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This low-boiling fraction contains about 43 per cent phenolic compounds, 26 per cent unsaturated hydrocarbons, and 31 per cent saturated hydrocarbons. A catalyst containing copper gives a lower yield of oils. I n no case is there an appreciable increase in methanol. 6-Experiments with cellulose demonstrate that the increases in methanol yield observed with wood are not due to the cellulose content. With nickel and hydrogen under 200 atmospheres practically all of the cellulose, or 98 per cent, is converted to volatile products, of which a large percentage are liquids of the general type mentioned above under 5. 7-In substituting nitrogen for hydrogen 86 per cent of the cellulose is converted to volatile products in the presence of nickel. Conclusions
From these data it can be concluded that it is possible to convert the cellulose molecule into volatile products but that no success has been met with in controlling this reaction so as to obtain methanol. When reaction takes place the products are phenols and unsaturated and saturated hydrocarbons. Although high in some cases, there is no reason why the methanol yields observed should not have been derived from the methoxyl in the original wood, since according to Hawley only 70 per cent of this methoxyl is ordinarily recovered as useful products in wood distillation.
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The results obtained when distilling cellulose under pressure in an atmosphere of nitrogen bring up the question as to the mechanism of hydrogenation in certain processes. Thus, it is claimed that in the berginization of coal the 5 per cent of hydrogen consumed in the process are converted into gaseous products and do not enter into the 1iquids.lE Whether the decomposition of cellulose and wood to form phenols and hydrocarbons will meet with any commercial success would seem to depend largely upon the develop ment of suitable equipment for continuous operation. The fact that the reaction goes almost quantitatively makes the process compare favorably with the berginization of coal. The effect of the inert nitrogen pressure suggests as a possibility the substitution, for hydrogen, of the gases generated by the reaction itself. The catalyst field has barely been touched upon. I n continuing this investigation the mechanism of reaction will be studied for the dry distillation of cellulose and wood in atmospheres of hydrogen, carbon monoxide, and nitrogen, using different types of catalysts. Acknowledgment
The writers wish to acknowledge the assistance rendered by E. V. Fasce in the examination of the liquid products. 16 Tropsch, Lecture delivered at the Institute of Chemistry, State College, Pa., July, 1927.
Effect of Temperature on the Rate of Decomposition of Nitrocellulose' R. W. Ryan and E. A. Lantz HERCULES EXPERIMENTAL STATION, HERCULES POWDER COMPANY, KENVIL, N. J.
An improved method of studying the rate of evolution T A B I L I T Y tests for an elevated temperature and of nitrogen oxides from heated nitrocellulose at various nitrocellu~ose fall into results are not necessarily inthree classes: (1) the sotemperatures has been developed. dications of stability a t orIt is shown that the logarithm of the rate of evolution dinary temperatures. called 'ItraCe tests,! in which of nitrogen plotted against temperature gives a straight F r e q u e n t l y a sample of the time taken to color a very line. The stability of the nitrocellulose sample exnitroce~u~ose may be consensitive reagentpaper is amined is largely responsible for the slope of the residered stable by one test but noted; (2) tests in which the suiting line. From the determination of the temperaunstable when sdbjected to temperature of the nitrocelluture coefficient of the decomposition rate, an idea another test, This is espelose is raised to the point of the stability of nitrocellulose at lower temperatures cially true when two tests, w h e r e decomposition is so is Obtained* such as the Abel K I and Gerrapid as to be detected by less Additions of small amounts of various salts change man test, are applied to the sensitive reagents or by the observance of fumes; and (3), the stability of nitrocell~lose,as shown by the change sample, It was therefore in the temperature coefficient Of the decomposition deemed advisable to establish, the tests which are dependent rate. This method is a valuable means of determining if possible, a correlation beon the quantitative d e t e r the effects various materials will have on stability. tween the various methods of fination of the products ,f decomposition. Probably j u d g i n g s t a b i l i t y . The the best known examples of these methods are, respectively, method described herein is the result of an extensive study the Abel K I test, the 135' C. or German test, and the Will on the subject and is offered as a better means of studying test. All of these tests are open to criticism. Often the relative stabilities of uncolloided nitrocellulose. This method of testing the stability of nitrocellulose is Abel K I test is a measure of the accumulation of nitrogen oxides over a period of time and is not a true indication dependent on the determination of the rate of evolution of the keeping qualities of the nitrocellulose.2 Further- of nitrogen oxides from heated nitrocellulose at two or more more, unless it is carried out under strictly defined conditions, temperatures. The method of measuring the decomposition results may be obtained which may lead to erroneous con- is a modification of that outlined by Philip,a who measured clusions as the test paper is easily affected by traces of the rate of decomposition of nitrocellulose heated in air substances present in the atmosphere. The main objection at 135' C. by absorbing the nitrogen oxides formed in a to the German and Will tests is that they are conducted a t potassium iodide solution. I n order to adapt the method to lower temperatures the original apparatus and method of 1 Received August 16,1927.
S
:Robertson, J . SOC.Chem. Ind..
39, 133 (1910).
a Ingenibs
Vetenskaps Akedcmeins, Handlingar 38.
January, 1928
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and acid gases by passing through a 5 per cent sodium hydroxide solution, dried with calcium chloride, and then filtered through a cotton fdter to remove any dust picked up in the calcium chloride drying tube. After leaving the reaction tube, the stream of air was passed through a 5 per cent potassium iodide solution, which absorbed as NOz the nitrogen oxides given off by the nitrocellulose. The absorption tube was fitted with a capillary tip to insure good break-up of the air stream containing the NOz. It was kept cool by a water jacket through which the waste water from the condenser circulated. This cooling was essential, for otherwise considerable iodine was lost by evaporation. With a proper absorption tube, 99 per cent of the NOn was absorbed by one tube. The liberated iodine was titrated by the electrometric method described by Foulk and B a ~ d e n . ~ Reagents
Figure !-Apparatus for Determining Rate of Evolution of Nitrogen from Nitrocellulose
operation had to be modified considerably because of the lower rate of decomposition. Apparatus
It was necessary to design an apparatus capable of keeping the temperature of a nitrocellulose sample constant over a long period of time. The device finally chosen was an all-glass vapor bath fitted with a reflux condenser and a side arm to return the condensed liquid to the bottom of the bath. Such an arrangement keeps a constant temperature for a long time, the only variation being the change of boiling point due to barometric variation. A special form of decomposition tube is used for holding the sample under examination. The preheating coil serves to heat the incoming air to the temperature of the sample. The thermometer used to register the temperature of the sample was graduated to 0.1" C. and the bulb was immersed in the sample during the run. Figure 1 shows an assembly of the complete apparatus. The air used to sweep out the products of decomposition rom the reaction tube was first freed from carbon dioxide
POTASSIUM IODIDE-A 5 per cent solution was used to absorb the nitrogen oxides liberated by the nitrocellulose. The solution must be neutral, since alkali will react with NOz giving low results. SODIUM THIOSULFATE--AI1 approximately 0.01 N solution of sodium thiosulfate was used to reduce the liberated iodine. The solution was prepared by dissolving 2.5 grams of NazSz03.5HzO to 1 liter of distilled water freed from oxygen and carbon dioxide by boiling. The strength of the solution was determined by titrating against a known weight of recrystallized iodine dissolved in a potassium iodide solution. Experimental Procedure
The rates of decomposition of nitrocellulose were determined a t three temperatures. Commercial meta-xylene was used for temperatures of 136-140" C., butyl alcohol a t 116-118' C., and distilled water a t 99-100' C. The main differences in temperature a t any given point were due to varying compositions of the xylene and butyl alcohol. When the bath was once charged, the temperature varied only with the barometric pressure. In a few cases butyl acetate was used for temperatures between 120' and 124" C. The samples of nitrocellulose were first air-dried and then last traces of moisture removed in a vacuum desiccator charged with phosphorus pentoxide. At the higher temperature 2 grams of sample were used, while a t the intermediate and lower temperatures 5 grams were taken to shorten the time required to liberate a titratable amount of iodine. Each sample was allowed to come to bath temperature before the absorption tube was attached. At the lower 4
J. A m . Chem. SOC.,48, 2045 (1926). 5W
400
3.W
2.W
I Ob
6 T 70. 75' 80' Us' 90' 95' lpb 105' /IO' 115' IM 17s' UO' ,HMO'
Figure 2
Figure 3
Figure 4
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temperature the time required to reach bath temperature was about 15 minutes, but slightly longer periods were necessary for the higher temperatures. I n addition, a somewhat longer period was necessary to reach a uniform rate of evolution of nitrogen oxides. This time varied with the temperature. One hour a t 100-140' C. was sufficient. The time of establishing the constant rate of evolution of nitrogen oxides from the nitrocellulose varied from 1 to 2 houra a t the higher temperature to 16 to 20 hours at the lower temperature. Titrations were made a t intervals of time depending on the temperature of the experiment. (Thirty minutes a t 137-140' C., 1 hour a t 116-118' C., and 3l/2 to 4 hours a t 99-100" C.) During the experiment the rate of air passing through the apparatus was not changed. The rate of flow of air showed no influence on the experiments so long as the preheating of air was sufficient or the absorption capacity was satisfactory. However, if the rate of air was changed during the experiment, a slight change in rate of decomposition was noticeable a t first, but this soon became normal again. From 4 to 5 liters of air per hour were passed through the apparatus. (This comparatively high rate was probably responsible for the fact that no trouble with condensation of NO2 HzO was noted as in the Will test where the rate of flow of carbon dioxide is only 1 to 1.5 liters per hour.)
+
Results
A straight line is obtained when the logarithm of the rate of evolution of nitrogen oxides expressed as N2 is plotted against temperature. This has been made the basis of the new stability test herewith presented. This test is dependent on the temperature coefficient of the decomposition reaction rate and will hence be the temperature coefficient test. In Table I are given a few of the results representative of tests made on a large number of nitrocellulose samples. Most of the nitrocellulose examined was representative of that used in the manufacture of smokeless powder, although several tests were also made on lower nitration material. Applications of Test
As A ~ I E A S U ROFE STABILITY-The data obtained in the temperature coefficient test can be interpreted much more clearly if the results are shown graphically. Figure 2 shows some of the results of the nitrocellulose samples given in Table I. At higher temperatures there is practically no difference in samples of the same nitration, but as the temperature decreases the samples show greater differences. The lower the temperature a t which samples are compared the easier it is to show differences in stability. For this reason the lines representing the temperature coefficient of the decomposition rates in Figure 2 are extended below the point of the lower test in order to contrast differences in samples more vividly. With such a test it is much easier to predict the stability of nitrocellulose a t ordinary temperatures than with a test run a t only one temperature. N o l e F o r convenience log 10s rate is plotted instead of log rate.
Figure 3 shows results on four samples of different nitrogen content. At higher temperatures the rate of evolution of nitrogen is greatly dependent on the percentage nitrogen present. However, a t the lower temperatures this is not the case because samples of lower nitrogen content may have a considerably higher rate of decomposition due to poorer stability. Several samples were examined during various stages of purification. Each stage of purification showed a change in the temperature coefficient test, the greatest change being noted at lower temperatures.
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It will be noted that results of the various tests given in Table I are not necessarily in agreement. The Abel K I tests are those given by the material a t the time of running the temperature coefficient test. When first made, the samples gave a much longer K I test. The Abel K I test could be increased considerably by washing with water while the temperature coefficient test remained unchanged. T a b l e I-Decomuosition
of Nitrocellulose-Comoarative
Testa T E M P E R A T UCOEFFICIENT RE Tesr HEATTESTS Decomposition S A M P L E NITROGENAbel K I German Temperature rate Pev cent a C. Mg.Na/g.NC/horrv 12 13.26 5 26 138.0 0.61 123.2 0.11 99.5 0.0037 13 13.22 4 25 139.2 0.87 117.0 0.050 99.5 0.0048 15 13.10 10 24 137.8 0.74 118.2 0,059 99.5 0.0054 20 12.86 5 25 136.0 0.53 118.7 0.055 99.5 0.0048 21 13.01 5 27 136.0 0.61 123.6 0.118 99.5 0.0054 27 13.19 47 30 137 5 0 71 117.0 0.042 99 5 0.0041 33 12.13 38 34 137.6 0.67 117.0 0.041 99.5 0.0041 44 13.07 34 25 138.7 0.86 116.2 0,051 99.3 0.0052 46 13 20 34 27 138,6 0.85 116.0 0.046 99.0 0.0048 68 13.25 29 30 138.5 0.83 117.2 0.055 99.5 0.0060
As A METHODOF STUDYINGTHE EFFECTOF ~ ~ T E R I A LON S STABILITY-The presence of certain
VARIOUS materials in nitrocellulose changed the stability of the sample. The effect of the addition of small amounts of various salts to nitrocellulose was studied. The salt was dissolved in sufficient water to wet the nitrocellulose thoroughly, after which the water was evaporated leaving the salt adsorbed on the fibers. In Figure 4 are shown results obtained with various salts. The change in the temperature coefficient test by the addition of such small amounts of impurities is a further indication that the temperature coefficient of the decomposition rate is dependent on stability and is therefore a good means of determining stability. F u r t h e r Work in Progress
The study is still under investigation and with more precise methods it should be possible to establish the rate of decomposition a t temperatures below 100' C. The work on salt effect is also to be continued. ~~
Commercial Standardization The steadily increasing use of specifications as a n aid in industrial and governmental buying is reflected in the National Directory of Commodity Specifications, issued by the Bureau of Standards. I n compiling this book, the bureau found more than 27,000 specifications covering 5000 commodities. The bureau is prepared to aid those industrial and commercial groups desiring to establish standards of grade and quality for their products or their purchases, or to secure relief in instances where the current variety in grades, qualities, and specifications is a burden on the producer, and a handicap to the purchaser. The bureau's service includes a certificate and labeling plan wherein goods manufactured according to commercial standards approved by the bureau may be so labeled and certified to by the manufacturers. This affords a greater protection to the purchaser and a t the same time strengthens the manufacturer's selling arguments.
