ANALYTICAL EDITION
20
A
B
C D -INNER
Figure 7-Effect
E
F
G H I J TUBE SAMPLES-
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K
L
M
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of Bomb Aging on Tensile Strength a n d Shear Product
“short” while the new tube showed no Lishortness.” The worn tube also showed a very weak and grainy tear. The importance of developing high-speed tensile tests or their Table IV-Decrease El“.-
!
of Various Criteria on Aging
!
Loss I N BOMBA T 50 HOURS, Loss 6OoC., 20.4 ATM.
Tensile Shear product
%
+2119
Average
I
15 17 4 16 39 28 +2 33 2 11 9 50 16
AIR A T 90° C., 48 HOURS
IN
Tensile
Shear product
%
%
%
25 70 43 44 49 45 42
54 93 51 74 71 77 57 78 23
63 96 68 89 76 76 60 75 11 65 73 78 70 64 69
60
24 27
80
33
50
69 40 43 45
66
1
29 64 61
Size 1, 29 X 4.40; size 2, 31 X 5.25; size 3, 33 X 6.00; size 4, 35 X 5.
VOl. 1, KO. 1
equivalents to show up this property of “shortness” in vulcanized rubber is evident. Figure 7 and Table IV show the effect of artificial aging on the tensile and shear product values of several makes of inner tubes. The oxygen bomb.test (50 hours a t 60” C. and 20.4 atm.) and a 48-hour air test a t 90” C. are shown. The tensile deteriorations were smaller than the shear product deteriorations in nearly every case, except in the 90” C. air test, which was so severe that tensile was reduced to about the same extent as shear product. The heat resistance of heavily pigmented tubes proves better than that of the rich gum tubes. The sensitivity of the tongue shear test to overcure is compared with tensile and tensile product in Figure 8. No doubt there may be cases where no greater sensitivity is s h o w n . T h e case given shows a tube stock cured with an ultra-accelerator. The s t o c k showed very little decrease of tensile on long overcures. O t h e r t e s t s showed e v e n t h e slightly overcured samples-to be poor in SHEAR PRODW s n i t e of t h e i r +.good . I I 6’ df , l e , ,?, tensiles. On s e r v i c e 5LA0 CURES e 141 ‘t tests tubes made from Figure 8-Shear Product us. Tensile or this stock developed Tensile Product on Overcures very poor resistance to sudden stress, weak shear resistance, and exceedingly poor tearing qualities. Further studies of its applications are being made.
1
I 1 I
Acknowledgment
The writer wishes to express his appreciation to W. E. Glancy, N. E. Tousley, and others who have assisted so much in the perfection of this test through their helpful suggestions.
Determination of Small Amounts of Carbon Monoxide in Ethylene’,’ Wright M . Welton with N. L. Drake UNIVERSITY O F
MARYLAND, COLLEGE PARK, 1WD.
HERMAN and others3 have reported one fatality and two cases of dangerous poisoning which were definitely shown to have been caused by the presence of carbon monoxide in ethylene administered as an anesthetic. The specifications of ethylene for anesthesia found in “Yew and Non-Official Remedies” for 1927 require that the gas show a negative test for carbon monoxide according to a method worked out a t the Bureau of Mines.4 This test will detect with certainty carbon monoxide in ethylene down to 0.02 per cent by volume, and probably down to 0.01 per cent by volume. have shown that 4 parts of carbon monoxHenderson et
S
Received July 11, 1928. From a thesis submiited b y Wright M. Welton to the Graduate School of the University of Maryland in partial fulfilment of the requirements for the degree of master of wience. 8 Sherman et al., J. A m . Med. Associi , 86, 1768 (1926). 4 Ibid., 88, 322 (1927). 6 Henderson et&, J. I n d . H y g , 8, 72, 137 (1921). 1 2
ide per 10,000 of air is the maximuin concentration to which a normal person can be exposed for an hour without noticeable effects, and that 1 part of carbon monoxide per 10,000 of air (0.01 per cent) is the maximum concentration that can be tolerated without ill effects by a normal individual who is exposed continuously for seven hours a day. It seemed to us worth while, therefore, to develop a method that would determine with certainty concentrations of carbon monoxide in ethylene well below those which would give a positive test .with hemoglobin. The present paper reports the first results of the investigation. The possible interference of impurities which may be found in commercial ethylene with the determination will form the subject of a future communication. It seemed that the simplest method of attack was to absorb the ethylene in fuming sulfuric acid of 25-30 per cent SO, content, and then to pass the residual gas, diluted with air, over hot iodine pentoxide, absorbing the iodine evolved in
January 15, 1929
INDUSTRIAL ALTD ENGINEERIiVG CHEMISTRY
potassium iodide solution. Preliminary experiments demonstrated conclusively that it would not be possible satisfactorily to absorb ethylene at room temperature in a reasonably short series of gas washing bottles, so a modified gas pipet was used for the purpose. The residual gas was diluted with air and passed through scrubbers to insure the removal of the last traces of ethylene. In order to gain familiarity with the method, several determinations of carbon monoxide in carbon monoxide-air mixtures were carried out. These experiments revealed to us that several important precautions which should be taken in the determination have either been overlooked or have not been sufficiently emphasized.
21
in the laboratory air, and to determine the effect of temperature on the evolution of iodine by our iodine pentoxide, the following experiments were conducted. Air drawn from outside the laboratory and scrubbed with acid permanganate and sodium hydroxide solutions was passed ovkr iodine pentoxide a t 160" C. to free it from any carbon monoxide it might contain. Any iodine evolved was then removed from the air by scrubbing with potassium hydroxide solution, and the resultant moist air was passed over stick potassium hydroxide and then through a drying tube containing phosphorus pentoxide. From here the air passed through a second tube containing iodine pentoxide that could be kept a t any desired temperature. Iodine evolved was trapped in 5 cc. of potassium iodide containing 1 cc. of 1 per Preparation of Iodine Pentoxide cent soluble starch, and t,itrated a t the conclusion of the exThe purity of the iodine pentoxide is probably the most periment with 0.0001 N sodium arsenite. In each experiment imuortaiit single factor necessary to success. We wish to 2.3 liters of dry carbon monoxide-free air mere Dassed over the iodine pentoxide. The reemphasize again, as have sults of the experiments are D a v i e s and Hartley6 and expressed in Figure I, which Edell,' that iodine pentoxide A method of determining small amounts of carbon shows the amount of iodine to be used for the determinamonoxide in ethylene has been developed. Ethylene is found in t h e p o t a s s i u m tion of small amounts of first removed from the gas under examination by means iodide solution plotted, as carbon monoxide should be of 25 per cent oleum, and the residual gas, diluted with cubic centimeters of 0.001 N p r e p a r e d from iodic acid air, is freed successively from traces of ethylene by 60 iodine, against temperature. made by chloric acid oxidaper cent oleum, from SOa by 98 per cent sulfuric acid, It is significant to note that tion of p u r e r e s u b l i m e d from SOz by soda lime, and from moisture by Pz05,and the magnitude of the blank iodine.8 Too m u c h c a r e is finally passed over hot 1205, with subsequent titraobtained in a carbon moncannot be taken in prepartion of the iodine liberated. The more important preoxide determination will be ing the reagent, and pentcautions in the determination of carbon monoxide in affected little by temperaoxide ~ d i i c hhas been careair by means of the iodine pentoxide method are disture, provided the analysis lessly p r e p a r e d mill give cussed. The method has been used for determining is conducted at a temperablanks that v a r y widely carbon monoxide in mixtures containing as little as 5 t u r e below 180" C. and from day to day and are parts of carbon monoxide per 100,000 of mixture, and above the temperature a t much higher than those obcould be satisfactorily employed with even lower conwhich o x i d a t i o n of t h e tained with a good sample centrations. monoxide is complete. We of reagent. Lamb's method chose 170" C. as our workof pieparing iodine penting temperature be cause oside ifas used in making our reagent, and was founud t o be the only method on which there was available a simple means of keeping the oil bath a t that temperature. There is no reason t o believe that any me could depend to give a uniformly satisfactory product. other temperature in this neighborhood would not be equally Effect of Temperature on Decomposition of Iodine satisfactory. It would not, however, be advisable to work Pentoxide above 180" C., as the rate of decomposition of iodine pentoxide can be seen from the figure to increase rapidly above The temperature a t which iodine pentoxide will completely 180" C. From available work and our own experience it is oxidize carbon monoxide was determined by Gautier t o be evident that oxidation of carbon monoxide to carbon dioxide 100" C.9 Various investigators since that time have em- is rapid and complete a t 170" C. ployed temperatures varying from 100" t o 200" C.lo No Drying the Gas Sample one, however, has taken the trouble t o determine systematically the manner in which temperature affects the decomThe necessity of having dry gas has not been emphasized position of iodine pentoxide. Obviously this decomposition of the reagent is an important factor in the determination, sufficiently. Better results in our analyses were always because it must be uniform a t any given temperature if obtained when gas dried over phosphorus pentoxide was dependable results are to be obtained. Furthermore, it used. The single point in Figure 1 labeled "moist air" would be very desirable t o have the amount of iodine liberated was obtained in the same way as the points of the other curve, by decomposition of the reagent a relatively small fraction of except that air humidified by bubbling through 10 per cent sodium hydroxide solution was passed directly over iodine the total iodine evolved in a determination. Our experience is in accord with that of Edell,' who found pentoxide a t 170" C. without drying. In our first experiments 98 per cent sulfuric acid was used that the best iodine pentoxide he could make liberated small quant,ities of iodine on heating. I n order t o determine t o dry the gas. In one experiment, however, enough iodine whether, as Seidell has claimed,'l this evolution of iodine is mas added to the absorption bulb a t the beginning of the caused by the presence of small amounts of carbon monoxide run to give a color with the starch. As the experiment proceeded the color of the indicator gradually bleached, and 6 Davies a n d Hartley, J . SOC.Chem. Ind., 45, 164 (1926). actually several drops of 0.001 iV iodine were needed to restore 7 Edell, IND. ENG.CHEM.,20, 275 (1928). the blue color a t the conclusion of the test. It was necessary, Lamb e t al., J . A m . Chem. Soc., 42, 1636 (1920). therefore, to introduce in the scrubbing train, subsequent to 8 Compt. rend., 126, 793, 931, 1299 (1898). 10 Tausz and Jungmann (Gas Wessevfech, 70, 1049 (1927)) recommend a the 98 per cent sulfuric acid, soda lime and then phosphorus temperature of 120-130° C. if the gas contains hydrogen, and one of 195' C. pentoxide. Thorburn12 has also noted that concentrated
-
if no hydrogen is present. 11 Seidell, J. IND. ENG.CHEM.,6, 321 (1914).
12
Thorburn, J . SOC.Chem. Ind., 46, 355 (1927)
Vol. 1, No. 1
ANALYTICAL EDITION
22
sulfuric acid is unsatisfactory as a final drying agent in this determination. Titration of the Iodine
The use of 0.001 N sodium thiosulfate solutions was soon abandoned. Even when made from carefully boiled distilled water, thiosulfate solutions decomposed far more rapidly on standing than did arsenite solutions of similar strength. Figure 2 gives a good idea of the relative stability of the two solutions. Although the 0.001 N arsenite solutions did not decompose appreciably up to the end of 5 days, we chose to make up our 0.001 N and 0.0001 N solutions fresh each day from a 0.1 N solution whose normality was checked at frequent intervals throughout the duration of the experiments.
Figure 1-Effect of Temperature on Stability of Iodine Pentoxide
Sodium arsenite solutions which were 0.001 N a n d 0.0001 N were used interchangeably. It was found more convenient to reach the proper end point with the more dilute solution, and 0.0001 N arsenite was used in most of the work. Numerous experiments with 0.001 N and 0.0001 N solutions showed that no appreciable error was introduced by the use of the more dilute solution. The titration was carried out in the absorption apparatus to avoid the necessity of dilution during transfer to another container.
absorbed in boiled potassium hydroxide solution (2:3) and about 100 cc. of monoxide collected in a gas buret and aE lowed to stand over dilute potassium hydroxide for several days. Measurement of the residual gas after shaking a known amount of the carbon monoxide with ammoniacal cuprous chloride showed the purity of the gas. As the impurity was undoubtedly air, the volume of residual gas was multiplied by five-fourths in calculating the purity of the original sample, as oxygen is absorbed by the ammoniacal cuprous chloride. Apparatus and Method
The apparatus used is shown in Figure 3. The measuring bulb (7), carefully calibrated and water-jacketed, had a volume of 526.25 cc. a t 22.1" C., and contained mercury as a sealing fluid. It was connected to the leveling bulb (5). For removing ethylene, an absorption pipet (6), containing glass rods and filled with fuming sulfuric acid (25 per cent SO3),was provided. The mercury trap (8), with its attached manometer (9), and the U tube (10) containing 98 per cent sulfuric acid served to prevent any fumes from the 60 per cent oleum in the scrubbing train (11, 12, 13) from getting into the measuring bulb. A trap (14) containing 98 per cent sulfuric acid served to protect the iodine pentoxide from oleum fumes, and the drying tube (15), containing soda lime in one arm and phosphorus pentoxide in the other, prevented the entrance of sulfur dioxide from the sulfuric acid and moisture into the iodine pentoxide tube. The iodine pentoxide was contained in a 5-mm. glass tube coiled as shown in the figure (16) to allow preheating the gas. The tube contained iodine pentoxide for about 5 inches of its length, in particles of such a size that they would pass through a 15-mesh sieve and be retained by a 20-mesh sieve. An electric hot plate maintained the Crisco bath a t 170" C. The exit from the iodine pentoxide tube was drawn down to small bore and inserted into the inlet of the absorption apparatus (17), which contained potassium iodide starch solution. The
Purity of Ethylene
The ethylene used in the investigation was obtained from a cylinder of compressed gas. Blank runs using one bulb of ethylene followed by two of air showed iodine evolved equivalent to 1.3 cc. of 0.0001 N arsenite. Although this blank value is larger than that obtained when three bulbs of air were used,l3 if we calculate from the iodine evolved the amount of carbon monoxide present in the ethylene, this amount can be no greater than 1 part per 100,000 of ethylene. Furthermore, i t may be that some impurity other than carbon monoxide in the gas caused this greater evolution of iodine. I n a future communication we will give the results of determinations run on ethylene which has been purified by fractional distillation. The lower limit of certain detection of carbon monoxide in ethylene by the official hemoglobin test is 0.02 per cent. The ethylene used here, therefore, contained no more than 0.05 of this amount. As was to be expected, it gave a negative test by the official hemoglobin method. Preparation and Purity of Carbon Monoxide
Carbon monoxide was prepared by the action of concentrated sulfuric acid on oxalic acid. The carbon dioxide was 18 Iodine was evolved in such determinations equivalent to 0.55 cc. of 0,0001 N arsenite.
Figure 2-Relative Stability of 0.001 N S o d i u m Arsenite and Thiosulfate Solutions
joint was then covered with pressure tubing. There were no rubber connections from the measuring bulb to the joint between the iodine pentoxide tube and absorbing apparatus. All stopcocks were lubricated with a little phosphorus pentoxide moistened with water. The absorbing solution was 5 cc. of a 1 per cent potassium iodide solution and 1 cc. of a 1 per cent solution of soluble starch, both freshly prepared. I n order to familiarize ourselves with the operation of the apparatus, several determinations of carbon monoxide in carbon monoxide-air mixtures were made. As we believe that the results are more accurate than most of those in the literature, particularly in view of the small size of the sample used, they are included with those obtained from carbon monoxide-ethylene mixtures.
January 15, 1929
INDUSTRIAL AND ENGINEERING CHEMISTRY
23
evolved was equivaThe procedure was l e n t t o 1.3 cc. of very nearly identical 0,0001Narsenite. In w h e t h e r air-carbon t h e a n a l y s e s , howmonoxide o r ethylever, we did not use e n e - c a r b o n monoxthese averages. The ide m i x t u r e s were b l a n k t o be s u b being analyzed, ext r a c t e d was detercept that in the ethylmined a t the compleene-c a r b on mono xtion of each experiide analyses t h e ment by running an ethylene was first abexactly similar experisorbed and the residment using c a r b o n ual gas, diluted with monoxide-free gas. air, handled as in an air-carbon monoxide T h e cause of the analysis. considerably higher blank in the experiThe gas measuring ments with ethylene b u l b was first filled Figure 3-Apparatus Used may mean that a little with gas s a t u r a t e d 2 3-Acid KMnO4 SO8 ROH carbon monoxide with w a t e r v a p o r . 4-Dilute 5-Leveling bulb, with mercury (about 1 part to 100,Barometric pressure 6-Fuming H&O4-25% SOs 7-Gas balloon flask in water jacket 000 parts of ethylene) K I and 1 cc. and water-jacket tem- 8-Mercury trap 9-Manometer is present in the gas, perature were r e a d , or that some other imand the mercury was then adjusted a t the calibration mark in the capillary tube be- purity is interfering. low the bulb. The difference in pressure inside and outside Monoxide in the Scrubbing Train of was measured, the stopcock to the train was opened, and the The retention of carbon monoxide in the scrubbers is a gas was forced through the system by elevating the leveling bulb. The Dressure at the manometer generally amounted to Dossibilitv. The fact that in 12 of the 15 analvses of air50-55 mm. k i d this pressure served as auseful guide in avoid- konoxide mixtures too little monoxide was foknd might ing the freezing of the 60 per cent oleum in the scrubbing tubes. cause one to think that this was taking place. Four of the Two bulbs of air taken from out of doors and scrubbed with analyses of the ethylene-monoxide mixtures show positive acid permanganate and sodium hydroxide were then forced errors, seven show negative errors, and one shows no error. through the apparatus subsequent to the sample. I n more The evidence here, then, is not nearly as strong as in the other than ten instances where a third bulb of air was forced through analyses. the train after the completion of an analysis, no blue color in a fresh solution of potassium iodide starch in the absorption PARTSCARBON MONOXIDE PER 100,000 PARTSOF GAS MIXTURE apparatus could be detected. When the gas to be analyzed No. Computed Found Error had been displaced by mercury, iodine could be found in the 22.3 la 20.7 -1.6 absorption bulb equivalent to about 16 per cent of the total 22.3 lb 22.0 -0.3 22.3 21.0 -1.3 IC monoxide in the gas. When the first bulb of pure air had 2a 12.2 11.9 -0.3 passed into the train, iodine had been absorbed equivalent 12.2 -0.7 11.5 2b 11.4 -0.8 12.2 2c t o about 81 per cent of the total. Consequently, the second 3a 8.2 -0.2 8.4 bulb of wash air carried over only about 3 per cent of the 8.4 3b 7.7 -0.7 8.4 -0.6 3c 7.8 total iodine liberated. I n every case all of the iodine was held 4a 5.1 5.2 +0.1 in the first bend of the absorption apparatus, as shown by the 5.1 $0.4 4b 5.5 4.6 -0.5 5.1 4c absence of blue color in the second bend, indicating that 5a 2.8 2.2 -0.6 absorption was complete and that air did not liberate iodine 2.5 -0.3 5c 3.0 +0.2 from the potassium iodide solution. When ethylene-monoxide mixtures were analyzed a bulbful of gas was pumped into the absorption pipet, and, after the PARTS CARBON MONOXIDE PER ~00,000PARTS OF GAS MIXrURR greater portion of the ethylene had been absorbed, the residual NO. Computed Found Error gas was diluted with about 100 cc. of air from out of doors, scrubbed as before. The absorption of a bulbful of ethylene la 19.7 20.3 +0.6 20.2 $0.5 required between one and two hours. The addition of air IC 18.4 -1.3 toward the latter part of the absorption helped to prevent 2s 14.9 13.5 -1.4 12.8 -2.1 2b the solution of carbon monoxide in the sulfuric acid by cutting 14.3 -0.6 2c ~. down the partial pressure of monoxide in the mixture, al3a 8.6 9.4 +0.8 9.3 $0.7 3b though undoubtedly it slowed up the ethylene absorption. 8.5 -0.1 3c The residual carbon monoxide-air mixture was diluted with 4a 5.3 4.9 -0.4 5.1 -0.2 4b scrubbed outside air to the volume of the measuring bulb, 4c 5.3 $0.0 5.3 forced into the train, and followed by the usual amount of wash air. A part of the first bulb of wash air was used to That the returning of carbon monoxide to subsequent analyrinse out the capillary tubes of the absorption pipet. ses is not important is evident from the following consideraBlank runs using three bulbs of air produced an average tions. Every analysis was followed by a blank determinaiodine evolution equivalent to 0.55 cc. of 0.0001 N arsenite. tion. All of the analyses of air-carbon monoxide mixtures When one bulb of ethylene from a cylinder of compressed were conducted with the same acid in the train, and blank ethylene was used, followed by two bulbs of air, the iodine determinations which were run on the completion of the last
.
ANALYTICAL EDITION
24
air-carbon monoxide analysis did not vary significantly from those which were made when the acid was fresh. We conelude, therefore, that no appreciable error was introduced by the returning of carbon monoxide from the scrubbing train to mixtures t o be analyzed. Similarly, in the case of ethylene-monoxide mixtures there
Vol. 1, s o . I
was no tendency for the blank determinations to increase as the number of analyses increased. The acid in the scrubbers was changed between the air analyses and the ethylene analyses, and the same acid was used throughout the series of ethylene analyses. The experimental results are given in Tables I and 11.
Use of the Refractometric Method in Determination of Oil in Avocados' B. E. Lesley a n d A. W. Christie FRUITPRODUCTS LABORATORY, UNIVERSITYO F
T
HE oil content of avocados is a valuable index of maturity and market value in determining the proper time of picking and shipping. Furthermore, the California Fruit and Vegetable Standardization Act (Chap. 350, see. 11) states that "Avocados shall not be considered mature when the edible portion shows an oil content of less than eight per cent by weight by chemical analysis." The California Avocado Growers Exchange found it necessary to have frequent oil analyses made by the ether extraction method, which was so expensive and time consuming that they appealed to the University of California to develop a rapid and inexpensive method suitable for their purpose. The method developed by us and described in this paper is not only suitable for the determination of oil in avocados but also, if a suitable factor is used for its determination, in other materials high in moisture content. Wesson2has described a method for determining oil in oil mill materials based on the extraction of the oil from the material by means of a measured amount of a suitable solvent having a refractive index sufficiently different from that of the extracted oil to produce relatively large changes in the refractive index with small amounts of oil dissolved in the
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CALIFORNIA,
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5 milliliters of Halowax oil into the mortar. Grind carefully for about 5 minutes. The oil quickly separates from the mass, so that a drop can be conveniently picked up on a stirring rod. Separate a drop of the oil mixture, and determine the refractive index, observing the temperature also. Grind for about 1 minute more, and repeat the refractive index determination. Continue grinding and reading until a constant value is obtained. Correct the reading to 25" C. by adding 0.0004 for every degree above 25" C., or subtracting 0.0004 for every degree below 25" C. Application of Method
This method was applied to several samples of avocado paste on which the oil had already been determined by the official ether extract method. A graph was prepared by plotting the percentage of oil by ether extract and refractive indices of mixtures at 25" C. The result was practically a straight line. This graph is presented in Figure 1. By drawing this graph to a larger scale than here presented and extrapolating it was observed that the theoretical refractive index which would be obtained from a sample of avocado containing 0 per cent oil would be 1.63215, whereas the refractive index of the Halowax oil used was 1.63535. This difference of 0.00320 is probably due to the presence of some substance other than oil, which will dissolve in Halowax oil, lowering the refractive index. It is believed that this figure is correct for all samples within the limits of error of the method, which is not greater than 1.0.3 per cent. Unfortunately, all shipments of Halowax oil do not have the same refractive index. Variations in refractjive index as high as +0.002 have been noted by the authors. For this reason the use of the graph in converting refractive indices to percentage of oil may be inconvenient or cause error. The following formula was considered more correct and convenient : (a - 0.0032) - b = c d where a = refractive index of Halowax oil a t 25" C. b = refractive index of mixture oil a t 25' C. c = per cent oil in sample d = change in refractive index per per cent of oil in sample
From the slope of the line (Figure 1) it is seen that cl 0.001555 per cent oil.
=
Practically all Czechoslovakian producers of potato starch are included in an organization which has recently been formed in that country. The uncertain outlook for the industry in general, together with a poor crop of potatoes in Slovakia and good crops in neighboring countries, hastened the formation of the cartel.
