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1920
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
4-An increase of about 23 per cent in the yield is obtained by the laboratory investigations over the best laboratory yield obtained by Hixson and McKee,l t h a t is, 75 per cent instead of 5 2 per cent. Under large-scale working conditions the presence of the necessary small amount of water in the melt may reduce the yield slightly, although i t is possible t h a t this may not be t h e case. We wish t o call attention t o the accuracy of the method employed for determining the carvacrol in all of this work. By extracting with ether the acidified solution after fusion, a crude carvacrol is obtained t h a t is contaminated by other extractive matter. The purity of the carvacrol extract varied from 75 t o 9 9 per cent, and depended upon the conditions of the fusion and the care employed in drying the ether extract. Schorger2 weighed the ether extract and considered it as carvacrol. There is no doubt t h a t his best yield of 5 2 . g per cent is for this reason too high. He employed potassium hydroxide for his open-pot laboratory fusions and states t h a t the yields are very poor a n d hard t o duplicate. Hixson and McKeel extracted the crude carvacrol with benzene, removed the solvent by distillation a n d fractionated the product, taking the distillate between 2 2 7 ' and 2 4 5 ' as carvacrol; or removed the carvacrol by distillation of the acidified material with steam. Even if this material obtained by either method is further purified, as they state13 it seems reasonable t o expect t h a t i t still contains impurities. SUMMARY
I-An apparatus especially suited t o laboratory studies of caustic fusions is described. 11-The various factors of temperature, time, and concentration affecting the fusion of sodium cymene sulfonate with sodium hydroxide have been studied, a n d i t is shown t h a t by conducting t h e fusion in a n autoclave yields of carvacrol as high as 75 per cent a r e readily obtained, as compared with less t h a n 60 per cent by fusion in a n open pot. 111--The fusions of other sulfonic acids are being studied.
THE USE OF HYDROGENATED OILS IN THE MANUFACTURE OF TIN PLATE By W. D. Collins and W. F. Clarke BURBAUOF CHEMISTRY, DEPARTMENT OB AGRICULTURG, WASAINGTON, D. C. Received August 4, 1919
The manufacture of tin plate in the United States consumes from 5,000 t o IO,OOO tons of palm oil per year. Many substitutes have been tried without success, and there has developed in the industry a general belief t h a t no satisfactory substitute exists. Tallow was used in t h e early manufacture of tin plate, but for many years palm oil has been the only oil used in tin pots.
' LOG. Cit.
THIS JOURNAL, 10 (1918), 260. a "This was done by redistilling the product obtained from the fusion
2
liquor b y either of the two methods mentioned. No difficulty was experienced in getting a product with a fairly constant boiling point."
I49
When shipping difficulties arose on account of t h e war a shortage of palm oil was threatened. With the increased demand for tin plate some pressure was brought t o bear t o secure the palm oil said t o be essential for production. At this time attention was called t o a patent1 which covers the use of glycerides or esters of saturated f a t t y acids, all kinds of hydrogenated oils and fats, and artificial esters produced from palmitic acid, stearic acid, or other saturated acids. Available statements in regard t o this process were not in agreement as t o its practicability and economy. The work reported in this paper was undertaken t o secure definite information as t o the conditions of satisfactory production of tin plate without palm oil. PROCESS O F MANUFACTURE
To make tin plate, cleaned sheets of steel are thrust singly into a bath of molten tin, entering through a layer of zinc chloride flux which covers part of t h e surface of the tin bath. The sheets are carried by rolls up out of the tin through oil which floats t o a depth of about 15 in. over t h e tin. The oil serves t o prevent oxidation of the surface of t h e tin bath, and t o dissolve tin oxide which may be formed. The temperature of t h e tin is around 315' C. (600' F.), and t h a t of the oil near the surface about 240' t o 2 5 0 ' C. It is evident t h a t oil for this purpose must stand a high temperature without undue volatilization or decomposition. WitP palm oil care must be taken t h a t the temperature does not become too high, since a t higher temperatures the oil polymerizes, loses its power t o keep the plate clean, and is carried out on the plate in excessive amount. PRELIMINARY LABORATORY E X P E R I M E N T S
Before attempting a practical test a few experiments were made t o observe the effect of heat on different oils. The vegetable oils obtained in the United States are all too volatile t o be worth considering for continuous heating a t 250' C. The only easily available hard oil is cottonseed oil hydrogenated t o different degrees of hardness. For preliminary heating experiments there was a t hand a lard substitute consisting of cottonseed oil hardened t o a n iodine number of 9 7 and some cottonseed oil hardened t o a n iodine number of about 19. Lots of about I O O g. of oil were heated in porcelain crucibles which were set in holes in asbestos board over Bunsen burner flames. The temperatures were not regulated very closely and varied from 200' t o 300' C. a t different times.2 Buttons of tin weighing about 50 g. and oxidized by previous heating in the air were placed in t h e bottoms of the crucibles. The oils were heated seven times, usually 5 or 6 hrs. a t a time. The weights of oil and of tin were obtained after each heating. T h e tin was oxidized each time b y heating in the air, and fresh oil was added t o replace the loss during heating. At t h e end of t h e seventh heating the palm oil and the lard substitute U. S. Patent 1,242,532 (October 9, 1917). readings in the laboratory heating tests were taken with thermometers not wholly immersed and were not corrected. They are, therefore, all low, but comparable for the different oils. 1
* Temperature
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T H E JOURNAL OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
had polymerized t o such a n extent t h a t they would have been entirely useless in a tin pot, so they were rejected and a fresh lot of palm oil was compared with the same hard oil and another material which had been offered as a n improvement over the very hard oil. This material, a by-product fat, was more like palm oil in its physical properties and enough cheaper t h a n the hardened cottonseed oil t o make i t more economical if i t could be used. The lots were heated eight times more, when the palm oil and the by-product f a t were so polymerized as t o be useless. The very hard product was still in fair condition. The behavior of palm oil in the crucibles resembled its behavior in a tin pot, t h a t is, with successive heatings i t became more viscous when hot, and harder when cold; the loss from fresh oil was more rapid t h a n after i t had been heated for some time; and i t brightened the oxidized tin. The lard substitute resembled palm oil, but i t polymerized somewhat more easily. The by-product fat, which contained more free fatty acids t h a n any of the other samples, attacked the oxidized tin much more vigorously. I t lost more weight t h a n palm oil a t lower temperatures, and polymerized in about the same time. The heating tests indicated, on the whole, t h a t the lard substitute and the by-product material would not give as good service as palm oil in a tin pot. The very hard oil did not clean up the oxidized tin well during the first few heatings, but as the heatings continued, i t became softer when cold t h a n it was when fresh, and cleaned the oxidized tin well. At first the hard oil was much more fluid t h a n palm oil when melted, but after several heatings i t became somewhat thicker when melted. I t lost much less weight than palm oil during the heating. These experiments indicated t h a t a very hard hydrogenated cottonseed oil might be expected t o stand the heating in a tin pot without any disagreeable consequences in the way of unpleasant odors, excessive loss f @ m volatilization or from polymerization with consequent carrying out of oil on the plate leaving the bath. C O M M E R C I A L TEST
I n order to learn how the hardened oil would work in a tin pot, arrangements were made for an operating test. Through the kindness of Dr. David Wesson enough hardened cottonseed oil was secured t o make a fairly thorough test. The first lot obtained had an iodine number of about 3. A second lot had a n iodine number of about 17. This latter was the hardest oil which could be secured a t t h e time without having a special run made. as was done for the first lot. There was no detectable difference in operation between the two lots. The experiment was carried on a t a tin plate plant which had been in operation less t h a n a year. T h e equipment was therefore new and uniform throughout the plant, but had been operating long enough t o be broken in and running normally. The tin pots were of the type most widely used in this country, with 84-in. rolls. The plate was cleaned by a machine
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So. z
of the usual type. Ground peanut hulls were used for cleaning. At t h e s t a r t of the experiment all the oil was removed from one pot a t the regular Saturday cleaning. Eight hundred and fifty pounds of hardened oil were added t o the pot, and, on the basis of the preliminary heating experiments, the superintendent of the plant was urged t o keep the oil as hot as possible over Sunday while t h e mill was not in operation. However, on account of unfortunate past experience with substitutes for palm oil, the foreman in charge kept t h e pot with hardened oil a t a lower temperature t h a n the pots with palm oil, which are normally kept much below the working temperature over Sunday. When t h e plant started Sunday night very unsatisfactory plate was produced on Stack 9, where the hardened oil was in use. The plate continued poor for several turns after the other stacks began to produce satisfactory plate. It was not possible t o clean t h e oil from the plate by one treatment, even when t h e pressure of the rolls in the cleaning machine was increased, and fresh peanut meal was added more often t h a n usual. Recleaning removed all the surplus oil and gave a marketable plate, though the product of the first few turns was not u p t o the average quality of t h e plant. The first plate made was not very bright. An average sheet selected from one of the other stacks by t h e manager appeared much better than an average sheet from Stack 9. Analysis of 1 2 samples from each of these two sheets showed a n average of 1 . 3 3 lbs. of tin per base box for the sheet from Stack 9, and I . 72 for the other. Two sheets from Stack 9, taken during the second t u r n of its operation with hardened oil, carried I. I O and I.2 1 lbs. per base box. Five other sheets taken as representative sheets from Stack g during a period of I O wks. carried 1.47, 1.33, 1.58, 1.58, and I . 55 lbs. of tin per base box. After the first three days the plate from Stack 9 appeared t o be in every way as good as the average product of the plant. At t h e beginning of the second week the first sheets made on all stacks in t h e plant were compared, and the plate made on Stack 9 was in no way different from t h a t made on tlhe other stacks. The loss of oil by volatilization during the first week was much greater t h a n t h e loss during subsequent weeks, The quantity added each day during a n y week was much less for Stack g t h a n for those using palm oil. After the first week no special attention was given t o Stack 9, except t o make sure t h a t no palm oil w a s added, This was not difficult, as the tinners all preferred the hardened oil. It was operated with hardened oil alone for 1 2 wks. When the supply was used up additions of palm oil were made as required, with no effect on the operation of the machine. The plate produced with hardened oil was not noticeably different from the rest of the plant product. Some observers thought t h a t t h e front edges of the plate from Stack 9 were a little better t h a n the average. The quantity of oil carried o u t on the plate appeared much less with the hardened oil.
Feb., 1920
T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
151
TABLEI-Loss OB WEIGHTON HEATING100 G. OB OIL FOR 5-HR. PERIODS AT THE TEMPERATURE INDICATED IODINE L~SS D U R I ~ GE A C H PERIOD ~ ----TOTAL~LOSS AT ENDOB ~ A C HPERIOT
.200'
NUMBER 54 Palm oil.. . . . . . . . . . . . . . 17 Hardened cottonseed oil. . , . Rendered tallow.. . . . . . . . . . . . . 35 Unrenderedtallow.. . . . . . . . . . . 32.5 By-product fat. . . . . . . . . . . , 32 Hardened herring o i l . . . . . . . 60 OIL
..
. . . . . .. . .. .. .
5.3 1.8 0.7 2.0 11.3 2.4
220 4.8 1.8 1.2 1.3 16.9 3.8
240 5.4 3.1 2.4 2.7 15.8 4.5
260 10.4 7.2 4.7 1.1 5.5 5.8
Although palm oil is not very disagreeable for the operator, the hardened oil was enough better in this respect t o be noticeable. The hardened oil in actual use did not show any tendency t o polymerization, although a t several times i t was heated t o temperatures much higher t h a n would be safe with palm oil. There is also less danger of setting fire t o the hardened oil when cleaning t h e tin pot. There would seem t o be no reason t o expect economy in the consumption of tin with t h e use of hardened oil, unless t h e weight of coating on the plate should be decreased. Six weeks after t h e hardened oil was used up the tin house records were examined by the superintendent of the plant and one of the authors of this paper. The production of plate and consumption of tin and oil on Stack g were compared with the values for the other stacks in t h e mill for several weeks preceding, for the I 2 wks. of the test, and for the succeeding 6 wks. The following conclusions were reached: Over a considerable period Stack g does not differ materially from the average in performance. The tin consumption with hydrogenated oil was not appreciably different from t h a t with palm oil. During the 1 2 wks. of the test the oil used per base box was not over "4 of the average amount of palm oil used under similar conditions. I O D I N E NUMBERS OF OIL SAMPLES
No extensive analyses of oil samples were made. T h e first and second lots of hardened oil used had iodine numbers of 3 . I and 1 6 . 7, respectively. At the end of the first week of use the hardened oil in the tin pot had an iodine number of I 7.0. Samples on successive weeks gave values of 1 9 . 6 , 2 1 . 2 , 2 4 . 2 , 2 5 . 3 , 3 3 . 4 . After the sixth week t h e values varied between 3 0 . 5 and 3 5 . 3 for the remaining 6 wks. of the test. Beginning a t t h e thirteenth week, when palm oil was added, samples taken for 6 wks. had iodine numbers from 50. 2 t o 4 1 . 0 , with no regularity in the variations. At about t h e middle of t h e period of use of hardened oil samples were taken on one day from 1 4 pots operating with palm oil. The iodine numbers varied from 4 1 . 7 t o 5 3 . 6 , the average being 4 5 . 0 . Iodine numbers were obtained for several samples of beef tallow which had been heated in crucibles for different lengths of time. The original tallow had a n iodine number of about 3 2 . After heating for 5 hrs. a t about 200' C., 6 . 5 hrs. a t 2 2 0 ' C., and 7 hrs. a t 240' C., t h e iodine number was 24. 2 . Further heating for 6-hr. periods a t 260') 280') 290') and 300' did not produce much change in the iodine number. It was from 2 2 . 3 t o 2 4 . 5 for these samples. These results indicate t h a t palm oil in a tin pot will have a n iodine number around 4 5 , hydrogenated cottonseed oil about 3 2 , and tallow about 23.
280' 16.5 10.4 7.2 5.2 9.2 12.0
300'
....
15.8 18.9 11.6 7.4 15.9
200' 5.3 1.8 0.7 2.0 11.3 2.4
220 10.1 3.6 1.9 3.3 28.2 6.2
240' 15.5 6.7 4.3 6.0 44.0 10.7
260 25.9 13.9 9.0 7.1 49.5 16.5
280' 42.4 24.3 16.2 12.3 58.7 28.5
300
....
40.1 35.1 23.9 66.1 34.4
HEATING TESTS
At the conclusion of the commercial test further experiments were conducted t o determine losses on heating of t h e oils which had been used in t h e t i n pots, together with some similar materials which were a t hand. The palm oil and hardened cottonseed oil were from lots used in t h e experiment a t t h e plant. Beef kidney fat, purchased a t a local market, was used rendered and unrendered. The by-product f a t has been described above. A sample of Alaskan herring oil which had been hydrogenated until i t had a n iodine number of 6 0 was obtained from the Oil, F a t and Wax Laboratory of the Bureau. Samples of about IOO g. of the oils were heated in crucibles for from 4 t o 7 hrs. a t each temperature from zooo t o 300' C., inclusive, by 20' stages. Table I shows the loss calculated on a basis of I O O g. original weight and a 5-hr. heating period a t each temperature. The losses are given both for t h e individual periods and as total losses from the beginning of the heating to t h e end of each period. The great loss of the by-product f a t indicates clearly t h a t there would be no advantage in using i t when other materials were available. No values were obtained for palm oil above 2 8 0 ° , because a t this temperature the oil polymerized t o such a n extent t h a t i t would be unfit for use in a tin pot. The behavior of t h e hardened cottonseed oil and of the palm oil is in agreement with their action in the tin pot. Tallow acts much like the hardened cottonseed oil in heating, and is said t o resemble i t in actual use. The chief objections t o t h e use of tallow are said t o be its unpleasant nature, as it decomposes in storage, and the greater difficulty in cleaning i t from the plate, as compared with palm oil. The behavior of the hardened herring oil was very interesting. Although much softer t h a n any of t h e other products except palm oil, having an iodine number of 6 0 , i t lost weight slowly on heating and showed very little tendency t o It seems polymerize on prolonged heating a t 300'. entirely probable t h a t a more completely hardened oil of the nature of this sample of herring oil might prove superior t o t h e hardened cottonseed oil for use in t i n pots. It must be understood t h a t these laboratory heating tests only indicate in a general way t h e probable relative losses in actual use. SUMMARY
Laboratory heating tests give useful indications of the relative values of different oils for use in tin pots. During 1 2 wks. a tin pot using hydrogenated cottonseed oil operated somewhat better t h a n with palm oil. The consumption of hardened oil was distinctly less t h a n the consumption of palm oil. There was no appreciable saving of tin. If palm oil should be unobtainable for the manufac-
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THE JOURNAL,OF INDUSTRIAL A N D ENGINEERING CHEMISTRY
ture of tin plate, i t could be replaced by hydrogenated cottonseed oil with no loss in operating efficiency. With the industry adjusted t o the use of palm oil, the higher cost of hardened oils probably balances t h e advantage t o be obtained by their use, leaving little if any margin t o pay for the privilege of using the hardened oils. Heating experiments indicate t h a t a hydrogenated fish oil might be obtained which would be satisfactory for use in tin pots, though hardened t o a less degree than is necessary for the best results with cottonseed oil. LEAD COATED IRON’, By Charles Baskerville COLLEGE OF THE CITYO F NEWY O R K , NEW YORK,N. Y.
Protective coatings for the prolongatio‘n of t h e life of iron and steel fall i n t o three general classes, well described in a report from the Bureau of Standards (1919)as follows: I-Metallic coatings. a-Coatings in which the iron to be protected is itself converted a t the surface into some less corrodible compound. 3-Organic coatings (varnishes, paints, enamels, etc.). The present paper has t o do with the first of t h e three classes and is especially concerned with the use of lead and lead-antimony alloy as protective agents. If the iron be completely covered by another metal its life depends upon the ability of the covering metal t o withstand the corrosive action of air and water t o which i t may be exposed. This is materially affected by the presence of various chemical fumes and gases such as sulfur dioxide, nitrogen oxides, chlorine, sulfuric acid, alkali-mists, etc. Mechanical strains, vibrations and the rough handling which usually obtains during packing, transportation, installation, etc., may bring about ruptures and scaling in the protective coating and thus expose t h e iron or steel which may have been originally perfectly covered. The best manufacturing practice seeks a perfect coating initially but experience has shown the necessity for subsequent precautions because, where two metals, which always have a potential difference, are in juxtaposition in the presence of electrolytic water (acidulated, alkaline, or saline) electrolysis sets up with corrosion of one of them. If the iron be the electropositive member of the couple, it corrodes-the corrosion being activated by the presence of the other metal. Aluminum and zinc are electropositive t o iron, and therefore are theoretically the best practical metallic protective coatings for iron, where t h e coating is broken, as they bear the burden of corrosion. Zinc forms several alloys with iron which are also electropositive t o iron in a lesser degree. Tin, lead, copper, antimony and most of their alloys are electronegative, and hence facilitate the corrosion of the iron if i t is incompletely covered or exposed b y abrasion or other rough treatment. Practice has shown the importance of painting sheet tin and galvanized iron t o fill in the broken coating. 1 Presented at the 57th Meeting of the American Chemical Society, Buffalo, N. Y., April 1 1 to 13, 1919. 8 Most of the experimental work described was done by M i . V. A. Belcher.
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Since lead is the cheapest of all the metals used for coating iron, and in addition gives the covered metal certain other desirable qualities, a commercial method of application has long been sought. It is hardly justifiable t o incorporate here a bibliography on t h e subject. The most successful of the numerous efforts in this direction is the well-known terne plate, an alloy of about 75 per cent lead and 2 5 per cent tin, but this involves the use of costly tin. Lead has been successfully sprayed on iron by a n atomizer (Schoop process) and the process is well suited for certain detailed protective work, but i t is far too expensive in expert labor and time for tonnage production. Modern interest in electronic conceptions and in the difference in properties of metallic allotropes caused us t o investigate the processes covered b y United States patents granted t o Goodson,l which, briefly, consisted in subjecting a column of molten lead of small cross section in motion t o the influence of an alternating current of low voltage and high current density for several hours, i t being asserted t h a t the lead thus became “activated,” the molecular distribution effecting such change in physical condition t h a t i t would attach itself so firmly t o iron t h a t when the lead solidified it would not shrink away from the iron and leave exposed surfaces. Evidence of the production of a n iron-lead alloy binder did not appear. The conditions detailed in the patents were carried out most conscientiously, with such additional advice and assistance as the inventor was able t o give. It is hardly necessary t o describe the apparatus used. Some promising results were obtained, but on checking up with metal not treated electrically the results were virtually duplicated. Since i t seemed t h a t t h e problem of successfully and economically coating iron and steel with lead was not unsolvable, investigations were prosecuted along other lines and resulted in the production of products satisfactory for some purposes. I n working out a process for using lead and leadantimony alloys as a protective coating on sheet iron and steel, the fundamental problem was t o find a binder which would tie iron and lead firmly together. After much experimentation a preliminary coating of antimony proved t o serve the purpose. Melted lead shrinks materially when i t solidifies. Antimony tends t o overcome this shrinkage, as is well known from the conduct and composition of type metal. Moreover, the alloy formed is harder than lead. With a preliminary coating of antimony followed by dipping in lead, the latter acquires an increasing percentage of antimony. This fact, together with the other observations, caused us t o use a lead-antimony dip (eutectic of 1 2 . 5 per cent antimony) in the production of “protected iron” on a technical scale. Bending, twisting and hammering tests proved t h a t the iron foundation would break before the coating. Photomicrographs clearly disclosed the antimony binder. About 800 shingles, 9 X 16 in., of mild steel, of 24 1 U, S.Patents 789,690; 789,215; 900,846; 900,847; 978,448; 1,061,066; other applications pending.
