July, 1932
INDUSTRIAL AND ENGINEERING CHEMISTRY
series of experiments. It is believed that consumption of glycol can be materially decreased in larger-scale operation. ADAPTATION TO CONTINUOUS PROCESS The dehydrations described previously were all made as separate batch experiments. Laboratory experiments were then made in order to determine whether this method of dehydration could be adapted to continuous operation. For this purpose it was necessary to add an excess of glycol to the glycoloxide in order to bring the crystallizing point of the glycol-glycoloxide mixture down below the boiling point of alcohol. A mixture of 5 moles of ethylene glycol to 2 moles of sodium hydroxide when dehydrated, crystallized a t about 95 " C.; a mixture of 6 moles of glycol to 2 moles of sodium hydroxide crystallized a t about 60' C.; and a mixture of 7moles of glycol to 2 moles of sodium hydroxide was still fluid a t 40" C. The last named mixture was used in the continuous experiment. Alcohol (92.5 per cent by weight) was boiled in a glass still, and the vapors were passed up a packed column 4 feet long. The dehydrating mixture was added to the column a t a point about 1 foot from the top, a t the rate of 150 grams for every 100 cc. of alcohol distillate collected. After a little time had been allowed for the system to reach equilibrium, two successive 100-cc. pcirtions of the distillate were collected separately and analyzed. One of these was 99.5 per cent (by weight) alcohol, and the other was 99.2 per cent. This experiment serves to show that 99 per cent alcohol can be obtained by a continuous process with sodium ethylene glycoloxide. In large-scale operation, of course, the aqueous alcohol would be fed to the column a t a point near the bottom while a reboiler a t the bottom of the column would supply the necessary heat. The dehydrating mixture would be continuously drawn off and dehydrated under vacuum in a separate system.
791
APPLICATION TO DEHYDRATION OF OTHERALCOHOLS The principle of dehydration with sodium ethylene glycoloxide was applied to tertbutyl alcohol and to isopropyl alcohol. I n the former case, starting with commercial krt-butyl alcohol which had a specific gravity of 0.80560 a t 25"/25" C., and which would not crystallize a t 0" C., it was possible to obtain alcohol of crystallizing point 18" C. and specific gravity of 0.78254. Starting with isopropyl alcohol of specific gravity 0.80884 a t 25" C., it was possible to obtain a dehydrated product with specific gravity 0.78714 a t 25" C. SUMMARY AXD CONCLUSIOX The alkali salts of high-boiling alcohols, glycols, and glycerol can be used for the dehydration of the lower-boiling alcohols which are difficult to dehydrate by ordinary means. Sodium ethylene glycoloxide is an efficient dehydrating agent for aqueous alcohols, and has the merit that it can be readily regenerated for repeated use. The only feature which would apparently militate against its use on the large scale is the gradual decomposition which takes place in presence of some metals, resulting in ultimate loss of the glycol. This decomposition can be minimized by the avoidance of high temperatures in the dehydration, by the use of partial vacuum, or by operation in containers which do not have a catalytic effect on the decomposition of the alcoholate. It is anticipated that the selection of the proper material for the construction of a plant employing this method will minimize the decomposition to a point where it would no longer be a serious cost factor. LITERATURE CITED (1) Cross, C. F., and Jacobs, J. M., J. SOC.Chem. Ind., 45, 320T (1926). (2) Kyrides, L. P., U. S. Patent 1,712,830 (1929). (3) Walker, T. K., J. SOC.Chem. Ind., 40, 172T (1921). RBCEIVED January 11, 1932.
Corrosion of Bronzes by Vinegar E. M. MRAKAND J. C. LE ROUX,Fruit Products Laboratory, University of California, Berkeley, Calif. NUMBER of bronzes are used in the vinegar industry, but there has been little published to show the degree of corrosion of various bronzes by this medium under various conditions. According to St. John (5),a considerable amount of work has been done with wrought brasses, but information dealing with foundry brasses and bronzes is incomplete and unsatisfactory. Seiler (6) found that a phosphor-bronze, containing 90 to 91 per cent copper, 8 to 9 per cent tin, and about 0.25 per cent phosphorus, was resistant to corrosion by tan liquors provided the metal was free from iron, lead, and zinc. Philip (3) attributed trhe corrosion of common brass to local zinc-copper couples on the surface of the metal. Ben& ( 1 ) stated that the corrosion product of an acid-resisting bronze was proportional to the time of immersion. Mrak and Cruess (2) found that a tin-copper bronze corroded faster in citric acid than in tartaric acid, and that corrosion in pure acids was faster than in tomato, lemon, or grape juices. In order to determine the corrosion resistance of several bronzes that have been used or been recommended for use in the vinegar industry, eighb bronzes and their chief components (copper, tin, and lead) were exposed under three sets of experimental conditions-namely, in still, agrated, and sprayed vinegar. These three test, conditions were used, since Rawdon and Groesbeck ( 4 ) have shown that metals
A
corrode differently when exposed to difTerent corroding conditions. hfETHOD AND -4PPARATUS
The metals used were cut into strips 5.5 X 2.5 X 44.7 mm. The copper, tin, and lead strips were but 0.6 mm. in thickness. The metals were cleaned by burnishing with a cloth burnisher and then washing in ether and alcohol, after which they were dried in a desiccator over CaClz and then weighed just before using in the corrosion tests. The composition of the bronzes used is given in Table I. TABLE I. COMPOSITION OF BRONZES BRONZE Cu
%
Sn %
Pb
%
Zn %
JfETAL
P %
Fe %
AI
Mn
%
%
C
Cider vinegar, standardized to 4.27 per cent acid as acetic by the addition of distilled water or glacial acetic acid, was used in these tests.
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INDUSTRIAL AXD ENGINEERIKG CHEMISTRY
AND METALS FIGURE 1. CORROSION OF BROXZES TESTEDBY SIMPLE IMMERSION I K V I N E G A R
In the still or simple immersion tests, strips of metal were suspended in 325 cc. of vinegar in quart milk bottles and allowed to stand for the desired period. Aeration tests were conducted in similar manner, except that air was drawn through the vinegar at the rate of 50 cc. er minute by an aspirator. The apparatus usetin the spray tests was a modification of that used by Rawdon and Groesbeck. The metal strips were suspended in a bell jar near the top. The base of the bell jar stood in an enamel pan containing 1500 cc. of vinegar. An atomizer installed on one side of the bell jar near the base sprayed the vinegar into the jar, where it was distributed as a mist by the use of a baffle plate. An outlet at the to of the jar mitted the spray to move upward. The b a d plate actec!% a receptacle t o catch the liquid dripping off the metal strips. The concentration of spray was controlled by controlling the pressure of the air assing through the atomizer. In this test the vinegar was re Paced every 24 hours. When the corroied metals were removed they were washed in distilled water and alcohol and then dried in a desiccator several hours before weighing.
Yol. 24, No. 7
FIGURE2. CORROSION OF BRONZE1 UNDER THREETYPESOF CORROSION TESTS the duplicates did not check reasonably close. It was more difficult to obtain reproducible results in the spray than in the other tests; however, many of these tests were repeated a number of times, and the data given in Table I1 and Figures 1 and 2 are considered representative for corrosion under the given conditions.
DISCUSSION
The rate of corrosion was obtained for all the metals under the three types of conditions, and only the typical results are shown. Figure 1 is typical of the differences found between the rates of corrosion of the various metals under similar conditions. Figure 2 is typical of the difference found in the rate of corrosion under different conditions. It is apparent from Table I1 that all metals tested, except tin, corroded most in the spray tests and least in the simple The data are expressed as loss of weight in milligrams per immersion tests. Tin, however, corroded most in the square decimeter of surface. Loss in volume of metal per aerated vinegar and least in the spray tests. After 100 hours given area of surface, or penetration in millimeters were not of exposure in the spray tests, tin maintained a smooth surface as reliable as loss in weight per given area, since the former on which appeared a thin white film, whereas after the same two necessitated the use of the specific gravity of the metals. exposure in the other tests the surface was considerably I n the alloys the specific gravity may have changed because eroded and pitted. The presence of tin in bronze 1, however, did not seem to inhibit the increase in corrosion of this bronze of selective corrosion. in the spray. Rapid oxidation was undoubtedly responsible TABLE11. CORROSION OF METALSUSDER VARIOCS TEST for the great increase in the corrosion of the metals in the CONDITIONS spray tests. I n the case of tin, this rapid oxidation probably (In mg. per sq. dm. of surface for 100-hour period) favored the formation of a protective film. SIMPLE AERATED SPRAIED Lead corroded more rapidly than any of the other metals METAL IYMERBION VINEGAR \'Ih.EG 4 A tested. The presence of lead in bronze apparently decreased 498.8 593.0 Bronze 1 71.9 3 9 i .6 481.3 49 146.6 the resistance of bronze to attack by vinegar in the three 461.2 682.5 47 253.5 491.9 ?607,0 44 254,7 tests used. In all tests the corrosion and lead content of 580.9 116.9 402. n 12 bronzes 49, 47, and 44 varied in the order named a t the 478.7 103.2 334.3 22 709.0 67.0 273.0 66 end of the 100-hour period. No direct relation, however, 298.2 852.6 69 68.6 between the lead content of the bronzes and its corrosion was 212.0 S37.1 33.6 found. These three bronzes, particularly 44, have been used 349.0 41.9 106.5 1491.0 8826,s 324.7 in the vinegar industry primarily because of their supposed acid-resisting properties. Bronzes 66 and 69 corroded with a clean surface when All tests were conducted a t a temperature of 20" * 2" C. All tests were made in duplicate and were repeated when immersed in vinegar, but in the spray a dark scaly precipitate
July, 1932
I N D U S T R 1.4 L A N D E N G I N E E R I N G C H E M I S T R Y
formed on their surfaces. This material tended to flake off as corrosion proceeded. All bronzes tested corroded sufficiently under all conditions used to cause considerable contamination of the vinegar with heavy metals. Since the contamination of foods with heavy metals is undesirable, it is inadvisable t o use any of the bronzes tested in the vinegar industry, and it is particularly inadvisable to use the three containing a high percentage of lead.
799
LITERATURE CITED (1) Benik, Korrosion u. MefaZZschutz, 5 , 247 (1929). Food I & , 1, 559 (1929). (2) Mrak and (3) Philip, Trans. Faraday SOC.,11, 244 (1915). (4) Rawdon and Groesbeck, Bur. Standards, Tech. Paper 367 (192s). (5) St* & A z z o y s ~ 242 (6) Seiler, Gerber, 55, 209 (1929).
cruess,
January 23, 1932,
Some Studies in the Fat-Liquoring of Chrome Leather 11.
Effect of Various Oils upon Oil Adsorption and Strength of Leather
EDWINH . THEIS,Department of Chemical Engineering, Lehigh University, Bethlehem, Pa., S. HUNT,Research Laboratories, Hunt-Rankin Leather Co., Peabody, Mass.
AND
FRANK
S -4 p r e v i o u s p a p e r the
1. Raw n e a t ’ s - f o o t oil and Characteristic oil-adsorption curves are obs u l f o n a t e d neat’s-foot oil, the writers discussed the effect tained f o r various mixtures of raw and sulfonated mixtures varying from 100 per of hydrogen-ion concentracent raw oil to 100 per cent suloils used in the fat-liquoring of chrome-tanned tion upon oil adsorption and fonated oil. calfskin. I f is shown that the percentage of showed that, as the p H value of 2. Raw cod oil and sulfonated sulfonated oil added to raw oil drasiically the skin or fat liquor varied, the cod oil. amount of oil adsorbed by the 3. Raw cod oil and moellon affects the amount of oil adsorbed by the leather. oil. chrome leather varied also. I t The efeci of p H ralue, the oil concentration, 4. R a w neat’s-foot oil a n d was further shown that each ins u l f o n a t e d castor oil, the fat and stability of the f a t liquor upon the oil addividual fat liquor gave a charliquors being adjusted to pH 4 and sorbed during the period qf fat-liquoring are acteristic absorption curve over pH 9. giuen. A comparison, with relation to oil 5. Raw cod oil and sulfonated a pH range of 1 to 12. If a mixc a s t o r oil, t h e r e s u l t i n g fat ture of oils was used, the charadsorpfion by the leather, of some sixteen different liquors being adjusted to pH 4 and acteristic curve of the pure oil f a t liquors is shown. The effect of moisture conpH 9. was changed in proportion to 6. Sulfonated cod oil and salted the chrome leather upon oil adsorption tent of the mixture used. egg yolk, adjusted to pH 4 and is given. pH 9. The experimental work was 7 . Raw c a s t o r oil a n d sulextended to include the followfonated castor oil. ing effects: mixtures of raTv and sulfonated oils upon oil 8. Raw neat’s-foot oil and egg yolk. adsorption and ultimate strength of the leather; moisture in 9. Temperature of fat-liquoring upm oil adsorption and releather before fat-liquoring upon oil take-up and strength of sultant strength of leather. finished leather; and mixtures 10. Comparison of sixteen different and varied fat liquors. of different oils upon oil adsorp11. Effect of pH, oil concentration, and stability of fat liquor tion, strength of leather, and dis- upon oil adsorption and ultimate strength of finished leather 12. Effect of skin moisture and degree of washing before fatt r i b u t i o n of oil throughout the liquoring upon oil adsorption. skin.
EXPERIMENTAL PROCEDURE Chrome-tanned calfskin, direct from shaving, was cut into pieces, 2 X 4 i n c h e s , and fat-liquored in the oil e m u l s i o n s to be noted a t 120” F. (48.9’ C.) a n d for 30 minutes. ilt the duration of the fat-liquoring period, the skin mas removed and dried slowly (room temperature:, and the oil adsorbed was determined, using bP L R C20f N T S U40L F O Nb0A T t D BOOIL !OG’ low-boiling p e t r o l e u m ether as FIGURE1. EFFECTOF t h e e x t r a c t i v e . At the same MIXTURESOF SULFON- time the tensile s t r e n g t h a n d ATED A N D R ~ NEAT’Sw the tearing strength of the fatFOOT OJL ON OIL liquored leather were determined. ADSORPTION AND STRENGTH OF FINSHED The following s l s t e m s were studied: LE.4THER
When raw and sulfonated oils are mixed, and c h r o m e l e a t h e r is fat-liquored in such emulsions, the oil adsorption and strength of the l e a t h e r v a r i e s with the m i x t u r e . Figure 1 shows the effect upon strength n e c e s s a r y for tear and upon oil adsorbed, of mixtures of raw and sulfonated n e a t ’ s - f o o t oil. It is r e a d i l y seen from Figure 1 that with raw n e a t ’ s - f o o t oil a l o n e the oil adsorbed by the chrome leather is v e r y small, b u t , a s t h e p e r c e n t a g e 9f s u l f o n a t e d oil added increases, the oil adsorbed becomes i n c r e a s i n g l y greater, p r o b a b l y b e c a u s e of t h e in-
10
PER
40 60 80 100 CENT SULFONATED OIL
FIGURE2. EFFECTOF MIXTURES OF SULFONATED AND RAW COD OILS ON OIL ADSORPTION AND STRENGTH (TEAR) OF
LE.4THER
