lNA4LYTICALEDITION
NOVEhIBER 15, 1940
cipitated with ammonium hydroxide from a sulfuric acid solution, dissolved in hydrochloric acid, precipitated by hydrolysis as the basic chloride, filtered, washed, ignited, and weighed as titanium dioxide. Attempts were made to precipitate the titanium with ammonium hydroxide, ignite to the oxide, and weigh. This method was finally discarded on account of high results. Comparison of the volumetric method with the basic chloride and the cupferron methods shows a n average percentage deviation of -0.03 and -0.08, respectively. Certain precautions (no more severe than those required with a Jones reductor) must be observed in the volumetric method. I n preparing the zinc column the glass m-001 should be well packed; otherwise the smaller pieces of zinc (through constant reaction with the sulfuric acid solutions) will pass through to the ferric sulfate solution and give high results. It is advisable to repack the funnel after about every twenty analyses, and to run a blank for every two or three determinations. The zinc may be used again for repacking, providing it can be retained on a 30-mesh sieve. The relationship of time for the zinc to be in contact with the titanium solution before filtering, and the concentration by volume of the sulfuric acid was determined (Table 11). I n each case, good results were obtained only when the solution took on a distinct violet color. The more concentrated the acid the less time required for contact with the zinc. I n the case of a 5 per cent sulfuric acid solution, it took a t least 15 minutes for reduction in the beaker, for a 10 per cent solution about 10 minutes, and for a 15 per cent solution about 5 minutes. Tests were made on titanium solutions which were not treated with zinc and acid before passing through the reductor. Low results were obtained, and in no case could they be duplicated.
673
A Modified Jones Reductor J. E. EDWARDS 1.54 Hillcroft Crescent, Oxhey, Watford, Herts, England
T
HE apparatus described below may prove of use in some applications of the Jones reductor. It allows reduction of
warm solutions (when reduction will be more rapid) which might be reoxidized by air a t higher temperatures. Solutions of iron can be reduced very rapidly by this means.
FILTER
PUMP
TABLE Ir. RELATIOXSHIP BETWEEN TIMEAND ID CONCENTRATION Time ?din. 5 10 15
20 25 5
10 15 20
5 10
15
1
(0.04930 gram of Tion taken) Concd. HnSO, TiOn Found Vol. 70 Gram 0.04597 ? 0.04767 0.04946 5 0.04924 5 0.04969
!
10
10 10 10
15 15 15
0.04741 0.04924 0.04980 0.04942 0.049 13 0.04936 0.04924
Deviation
Gram
- 0.00333 +-0.00163 0.00016 - 0.00006
+ O . 00039 -0.00186 0.00006 +0.00050 +0.00012 0.00017 +0.0000~ 0.00006
-
-
Summary An accurate volumetric method is described for the determination of titanium dioxide. Results compare favorably with those obtained by two standard gravimetric methods. The advantages are the elimination of the use of amalgams, availability and inexpensive nature of the apparatus, and ease of assembly.
Literature Cited (1) Hope, H. B., Moran, R. F., and Ploetz, A. O., IND EKG.CHEiu., Anal. Ed., 8, 48 (1936). (2) Jarmus, J. M., and Willets, W.R., Paper Trade J., 9 8 , 4 1 (1934). (3) Lundell, G. E. F., and Knowles, H. B., IND.ENQ. CHmr., 16, 723 (1924). ( 4 ) Lundell, G. E. F., and Knodes, H. B., J . Am. Chem. SOC.,45, 2620 (1923). (5) Marignac, C . , 2. anal. Chem., 7 , 111 (1S68). (6) Neumann, B., and Murphy, R. K., 2. a n y e & . Chem., 26, 613 (1913). (7) Newton, H. D., Am. J . Sci., 25, 130 (1908). (8) Pisani, F., Compt. rend., 59, 289 (1864). (9) Thornton, W. M., Jr., “Titanium”, A. C. S. Monograph 23, p. 90, New York, Chemical Catalog Co., 1927. (10) Wells, H. L., and hlitchell, W. L., J . A m . Chem. SOC.,17, 878 (1895).
FIGURE 1
The exit tube of the Jones reductor (Figure 1) is fitted with a three-way tap, one tube opening to the air and the other being connected by means of a vertical glass tube to the top of a cooling coil surrounded by cooling water. The lower end of the coil is connected to a Witts filter apparatus, in order that the solution may be collected in a beaker. As set up for use, the Witts filter apparatus was connected to a water pump to draw the sample through the system, the waste m-ater passing through the jacket of the cooling coil. The tubing should be about 4 mm. in internal bore; under these conditions the liquid passing through will completely fill the tube. To use the apparatus a beaker is placed in the Witts filter apparatus and the water is turned on, only a slight vacuum being required. A little warm water is poured into the Jones reductor and the three-way tap is turned to allow the water t o pass to the beaker. The warm solution to be reduced is passed in the usual way, followed by a little wash water. The three-way tap is turned to allow air to enter the tube, so that all the liquid passes from the tubing into the beaker. Under these conditions the solution after reduction does not come in contact with any air until cold. The cooling coil used was the damaged coil condenser of a Soxhlet extraction apparatus.
