I N D U S T R I A L A N D ENGINEERING CHEMISTRY
November, 1929
certain exceptions to the general rule, even when dealing with closely related catalysts, It is doubtful if the decomposition method Of testing for a given synthesis find a very wide application, but it should prove Useful in a preliminary narrowing of the field in the case of high-pressure syntheses, leaving less work to be done under the more difficult experimental conditions obtaining at high pressures. Literature Cited (1) Adkins and Perkins, J . Phys. Chem., 32, 221 (1928). (2) Bur. Mines, Bull. 197.
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(3) Frolich, J . SOC.Chem. Ind.. 47, 173T (1928). (4) Frolich, Fenske. Perry, and Hurd. J . A m . Chem. SOC.,111, 187 (1929). (5) Frolich, Fenske, and Quiggle, IND. END.CHBM.,20, 694 (1928). (6) Frolich. Fenske, and Quiggle, J . A m . Chem. Soc., 111, 61 (1929). (7) Frolich, Fenske, Taylor, and Southwich, IND. END. CHBM.,20, laat (1938).
i:i
Z ~ r , S , e ~ , " , " , C " ~ ~ ~ o ~ ~ ~ , ~ 6 d 11 n ~(1915), 31q"~~~!.sa, (10) Patart. Bull. soc. encour. i n d . nal., 137, 141 (1925). (11) Peters and Baker, IND. ENG.CHBM..18, 69 (1926). (12) Romijn. 2. anal. Chem., 36, 19 (1897). (13) Smith and Hawk. J . Phys. Chem., 32, 415 (1028). (14) Starch, I b i d . , 32, 1743 (1928).
Titanium White' A New Method for Its Preparation Foord von Bichowsky TITASIACORPORATION, GLESDALB, CALIF.
A simple process is describedfor conuerting titanium nitride into titanium white h.y the employment of nitric acid and catalysts. The white so made has a uniquely Low speciJic gravity. ITAKIUM white, or chemically pure titanium oxide (Tion),is becoming an important article of commerce. Owing to its covering pomer, its inertness, and its nonpoisonous quality, it is of primary value as a pigment. The oxide is also finding use in the rubber ( 2 ) , linoleum (Ii), and other industries ( 5 ) . The principal drawback t o the much wider use of this oxide is its cost. The titanium white is expensive, not because of the scarcity of the mineral ilmenite (Fe0.Ti02) from which it is made, but rather becauqe of the numerous steps necessary to make an oxide free from traces of iron; for iron seriously affects its whiteness. When this fact was discovered, plans began to be proposed for keeping the titanium oxide uncontaminated with iron ( 4 ) . Of these methods the one proposing to convert the ilmenite into a mixture of titanium nitride and iron and then to remove the iron by means of dilute sulfuric acid has much to recommend it. Titanium nitride is easily prepared by heating ilmenite and carbon in an atmoqphere of nitrogen. One thus obtains, after treatment with dilute acid, a concentrate high in titanium and very low in iron. Such a titanium nitride concentrate can be readily converted into ammonium sulfate and titanium compounds through boiling with strong sulfuric acid, as Friedel and Guerin (9) indicated in 1876. Thirty-four years later Bosch (3) showed that this could also be accomplished by employing other oxidizing agents. I n 1920 Farup ( 7 ) patented a combination of quite similar methods and proposed to manufacture titanium white thereby.
T
Development of Method
This company has been interested for a number of years in extending the uses of titanium nitride (Ti?h'?) and titanium cyanonitride (TiSCN,). Some time ago, during an attempt to remove traces of lead fluoride, by means of strong nitric acid, from a sample of finely ground titanium nitride, containing graphite, it was observed that, after standing a day in a warm place, bubbles of gas were being given off from the nitride. This was unexpected, as the literature distinctly states (6, IO) that titanium nitride is unattacked by pither cold or boiling nitric acid, in which, of course, lead fluoride is soluble. The beaker containing the titanium nitride and nitric acid mix-
* Received
July 17, 1929.
ture was therefore set aside. At the end of a month the nitride had all been converted into a bluish white titanium oxide mixed with graphite. EXPERIMENTS USING NITRIC A c m S o m e small-scale experiments were next undertaken. I n one test a gram of titanium nitride was stirred into 15 cc. of a weak nitric acid made by diluting 1 volume of nitric acid (sp. gr. 1.42) with 2 volumes of water and the suspension heated, a t about 60" C., on the water bath and stirred. I n a few days the brasscolored nitride was changed completely into the oxide of titanium. This oxide was in an extremely fine state of division. EXPERIMENTS WITH SODIUMNITRATE AND SULFURIC Arm-Interesting as this was from a laboratory standpoint, its commercial employment was handicapped by the fact that nitric acid is a rather expensive reagent. To overcome this disadvantage it was suggested that the acid be generated in situ. Therefore 2 grams of sodium nitrate were added very gradually to a suspension of 1 gram of titanium nitride in 10 cc. of concentrated sulfuric acid. The acid mixture was kept at 50' C. At the end of 100 hours the acid was cooled and poured into 250 cc. of cold water. Practically all the titanium dissolved and upon filtering and subsequent boiling hydrolysis occurred and titanium oxide separated. I n this case about one-third of the nitrogen in the titanium nitride was recovered as ammonia. When this esperiment was repeated with dilute sulfuric acid and a saturated aqueous solution of sodium nitrate, the r e action, once the temperature began to rise, went very violently and gave off heat, so that it was necessary to add the nitrate solution very gradually and to employ cooling to prevent the contents from foaming over the sides of the b a k e r . When the reaction became violent, copious brown fumes were evolved. If the conditions were carefully regulated, after filtering off any unconverted nitride, silica, etc., a clear yellowish sqlution was obtained, which, concentrated under vacuum, gave as end product a hitherto undescribed acid sulfate of titanium. A more complete description of this sulfate and other new acid titanium alums will be given in a later paper. The filtrate before evaporating was tested for ammonia, but with negative result. RECOVERY OF K;ITRoGEN-It is evident, therefore. that nitric acid alone or in the presence of water and sulfuric acid
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can completely oxidize titanium nitride to titanium oxide or sulfates, and that nitric acid is reduced to nitrogen and brown nitrogen oxides so t h a t all the nitrogen of the titanium nitride is apparently lost. This is a serious loss, as combined nitrogen is valuable. Experiments were therefore begun with the object in view of slowing down the reaction so that the oxidation would not be so violent. It was hoped that in this way some nitrogen might be recovered as ammonia. A kilogram of a crude titanium cyanonitride having the following analysis was set aside: Per cent 71 00 s 05 14 30 0 56 1 5s 4 51
Titanium Carbon Xitrogen Iron Si02 Oxygen (by diff )
Vol. 21, No. 11
ing a glass stopcock. After all the air in the apparatus had been displaced with carbon dioxide, 3 cc. of water containing 0.1 cc. sulfuric acid together with 0.02 cc. phosphoric acid and 0.2 cc. nitric acid were allowed t o drop through the thistle tube onto the cyanonitride. The gases given off were collected over a sodium hydroxide solution. The residual material in the flask was analyzed for combined nitrogen-that is, for ammoniacal, nitric, and nitride nitrogen. Table 111-Gases Evolved during Reaction TEMPERATURE OF WATERBATH h'rmocm c NITROGEN XITRICOXIDE COMBINED 0 c. cc. cc. Per cent 0.0 7.5 6.7 8.3 6.0 7 5 4.0 10.1
These figures were not sufficiently uniform to allow of any definite conclusions as to the course of the reaction. All that can be said is that the action of nitric acid a t the higher temperature (80" C.) was strongly oxidizing, since nitric oxide was absent from the reaction gases. It is probable that this exothermic action of nitric acid on titanium nitrogen compounds could be employed in the laboratory preparation of nitrogen gas. PHOSPH.4TE I O N A S KEG.4TIVE C A T S L Y S T - T ~following ~ two parallel experiments show even more markedly the value of the phosphate ions as a negative catalyst in the above type of reaction. Into each of two small beakers, equipped with thermometers as stirring rods, were placed 31 grams of titanium cyanonitride, 30 cc. of water, and 20 grams of concentrated sulfuric acid. When the contents of the beakers had reached a constant and equal temperature, to one were added 3 grams of sirupy phosphoric acid as a n inhibitor and 20 grams of strong nitric acid were poured simultaneously into each T i t a n i u m Oxide beaker. N2 RECOVERED
On the basis of its nitrogen content the material was assumed to contain 78.64 per cent of cyanonitride, the remainder being a mixture of graphite, titanium suboxide (Tiso,), etc. A weighed quantity of the cyanonitride was placed in a small Kjeldahl flask with a number of glass brads to prelent caking of the cyanonitride. A definite quantity of Tvater was added and then enough sulfuric acid to unite with all the ammonia that could theoretically be recovered. Finally, enough nitric acid (sp. gr. 1.42) was added to oxidize the titanium in the titanium cyanonitride to titanium dioxide. The mixture was heated for 30 hours on the water bath a t 70" * 5" C. The Kjeldahl flask was equipped with a reflux condenser. In order to prevent irregular action the flask was shaken a t regular intervals. At the end of the experiment ammonia was determined by adding strong caustic soda FOIUtion to the contents of the flask, and distilling the ammonia into tenth-normal acid. Table I-Recovery
TisCh'r Grams
of Nitrogen i n Preparation of f r o m T i t a n i u m Nitride HzSO4
cc.
HNOa
cc.
HnO
cc.
A S "3
Per cent
Table IV-Effect TIME 1.OoP.M
It will be observed t h a t the maximum quantity of nitrogen recovered as ammonia was only a little more than half the nitride nitrogen. ACTIONOF I~HIRIToRS-It was thought that better results might be obtained if some substance having a negative catalytic or inhibitive action were added to the reactants. A number of substances were tried, but of these phosphoric acid or phosphates gave the most satisfactory resultq. The experiments described above were repeated with the addition, in every case, of 0.1 cc. of sirupy phosphoric acid. The amount of water was the only variable. Table 11-Effect
of Adding Inhibitor o n Nitrogen Recovery NITROGEN RECOVERED WATER AS X'HJ cc. Per cent 3.43 5 6.10 10 20
30 40
6.87
7.33 7.33
Increasing the amount of sulfuric acid or inhibitor gave no increase in yield. Adding more nitric acid markedly decreased the yield. GASESEVOLVED DURING REACTION-In order to determine what gases were being given off during the reaction, 0.25 gram of the cyanonitride mas placed in a small flask having a side outlet tube connected to a Schiffs nitrometer tube and closed with a glass stopper through which passed a thistle tube hav-
1.04 1.07 1.10 1.12
of Phosphoric Acid o n Violence of Reaction OF BEAKER CONTENTS TEMPERATURE No phosphoric acid With phosphoric acid 30 30 31 38 32 54 31.5 65 31 75
It was thereupon necessary to employ external cooling and vigorous stirring to prevent the contents of the first beaker from foaming over. However, the contents of the second beaker reached only 65" C. after standing for 3 hours. Method for Preparation of Titanium Oxide and Recovery of Ammonium Sulfate*
One part by weight (35 grams) of the impure titanium cyanonitride was stirred into 20 parts by weight of water which was contained in a 1500-cc. beaker. Kext 1 part of commercial sodium nitrate and 0.1 part of sodium phosphate were added to the water, and when these had dissolved 1.5 parts by weight of concentrated sulfuric acid were added. The materials were stirred constantly while warming, to not above 80" C., on the water bath. The reaction went smoothly and, after 24 hours and when no more reddish colored cyanonitride was discernible and no more gas was given off, the beaker was filled with water and the stirring discontinued. The white titanium oxide was allowed to settle and the excess water, which contained ammonium sulfate and sodium salts, was siphoned off. This washing by settling and decantation was continued until the wash water was free of titanium and only faintly acid. The dioxide of titanium so obtained was 2 Patent applications have been filed upon these new materials and procedures.
I N D U S T R I A L A N D ENGINEERING CHEMISTRY
November, 1929
so finely divided t h a t it passed through filter paper. I n order to remove the last traces of the difficultly volatile sulfuric acid remaining in the titanium oxide paste, it was neutralized with ammonia. However, titanium oxide does not settle out well from neutral or basic solutions of this type, so a little dilute hydrochloric acid was added to facilitate the final washing of the oxide. After these washings had removed the last of the ammonium sulfate, hydrated titanium oxide which settled out was evaporated to dryness a t 100' C!. The wash waters were also concentrated. There were recovered therefrom 11 grams of ammonium sulfate, which represented 47 per cent of the combined nitride nitrogen. Properties of Titanium Oxide Produced
The dry titanium oxide from this experiment had a specific gravity of 2.72, which was much lighter than the forms of titanium dioxide previously known, which had a specific gravity of a t least 3.3 (1). Such a light-weight pigment would be especially adapted for ready mixed paints and lacquers. This sample of oxide, after being dried a t 160" C., lost 8.2 per cent of its weight. The resulting material was slightly hygroscopic, but that dried a t 100O C. remained practically constant in weight. The ground titanium oxide had a soft, almost talc-like, feel when rubbed between the fingers. Coarse particles were absent. The experiment showed the necessity of using only titanium nitrogen compounds low in dark-colored impurities such as the suboxide, unreduced ilmenite, or graphite. These impurities are only partially attacked by the nitric acid and remain in the finished product giving it a bluish gray shade. Repetition of the experiment with a small amount of a purer material gave an excellent white.
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Preparation of Pure Titanium Nitride Since working out these experiments it has been found possible to prepare titanium nitride free from the suboxide. In fact, the preparation of titanium nitride in a correctly designed electric furnace (8) is a very simple operation, the current consumption being about one kilowatt-hour per pound of pure titanium nitride. Equipment for Large-Scale Manufacture
For the conversion of titanium nitride to titanium white on a large scale, only a reaction vessel, a series of settling tanks or a classifier, a drier, and grinder are necessary. The principal chemicals are Chile saltpeter and chamber acid. The byproducts are ammonium sulfate, amounting to a third of the weight of nitride used, and sodium sulfate. When one compares this simple equipment and process with the array of fusion kettles, crystallizing vats, hydrolysis tanks, filter presses, and sintering equipment now used in the manufacture of titanium white, he will a t once see that the new process has far more than novelty to recommend it. Literature Cited Bachmann, U. S. Patent 1,459,418 (April 8, 1924). Barton, U. S. Patent 1,322,518 (Sovember 25, 1919). Bosch, U. S. Patents 957,843 (May 10, 1910); 990,191 (April 18, 1910); 990,192 (April 18, 1910). Braidy, Industrie chimiqup, 15, 105, 242, 290, 486, 539 (1927). Brown, Chem. M e t . Eng., 35, 427 (1928). Caven, "Textbook of Inorganic Chemistry," Vol. V, p. 254 (1917). Farup, U. S. Patents 1,343,441 (June 15, 1920); 1,539,096 (June 2. 1925). FitzGerald and Kelleher, U. S . Patent Application 294,981 (July 24. 1928). Friedel and Guerin, Comfit. rend., 82, 973 (1876). Friederich and Sittig, 2. anorg. allaem. Chem., 143, 299 (1925) Fritz, Farbe Lack, 1917, 589, 603, 615.
Solubility of Ethylene Glycol' Some Ternary Systems H. M. Trimble and Glen E. Frazer DSPARTMPITOF CHEMISTRY, OKLAHOMA AGRICULTURAL A N D MECHANICAL COLLEGE, STILLWATER, OKLA.
E
THYLENE glycol is more or less soluble in water, the alcohols, the aldehydes, and the ketones-substances which resemble it in chemical structure. It is quite insoluble in the hydrocarbons and similar substances, but it may be brought into solution in them by the use of suitable dispersing agents. The writers undertook a study of some of the ternary systems which are thus formed, since they found no record of any such work in the literature. Apparatus and Materials
All the volumetric apparatus used was carefully calibrated, and suitable corrections were applied when necessary. The ethylene glycol was twice redistilled from the best obtainable commercial product, and the fraction that distilled over between 196.5' and 197' C. (cor.) was used. The refractive index of this product was 1.430 a t 20" C., and its density was 1.1131 a t the same temperature. Analysis indicated t h a t it was 99.8 per cent pure. The other substances used were the best obtainable. Most of them were redistilled. Determinations of their densities, boiling points, and refractive indices gave values which agreed cIosely with the best published data. The "absolute" ethyl alcohol was not prepared by the writers, but their tests t
Received August 3 , 1929.
showed that its alcoholic content was a t least 99.8 per cent b y weight. Experimental Method
The synthetic method was used in the determinations. Glycol cannot be measured satisfactorily using ordinary volumetric apparatus because of its tendency to adhere to the walls of the apparatus in thick films. It was weighed out, by difference, from a dropping bottle of the ground-in pipet type, and the volume taken was calculated. The other substances were measured by means of burets. To the glycol was added the desired amount of the second substance, with which it was immiscible, and then the dispersing agent was added to the disappearance of cloudiness. More immiscible substance was then added and the mixture was again titrated to the disappearance of cloudiness, and so on, to establish the various points on the curves. I n a few experiments this method was reversed; the dispersing agent first added and the mixture was then titrated to the appearance of cloudiness. Results found by the two methods agreed well. The titrations were carried out a t room temperature. Different determinations made for the purpose of checking results agreed well, though they could not, of course, always be carried out a t exactly the same temperature. The data and temperature given for each system represent the best of the determinations
