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INDUSTRIAL AND ENGINEERING CHEMISTRY
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the growth increased, nonsterile medium 4B was added to maintain a constant but high ratio of cells to volume. When a volume of 6 liters was reached (pH 4.0 to 5.5), the entire stagc was used as inoculum for 18 liters of nonsterile medium 4B. Using this procedure, a series of 81 experimental 24-lit,er tanks were run in order to determine the average yield and reproducibility of this method. Of these 81 tanks, 03 ivere not contaniinat,ed, while 16 tanks viere low in potency due to coiitarninaSucrose 40 grams per liter 10 grams per liter Defatted soya flour (trypsin tion and 2 were low due t o the failure of the agitation system. digested 2 hours a t 37’ C . ) 5 grams per liter Calcium carbonate The average riboflavin potency of all t,hc t,anlrs was 1617 per ml. The average potency of the 63 iioncontaminated tanks was 1917 Shake flasks containing 100 nil. of this medium ~ w r est>er per nil. The distribution of riboflavin yields among these 63 and inoculated from slants. Owing to the high iron level of this medium n o more than 100 ml. could be added to a 23-liter f c ~ tanks is tabulated below: 01-er 300-, por ml. mentation. This volume of inoculum did not supp 9 tanks Between 200 and 3007 per inl. 19 tanks cells to combat contaniinati0n; therefore, an intermed Between 100 and 2 0 0 y per ml. 27 tanks Below l O O y per ml. 8 tanks inoculum stage was introduced. Six liters of niedimn 4B \vert; sterilized in a bottle fitted with a porous candle aerator and ari ACKNOWLEDGMEXT air filter. The urea n-as sterilized separately to avoid decomposition. -4fter cooling, the urea was added to the sterile medium T h e authors wish to express their appreciation of P. R. Burkand 107’ b y volume of 24-hour soya medium shake culture was holder oi \-ale University who supplied the slant cultures of added as inoculum. During 20 to 24 hours’ growth at) 30” C. Candida qudliermondia and t o 1,. Kickerham of the Northern under vigorous aeration, the pH fell from 6.2 to 5.0 or loircr. Regional Iicsearch Laboratory, Pcoria, Ill., who supplied the Five per cent of this culture TWS then used to inoculate 24 liters cultures of Candida$aieri. of nonsterile medium 4B. Using t,his technique, pot,encies as high as 3257 per nil. were obtained, but in some runs the above LITERATURE CITED yields n-ere not obtained for unknown reasons. A summary of (1) Burkholder, P. R., Arch. Biochem., 3, lZl(1943). data from one experiment involving t,hree tanks using the above (2) Burkholder, P. R . . Proc. S a t l . Acad. S c i . 1;. S., 29, 166 (1943). technique is given in Figure 2. The curve of riboflaviii produc(3) Elvehjem, C. d.,J . B i d . Chem., 90, 111 (1931). (4) Pappenheiniw, A . M., and Shaskan, E., Ibid., 155, 265 (1944). tion is closely related to the yeast growth curve. ( 5 ) T a n n e r . F. W., Jr., Vojnovich. C., and Van L a n e n , J. M . , Science, I t was felt that a possible csplanat,ion for the occasional failures 101,180 (1945j. in the tanks might be due to the sterilized medium used in the (6) Waring, W. S.,and W e r k t n a n , C. H., A r c h . Riochem., 1, 303 (19431. secpnd stage of inoculum culture. -4 new technique was developed which eliminated the usc of st>erilcmedium. -4 sinal1 R E c m v n u April 26, 1948. Presented before t h e Division of Agricultural and volume (1 to 3 liters) of nonsterile medium 413 mas inoculated Food Chemistry a t the 113th Meeting of the .AMERIC.AS CHEMICAL RocIEw. with 100 ml. of soya medium culture and acratcd as 1x;fore. B s Chicago, Ill. were encountered. Under tank condibions the ycast was subject t o variation or degeneration and yielded substrains which did not produce riboflavin. A larger inoculum was required since this organism did not grow as rapidly as Candida guillieimondiu, Therefore a new medium was developed to obtain vigorous growth in the inoculum phase. The composition of t,his medium was as fo1lon.s:
Titanium and Zirconium Corrosion Stu Common Mineral Acids E. A . GEE1ASD L. B. GOLDEN C . S. Bureau of M i n e s , College Park, M d .
HE term “rare metals” has of metal per day, the price of sponge, V. E. LUSBY, J K . ~ $5.00 per pound in lots of 100 cvolved less from scarcity than University of Yluryland, College Purk, Md. pounds or more, is low in comfrom processing difficulties. ‘TitaIlium, for example, is the fourt’h parison t o t’he initial offering price Innst abundant st,ructural element of now common metals such a s aluminum and magnesium. The purity of this material is high, in the earth’s crust, but was neglected until recent,ly because with metal content in excess of 99.5%; primary impurities are of its brittle characteristics. Research by the Bureau of Mines, hon-ever, has resulted in a process for production of ductile metal, reputed t o be oxygen, nitrogen, magnesium, iron, and chlorine. Zirconiuni is available from the Fooie Mineral Company, arid current pilot plant tests have advanced t,o batches of 200 Philadelphia, Pa., alt.hough the current’ price is relatively high, pounds. Previous publications describe the method of preparation arid physical characteristics of titanium and zirconium, approximately $200 per pound. The magnesium reduction process, producing a less pure zirconium, can be operated t o produced by a modification of the Kroll process ( 6 , IO). number of industrial laboratories are now evduating the furnish material probably a t a small fraction of this figure. commercial pot,entialities of titanium, and one, t’he Pigments Corrosion is a primary consideration in utilizing conventional materials of construction and in developing new products. It Department of the E. I. du Pont de Nemours & Company, Inc., Wilmington, Del., has announced the sale of sponge and ingot was therefore neccssary to establish a corrosion laboratory where new product’ssuch as titanium and zirconium could be evaluated, metal. Although - -production is small, estimated a t 100 pounds and Current tests are now under way a t the Bureau Of Mines, $present address, E. I. d u ~ ~ de nx ; te ~ i l&~Company, ~r~ I ~ ~Wilming. , College Park, Md. t o n , Del.
August
1949
INDUSTRIAL AND ENGINEERING CHEMISTRY
Figure 1.
1669
Corrosion Testing Equipment
There are few quantitative data available on the corrosiori resistance of titanium and zirconium; t h a t which exists is questionable because of the variable purity of the metals tested. Dean reported that titanium has excellent corrosion resistance, being similar t o the various 18-8 stainless steels (3, 4). Concentrated sulfuric and hydrochloric acids were reputed to attack titanium rapidly, whereas it was resistant t o concentrated nitric acid and 570 solutions of nitric, hydrochloric, and acetic acids and ammonium and sodium hydroxides. Gillett thus suggested the use of titanium in chemical equipment because of its resistance t o many acids and alkalies ( 7 ) . Kroll stated that the corrosion resistance of titanium is comparable to that of zirconium (8,9). Gillett states that zirconium will resist nitric, and hydrochloric acids in all concentrations a t 100" C., and is not attacked by aqua regia a t room temperature ( 7 ) . Concentrated sulfuric acid will attack rapidly a t 100" C., but will not react if the strength
Titanium is resistant to sulfuric and hydrochloric acids only at low concentrations but is almost completely resistant to all concentrationsof nitric acid. As a corrosion
resistant metal in hydrochloric and nitric acids, its general behavior is comparable to Type 316 stainless steel. However, it is somewhat less resistant than the latter in sulfuric acid. Zirconium is relatively resistant to all concentrations of hydrochloric, nitric, and phosphoric acids, although it is attacked by high concentrations of sulfuric acid at elevated temperatures.
is reduced to 50%. It is reported also that the nietal, unlike tantalum, is resistant t o 10 and 50% sodium hydroxide at 100' C. APPARATUS
This paper describes the apparatus used and the results obtained when titanium and zirconium were exposed t o the corrosive action of various concentrations of sulfuric, hydrochloric, and nitric acids at different temperatures. A stainless steel, type 316, was subjected to the same tests t o obtain a basis for comparison. Figure 1 shows the equipment assembled to run 16 samples a t one time under controlled conditions of temperature and aeration. The apparatus consists of the following: water bath, plywood panel, immersion heaters, mercury thermoregulator, relay, and rectran, flowmeters, glass stopcocks (2- and 3-way), flexaframe rods and connectors, condenser (versatile) clamps, clampholders, circulating pump. The temperature in this bath is maintained at 35" * 0.1 O C. The rate of aeration of individual samples is controlled by means of glass stopcocks mounted on the plywood panel and is periodically measured by passing the air through flowmeters. The manifold arrangement of the stopcocks makes it possible for one flowmeter to measure the air being delivered t o each of four samples. Two other constant temperature baths are being operated, one a water bath a t 60" f 0.1 O C. and the other an oil bath a t 100' =t 0.1 O C. Figure 2 shows the specimen support with specimen in place, aerator, condenser, and the 1-liter Erlenmeyer flask which contains the acid solution. During actual testing, the aerator and specimen are totally immersed in 750 ml. of acid solution. The condenser is used only in the 60' and 100' C. baths. Figure 3 shows the aerator and specimen support in more detail. This apparatus conforms to the recommendations of the American 80ciety for Testing Materials a s contained in its Tentative Method of Total Immersion Corrosion Test of Nonferrous hIetals ( 1 ) .
1670
INDUSTRIAL AND ENGINEERING CHEMISTRY
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Vibrotool. The final surfacing was made with fine abrasive cloth ( S o . 3/0 emery). The samples then were degreased by rubbing with a water past,e of clean pumice powder and washed in distilled water. hfter a final washing in a mixture of 50% alcohol and 50% ether t'hey were dried and weighed to 0.1 mg. SIXBEH OF SAMPLES. All tests were run in quadruplicate because a statistical st'udy of totally immersed samples in corrosive mediums indicates that the average result of quadruplicate runs nil1 be within 770 oi the true value. This accuracy is usually considcrcd sat,isfactory for most corrosion-rewarch programs (1).
CLLU-INGSmcrarms AFTER TESTING.I t was found that the corrosion products could be removed easily from t'he metal simply by gentle scrubbing wit'h a rubber st'opper under running water. The samples were washed in distilled water, rinsed in the alcohol-ether mixture, dried, and weighed. EVALCATION OF RESULTS. The loss in weight per unit area during the test period was used as the principal measure of corrosion. Since neit,her the t,itaniumnor the stainless steel showed any severe pitting or selective corrosion, this method was considered valid. Corrosion rates were calculated from the loss in weight data and expressed, as milligrams per square decimeter per day and as mils per year. The relation between mg. per square dm. p ~ day r and mils per year is expressed by the equation 1437 m p . y . = m.d.d. x A-, where d = densit'y of the metal in d grams per cubic centimeter. TITANIUM T E S T S
Figure 2.
Test Fla& Showing Specimen Support, .4erator, and Condenser I1ETA L S
Titanium and zircoIiiurn sheet were obtained from the Salt Lake City, Utah, and the Albany, Ore., laboratories of the Bureau of Mines, respectively. Both metals are relatively pure with impurities below 1%. Titanium powder was consolidated by pressing, vacuum sintering, and hot rolling. It was then cold rolled to a 40% reduct,ion and aniicaled material was prepared therefrom by vacuum treatment for I hour at 1000" C. Spectrographic examination disclosed the follo\ving impurities: iron 0.1%; chromium, lead, magnesium, manganese, and copper, traces, 0.005 to 0.05y0. Sitrogen and oxygen, both present in the metal, were not determined. Zirconium was melted in graphite, forged, and h o t worked to 0.070 inch followed by cold work to filial thickness. Annealed metal was prepared by vacuum treatment for 1 hour at' 1000" C. Spectrographic analysis showed iron, chromium, and niangaxiese a s minor impurities with traces oE nickel, titanium, silicon, and magnesium. The method of consolidation, heat treatment, fabrication, and purity apparently all influence, to some degree, the resistance of the metal t o corrosion and care must be escrcised in coinparing data of va,rious investigators. The following data are presented in the hope they mill provide at least a partial base line for subsequent work. PREPARATION OF SPECIMENS.The metal samples were cut on a metal-cutting saw into 1-inch squares (oversize) from sheet stock 0.040 inch thick for titanium and zirconium and 0.050 inch thick for Type 316 stainless steel. These rough samples were machined to 0.003 to 0.005 inch oversize, surfaced with coarse abrasive cloth (No, 1/2 emery), and numbered with a
SLLFLJRIC ACID, The corrosion rates for annealed titanium, cold rolled titanium, and type 316 stainless steel in various concentrations of sulfuric a t 35' C. with aeration are shown in Table I. Annealed titanium is rapidly attacked by sulfuric acid in all concentrations above 5 %, whereas stainless steel shows resistance to active corrosion in acid concentrations as high as 25%. The maximum rate of corrosion for annealed titanium was found to be in thc neighborhood of 4070 acid. Stainless steel also shovied a maximum rate at this concentration. ' marked decrease in the corrosion rate of annealcd titanium in 7597, acid was noticed in a preliminary study; further investigation proved this minimum to be closer t o 657c acid. The rate for titanium increased as the acid concentration rose
TABLE I. Te. t Yolution,
%
1 3 a
10 23
40 50 63
75 96 3
TIT4NIUM
CORROSIO?i RATES-SULFURICACID
(H2S0b at 35O C.; with aeration) Type 316 Annealed Ti Stainless Steel Time, Mg./sq. 3111s/ hlg.,'sq. Mils/ Hr. dm./dag >ear dm./day year 144 0.42 0.13 144 ... .. 0.40 4s 1 26 ... 0:04 0 20 0 63 0.22 96 0.07 114 0 49 0.41 1 53 RO 4 1.13 0.20 123 48 0.16 34.8 0.87 96 109 0.13 0.73 40.4 144 126 6.52 203 36.2 64 8 48 O 2.16 12 104 "R _ 326 1.41 131 7.85 144 411 554 3078 48 210 1169 96 243,s 438 i4, 144 io69 474 2630 274 48 861 479 208 2662 652 96 412 2287 144 156 489 371 2064 126 40.2 48 342 1902 sa. 1 28.1 96 329 1830 26 144 81 4 609 110 99 2 311 48 132 51 736 96 160 164 41.9 914 144 131.6 2.08 11.56 177 48 556 1.67 177 9.30 96 556 222 1 4 1 697 8 30 1.49 ~~192 696 222 ,,. ..
Cold Rolled Ti hZp./sq. Mils/ dm./day year
... ... ... 1.2 ...
0.56
20s
o:is ..
0:g8
..
, it3
...
..
6 07
i94
... ...
..
1331
ii4
334
i67
..
... , . .
..
...
63.6
20.3
...
.. i 09
655
INDUSTRIAL AND ENGINEERING CHEMISTRY
AuCust 1949
1671
tween the results of various laboratories. KOpitting such as Fontana described was observed. HYDROCHLORIC ACID. It was found that annealed titanium metal shows better corrosion resistance toward various concentrations of hydrochloric acid a t 35" C. than Type 316 stainless steel. Table I1 shows that the corrosion rate for titanium increases only slightly with increasing hydrochlorir acid concentration up t o 5%. At 60" C. titanium is resistant to hydrochloric acid concentrations up to 3oJ, whereas stainless steel was found to be unsatisfactory in concentrations of acid as low as 1%. The results of this stJudy are given in Table 111. When the temperature was increased to 100" C. it was found that titanium is resistant t o concentrations of hydrochloric acid which are 1% or less. Results shown in Table IV are in fair agreement with data reported by Fontana (6).
TABLE 111. TITANIUM CORROSION RATES-HYDROCHLORIC ACID (HC1 at 60' C . : with aeration) Test Solution, %
Figure 3.
Time, Hr.
Annealed Ti Mil/ dm./day year Mg./sq.
Type 316 Stainless Steel Mil/ dm./day year Mg./sq.
Specimen Support and Aerator
CORROSION RATES-HYDROCHLORIC ACID TABLE IV. TITANIUM from 65 t o 96.5% sulfuric acid, which was the upper limit of this investigation. To determine the effect of annealing on the rate of corrosion, samples of the cold rolled metal were run in many of the same acid concentrations used on the annealed metal. When these results are compared in Table I, it may be seen that the rate of the cold rolled metal only exceeds that for the annealed metal in 10, 25, and 40y0sulfuric acid. At most of the other concentrations, the rates for the two metals are so nearly identical that their difference is less than the experimental error. Data for both the annealed and the cold rolled titanium given in Table I are shown graphically in Figure 4. Fontana reports cumulative coirosion rates of 6 , 265, and 240 mils per year for titanium in 3,65, and 93% sulfuric acid a t room temperature although the specific temperature and condition of the metal are not given (6). These data are a t variance with those reported here and are listcd to illustrate the divergence be-
CORROSION RATES-HYDROCHLORIC ACID TABI.ETT. TITAWTUM (HCl at 35' C.: with aeration) Test Solution, % 0.5
1
.o
5
7.5 IO
15 20 37
Time, Hr. 48 96
I44
48 96 144 48 96 144 48 96 144 48 96 144 48 96 144 48 96 144 48
Annealed Ti Mils/ dm./day year Mg./sq.
0.97 0.36 0.12 0.45 0.49 0.42 1.40 1.44 1.20 21.4 24.4 47.7 130 129 133 159 179 203 253 353 394 6250
0.31 0.12 0.04 0.14 0.16 0.13 0.45 0 46 0.38 6.82 7.78 15.2 41.4 41.4 42.4 50.8 57.2 fi4.7 80.7 113 126 1990
(HCl at 100' C . ; 4 8 hours; with aeration) Annealed Ti Test Solution, Mg./sq. dm./day R?il/year % 1
2 3
Type 316 Stainless Steel Mild dm./day year 0.32 0.13 0.14 0.45 0.22 0.16
301
5411
.. .. .. .. ..
..
.. .. .. ..
.. ..
a
TITANIUM CORROSION RATES-NITRIC ACID
at 35" C . and 100' C.: 144 hours: with aeration) Test Annealed Ti Type 316 Stainless Steel Solution, Mg./sq. Mils/ hlg./sq. Mils/ dm./day year % dm./day year At 350 c. 5 0.24 0.08 0.41 0.07 0.50 0.09 10 0.51 0.16 0.47 0 . OR 20 0.57 0.18 0.38 0.07 30 0.84 0.27 0.41 0.07 4n 0.72 0.23 , ! I0 0.72 0.23 0.50 o.nn 0.18 0.28 1 .oo fin 0.87 69.50 1.40 0.45 2.46 0.44 A t looo C. 1.08 0.19 5 1.90 0.61 1.29 1.29 0.23 4.03 Bc%ng (165" C.) and no naerated 10.40 3.31 107 19.30 66 4 8 hours. ("OX
.. .. ,.
.. .. ..
.... .. .. ..
TABLE V.
177
.. ..
0.43 307 538
NITRIC ACID. Both titanium and stainless steel exhibit remarkable resistance to corrosion a t 35" C. in all concentrations of nitric acid. The rates are almost identical for every acid concentration studied. Results of tests are presented in Table T'. Tests conducted in 5 and 10% nitric acid at 100" C. showed rates for titanium slightly higher than those a t 35" C. for comparable concentrations of acid. Stainless steel also showed but slight increase. Comparison tests with Type 316 stainless steel showed a considerably greater rate in boiling, 650/, nitric acid, than that exhibited by the titanium. Annealed titanium when tested in fuming nitric acid (90%) a t room temperature for 10 days suffered a negligible weight loss (0.18 mg. per square dm. per day or O.OG mil per year) and showed
Mg./sq.
1.75 0.74 0.79 2.5 1.2 0.90 650
1.35 963 1687
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
1672
Vol. 41,, No. 8
tratioris oC sulfuric acid up to 80% a l 35' C. aiid the maximum rate of corrosion occurred at approximately 90%. At 60" and 100" C. active corrosion took place a t acid concentrat,ions above 75%. The superior corrosion resistance in these media of zirconium t o both Type 310 st,aiiiless steel :tiid titanium is most striking. H ~ - I ) R O ~ H L ~ R.Icru. IC Zircoriiuni ah0n.s excellent resistance toward a relatively wide range of hydrochloric acid concentratioris at 100" C. (Table VII). Corrosion rat,e increases only slightly with inci,easing hydrochloric acid concentrat,ions. This behavior is iii marked contrast t o both titanium and stainless steel.
\-II.
T.4BLE
CoRRoSIOX RATES-HYDROCHLORIC
;/IIRCOXll'\I
XCI1)
(11Cl n t 100' C.;
'rest Solution, %, 5 10
Figure 4. Comparison Curve for Annealed Titanium and Cold Rolled Titanium
no visible signs of aLtack. Type 316 staiiilesa steel also showed no att,ack aiid a very slight loss in weight (0.45 mg. pcr square din. per day or 0.08 mil per year) under comparable test conditiona. MISCELLSNEOGS TESTS. Titanium is amenable to anodizing arid the authors have found that the rate of attack in many media can be markedly lowered thereby. At low concentrations of iiitric acid ( < 1%) titanium can tolerate hydrochloric acid coiiceritrations above ZOyo without severe attack. Confirniing the results of previous investigators thc nietal was found resi~t~arit to boiling glacial acetic acid, and 107, sodiuiii hydroxide. Tests with various food juices also showed 110 attack. The outstanding attribute of tit,aiiiuni mith regard t o corrosion is its resistance to sea water. Bureau of Mines tests, as well as those of ot,her investigators, indicate it is superior to alloy steel, inonel, arid iiicliel in t,hisrespect ( 2 ) . ZIRCOlVIURiI TESTS
SULFURIC ACID. Corrosion rates for cold rolled zirconiuiii in various concentrations of sulfuric acid at 35", BO", and 100" C. with aeration are shown in Table VI. Comparative values for Type 316 stainless steel are included. Cold rolled zirconium mas attacked very slight,ly in ooncen-
TABLEVI.
ZIRCONIUM CORROSIONRxrEs-SuLrcmc
Acm
(HsSOa a t 33', 60". a n d 100' C . ; 144 hourp: with aeration) Test Cold Rolled Zr T y g e 316 Stainless Steel Mg./sq. Aril/ Mg./sq. Mil/ Solution, dm./day year year dtn./da): 70 At 350 c. 0 09 .,.. ... 10 0 24 20 30
% 60 Z? I D
80 82,5 85 C 90" 96.5
" 25%
HzSO6.
0.36 1 54 1.84 1.66 1.90 1.53 5 255 1095 3910 7351 3418
0.08 0 34 0.41 0.37 0 42 0.34 1.11 56 3
,
1. 4 I n 438 411
iiiob
329 6 164
...
914
. . .
... ...
.,..
242 864
...
. . .
....
1620 752
65% H ~ S O A . 48 hours.
...
.
7 ,85" 2435 2287
72 hours.
MiI/year
0 . a9 0.43 2.62 3.13
0.09 0.10 0.58 0.69
TABLEVIII. 'rest Solution,
('ORROSION
%lRCONICM
(HKOJ at, 3.5O C.: 144 honrb; Cold Rolled Zr Mg./sq. dm./day
%
AIil/year
0.01 0.01 0 ,0 2 0.01 0.87 0,233 0 . 6!1 'I
RATES-NITRIC
ACID
with aeration) Type 316 Stainless Steel Mg./sq. dm./day Mii/year 0.50 0.0s 0.47 0.08 0.38 0.07 I ) . 07 0.41 0.09 0.50 0.18 1.00 2.46" 0.44'L
4 8 ho11rn. ~~
KITRICACID I n coiiceiitiatioiis of nitiic a u d froiri 10 to 69.5Yo a t 35' C., cold rolled zii coiiiuin showed negligible coirosioii ab did titanium and Type 310 c~ainleassteel (Table VIII). PHOSPHORIC ACID. Coiiosion iatcs for zirconium 111 ~rarious concentrations of phosphoric acid are shon n in Table I S ~
TABLEIX.
~
~~~~
~
~~
ZIRPOXILnr CORROSIOX RATES-PHOSPHORIC ACKD
(HaPOd at 35O, G O o , a n d l0OY C.; 144 hours; with aeiation) Test Cold Rolled Zr S0lUtIOU, 70 ;LIp./sq. dni./day Mil/year A t 350 c. 0.05 10 0.23 20 0.37 30 0.44 40 0 .49 50 0.49 en 0.53 70 0 56 80 0.50 85 At 6 0 O C. 0.46 50 2.07 0.46 2.07 60 0.74 75 3.37 1.56 i.10 85
At 1000 c. 70 75 80 83
41.9 81.h
112.0 196.0
9.27 18.0 24.8 43 . 3
...
8 30
d
RIg./sq. dm./day
15 20
Various c o n ~ r n l r ~ t t i uof n~ sulfuric acid at 35' C. for 144 hours
114 h o u r s ; with aeration) Cold Rolled Zr
1.49
6
24 hours.
Zirconium shows a negligible rate of attack in all coricentrations of phosphoric acid at 35' and 60" C.; a t 100" C., however, the rate a t concmti~xtionsabove 7OY0 phosphoric acid becomes appreciable. MISCELLANEOUS T ~ s r s .-411 saniples of Bureau of Mines zirconium dissolved conipletely in aqua regia over a 24-hour period. Metal produced by the Foote llineml Company was resistant as purchased, although any significant, amount of cold work ce,used this material t u b r l i e ~ esiiiiilnr tci the Il(urcau of Mines mc.t:il.
August 1949
INDUSTRIAL AND ENGINEERING CHEMISTRY ACKNOWLEDGMENT
1673
E. S.,L o n g , J. R , W a r t m a n , F. S.,a n d A n d e r s o n , E. L., Metals Technol., 13, 12-13 (1946) (Tech. Pub. 1961). (4) Dean, R. S., a n d Silkes, B., U . S. Bur. Mines, Inform. Circ. 7381 (November 1946). ( 5 ) F o n t a n a , M . G., IND. ENG.CHEIM., 40, No. 10, 99A (1948). (6) Gee, E. A., L o n g , J. R., a n d W'aggaman, W. H., MateriaZs & Methods, 27,75-8 (1948). (7) Gillett, H. W., Foote Prints, 13,No. 1, 5-7 (1940). (8) K r o l l , W . J., Mttallwirtschaft, 18,77-80 (1939). (9) Kroll, W . J., Trans. Electrochem. Soc., 78, 35-47 (1940). (10) W a g g a m a n , W. H., a n d Gee, E. A., Chem. Eng. .\'ews, 26, 377(3) Dean,
Special acknowledgment is made to .kiton Gabriel, assistant chief, Metallurgical Division, Bureau of Mines, and Wilbert J. Huff, chairman, Department of Chemical Engineering, University of Maryland, for assistance and criticism. Experimental work on titanium by the junior author will be offered as a part of a thesis in partial satisfaction of the requirements €or the degree of Doctor of Philosophy in chemical engineering a t the University of Maryland.
81 (1948). LITERATURE CITED (1) Am. SOC. Testing
Materials, Standards, pp. 793-802 (1946), A.S.T.M. Designation B185-43T. (2) B r a d f o r d , C.I., U. S. Navy Dept., Office of Naval R e s e a r c h , Tit a n i u m S y m p o s i u m , p a p e r 6 (December 1948).
RECEIVED September 30, 1948. This s t u d y is part of a joint research project on the corrosion resistance of metals by the Metallurgical Division of t h e Bureau of Mines and the Department of Chemical Engineering of the University of AVaryland.
Di-tert-butyl Peroxide and 2,2-Bis(tert-buty1peroxy)butane J
PREPARATION, ANALYSIS, AND PROPERTIES F. H. DICKEY, J. H. RALEY, F. F. RUST, R. S. TRESEDER, AND W. E. VAUGHAN Shell Development Company, Emeryuille, Calif.
Di-tert-bu tyl peroxide and 2,2-bis(tert-butylperoxy)butane are two new liquid compounds, the properties of which have been studied extensively. They possess predictable decomposition characteristics and other properties which render them of value.
T
HE rapid growth of the held of synthetic resins and elas-
tomers in the past decade has been paralleled by a stimulus in the development of chain reaction initiators or catalysts, principally in the domain of the organic peroxides. A considerable number of such compounds has been added to the formula indexes, and some of these new materials have demonstrated promise in industrial applications as polymerization catalysts, as Diesel fuel ignition accelerators, and as tools in organic syntheses. Two of these compounds, di-tert-butyl peroxide (DTBP) and 2,2-bis(tert-butylperoxy) butane (2,2-PB), both of which are presently available, have been rather extensively investigated in these laboratories in regard to their syntheses, fundamental chemical reactivity, and industrial applications. This work revealed that certain characteristics of these chemicals render them highly advantageous for commercial use. This paper presents data relating to the compounds, and their stabilities and controlled decomposition rates are compared with those of other commercial peroxides;. The following paper (29) describes application data, particularly In polymerizations. PREPARATION
Di-tert-butyl Peroxide (8'4). The earliest mentions of this compound in the literature appear to be l ? and 8%'. It may he obtained by the hydrogen bromide catalyzed oxidation of isobutane (23,25); this reaction is discussed elsewhere ( 4 , 20, 21) in some detail regarding the mechanism. Di-terthutyl peroxide may be synthesized in high yield also by the interaction of tert-
butyl hydroperoxide and lert-butyl alcohol in the presence of sulfuric acid ( I S , 18,24). CH3
1 1
CH3-C-OOH CH3
+ HO-
XH3 I
-CH3
+
CH3
AH3
I
+ H20
(1)
CHI
,4third method of preparation is reaction of an alkali or alkaline earth metal salt of tert-butyl hydroperoxide with a tert-butyl halide (IO),for example: CHa C~3-L-OONa bH8
CH3
+ CI-d-cH, I
-+
CH3 CHI
CH3
CH3-(&--00-&-CHa CHI I AH3
+ NaCl
(2)
This peroxide is not an oxidizing agent in the ordinary sense of the term nor is it especially reactive chemically in other ways. It is virtually insoluble in water and is stable thermally a t temperatures below approximately 80" C. A ternary azeotrope of composition-44.0% di-tert-butyl peroxide, 49.3% tert-butyl alcohol, 6.7% water, boiling point 77" C.-has been used for separating the peroxide from certain mixtures ( 17 ) .
