PRODUCTION of the pulp. And for certain conditions of the first hydrolysis step, residual pentosan content remain* d practically independent of cooking conditions. After pulping, the cellulose was bleached by a seven stage process. The bagasse was hydrolyzed, pulped, and bleached to dissolving pulp in pilot plant equipment. Then the pulps were converted to rayon in a commer cial plant. This pulp had an alpha cellulose content of 94 to 96%, a pento san content of 2 to 3 % , and an ash content of 0.59fc. The pulp's alpha cellulose content therefore runs better than wood pulps (90 to 95%), b u t not as great as pulp from cotton linters (997c and h i g h e r ) . Tenacity of the rayon filament is 2.1 to 2.2 grams per denier, and its elonga tion is 15 to 19%. These figures com pare favorably with those for rayon from other pulp sources, says Locus.
Taking Out the Fluorides W h e r e fluoride level is too high, alumina process prom ises removal at low cost Fluorides in drinking water may be either ACS NATIONAL MEETING good or b a d de Water, Sewage, pending on the c ο η c e η t r a& Sanitation tion. Best fluo Chemistry ride level is now generally ac cepted as around 1 p.p.m. W h e n it goes above 1.5 p.p.m. more people get mottled teeth. In this country, there are some 600 public water supplies serving about 1.5 million people which have more than 1.5 p.p.m. fluoride. At the present time only a couple are trying to remove the excess fluoride. The reason: it's costly. Now, though, there is some hope that fluorides can be removed at a cost rea sonably within the average cost of water treatment. E. A. Savinelli and A. P. Black of University of Florida (Savinelli is now with Du Pont) told the Division of Water, Sewage, and Sanitation Chemistry they have a proc ess to take out fluorides using activated alumina for ion removal, then an alu minum sulfate solution to regenerate the alumina. It works this way: ST
r
• Water is fed down through a col umn of activated alumina. • As it progresses down through the column, it swaps fluoride, carbonate, and bicarbonate ions for sulfate ions. 78
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• When the alumina is exhausted (after it has taken up some 1500 to 2000 grains of fluoride and other anions per cubic foot), it is regenerated by passing aluminum sulfate solution through the bed. During regeneration, the alumina bed takes up sulfate ions, releases the fluoride and bicarbonates it had previously removed from the water. • Shows Economic Promise. Cost of fluoride removal by this process is some one third to one half that b y any other existing method, Savinelli says. For example, work at Bartlett, Tex., which has water with a high fluoride level and considerable hardness, showed that the process cost about $50 to $60 per million gallons. Other studies in areas of lower fluoride levels and less hardness yield estimates around $25 per million gallons. T h e r e is hope for lowering this cost even further, Savinelli declares. Work is now under way at University of Florida on ways to increase the selec tivity of the alumina for fluoride over the competing carbonates and bicar bonates. And, by adding sulfuric acid to régénérant solution from the column (containing precipitated aluminum hydroxide) and reusing it, costs may be lowered even further. Black says he should have results on this part in about a vear.
Flow by Total Count Simplicity of new w a y of measuring flow rates suggests key role among methods o f flow determination Measuring radiotracered liquids flowing ACS NATIONAL MEETING through pipes yields a new Petroleum and strikingly Chemistry simple method for measuring flow rates. Dubbed the "total-count" technique, the method is based on measuring total number of counts from a tracer as it flow's past a detector. The total count bears a simple inverse relation to the flow rate, and this property makes it useful for measuring not only flow rates but also other quantities related to flowing streams. The method has given straightforward answers to a variety of problems in refineries, Donald E. Hull of California Research told a Symposium on Nuclear Technology in the Petroleum and Chemical Industries jointly sponST
sored by the Divisions of Petroleum Chemistry and Industrial and Engineering Chemistry. It measures flow rates in pipes where no meters exist or w h e r e they have defaulted. Too, it measures leak rates between cross-streams and liquid entrainment in distillation units. It can also be used to measure gas flow rates and even applies to open streams. In short, it can measure flow wherever a fluid flows in a definite course. In the new method a measured amount of radiotracer is introduced into a flowing stream. A counter is fixed in or near the stream some distance below the starting point so that it accumulates a certain number of counts when the tracer is passing. The number of counts recorded doesn't depend on distribution of the tracer along the stream. If the tracer mixes homogeneously across the p i p e , a radioactive atom passing the counter has a certain chance that it will discharge the counter. This chance is not affected by the presence of neighboring radioactive atoms. But if the flow rate of the tracer atom past the counter changes, the chance of its tripping the counter changes. If the flow rate increases, the time an atom is in the vicinity of the counter decreases, and the number of counts decreases in proportion. As a result, the total count, N, is inversely proportional to the flow rate, Q. Mathematically, it can be shown that Ν =A/Q
• F
where A is the amount of tracer a n d F is characteristic of the isotope, the counter, and the geometric relation be tween the counter and stream. F, fortunately, is very simply de termined in the lab—giving an absolute measure of flow rates. A piece of pipe similar to the one used in the flow measurement, and several inches longer at both ends than the counter t u b e , is filled with a solution of the tracer at a known geometric configuration as in the field test, and the counting rate is measured. The rate is proportional to the concentration and can b e ex pressed as counts/microcurie times gallons/minute—just the dimensional units required for F in the above equation. The total count of the tracer is then observed as the measured tracer passes the scaler, and, after allowing for back ground counting, the flow rate, Q, is calculated. • Accuracy of Total Count. T h e ac curacy that can be expected in flow rates measured by the technique de pends on several factors. Sources of error which can affect the relative val ues obtained in successive tests a r e :
PRODUCTION • Statistical error of counting. • Difference in mounting t h e tubes on the pipe from test to test and from the lab calibration test. • Retention of tracer in its container, injector, and connections to t h e line. In the average plant test, t h e cumulative resultant of these sources of error is a standard deviation of 2 to 59c. In addition, there are sources of a b solute error in assumptions using pipe factors measured in the lab for field tests :
Chester A. "Warner presents Precision Scientific A w a r d t o C. Gardner Swain
C. Gardner S w a i n Precision Scientific Co. A w a r d in Petroleum Chemistry Special tailor-made catalysts for many purposes may come from work of C. Gardner Swain, recipient of the Precision Scientific Co. Award in Petroleum Chemistry. H e and his coworkers have created a catalyst which, can act simultaneously as a n acid and a base in a concerted reaction. This single molecule with t h e combined effect of acid and base is more active as a catalyst than a functionally equivalent mixture of compounds. Swain, now 3 9 , has done much toward clearing u p "concerted" mechanisms of organic reactions. H e has investigated the role of polar molecules in solvolysis of alkyl halides b y kinetic methods and has developed theories and mathematical correlations of displacement reactions based on kinetic data. Result: It is now possible to predict with considerable certainty t h e rates of many organic reactions heretofore undetermined. Swain is not directly engaged in the petroleum field, and his work has been with compounds other than hydrocarbons. But the petroleum industry depends to an increasing extent on fundamental organic chemistry. Swain was born in Quincy, Mass., and has bachelor and doctor degrees from Harvard. He rapidly advanced from instructoi to associate professor a t MIT. As a Guggenheim fellow in 1954—55, he did research at University of London.
• The sensitivity of each of the counter tubes is equal to that of t h e tube used for calibration. • T h e contribution to the counting rate from solution more than 6 inches beyond the ends of the counter tubes is negligible. • No corrosion or deposits have affected the wall thickness of the pipe in the field. The last factor est source of error ficult to estimate, as much as 10%
is probably the largin the method, is difand could amount to in old pipes.
Polyethylene Tests Better grading of polyethylenes should result from a new oxidation stability test As polyethylene production rises t o record ACS NATIONAL MEETING heights, methods of testing its Polymer properties are Chemistry becoming more and more important. O n e of the most vital properties—relative stability to oxidation—can now b e quickly and easily measured with a procedure worked out by Electric Storage Battery. Theodore H. Meltzer of ESB, together with J. C. Duddy and J. J. Kelley, finds that the time required to ignite a mixture of polyethylene and lead peroxide at a given temperature can be used to compare the relative stability of various types of polyethylenes. And the method is more accurate than melt index, Meltzer told the Division of Polymer Chemistry. Methods of shaping polyethylene into consumer products involve heating the polymer to increase plasticity. As it heats, it oxidizes more easily. But stability problems are not limited to processing or even to high temperature uses. Since light catalyzes the reaction of polyethylene with oxygen,
Time it takes for polyethylene, mixed with lead peroxide, to ignite on a hot plate is a new way to grade this plastic's oxidation resistance. T. H. Meltzer, Electric Storage Battery Co., tries it polyethylene oxidizes at normal temperatures, too. But so far no one has found a really good stability test. The melt index, widely used in grading polyethylenes, isn't sensitive enough. Meltzer believes the ESB test is the answer to greater sensitivity. • Redox t h e Key. ESB's oxidation test is based on a dry oxidation-reduction system which reacts at elevated temperatures. Lead peroxide i s the oxidant, and polyethylene is the r e d u c tant. The mixture is heated on a hot plate to between 230° and 280° C . Ignition occurs in less than a minute; the time interval between placing t h e mix on the hot plate and ignition varies with the stability of the resin. Oxidation stability of various types of polyethylene can be compared by plotting ignition times vs. temperatures, which yields a straight line on semilog p a p e r . In addition to its simplicity and speed, die oxidation test is quite sensitive to small amounts of antioxidants which are used to enhance poly ethylene's properties. Polyethylene oxidizes by a free radical mechanism, and like other free radical reactions, oxidation can be inhibited by common antioxidants such as amines and phenols. ESB's test can record differences between various formulations of inhibited polyethylene which appear to have identical stability when compared by the melt index. APRIL
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