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Literature Cited (1) Adkins, H., and Connor, R., J. Am. Chem.SOC., 53, 1092 (1931).
(2) Arms, R. W., Univ. Ill. Eng. Expt. Sta., Bull. 128 (1922). (3) Bancroft, W.D., J . Phya. Chem.,27,851 (1923). (4) Bartell, F. E., and Miller, E. J., J Am. Chem. Soc., 44, 1866-80 (1922). (5) Berger, E., and Delmas, JJ., Bull. 80c. chim., [4]29, 68 (1921). (6) Brandt, L., Chem.-Ztg.,44 I, 881-2 (1920). (7) Cocagne, P., J. Inst. Metals, 31, 533 (1924). (8) Euler, H.von, and Josephson, K. O., Brennstof-Chem.,1, 63-6 (1920). (9) Fukuda, Y.,and Oshima, Y., IND.ENO. CHEM., 26, 1158 (1935). (10) Gwosdz, J., Z.angew. Chem., 31, 137 (1918). (11) Hedvall, J. A.,Suensk Kem. Tid., 32,99-103 (1920).
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(12) Kolthoff, I. M.,Rec. trau. chim., 46, 549-73 (1927). (13) Krauoh, C., “Testing of Chemical Reagents for Purity,” tr. by Williamson and Dupre, New York, D. Van Nostrand Co., 1902 (14) Neumann, B., Kroeger, C., and Fingas, E., 2. anorg. allgem. C h m . , 197, 321-38 (1931). (15) Parr, 8. W.,and Staley, W. D., IND. ENQ.CHEM.,19, 820-2 (1927). (16) Patrick, W.A,, British Patent 159,508 (1921). (17) Sohn, C. H.B., and Wieland, H., Ibid., 205,240 (1922). (18) Taylor, H.S., and Kistiakowsky, G. B., J . Am. Chem. SOC.,49, 2470 (1927). (19) Taylor, H.S., and Neville, H. A.,Zbid., 43, 2055-71 (1921). (20) Thomae, C., Chem.-Ztg., 43 I, 747 (1919). RECEIVED August 1, 1935
Cause of CcCrystallization” of Tung Oil Vehicles JULIUS HYMAN
AND THEODORE GREENFIELD Velsicol Corporation, Chicago, 111.
The cause of “gas-checking” or “crystallization” of raw or low-temperature bodied tung oil vehicles lies in the presence of traces of nitrogen dioxide in the atmosphere. The critical nitrogen dioxide concentration necessary to produce crystallization in a given standard varnish under controlled conditions is 4 parts in 10 million parts of air. The possible action of traces of nitrogen dioxide in other phenomena is suggested.
tung oil film. This view was contradicted by experiments of Auer (2) who contended that crystallization was caused by the action of ultraviolet light. Mere (6) found that ultraviolet light was not essential in the production of tung oil crystallization. Boecking (4) observed that crystallization occurred when tung oil dried in an atmosphere containing products of combustion. He made several important observations along this line. One was that crystallization of a drying tung oil film occurred when the film was in contact with the products of combustion of hydrogen gas. Another was that the presence of an electrically heated coil was sufficient to produce crystallization. Bauer (3) found that fumes of nitric acid were capable of causing severe crystallization and developed a method based on this observation for testing tung oil vehicles.
Nitrogen Dioxide Responsible for Crystallization As a result of an investigation carried out by the authors, it now appears that the cause of ordinary crystallization of
@A
LTHOUGH the phenomenon of “crystallization” or “gas-checking” of tung (China wood) oil has been known to varnish makers since the oil was introduced commercially, the cause of this unique behavior received little scientific attention prior to the last decade. Authorities in the field of the drying oils, such as Fahrion, Eibner, Wolff, and others, were content to discuss it from its physical and colloidal aspects, disregarding the common knowledge that crystallization did not invariably accompany the drying of a tung oil film.
Review of the Literature In 1924 Schmidt (9)purported to show that crystallization was due to the action of traces of water vapor on the drying
tung oil vehicles is to be found in the presence of traces of nitrogen dioxide (NOz) in the atmosphere surrounding the drying tung oil vehicle film. For example, when a small quantity of nitrogen dioxide is introduced into a bell jar containing a film of low-temperature bodied tung oil vehicle, crystallization sets in almost immediately. The same effect is noted when similar films dry in the presence of electric sparks.
Methods and Results In order to check these observations accurately, a standard 30-gallon ester gum-tung oil varnish was prepared, and films made therefrom were subjected to a number of critical tests. The standard varnish was prepared as follows: Two hundred and forty grams of raw tung oil were bodied in a liter beaker between 220’ and 230’ C. for about an hour, until a drop of the oil, on cooling, showed a 3-inch (7.6-cm.) “string.”
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described in the government speeifioation for the determination of the "gas-proofness" of interior varnishes (6). The holes in the steel phte were fitted with appropristo rubber stoppers, through which were introduced (a) a glass tubesnanifold, which connected with the vacuum pump, manometer, special gas mixture (obtained from the Olio ChemIcsl and Manufacturing Company in B cylinder under 1500 pounds per square inch pressure), and atmospheric exit; (a) a wlre connected with the secondary of spark coil, the other terminal of the aecondary being connected with (e) a drawn copper tube, connected with a tank of ethylene oxide gas (obtained from the Carbide & Carbon Chemicals Corporation). It was found that, because of the peculiar heat-eondueting properties of the Iielium-oxygen mixture, ordinary wick lamps could not be used with the heavier fuels, while tho lighter liquid fuels, such, as alcohol, would volatilize in the vacuum to such an extent that explosions were likely to result from ~bspark, when the lielium-oxygen mixture was introduced. All gas connections were made with rubber pressure tubing, and all sed5 were covered with a heavy adhesive stopcock grease manufactured in this laboratory. The vssnish was flowed out at intervals on semi-circular tin plates, after the manner of the federal gas test for interior varnishes, allowance being made for the t,ime required to evacuate !,he system. All tests were made away from direct, sunlight. In carrying out the flame experiments, the flowed-out test plates were placed on the tripod (equipped with a baffle plate, not shown in the illuutration, to prevent the gas flame from striking the test plates directly), and the bell jar was then sealed down with the heavy grease. The v&cuurn pump wa8 started and allowed to run for 7 or 8 minutes until the pressure within the system wm reduced to a few millimeters or less. The helium-oxygen mixture was thereupon introduced until the pressure wit,hinthe system WAR almost, atmospheric. The spark
FIGURE1. APPABATU~ FOB FLAME m SPARK EXPERIMEWB
The oil was removed from the fie, and sufficient p e t r o l e u m spirits was added to reduce the temperature of the mixture to 175" C. One hundred grams of pale ester gum of low acid content were added and allowed to dissolve. (If necessary, the t e m e r a t u r e of the mixture shoub be kept around 150" C. until s o l u t i o n i s c o m p l e t e . ) Enough petroleum spirits was then added to bring the total wei ht of the contents of the be& to 680 grams. Finally, 0.24 gram of cobalt, in naphthenate soap combination, was added to the varnish, which was then thoroughly stirred and fictered through a 150-mesh screen.
In order t o ascertain whether crystallisation w o u l d o c c u r in R nitrogen-free atmosphere, experiments with (a) flames and (b) sparks were carried out in a n atmosphere composed of 80 per cent by volume of helium and 20 per cent by volume of oxygen. Figure 1 is a sketch of the type of apparatus used :
A.
Plate exposed in helium-oxygen s h o a p h e i e Lo ethylens orrde Same; no crystallisation.
R
Piate oxposed i n heiiurn-orrgen, stmnaplieie to nnsrk: P O V P ? ~eryatsilicatron.
The apparatus consisted of s flat steel olate through which bad been billed three holes, a heavy glass bell jar (37.5 cm. in heieht End 20 cm. in diameter). a n d a tripod f o r h o l d i n g the test panels. The a p p a r a t u s was mmewhat similar to that
FIQUEX2.
TYPICAL RESULTS EXPERI-
OF h M E AND SPARK MENTE
C.
Plate ernnned in Berere
sir t o ethylene oxide flame: riYstallirstion.
D. Plate errmred in sir tospark: ~ e v e r
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was then passed momentarily
top and the two sides of the cabinet were fitted witti large elass windows. The case could 6e opened from the one side, which was fitted at the top with hinges. A hole was bored in manually so that it burned for one end ofthe cabinet. throueh 3 or 4 minutes. which was placed the'shaft 'bf In the spark tests the same a Winch (25.4cm.) electric nrocedure was followed excent tan. At the other end of the that. instead of the ethylene cabinet two wires leadina from the secondarv of a m d e l T Ford spark -rail were introduced. The coil w&5 actuated tlnuousiy'for 3 miiutes bv a 6-volt stewdown radio timsforrner attiched t o the 110-volt a. c. lighting circuit. Typical results of flame and The wires from tbe secondary spark experiments in air and were attached to two snark plum arranged in series, &ch the helium-oxygen mixture wit5 'spark"g.qs 0.060 inch FIGURE 3. WOODEN CABINET FOE ~ U A N T I T A T I V E STUDY OF are s h n m in Figure 2. In the (O.l27em.)across. The tripod CRYSTALLI~IATION o r d i n a r v air exueriments stand nsed in t,hebell iaremeriboth flank and siark platob rnents was nsed to hoid the'teat plates, and interspersed between the tripod and the fan propeller exhibited abundant crvstallization. In the helium-oxveen NB8 a baffle to shield the test plntes fmm too vigorous drafts. experiments the h e plates were free from crystall&t&n, The spark plugs were calibrated for their nitrogen dioxide hut the spark plates crystallized badly. The cause of the production by the use of the conventional Ismp-dfur a helium-oxygen spark crystallization appeared to be the result ( 2 ) for determining the sulfur content of kerosene, etc. dioxide is absorbed by sodium carbonate according to the equaof one of two possible causes: Either (a) the helium-oxygen tion: mixture contained a small quantity of nitrogen, or (b) ozone 2NOs + NasCOa --+ NxNOr -t NaNO, + Con formation was responsible. The possibility of ozone as the cause of crystallization was ruled nut by passing oxygen through a Siemens ozonizing tube connected with a Ford automobile spark coil (actuated in &rim) were suhstitnted for the ordinaGy ke;oseEe iambs and by three ordinary dry cells), and thence to a bell jar conwere inserted into the "chimneys" of the ap aratus; they were held in place by narrow perforated corks. &enty cubic centitaking a drying standard varnish film. The presence of meters of sodium carbonate solution was used in eaeh apparatus. ozone was shown not only by the odor of the effluent gas, This solution was nrenared bv dissolvine 2.361 Erams of sodium but by its action on acidified potassium iodide solutions. Plates dried free from crystalliaation in such an atmosphere. It wa,s therefore concluded that the helium-oxygen mixture in titxation, exkrwed i i cubic centimetprs, between the blank used contained a srnaU quantity of nitrogen, sufiicient to produce nitrogen dioxide in the heat of an electrical spark, dthough insufiicient for its production in the heat of a flame. to be omd&ina 0.056 eo. of nitroeen diixidc Der minute. Since only two oxides of nitrogen-namely, nitrous oxide T h i crystallrzation determinatYon8 were c k i e d out by Grst and nitrogen dioxide-are stable when diluted with large obtaining the dust-free drying time of the standard varnish volumes of air, the possibility still existed that nitrous oxide under the tost conditious, then Bowing out plates, and placin (NzO) might have precipitated the crystallization. In them in the osbinet ahout 12 minutes mior to their noma? order to check this hypothesis, experiments were performed in which nitrous oxide (prepared by heating ammonium - ~ nitrate and washing the resulting gas well with a saturated at low' speed throughout the test. the^ odset of-crystallization solution of ferrous sulfate) was introduced into a hell jar could he observed through the windows. Direct sunlight was not allowed to fall on the test panels. containing a drying standard varnish film. At no time could crystallization be observed. Figure 4 shows photographs of representative plates St would therefore appear that nitrogen dioxide, and only demonstrating the limit of nitrogen dioxide required for that, is responsible for the phenomenon now generally referred crystallization. For the standard varnish used, i t was found to as gas-checking or crystallization. that 4 parts of nitrogen dioxide in 10 million parts of air were The quantitative study of crystalfieation was slightly comsufficient to cause crystallization, plicated because of the corrosive nature of nitrogen dioxide. The following arrangement was finally adopted: Discussion between the wire and the gas inlet tube, and, simultaneously.
! % ~ ~
.~~-"-
A wooden cabinet (Figure 3) w a constructed, 75 X 75 X 125 om. in size, with a volume of approximately 700,000 cc. The
FIGURE 4. REPREBENTATWE PLATE8
SHOWWO
Reynolds (8)found that the quantity of nitrogen dioxide in the air in London varied from 0.03 p. p. m. in foggy weather
LIMIT OF NITROQEN DIOXIDEREQUIRED FOR CRYBTALLIZATION
~ "
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INDUSTRIAL AND ENGINEERING CHEMISTRY
to 0.008 p. p. in. in summer, a i d that couutry air contained about one-sixth those amounts. It is well known that films of raw tung oil, free from drier and drying in the absence of light, crystallize even in fame-free surroundings; therefore, the extreme sensitiveness of the crystallization reaction of tung oil toward nitrogen dioxide may he appreciated. Certainly, no more delicate qualitative test for nitrogen dioxide exists. The crystallization caused hy ultraviolet light, as observed by Auer (a) may be accounted for on the hypothesis that the ultraviolet light in the sun’s rays produces minute quantities of nitrogeii dioxide. Indeed, Rajvansi and Dbar (7) found that sunlight produced demonstrable a,mounts of nitrogen dioxide in air dissolved in water. The knowledge that small quantities of nitrogen dioxide are produced by ordinary atmospheric combustion, by electrical sparks, and by sunlight, gives rise to interesting speculations along a number of technical lines, in view of the known catalytic activity of nitrogen dioxide. Recently, for example, Smoker, Jordan, and Fulweiler (10)discovered and demonstrated the polymerizing action of traces of nitrogen dioxide on certain unsaturated constituents of illuminating gas. I n the field of surface finishes, the phenomenon of afteryellowing appears from preliminary experiments conducted here to he connected directly with the absorption of nitrogen dioxide. Tests have revealed that those finishes most prone to after-yellowing are most easily yellowed on exposure to nitrogen dioxide. The yellowing of paper with age, and the
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fading of inks on exposure to sunlight may well he allied phenomena. The realization that flames produce nitrogen dioxide may also throw new light on the phenomenon of pre-ignition (knocking) in gasoline motors. It is well established that traces of nitrogen dioxide exert a powerful positive catalytic effect on the vapor-phase oxidation of hydrocarbons. It is iuteresting to observe that knock inhibitors (or their d e composition products) are always compounds which either (a) avidly fix nitrogen dioxide in the form of metallic nitroxyl~or aromatic substitution compounds; ( 6 ) reduce Mravalent nitrogen to less positive valence states or, indeed, to elementary nitrogen; (e) seek to interfere with the possible formation of nitrogen dioxide; or (d) add sufficient nitrogen dioxide to the system to erase the effect of the small quantity of nitrogen dioxide resulting from cornhost,ion.
Literature Cited (1) A. S. T. X, Standards, D90-30T (1930). (2) h e r , Farben-Ztg., 31, 1625 (1926).
( 3 ) Bsuer, IND.END.CHEM.,18, 1249 (1926). (4) Boeoking, Farba-Ztg., 31, 1910 (1926). ( 5 ) Bur. Standards, Circ. 117,2nd sd.,1922. (6) Mcm, Farbe u. Lack, 31, 332 (1926). (7) Rajmnsi and Dhar, I . P h m Chem.. 36, 575 (1932). (8) Reynolds, J . Soc. Chem. Ind., 49, 168T (1930). (9) Sohmidt, Fa7ben-Ztg., 29. 1261 (1924). (10) Smoker. Jordan. and filweiler, paper presented before Division of Gss and l h l Chemidry at 89th Meeting of A. C . S., New York. N. Y., April 22 t o 26, 1935. R E C I ~ Y E .August D 9. 1935
The Alchemist Artist Unknown In presenting No. 62 in the Beroleheimer series of Alchemical and Historical Reproductions we express our appreciation to Prof. Ralph E. Oesper of the University of Cincinnati, who loaned u9 a photograph purchased in England. As the name of the painter responsible for the original does not appear on the photograph, we are compelled to guess who he was. As the alohemieal paintings of David Teniers, the Younger, Jan Steen, Adrian van Ostade, and other painters of the Flemish school are all known and cataloged, it is our surmise that David Tenien, the Elder, may have painted the original, although the location of the latter is unknown. A detailed list of the first sixty reproduotiom, together with full partioulara for obtaining phutograpilie copiee of the origin&laappeared in OUI isme for Janusry. 1936, pnge 120. where ako will bsfound Heproduotion No. 61.
