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INDUSTRIAL A N D ENGINEERING CHEMISTRY
Vol. 18, No. 5
Chart 111-Rise of Tern erature of Rubber during Stressing a t Room fernperatwe of 24O C.
Chart IV-Rise
eter. Although the temperatures indicated in this way were lower than the actual temperatures due to the lag in the couple reaching the sample temperature and also due to the heat conducted away by the leads (No. 34 wire), the results are a t least comparative and show a decided rise in temperature while the sample is being tested. These temperature measurements are shown in Charts I11 and IV, corresponding with the tensile determinations shown in the previous charts. There is a rise in temperature amounting to from 6' to 12' C. under the usual conditions of testing. Although the air cooling does not maintain the sample a t room temperature, it does prevent as high a temperature rise as occurs when the test is made in still air.
this paper, the following results were obtained: The temperature rise is from 6" to 12' C. when tested in the standard manner. Cooling with the fan reduces this temperature rise so that i t is from 3" to almost 9' C. This cooling changes the stress-strain relations of the rubber, moving the stress-strain curve toward the stress axis. In one case the breaking load is 700 pounds per square inch greater and the ultimate elongation 20 per cent less due to the cooling by the fan. In general, the greater the time of cure of any particular compound the greater the rise in temperature when stressed, but as the cure is increased the rubber becomes less susceptible to the temperature. The pure gum stock (1) usually changes in tensile properties with changes in temperature more than the compounded stocks ( 2 and 3). From the results of these tests it will be seen that, although the room temperature is maintained constant, the temperature of the rubber during stressing gradually rises as it is elongated and, therefore, the tensile values are not values obtained a t constant temperature. As the tensile properties of rubber are used as criteria in the studies of rubber technology, this change in tensile properties due to the heat generated in the stressed rubber should be considered when precision is desired.
Conclusions
When stressed, rubber generates heat at such a rate that the temperature of the rubber rises considerably above room temperature and this temperature rise due to the heat generated in the rubber causes changes in its tensile properties. The effect of the temperature rise upon the tensile properties of rubber is rnodsed by the nature of the compound, the cure, the room temperature, and other test conditions. With the compounds prepared and tested as described in
of Tern erature of Rubbe: during Stressing a t Room g e m p e r a t w e of IO c.
The Backhaus Process for Carbon Dioxide Purification' By William C . Moore u. s.
INDUSTRIAL ALCOHOL CO., BALTIMORE, MD.
T T H E Curtis Bay, Md., plant of this company blackstrap molasses is used as the raw material for alcohol manufacture. Here fifteen fermenters, each with a capacity of more than 125,000 gallons of mash, are in use, the cycle being such that in general five are refilled daily. The gas from these fermenters is collected during the period of most rapid fermentation, forced by Root blowers through a Feld scrubber operating on water, and thence through the purification system to the compressors.
A
1 Presented before the Division of Industrial and Engineering Chemistry a t the 69th Meeting of the American Chemical Society, Baltimore, Md., April 6 t o 10, 1925. Received November 14, 1925.
The Feld scrubber removes entrained material and nearly all the alcohol, aldehyde, etc., in the gas. Nevertheless, the very slight amounts of impurities remaining after the thorough washing in such a scrubber must be removed by further treatment before the gas can be used in carbonating beverages. In the Backhaus process this further treatment consists in passing the gas through active carbon.2 The carbon purifiers used are cylindrical vessels 3.5 feet in diameter and about 13 feet high. Within the cylindrical jacket are placed cooling coils, and about these tubes the active carbon is packed. The washed carbon dioxide enters 2
U, S. Patents 1,510,373 and 1,493,183. Other patents applied lor.
May, 1926
INDUSTRIAL A N D ENGINEERING CHEMISTRY
the purifier at the bottom and passes out a t the top. Two such purifiers are used in series. The internal tubes serve three purposes. In the first place, the heat of adsorption of carbon dioxide by active carbon is quite marked,3 and for effective purification the gases must be kept at temperatures lower than 110’ or 120’ F. When a purifier is first cut into service, cold water is circulated through these tubes. In the second place, the carbon after use, has to be revivified by steam. During the revivification high-pressure steam is circulated through the tubes, while low-pressure steam is reactivating the carbon. Lastly, after steaming, it is absolutely essential that the carbon be thoroughly dried before being used. Dry, pure nir is therefore forced through the mass, steam being circulated through the coils until the issuing warm air is dry; then the carbon is cooled by water circulation in these same coils. After passing the purifiers the gas goes to the compressors. There are two of these of the three-stage type intercooled, each with a rated capacity of 600 pounds per hour. From the compressors the gas goes to the filling rack after passing through a series of water-cooled coils. The cylinders used are of the regulation 20- and 50-pound types, I. C. C . , Class 3. When a cylinder is returned by the trade, the valve is removed, examined, and repaired if necessary. The cylinders are inspected, washed if necessary, then steamed and dried, flushed out with carbon dioxide, refitted with valve, and refilled. Constant tests are made for percentage of carbon dioxide, and each cylinder is individually examined for quality before being shipped. When so purified, carbon dioxide is an odorless gas with a very slight, pleasant, pungent effect on the nostrils. The water content is low-less than 0.1 per cent by weight. I n this laboratory it has been found so far that odor is an excellent test for purity, since exceedingly small amounts of odorifa Bancroft,
“Applied Colloid Chemistry,” p. 26.
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erous substances will give distinct evidences of their presence. For example, sporadic cases were noted of cylinders filled in the regular way, but the odor was suggestive of bread dough. It was found that this peculiar odor was caused by carbon dioxide in conjunction with red lead containing linseed oil, which had been used by the pipe-fitters in assembling the apparatus. Prompt measures were taken to prevent red lead from getting inside the pipes and the trouble was eliminated. Similarly, care had to be taken to prevent oil used by pipe-cutters from getting inside the pipes. In order to keep oily odors absolutely out of the cylinders, the compressors are lubricated with the highest quality glycerol. The valves used have a leather retaining washer. Some of these were found occasionally to cause an odor in the gas, so that the composition of the filler in this leather was changed. Valves themselves sometimes cause odor, due to careless handling so that fruit sirups, etc., have come in contact with them. Wintergreen and peppermint have been noted in inspecting cylinders, and of course such cylinders represent an absolute loss as the gas had to be released in order to remove the offending valve. A new purifier has to be handled very carefully after steaming, else when it is dried the carbon will catch fire. A new machine, therefore, is always dried the first time with carbon dioxide. On later cycles this is unnecessary. Since the gas is collected only during the period of most actire fermentation, a gas-holder of 50,000 cubic feet capacity is provided to furnish a compression supply while fermenters are being cut in or out. The raw gas only is stored in the holder. -411 gas is purified immediately before compression. The quality of the gas is so high that customer adjustments have been made on only about 150 pounds of gas out of a total of over 5,500,000 pounds shipped, and the operation is so well in hand that this quality can be continuously maintained.
A. C. S. Committee Reports Committee on Industrial Alcohol During the last year a number of things bearing on the industrial alcohol question have claimed the attention of the committee. With the failure of the Cramton Bill t o pass during the last session of Congress, the administration of the National Prohibition Act and other laws governing industrial alcohol was left in the hands of the Commissioner of Internal Revenue, the officer charged by law with the enforcement of these acts. The Treasury Department, for the dual reason of providing more efficient enforcement and of relieving the Commissioner of Internal Revenue, who is more than busy with income tax matters alone, assigned to General Andrews, Assistant Secretary of the Treasury, the administration of the prohibition and industrial alcohol laws. The Assistant Secretary, directing both the Coast Guard and the prohibition and alcohol branches of the Internal Revenue, and acting through the Commissioner of Internal Revenue, has assumed active control of prohibition enforcement and industrial alcohol with the avowed determination of making the former effective and of lightening the burdens of legitimate manufacturers, distributors, and users of industrial alcohol. The Assistant Secretary appointed a committee of three before whom he might place matters in confidence pertaining to and related t o industrial alcohol, for their advice. Two are on this committee, the chairman members of the SOCIETY of the Committee on Industrial Alcohol and the editor of INDUSTRIAL AND ENGINEERING CHEMISTRY.There is hope and belief t h a t a small committee of this kind meriting the confidence of the department will prove helpful t o the Government and t o legitimate manufacturers and consumers of industrial alcohol. There are strong evidences that the department is
using every effort t o differentiate between legitimate users and diverters of alcohol-to aid the former and t o wipe out the latter. The Commissioner of Internal Revenue has discharged with his thanks the Alcohol Trades Advisory Committee he established three years ago to advise him. Every Congress has witnessed bills t h a t are sought t o change the administration of prohibition and alcohol laws. Most of these bills have been one-sided and objectionable. They have all sought t o establish a more or less autocratic control t h a t might have placed unnecessary and burdensome restrictions on legitimate business without providing means for relief from such abuses should they occur. Bills are now pending before Congress, S. 3022 and H. R. 8998, which have the endorsement of the Treasury Department and which provide, among other things, for a Bureau of Prohibition in the Treasury Department. These bills, which are really identical, aim to place additional obstacles in the way of diversions, t o provide greater efficiency in detecting and prosecuting infractions of the law, while at the same time safeguarding legitimate interests. In this they differ from most bills heretofore introduced. It is significant that about the only active opposition that has developed has come from quarters heretofore active in backing prohibition bills t h a t have ignored legitimate needs and rights. The tax reduction act which has just been passed provides for a tax reduction of 55 cents per proof gallon on tax-paid alcohol to take effect on January 1, 1927, and a further reduction of 55 cents t o take effect January 1, 1928. The present tax on 95 per cent alcohol is $4.18 per wine gallon, or approximately 1000 per cent of the cost of making the alcohol. The new law will, when in full effect, cut the tax in half, which is the amount of the tax t h a t was levied before the war. This committee did not take part in these discussions, although
