 3.215 8.92 1 1043 curves. The fact that there is no sharp break at any point 11E 2.529 6.99 1.0799 11A 8.864 8.87 1.1615 12A 7.719 7.73 1.1388 12E 1.203 3.34 1.0351 along the curves indicates that it is a gradual transition from 13A 6.746 6.75 1.1186 the structure in diIute solution to that of a complex in the con14A 5.823 5.83 1.1004 F Series, SOs/TiO, = 2.936 15A 5 .. 6 04 01 6 5 .. 0 1.0848 centrated solution. Figure 2 (right) clearly shows that the 16-4 3 3 62 5 1,0593 14.88 43.80 1.7168 17A 2.928 2.93 1,0473 2F 12.81 37.60 1.5720 addition of titanium causes a marked increase in refractive 18-4 1.446 1.45 1.0207 iF i(p,iy index. 5F 7.632 22.42 1 2954 B Series, SOa/TiOz = 1.259 Figure 3 shows the specific dispersion (n3 - nl) plotted 18 57 1.2360 61’ 6.331 2B 1B 24.13 21, 18 2 6 , 67 30.51 1.6932 1 ,5895 SF 7F 4 5.021 , 068 12, 1 4 .o1 73 1 .,11420 805 against composition. The effect of titanium on this property 3B 17.45 21.93 1.4466 9F 3.302 9 !4 1 1117 is especially pronounced in the right-hand graph where the 4B 14.76 18.61 1.3580 10F 2.557 7.01 1.0847 curve for sulfuric acid is a straight line, and the addition of 5B 12.65 15.98 1.2915 11F 2.001 5 85 1.0647 6B 113.~5 13.44 1,2366 12F 1.444 4.23 1.0448 titanium causes a sharp rise in the dispersion. The value for 7B 8.806 11.11 1.1874 8R 7.293 9.23 1.1501 G Series, S O d T i O ? = 3.004 a titany1 sulfate solution containing 24 per cent sulfur trioxide 9B 5.281 6.65 1.1031 is approximately sixteen times that for a 24 per cent solution 10B 3.899 4.91 1,0727 1G 14.31 42.97 1.6867 8642 11R 2 , 9 0 0 3 . 6 5 1 0 25 7311 zc, 12.4i 37 without titanium. 1 2 ~ 1.589 2.00 1 ,, 0 3Q 10.54 3 1 . 44 67 1.4550 4G 9.145 27.53 1 3761 The inversion of position in the concentrated basic solu50 7.570 22.71 1 2965 C Series, SOdTiO? = 1.591 6G 6.239 18 70 1.2359 tions is clearly evident by plotting the difference between the 1C 20.51 32.92 1.6553 7G 5.193 15.58 1.1907 green-yellow and the red-yellow lines against composition 2C 18.47 29.52 1.5626 SG 4.227 12.71 1.1808 3C 4c 14,62 16.71 26.71 23,56 1,412J 1.4919 10G 9G 2,751 3 453 180,.2471 1,0937 1.1199 (Figure 4). The effect of adding titanium to the acid is 5C 12.71 20.35 1.3439 11G 2.119 6.36 1.0704 especially pronounced. 6C 11.04 17.62 1.2875 12G 1.193 3.58 1.0364 Plotting of the density against refractive index produces 7C 8.493 13.55 1.2086 SC 6.094 9.72 1.1421 H Series, Sulfuric Acid practically a straight line. By plotting a series of curves for 9C 4.559 7.18 1.1017 IOC 2.333 3.69 1.0482 :!; varying acidities, it is a simple matter to determine the com3H .. .. 37.52 1.3591 position of a solution (both the titanium dioxide and sulfur D Series, SOa/TiOn = 2.069 4H .,,. 30.99 1.2857 trioxide content) by merely determining the refractive index 1D 15.54 32.18 1,5502 5H .. .. 26.00 1.2343 2D 13.64 28.22 1 457:3 6H ..,, 22.20 1.1960 and the density. 3D 11.64 24.12 1.3735 7H ., ,. 18.35 1.1591 4D 10.09 20.90 1.3148 8H 15.95 1.1344 Table I11 shows the specific refractivity of the solutions. 5D 8.778 18.16 13.27 1,1102 1.2647 9H These values were calculated according to Equation 1. For 6D 7.935 16.36 10H .... 1 2 . 4 1 1.1021 1.2341 :I:: all solutions the values approached that for water upon dilu9D 4.296 8.90 1.1156 13H .. .. 5.47 1.0527 tion. Here again the changes produced a smooth curve. 10D 2.989 6.20 1.0764 14H , ... 4.17 1,0312 1.0185 These values were subsequently used in calculating the molecu11D 1.967 4.06 1,0482 l5H .. .. 2.06 lar refractivity,

-

1A:y!4

i,t;gf

;:::;:

!:yf$

::::!:

:iz


1012

TABLE11. REFRACTIVE hDEX

Soln.

nz

1A 2A 34 4A 5A 6A 7.4 SA 9A 10A 11A 12A 13A 14A 15.4 16A 17A 18A

Water

nl

n3

A Series, SO%/TiOz = 1,001 1 ,52141 1 . 51547 1.53200 ,50765 1 .50 184 1.51835 ,47291 1 . 46798 1.48124 ,46004 1.45546 1.46773 ,44082 1 . 43667 1.44763 ,42466 1.42085 1.43083 ,41150 1 . 40790 1.41713 ,39948 1 . 39618 1.40482 ,38929 1.38618 1.39434 ,38090 1 . 37788 1.38558 ,37359 1 . 37075 1.37811 ,36808 1 . 36533 1.37239 ,36291 1 . 36017 1.36706 ,35845 1 . 35550 1.36259 ,36459 1.35195 1.35855 .34824 1 . 34572 1.35199 ,34521 34279 1.34879 ,33811 1.33621 1.34191 ,33250 1 . 33033 1.33564

ns

- nl

1,51295 1.48415 1.44523 1.42166 1 ,40468 1.39084 1 ,37845 1.36935 1.36792 1.35084 1.34588 1.33970

1,50699 1.47885 1.44101 1.41792 1.40132 1.38774 1.37558 1.36653 1.36526 1.34808 1.34355 1.33737

1.52344 1.49281 1.45212 1.42766 1.41003 1.39576 1.38301 1.37354 1.36183 1.35434 1.34959 1.34312

nz

n1

AKD

SPECIFIC DISPERSION ns

ns

- nt

Soln.

D Series, SOs/TiOz = 2.069

0 01653 0 01651 0 01326 0 01227 0 01096 0 00998 0 00923 0 00864 0.00816 0 00770 0 00736 0 00706 0 00688 0 00709 0 00660 0 00627 0 00600 0 00570 0 00531

B Series, 503/TiOz = 1.259 1B 2B 3B 4B 5B 6B 7B 8B 9B 10B 11B 12B

Soln.

0.01645 0.01396 0.01111 0.00974 0,00871

in ~~

2D 3D 4D 5D 6D 7D 8D 9D 10D 11D

1.46113 1.43850 1.41827 1.40429 1.39257 1.38565 1.37009 1.36453 1.35872 1.35002 1,34372

6E

7E 8E 9E 10E 11E 12E

1.48153 1.47661 1.45075 1.44644 1.42716 1.42347 1.41150 1.40810 1.39918 1.39608 1.38623 1.38336 1.37564 1.37293 1.36734 1.36477 1.36147 1.35898 1.35512 1.35267 1.35002 1.34754 1.34044 1.33821

0.00802

0,00743 0.00701 0,00657

0.00626 0.00604 0.00578

1.45656 1,46852 1 ,43446 1 44495 1.41471 1 ,42490 1,40103 1 ,40954 1,38969 1 ,39746 1.38259 1 ,39021 1 36747 1 ,37426 1.36191 1 ,36853 1.35616 1 ,36250 1.34754 1,35368 1.34142 1,34730 1.48971 1.45740 1.43311 1.41685 1.40414 1.39069 1.37991 1.37143 1.36532 1.35880 1.35360 1.34389

o.oii9e 0.01049 0.01019 0.00851 0.00787 0.00762 0.00679 0.00662 0.00634 0.00685 0.00148 0.01310 0.01096 0.00964 0.00875 0.00806 0.00733 0.00698 0.00666 0.00634 0.00613 0.00606 0.00568

F Series, SOs/TiOz = 2.936

1F 2F 3F 4F 5F 6F 7F 8F 9F 10F 11F 12F -~~

1.49118 1.45585 1.43429 1.41279 1.39878 1 ,38270 1.37101 1 ,36282 1.35634 1 .35079 1 ,34655 1.34256

1 ,48599 1.45246 1.43052 1.40930 1.39263 1.37979 1.37028 1.36026 1,35392 1.34842 1.34416 1.34023

1.49981 1.46377 1.44046 1.41802 1.40050 1.38706 1.37711 1.36670 1.36014 1.38442 1.35006 1.34598

nz

nl

n3

n3

- nl

G Series, SOs/TiOz = 3.004

E Series, SOs/TiOz = 2.775 1E 2E 3E 4E 5E

VOL. 32, NO. 7

0.01382 0.01131 0.00994 0.00872 0.00787 0.00727 0 00683 0 00644 0.00622

lG 2G 3G 4G 5G 6G 7G 8G 9G 10G 11G l2G

1.48299 1.45465 1.43048 1.41319 1.39578 1.38270 1.37303 1.36462 1.35801 1.35260 1.34798 1.34084

1H

1.40853 1.40056 1.38891 1.37883 1,37138 1,36543 1.35978 1.35682 1,35183 1.35054 1.34757 1.34463 1.34215 1.33850 1.33888

1.47797 1.45046 1 ,42679 1.40970 1.39273 1.37979 1.37028 1.36209 1.35553 1.35018 1.34554 1.33854

1.49126 1.46148 1.43639 1.41850 1.40060 1.38696 1.37711 1.36853 1.36183 1.35622 1.35119 1.34428

0.01329 0.01102 0,00960 0.00880 0.00787 0.00717 0.00683 0.00644 0.00630 0.00604 0.00565 0.00574

H S eries, Sulfuric Acid 2H 3H 4H

5H 6H

7H 8H 9H 10H 11H 12H 13H 14H 15H

1.40581 1.39786 1.38637 1.37625 1.36887 1.36301 1.35734 1.35338 1.34948 1.34825 1.34629 1,34236 1.33989 1.33629 1.33324

1.41245 1 ,40433 1 ,39266 1 ,38246 1.37505 1.36897 1.36327 1.35930 1.35525 1.35393 1.35102 1.34801 1.34651 1,34176 1.33870

0 00664 0.00647 0.00628 0.00621 0.00618 0.00596 0.00593 0.00592 0.00577 0.00568 0.00573 0.00565 0.00562 0.00647 0.00546

cally no excess sulfur trioxide is present, the solvent is water. By plot0.00600 ting rz, rl, and r3 as ordinates and 0.00590 0.00575 per cent sulfur trioxide as abscissa, straight lines were produced. It was then a simple matter to calculate the excess sulfur trioxide in the solution and obtain the value for the specific refractivity of the solvent by referring to the araDh. The values were dotted on a sheet of graphY paper llrge enough to give the desired precision. Table IV lists the calculated values for molecular refracTo determine the additivity of the refractivities, it was first tivity and dispersion. The significant feature of these results necessary to calculate the molecular refractivity of the titanyl sulfate in solution. The following formula was used for the is the fact that the value remains constant except in the most calculation : dilute solutions. The molecular dispersion shows this deviation exceptionally well. This increase is probably due to the formation of a product of hydrolysis which has a higher refrac100M 7Li - 1 100 - P tive index, and since an increase in the refractive index results R " = F [ ( G q (T)] in the increase of specific refractivity, there is a corresponding 100 - P '3) increase in the molecular refractivity. The average value = y [ r . rw] C Series, SOa/TiOr = 1.591

1C 2C 3C 4C 5C 6C 7C 8C 9C 1OC

1.49500 1.47094 1.45255 1.43229 1.41488 1.40144 1.38194 1.36653 1.35660 1.34421

1.48953 1.46610 1.44825 1.42840 1.41140 1.39786 1.37903 1.36338 1.35409 1.34193

1.50490 1.47896 1.45989 1.43868 1.42057 1.40626 1.38651 1.37028 1.36047 1.34776

0.01537 0.01286 0.01164 0.01028 0.00917 0.00840 0.00748 0.00690 0.00638 0.00583

~

~

2)

(r)

where R,

molecular refractivity of solute n, = refractive index of solution nw = refractive index of water r8 = specific refractivity of solution rYl = specific refractivity of water P = titanyl sulfate in solution, % M = molecularweight of titanyl sulfate d

=

=

density

To arrive a t such a figure, the titanium present in solution was first calculated as titanyl sulfate. The excess sulfur trioxide was calculated as sulfuric acid solution in which this titanyl sulfate was dissolved. I n the A series, where the ratio is 1,001 and practi-

FIGURE 3. RELATION BETWEEN SPECIFIC DISPERSION 4 N D TITANIUM DIOXIDEAND SULFUR TRIOXIDE CONTENTS OF TITANYL SULFATE SOLUTIONS


JULY, 1940

1013

TABLE 111. SPECIFIC REFRACTIVITIES Soln.

rz

ri

73

Soln.

c Series, SOa/TiO?

A Series, S03/Ti02 = 1.001

1h 2.4 3.4

4-1 5 -4 6A

7A 8A 9A 10.4 11.1 12.4 13.4 14.4 15.4 16.i

17.1 18.1 Water

B

0.17921 0.18029 0.18311 0.18436 0.18641 0.15821 0.19007 0.19180 0.19354 0,19506 0.19643 0.19770 0.19873 0,19979 0.20070 0.20211 0.20292 0.20449 0 20602

0,17745 0,18228 0.17885 0 18351 0,18147 0 18586 0 18278 0 18701 0,18489 0.18501 0,18673 0.19060 0.18861 0 19236 0.19040 0.19406 0,19217 0.19577 0.19368 0.19720 0,19509 0.19854 0,19637 0.19977 0.19738 0,20076 0.19846 0.20186 0 19935 0.20271 0.20088 0.20417 0,20163 0.20482 0.20328 0.20640 0.20480 0.20778

Series, SOa/TiOz = 1.259

1B 0.17750 2 0 0.18004 3B 0.18408 4B 0,18700 5B 0.18965 6 B 0.19206 7B 0.1943i ?B 0.19636 9B 0.19903 1 OB o.zno87 11B 0 20215 1LB 0 20392

0 18054 0.18278 0.18654 0.18932 0.19185 0.19420 0.19645 0.19835 0.20098 0 20283 o 20411 0 20.578

0.17576 0.17835 0.18256 0.18554 0.18825 0.19071 0.19306 0.19502 0.19770 0.19960 0.20092 0.20265

n

r2

1C 0.17617 0.17886 0.18101 0.18373 0.18629 0.18877 0.19233 0.19616 0.19862 IOC 0.20221 2C 3C 4C 5C 6C 7C 8C 9C

E 1E 2E 3E 4E 5E 6E 7E 8E 9E

10E 11E 12E

D Series, SOajT10* = 2.069 1D 2D 3D 4D 5D 6D 7D 8D 9D 10D 11D

0.17705 0.17554 0.18031 0.17886 0.18358 0,18221 0.18613 0.18480 0.18913 0.18726 0,19018 0.18883 0.19399 0.19276 0.19559 0.19433 0.19720 0.19594 0.19991 0,19863 0.20195 0.20073

obtained for the molecular refractivity of titanyl sulfate is 24.5, which compares favorably with 22.2, the sum of the atomic refractivities ( 1 ) .

Viscosity Measurements Table V gives the results of viscosity measurements on the solutions. The values for the A, C, and G series are shown in Figure 5, plotted against the titanium dioxide content. The rapid rise in viscosity is similar to that found with silicates which are definitely known to contain complexes a t concentrations comparable to these. Here, as in the refractive index curves,

0.17949 0.18261 0.18613 0.18825 0,19061 0.19218 0.1959'4 0.19751 0.19707 0.20180 0.20385

F 1F 2F 3F 4F 5F

6F 7F 8F 9F 10F 11F 12F

Rs

A Series, 24.82 24.87 24.62 24.59 5.4 24.49 6A 24.29 7A 24.32 RA 24.18 9A 24.25 10-4 24.26 11.4 24.31 12.4 24.34 13A 24.32 14.4 24.41 15.4 24.46 16A 24.60 17-4 24.48 184 24.53 Water 3.712

%SO!

FIGURE4. DIFFERESCE BETWEEX ANGLES ON REFRACTOMETER FOR TITANYL SVLFATESOLV-

9D 10D 11D

TIONS

98

56

0.16723 0.17176 0.17587 0.18030 0.18409 0.18747 0.19173 0.19338 0.19550 0.19756 0.19905 0.20074

rl

TJ

r3

G Series, SOdTi02 = 3.004

0.17327 0.17724 0.18137 0.18446 0.18703 0,19009 0.19291 0.19532 0.19725 0.19928 0,20110 0,20460

lG 2G 3G 4G 5G 6G 7G 8G 9G

0.16932 0.17334 0.17771 0.18122 0.18524 0.18861 0.19135 0.19399 0 1Y609 1OG 0.19806 11G 0.19995 12G 0,20270

0.16781 0.17196 0.17638 0.17993 0.18397 0.18733 0.19009 0.19278 0.19487 0.19683 0.10871 0.20146

0.17179 0.17555 0.17984 0,18332 0.18723 0,19048 0.19392 0.19585 0.19798 0.19959 0.20163 0.20465

K Series, Sulfuric Acid

0.17126 0,17646 0.17940 0.18367 0.18735 0.19066 0,19489 0,19648 0,19859 0.20063 0.20213 0,20381

1H 0.16384 2H 3H 4H 5H 6H 7H 8H 9H 10H 11H 12H 13H 14H l5H

0,16770 0.17398 0.17967 0.18386 0.18718 0.19030 0.19252 0,19473 0,19551 0.19713 0.19883 0.20026 0.20246 0.20455

MOLECULAR REFRACTIVITY ASD DIJPERSIOX R3 R3 - R I Soln. Rz Rl R3 R3 - R I S@a/Ti@z = 1.001 E Series, SOa/TiOz = 2.775 Ri

1E 2E 3E 4E 5E 6E 7E 8E 9E 10E 11E 12E

1F

SOa/TiOr = 1.591

3D 4D 3D 6D 7D

99

0.16875 0.17257 0.17721 0.18165 0.18539 0.18875 0.19207 0.19461 0.19671 0.19878 0.20030 0.20199

C Series, 23.69 23.73 23.67 23.61 23.55 23.60 23.50 23.56 23.61 23.83

1D 2D

32

Soln.


SOs/TiOr = 1.259

inc

24

0.16930 0.17356 0.17783 0.18105 0.18373 0.18692 0.18974 0.19219 0.19418 0.19619 0.10799 0,20154

B Series, 24.42 24.17 24.05 23.90 23.95 23.86 23.85 23.88 23.94 24.12 24.00 12B 24.04

1C

/6

0.17079 0.17501 0.17919 0.18238 0.16501 0.18816 0.19097 0.19340 0.19339 0,19741 0.19926 0.20374

1.4 2.4 3A 4A

2C 3C 4C 5C 6C 7C 8C 9C

a

ra

rl


TABLE I\'. Soln.

1B 2B 3B 4B 5B 6B 7B 8B 9B 10B 11B

0

rz

Soln.

r3

1.591 0.17452 0.17891 0 17728 0.18147 0.17952 0.18355 0,18229 0.18610 0.15491 0.15853 0.18740 0 19089 0.19122 0.19457 0,19487 0.19818 0.19737 0.20056 0,20100 0.20410 =

8D

24.04 23.79 23.70 23.55 23.59 23.54 23.52 23.49 23.55 23.63 23.64 23.38 23.32 23.37 23.34 23.29 23.22 23.27 23.26 23.22 23.29 23.49

25.12 24.81 24.64 24.46 24.47 24.39 24.51 24.33 24.44 24.59 24.60 24.49 24.37 24.39 24.33 24.24 24.12 24.14 24.09 24.10 24.15 24.31

D Series, SOa/TiOz = 2.069 23 06 23.18 23.13 23 00 23 58 23.12 23 20 23 23 23 21 23 52 23 56

1.08 1.02 0 94 0.91 0.88 0.85 0.99 0.84 0.89 0.96 0.96

1.11 1.05 1.02 0.99 0.95 0.90

0.87 0.83 0.88 0.86 0.82

2F 3F 4F 5F 6F 7F 8F 9F 10F 11F 12F

22.79 22.73 22.62 22.68 22.76 22.67 22.75 22.72 23.00 22.97 23.10 23.18 F Series, 22.20 22.08 22.40 23.25 22.55 22.42 22.58 22.67 22.74 22.81 22.84 23.68

21.43 22.38 22.28 22.37 22.48 22.44 22.48 22.42 22.53 22.54 22.56 22.79

22.20 22.26 22.27 22.50 22.61 22.60 22.63 22.70 22.70 22.80 23.23 24.18

1H 2H 3H 4H

9.60 9.62 9.66 9.69 9.67 9.10 9.63 9.72 9 68 9.12 9.70 9.69 9.69 9.63

1.07 0.97 0.99 1.77 0.85

0.77 0.81 0.84 0.89 0.75 0.88 0.86

SOa/TiOz = 2.936

21.82 21.93 22.09 22.01 22.22 22.13 23.73

22.94 22.94 23.04 22.90 23.06 22.95 24.61 23.10 22:45 23.28 22.50 23.28 22.24 23.24 22.91 23.96

G Series, SOa/TiOz 1G 2G 3G 4G 5G 6G 7G 8G 9G 1OG 11G 12G

23.50 23.35 23.27 24.14 23.33 23.21 23.29 23.26 23 42 23 29 23 44 23.65

21.82 21.94 21.93 22.16 22.32 22.30 22.26 22.40 22.38 22.48 22.i o 23.51

1.12 1.01 0.95 0.89 0.84 0.82 0.88 0:83 0.78

1.00 1.05

= 3.004 22.94 1.12 22.89 0.95 22.87 0.94 23.05 0.89 23.17 0.85 23.05 0.75 23.09 0.83 23.14 0 . 7 4 23.19 0.81 23,20 0.72 22.96 0.26 24.65 1.14

H Series, Sulfuric Acid

5H

6H 7H 8H 9H 10H 11H 12H 13H 14H l5H

in

so

9.54 9.56 9.61 9,62 9.61 9.64 9.56 9.64 9.61 9.66 9.64 9.63 9.61 9.60 9.79

9.68 9.69 9.74 9.77 9.77 9.79 9.73 9.82 9.79 9.82 9.83 9.84 9.85 9.81 in in

0.14 0.13 0.13 0.15 0.16 0.15 0.17 0.18 0.18 0.16 0.19 0.21 0.24 0.21 0.31

1014


0

4

8

/Z

16

7:

FIGURE 5. VISCOSITY us. TITANIUM DIOXIDE CONTENT

there is no maximum or minimum, but the rapid rate of change is signific a n t . P l o t t i n g of t h e fluidities produces a curve which approaches a straight line. In order to observe the behavior of solutions prepared b y a different method, a basic solution of a p p r o x i m a t e l y 1.5 acidity ratio was prepared by adding freshly precipitated orthotitanic acid to an acid titanium sulfate solution. Upon dilution a decided turbidity resulted, whereas in the solutions of the previous runs, no such action was observed. In diluting the concentrated solutions prepared from titanyl sulfate, t h e w a t e r was added

gradually with thorough agitation. This was found to be essential for clear solutions after we discovered that, if the required amount of water were added a t once, a permanent turbidity resulted, probably owing to the great local dilution and consequent hydrolysis. An illustration of the practical application of the findings of this investigation is shown by following the course of a typical hydrolysis. A solution containing 3.93 per cent titanium dioxide, with an acidity ratio of 2.37, was hydrolyzed by boiling according to Hixson and Plechner (7). At each hour a sample was removed and analyzed, and the refractive index recorded. Figure 6 shows the results of this hydrolysis. The curves for titanium dioxide content and refractive index can, by proper choice of scale, be made virtually to coincide, whereas the curve for sulfur trioxide content does not conform with either of the others. It is evident that by determining the refractive index of the solution, it is possible to follow the course of the hydrolysis, regardless of the sulfur trioxide content and that by determining the density a t the same time, it is a simple matter to arrive a t the complete analysis of the solution. This may be done by plotting the refractive index against density for a number of ratios. By connecting the points representing the same sulfur trioxide (or titanium dioxide) concentration, the complete analysis may be estimated with a fair degree of accuracy for any solution simply by obtaining the refractive index and density. This procedure provides a new, accurate tool for the control of the most important operation in the manufacture of titanium oxide; due consideration to be given to the presence of impurities. The time required is but a fraction of the time needed for the cumbersome analytical method now in use and does not require the services of a trained analyst. TABLE V. Soh.

AND FLUIDITY OF SOLUTIONS VISCOSITY

Viscosity Centipoise8

A Series, SOs/TiOz 3.6555 7A 2.6268 SA 2.1265 SA 1.8239 10A 1.5833 11A 1.4397 12A 1.3298 13A 1 ,2324 14A 1.1808 15A 1.0872 16A 1.0453 17A 0.9805 18A 0.8937 Water

B Series, SOa/TiOz 5.3210 4B 3.3575 5B 2.4179 6B 1,8679 7B 1.5471 8B 1.2797 9B 1.1446 10B 1.0690 11B 0.98104 12B

Fluidity Rhes

-

1.001

5C 6C 7c 8C 9c

1oc

4.5301 3.2089 2.1167 1.5235 1.2985 1.0735

D Series, SOa/TiOz 5.0780 3D 4D 3.5240 2.6909 5D 2.2969 6D 1.7076 7D 1.5298 8D 1.3815 9D 1,1874 10D 1.0711 11D Time / h s J

Soh.

Viacosity Centipoise8

Fluidity Rhes

E Series, SOa/TiOz = 2.775 0.22645 4.4160 4E 3.2542 0.30730 5E 0.40808 2.4505 6E 0.51024 7E 1.9599 0,59876 1.6701 8E 0.67088 1.4906 9E 0.74968 1.3339 10E 0.82263 1.2156 11E 0.96790 12E 1.0332

F Series, SOa/TiOz = 2.936 =

1.259

4F 5F 6F 7F 8F 9F

10F 11F 12F

4.5685 2,9982 2.2515 1.7895 1.5314 1.3579 1.2198 1.1421 1.0629

G Series, SOs/TiOz = 3.004 0.21586 0.33229 4.6326 4G

C Series, S03/Ti02 = 1.591

FIGURE 6. EFFECT OF TIMEIN THE HYDROLYSIS OF TITANITJM SULFATE SOLUTION

VOL. 32, NO. 7

0.22074 0.31163 0.47243 0.65640 0.77011 0.93156 2.069

5G 6G 7G SG 9G 10G

11G 12G

3.0095 2.2614 1.8637 1,5868 1.3994 1.2743 1.1506 1.0415

0.44220 0.53656 0.63020 0.71460 0.78475 0.86911 0.96016

H Series, Sulfuric Acid 5.7318 4.3615 3.0818 2.3583 1.9680 1.7068 1.5136 1.3894 1.2798 1.2518 1,1880 1.1195 1.0733 1.0083 0,95887

JULY, 1940


Literature Cited (1) Abegg, Handbuch der anorganischen Chemie, Vol. 111, Pt. 2, p. 440 (1909). (2) Arrhenius, 2. physik. Chem., 1, 288 (1887). (3) Blumenfeld, J., U. S. Patent 1,795,467 (March, 1931). (4) Briihl, Proc. Roy. Imt. U t . Brit., 18, 122 (1906); Ber., 46, 878, 1153 (1907), 41, 3712 (1908). (5) Fajans and Wust, “Textbook of Physical Chemistry”, New York, E. P. Dutton & Co., 1930. (6) Gladstone and Hibbert, Trans. Chem. Soe., 67, 831 (1895); 71, 822 (1897). (7) Hixson, A. W., and Plechner, W. W., IND.ENG.CHEM.,25, 262-74 (1933). (8) Jander, G., and Jahr, K. F., Kolloid-Beihefte, 43, 295-362 (1936).

1015

Jarmus, J. M., and Willets, W. R., Papct Trade J . , Jan. 4, 1934. Kanits, 2. physik. Chem., 22, 366 (1897). Mecklenburg, W., U. S. Patent 1,758,528 (May, 1930). Parravano, N., and Caglioti, V., Gazz. chim. ital., 64, 429-50 (1934). Rossi, A. J., and Barton, L. E.. U. S. Patent 1,196,030 (Aug., 1916). Thornton, W. M., Jr., “Titanium”, A. C. S. Monograph 33, p. 88, New York, Chemical Catalog Co., 1927. Thorpe and Rodger, Phil. Trans., 185, 397 (1894). Weiss, L., and Landecker, M., 2.anorg. Chem., 64, 71 (1909). Wintgen, R., and Lins, K., 2.angew. Chem., 49, 489-92 (1936). Work, L. T., and Ligorio, C., IND.ENO.CHEM., 29,213-17 (1937). Work, L. T., and Tuwiner, S. E., Ibid.. 26, 1263-8 (1934).

Corrosion of Copper by Sodium Halide Solutions F. J. ASSELIN AND F. A. ROHRMAN Michigan College of Mining and Technology, Houghton, Mich.

OLUBLE iodides have a pronounced effect upon the

a solution increases, the oxygen solubility must decrease and the conductivity increase. Similarly, as the concentration of the solution increases, the oxygen solubility must decrease and the conductivity increase. If we plot corrosion of copper against solution concentration or solution temper a tur e, .zs m a x i m a will b e encountered be.20 cause the oxygen factor and the conductivity .IS factor oppose each other. Davy (2) stated as early as .to 1824 that concentrated salt solu.os tions attacked copper less readily than did the more 0 0 20 40 60 80 loo dilute solutions. A consideration FIGURE 3. CORROSION O F COPPER I N of the oxidationSODIUM HALIDESOLUTIONS reduction potentials and the solubilities of the copper halides gives an indication of the FIGURE 1. SOLUBILITY OF OXY- FIGURE 2. COXDUCTIVITY nature of these reactions: GEN IN SODIUM CHLORIDE SOLU- OF SODITJM CHLORIDE SOLUSolubility Potential,

S

corrosion of copper and copper-rich alloys, whereas the soluble fluorides have but little effect. The purpose of this paper is to present experimental data on the nature of copper corrosion by the soluble halides. The presence of oxygen or oxidizing agents is necessary to promote the corrosion of copper in liquid media. Damon and Cross (1) gave clear evidence of the importance of oxygen during the corrosion of copper. The quantity of oxygen that can dissolve in a solution is dependent upon three factorsthe temperature of the solution, the concentration of the solution, and the solution and diffusion rates of the oxygen into the solution. MacArthur (3) gave results on the solubility of oxygen in many salt solutions. His data show that the oxygen solubility is nearly inversely proportional to the salt concentration. Figure 1 illustrates this relation.

TION

TIONS

The conductivity of a solution is a major factor in the corrosion of metals. It is known that the conductivity of all solutions increases with temperature, and that the conductivity of most solutions increases with the concentration. Figure 2, taken from data in several handbooks, shows the relation of the conductivity of sodium chloride solutions to normality. Considering only three factors (oxygen concentration, temperature, and conductivity), we can predict the possible behavior of copper in most solutions. As the temperature of

Halide CUZClZ CusBrs CUZIZ

Product 1 0 x 10-6 4 0 X 10-0 6 0 X lo-**

Reaction

+ C1CUD+ B r Cuo + ICuo

+e = CuBr + e - CUI + e = CuCl

Volt

+o

12

+0.05

-0.17

The values for the fluorides are not obtainable but might be considered as following the regular order of values according to the atomic number. Sheet electrolytic copper (99.95 per cent) was cut into squares of about 5 X 5 cm. (2 X 2 inches) so as to give a p proximately 0.5 sq. dm. of “apparent” area. These pieces were annealed and polished under similar conditions. They were then exposed to 400 cc. of the halide solution in 600-cc.

TITANIUM SULFATE SOLUTIONS - Industrial & Engineering

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