October, 1926
INDUSTRIAL A Y D ENGINEERING %HEXISTRY
saturated with lime when 0.5 gram is used. The degree of unsaturation will be greater the greater the rate. At low rates of stirring the two values will be equal. The effect of the rate of solution of hydrate can be seen from the run with U. S. P. lime, which gave a more finely divided hydrate. For the same stirring rate the ratio of the film coefficients is 1.48 compared with 1.53 for Glencoe lime. If the hydrate were extremely fine, the ratio would be expected t o be 1.0. Summary
Dry calcium oxide and calcium hydrate were found to absorb a negligible amount of carbon dioxide under the conditions of these experiments. The rate of absorption of carbon dioxide in milk of lime has been determined a t 25.5' C. with samples containing 0.5 gram and 10 grams of commercial lime. The effect of the addition of sodium hydroxide u p to 8.8
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grams per liter has been studied. The addition of 8.8 grams of sodium hydroxide per liter caused a considerable increase in absorption rate a t the highest rate of stirring. The rate of absorption was found to be practically constant over the range studied using 10 grams of lime. Using 0.5 gram of lime, the rate was found to be proportional to the distance from saturation. The rate of absorption using 0.5 gram of lime was found to vary with the rate of stirring but a t a rate somewhat less than the first power. The multiple-film theory of absorption offers a satisfactory explanation for the results obtained. Acknowledgment
The writers desire to thank the Xational Lime Association for financial aid in carrying out this research, and W. K. Lewis for his interest and suggestions.
Filtering Devices' By H. B. Gordon U N I T E D STATES T 6 S T I N C
I
CO.,INC., 316 HUDSON ST.,.\?E\%' Y O R K . 1- 1-
K' THE chemistry laboratory it is frequently necessary
to filter a large volume of a solution. There are a number of devices in use to assist in this work and to avoid the necessity of standing over the filter to pour in additional solution to replace that which passes through. Two devices for this purpose which the writer has found useful are illustrated in the accompanying sketch. Device A
At A is shown a device for filtering a liquid which is in a small-mouth carboy. The carboy, C, is supplied with a tight-fitting 2-hole stopper, through which pass two glass tubes, the siphon tube, S,and the air inlet tube, I . I n starting the siphon one may suck on the free end of S, but it is usually more coiivenient to blow into I , thus forcing the liquid out through S into the filter, F . The liquid continues to siphon over until its level in F reaches the free end of I , when it rises in I until it is slightly above its level in the carboy. The flow then ceases until sufficient liquid has filtered to permit air to enter I , when more liquid siphons over, and so on until the carboy is emptied. The free end of I should be half an inch or so above that of S. A section of rubber tubing on the inner end of the siphon makes it easier to adjust this end to the bottom of the carboy. -4convenient means for starting the siphon action is afforded by the side tube, K , attached to the air inlet tube. By closing the free end of I with the finger and blowing through K , the liquid is forced through the siphon. K is then closed by a stopcock or cap. Device B
When a large quantity of a solid is to be dissolved, it can usually be done most conveniently by suspending the solute in the solvent near its surface. This demands the use of a wide-mouth jar and makes the filtering device described above impracticable. I n this case the device shown a t B is of considerable assistance. The solution to be filtered is in the battery jar, J . It 1siphoned over into the filter as indicated in the sketch. 1
Received May 26, 1926
The siphon and filtctr ate both iupported on the iron rod, L, which in turn ia supported on the large ring-stand, R , by a large clamp, H . To hold L steady, its upper end is passed through a small iron ring, I I f . Unless the base of the stand R is very heavy, a weight should he placed on it to enable it to support its load more safely. The sketch represents the device when most of the liquid has been filtered. At the start, when J is nearly full of liquid, the clamp H is raised so that the top of the filter is slightly above the level of the liquid. The siphon is then started and continues without further attention except that occasioiially, when the liquid in the filter falls nearly to the end of the siphon, the clamp H is lowered until the top of the filter is again but little above the lerel of the liquid in the jar.
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INDUSTRIAL A N D ENGINEERING CHEMISTRY
Even this attention is only required at long intervals if the siphon is so set that it extends nearly to the bottom of the filter and the jar and filter are large. It is sometimes advantageous to replace the Iower funnel with a thistle tube the wide end of which is fitted over the tip of the upper funnel while its small end extends into the receiver.
Vol. 18, No. 10
A convenient means for filling the siphon is offered by the side tube, T , placed a t the top of the siphon. By closing the end of the siphon which is to be in the filter, placing the other end in the liquid in the jar, and applying gentIe suction at T,the liquid rises into X and flows over into the outer end until the tube is full. This method is not satisfactory if the bore of the siphon is less than about 7 mm.
Treatment of Packing-House, Tannery, and C orn -Pr od u cts Wastes”* By F. W. Mohlman THES A N I T A R Y DISTRICTO F CHICAGO, CHICAGO,
ILL
Method which has been used at Chicago f o r evaluating the e$ect of the major industrial wastes, with results experimental treatment of these wastes during the past jijteen years HE problems of providing a safe, palatable water supply and of satisfactorily disposing of this water after it has been used and discharged as sewage are greatly complicated by the presence of industrial wastes. Industrial wastes are often discharged directly into lakes or water courses, in which case the treatment problem may be even more difficult, owing to inhibitory substances in the waste which prevent or interfere with biological processes of treatment. Sometimes evaporation is the only solution of the problem. Industrial wastes may be divided broadly into those which affect the quality or treatment of water supplies, and those which produce nuisance and kill fish in streams not used for water supply. There are, of course, wastes which fall under both classifications, but it is generally possible to place certain types of wastes in one group or the other by consideration of their oxygen demand and ability to support bacterial life. I n the development of the disposal of the sewage from the $anitary District of Chicago, industrial wastes of the second type-liquid organic wastes with excessive oxygen demand and high bacterial content-have been of most importance. There is a water-supply problem in the Calumet District due to the obnoxious taste of wastes from by-products coke plants in the water chlorinated a t the 68th Street Pumping Station, but this problem is aside from the major one of the treatment of sewage and wastes now diverted through the drainage canal into the Des Plaines-Illinois Rivers. It has been known for many years that the industrial wastes greatly augment and complicate the sewage load contributed by the human population of the Sanitary District. I n fact, there are very few cities which do not have this same problem, though usually in lesser degree than Chicago. A complete plan for sewage treatment must take account of these wastes, and their effect should be measured and put upon the same basis as the human sewage. The total load of pollution may then be separated into human and industrial wastes, and the effect of treatment of a n industrial waste expressed in its human equivalent. This paper deals with the method that
T
1 Presented a s p a r t of the Disposal of Trade Wastes Symposium a t t h e Midwest Regional Meeting of the American Chemical Society, Madison, Wis., M a y 27 t o 29, 1926. 2 T h e investigation of the industrial wastes with t h e experimental work has been carried on b y t h e Sanitary Division of the Engineering Departm e n t of t h e Sanitary District of Chicago, of which E. J. Kelly is chief engineer, under t h e direction of Langdon Pearse, sanitary engineer, and F. W. Mohlman, chief chemist. T h e Packingtown investigation was begun in 1911 when George M. Wisner was chief engineer and Arthur Lederer was chief chemist. Mr. Wisner became consulting engineer in 1920.
of
has been used a t Chicago for evaluating the effect of the major industrial wastes, and the results of experimental treatment of these wastes during the past fifteen years, Oxygen Demand-Population Equivalents The results of sanitary chemical determinations such as oxygen consumed, albuminoid nitrogen, ammonia nitrogen, and total solids have little relation to those conditions in a stream which give rise to nuisance and kill fish. It is well known, however, that the production of nuisance and the killing of fish is primarily due to absence of dissolved oxygen in the stream. Consequently, i t is very desirable to place the load of pollution on a n oxygen basis and to balance the oxygen requirements against the oxygen available in the diluting water. A deficiency must be supplied by sewage treatment. Industrial wastes, whose oxygen demand is known, may be placed on the same basis as human sewage with regard to stream pollution or treatment, provided Tve know the proper per capita factor for oxygen demand. This factor was determined by tests a t the 39th Street Pumping Station in 1914 and at the Des Plaines Treatment Works in 1925 (Table I). Additional tests a t the Calumet Treatment Works in 1925 and at the 39th Street Pumping Station in 1920 support these data. The factor that has been used in the industrial-waste work has been 0.244 pound oxygen per capita per 24 hours (extrapolated 20-day demand). For shorter periods of incubation a t 20’ C., the following factors are used: Days
2 5
10
Pounds per capita 0.090 0 167 0.220
Population Equivalent of Industrial Wastes The three major sources of industrial wastes in the Sanitary District are packing-houses, the manufacture of corn products, and tanneries. The packing-house wastes are concentrated in an area of about one square mile on the South Side, discharged from approximately thirty individual houses in Packingtown; corn-products wastes are discharged by the main plant of the Corn Products Refining Company at Argo; tannery wastes are discharged by approximately twenty-eight tanneries scattered along the Korth Branch of the Chicago River. There are many industrial wastes of lesser significance, most of which have been investigated and evaluated. The results of the surveys of the packing-house and cornproducts wastes are shown in Tables I1 and 111.
