(1) The surface of high-velocity gas exposed for the entrainment of air in a jet type of burner is the surface of a thin cylinder of gas, the diameter of which is the size of the jet opening. In the annular-orifice type the surface exposed is thr: inside of a hollow cylinder the size of the air opening, and this surface is much greater than that exposed by a jet passing the same amount of gas a t the same pressure. Further, when the burner is used in combination with a Venturi throat, as shown in Figure 5, both inside and outside surfaces of the gas cylinder are used t o entrain air. ( 2 ) The air is drawn into a thin-walled cylinder of gas, and the gas and air are more intimately mixed than in the jet type of burner. is almost no danger of clogging due to dust and (q) There foreign particles in the gas. Should a particle of dust become wedged in the annular orifice, only a very small part of the effective area is lost, and it is practically impossible to close the annular orifice completely. On the other hand, one particle may practically close the effective area of a round orifice. (4) The annular orifice is really a center Venturi, which varies with the gas pressure and adapts itself to give maximum efficiency regardless of the gas pressure. The jet-type burner and F'enturi throat must be in definite relationship in order to obtain maximum efficiency. ( 5 ) The use of a regulating device on the air opcning of the annular-orifice type permits accurate control of the air and gas mixture and of the atmospheric conditions in the furnace. The gas-air ratio may :tlso be controlled by the pressure differential due to the absolute fire-box pressure. ( 6 ) Air a t 1100" C. which cannot be compressed or blown can be induced by a burner of this type.
(1) The annular orifice must be large enough to pass the required amount of gas a t the given pressure, and the orifice and the pressure must be such as to inspirate the required volume of air against the furnace back pressure. The area of the orifice and the gas pressure necessary under different conditions can be determined by a study of the curves in Figures 10 and 11, and reference to the standard handbooks. ( 2 ) The area of the center orifice must be sufficiently large t o pass the required volume of air a t a reasonable velocity. (3) The gas pressure required depends on the back pressure of the furnace, the temperature of the induced air, and the B. t. u. value of the gas used. (4) The induction burner works oil a weight, not a volume, basis. If the frictional losses and the general efficiency of the system were constant a t all temperatures, the mass of air inspirated would be constant. At higher temperatures there is a large increase in the frictional losses duc to increased volume and to increased velocity, and the decrease in the amount of the gas inspirated is not directly proportional to the increase in temperature, but varies with the density and chemical nature of the gas.
A discussion of the atinular-orifice type of burner would lie incomplete without a brief description of its application as an oil burlier (Figure 12). Air under pressure of 25 pounds per square iiicli is forced through the aiiiiular orifice, drawing the oil through tlie ceiiter orifice. The oil is very finely comminuted in bliis process. The air pressure aud the oil pressure may be regulated to give a combustible mixture of any desired B. t. u. value. The curves iu Figures 13 and 14 show the relationship between air pressure, oil level, and Burners of the annular-orifice type can be designed to oil consumption. The fuel-air ratio may be controlled meet any requirements, and a properly designed and care- by three methods: (1) variation in the size of tlie oil fully nianufactured burlier will give satisfactory awvice 11-it11 orifice, (2) variation in the air pressiut:, atid (3) variat>ioti very little care. In dwigning and operating a hwner of this i i i the oil level with reference to t.hc Iiuriier. The last type several factors must be horne in mind: method affords the best regulation.
-
Possibilities of Production of Radium and Vanadium from Carnotite' H. A. Doerner
Depletion of t h e high-grade ores, increased operating costs, a n d Belgian competition have discouraged domestic production of r a d i u m . A t present price levels t h e r e is little to justify t h e exploitation of c a l n o t i t e for r a d i u m . W h e n an ore which is treated for i t s v a n a d i u m cont e n t c o n t a i n s as m u c h as 1 per cent U 3 0 ~a, u r a n i u m conc e n t r a t e should be recovered as a by-product a n d saved for possible f u t u r e t r e a t m e n t f o r r a d i u m . Analysis of production costs leads t o t h e conclusion t h a t mechanical concentration of low-grade ore m i g h t be an i m p o r t a n t factor in reducing the cost of r a d i u m . As applied t o a shipping ore, no proved m e t h o d of t r e a t m e n t s t a n d s o u t above t h e o t h e r s for cheapness of operat i o n o r efficiency, a n d t h e r e is s m a l l probability that any
new m e t h o d will greatly change t h e cost of extracting r a d i u m from an ore. With t h e possible exception of t h e fluoride m e t h o d of Fleck a n d Haldane, only direct leaching m e t h o d s (with or without a preliminary t r e a t m e n t ) a r e applicable t o a d u s t concentrate from a low-grade ore. As compared t o an ore, t h e processing of s u c h concentrates requires more reagents a n d involves m o r e difficult filtrations. Preliminary roasting of t h e ore results i n i m p o r t a n t benefits, in regard to b o t h c o n c e n t r a t i o n and chemical t r e a t m e n t , which have not been sufficiently realized. These benefits apply particularly t o t h e carbonaceous ores a n d t o t h e modified nitric acid m e t h o d of extracting radium.
.. . . . . . . .. . . .
T
HE carnotite ores of Colorado and Utali were the
chief source of radium for many years. Originally these ores were worked oiily for their vaiiadiiini COP te it3arid were temporarily ahandoned when the 1.ich vai1adiuni deposits iu Peru were discovered. Later, about 1912, the presence and value of radium in those ores became appreciated, and carilotit,rr was treated priricipally for its radium content, the vanadiu~ii and uranium being conaidered a s by-products. 'Received November 20, I Y 2 Y . Published by permission Director, U. S . Bureau of Mines. (Not subject to copyright..i
01
the
In tlie fa,ll of 1922 news of the very ricli deposits of radiutii ore discovered ill the 13elgiaii Congo caused aliiiost complete wssation uf domestic production. The Congo ore uotitaitis pitchblende aiid a number of alteration products, iiicluding tlie new niiiierals bequerelite: curite, kasolite, stasit,e, a i d dewindite. Reports iiidicate that a considerable amount of ore coiitaiiiitig over 50 per cent L 3 0 8 has been produced. It seemed certain that radiuiii c ( ~ ~be l d extracted from the Coiigo ore a t a iiiuch lower cost tliari from t,lie relatively low-grade caruotite; uiid irl order t u preserve their elaburlttci producers made iuarket,ingorgwiiis:itioris, tlie Iargrr ;211ieric~an
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INDUSTRIAL AND ENGINEERIlVG CHEMISTRY
agreements with the Belgian syndicate to market the foreign product in this country. The price of radium has been held a t $70 per milligram. Extraction of radium from carnotite by the usual methods does not appear to be profitable a t that price. With one exception, all American firms ceased production after their accumulated stocks of ore had been treated. The United States Radium Company, which continued to treat carnotite for several years, has recently shut down its plant. Although there is probably a large profit derivable from the treatment of Congo ore it is not likely that the Belgium syndicate will meet sufficient competition to cause any reduction in the present quotations. It is not known how long the high-grade ore will last, but when it is exhausted the price of radium may be expected to advance. Vanadium from Carnotite and Related Ores
Carnotite contains the valuable element vanadium, which is not present in the Congo ore. The recovwy of vanadium is an important factor in the cost of extracting radium from carnotite, and under favorable conditions carnotite can be profitably treated for the vanadium alone. Vanadiferous sandstones are found ranging all the way from roscoelite (vanadium mica), containing little or no uranium, to a highuranium and low-vanadium carnotite. Ores containing 2 per cent or more u308 are classed as radium ore and are sold on the basis of the uranium content, which is proportional to the radium content. Only in exceptional cases have ores been evaluated on the basis of both the radium and vanadium contents, although the presence of vanadium has undoubtedly influenced the price of radium ore. Since the advent of radium from Congo ore, a large quantity of carnotite has been treated For the vanadium alone, the radium being discarded with the tailing. Since the entire cost of mining, transportation, and milling this ore is thus covered by the value of the Vanadium, the question arises as to whether the radium and uranium cannot also be recovered a t a profit, or a t least saved in such a concentrated form as to be available when market conditions justify further refining. Distribution and Variation of Production Costs
The National Radium Institute, under the technical management of the U s. Bureau of Nines, produced over 8 grams of radium by the nitric acid process. Published data (7) show that the total cost of production was S37.60 per milligram of radium, of which $17 represented the cost of the ore a t about $96 per ton, the balance being a treatment charge of $118 per ton of ore. These figures take no account of the value of the vanadium or uranium by-products or the cost of recovering them. The general level of wages and commodity prices has increased about 50 per cent since 1915, when the operations covered by the Bureau of Mines report were completed. Moreover, i t has been stated ( 5 ) and generally claimed by subsequent operators that “the mining costs resulting from the first systematic mining operations were faulty and errcneous, as they were based upon favorable physical conditions that were bound to disappear rapidly.” Barker (1) estimated that $62 per milligram of radium extracted represents the bare costs of mining and processing a 2 per cent UsOsore, and that after adding selling costs and a legitimate profit a selling price of $100 is not unreasonable. The fact that domestic production of radium ceased when the Belgian product came on the market a t $70 is very strong evidence that Barker’s estimate is close to actual operating costs. Evidently the methods used in the past are not adequate to meet present conditiom
VOl. 22, No. 2 .
To one not familiar mith the mining of carnotite, costs ranging from $100 to $200 per ton of ore for mining and transportation seem absurdly high. Detailed figures of actual operations (4, 7 ) are summarized in Table I, column 1. Tho value of the by-products vanadium and uranium, as well as the expense of recovering them, is not included in these cost data. The high mining costs are due to the necessity for careful selection and sorting of the ore from small scab tered ore bodies. The isolated situation of the deposits makes transportation costs high. I n column 2 are data obtained from the same source relating to the milling of low-grade (0.85 per cent Ud& average) ore obtained as a by-product in the mining of shipping ore. The dust concentrates produced by milling are more difficult to treat than the shipping ore and treatment costs for these are not available. However, subsequent research (2) has shown that by a modification of the original Bureau of Mines methods high recoveries of not only the radium, but also of vanadium and uranium, can be obtained from either a shipping ore or dust concentrate with little if any increase in operating costs. Estimates based upon the modified procedure (indicated by column 2, Table I) are used to s u p plement the othcr data. Table I-Costs
a n d Yields of Vanadium a n d R a d i u m f r o m Carnotite
UIOU in ore or con-
centrate, % “nos in ore or concentrate, %
(1)
(2)
(3)
2.66
3.00
2.00
1.00
4.30
5,00m
4.00
4.00
(4)
(5) b
(6)b
(7) b
2.50
3.00
2.75
5.00
5.50
5.00
COST P a R TON
Development $ 5.00 Mining 36.00 $ Transportation 35.00 33.00 Milling , 20.40 Overhead, royalty, 20.00 21.75 etc. Total cost of ore or concentrate 96.00 8 4 . 3 0 Treatment 118.00 125.00° Total 214.00 209.30
i:iS
..
$45.00 $ 5 . 0 0 $15.00 $20.00 $15.00 60.00 25.00 75.00 IOO.OO IOO.OO 35.00 35.00 35.00 35.00 35.00 . 15.00 2 0 . 0 0 25 00
..
...
20.00
5.00
5.00
5.00
5.00
130.00 70.00 145.00 180.00 180.00 125.00 125.00 150.00 150.00 150.00 275.00 195.00 295.00 330.00 330.00
RSCOVBRY
Radium, mg. 5.7 6.7“ 4.45 2.00 5.56 6.7 6.1 V201, lbs. 23.0 85.0‘ 68.0 6 8 . 0 85.00 9 3 . 0 0 8 9 . 0 0 UtOa, Ibs. 45.0 50.04 34.0 17.0 42.00 46.00 4 4 . 0 0 Cost per mg. radium $37.60 $31.30 $61.80 $97.50 $53.00 $49.25 $54.20 Assumed. b Costs per ton of concentrate.
The higher costs per milligram of radium in subsequent operations have been due primarily t o a lower average grade of ore and high expense for exploration and development of the more deeply buried ore bodies. Column 3 is based upon Barker’s (1) estimate of $150 per ton of 2 per cent UaOe ore and $125 for treatment t o recover the radium only. Production from Low-Grade Ores
The effect of grade of ore upon the cost of radium is further shown in column 4, in which the cost of radium from a 1 per cent ore is 63 per cent higher than from a 2 per cent ore, although the costs assumed for mining operations are less than one-third. If, however, an ore containing as much as 1 per cent us08 carries sufficient vanadium, and is so favorably located that the ore can be profitably treated for the vanadium alone, then the radium can also be recovered a t a cost considerably below the present market price, as part of the treatment cost and all of the ore costs are covered by the value of the vanadium. As high as 10 tons of milling ore may be exposed in the development of 1 ton of shipping ore (d), and this ratio tends to increase as the richer ore bodies become depleted. If production from a given area is increased tenfold, it is obvious that the mining cost per ton will be much lower and development and other overhead charges may be divided by 10.
February, 1930
a
I N D U S T R I A L A N D ENGINEERING CHE-MISTR Y
187
From these considerations assume that the costs per ton for 1 per cent ore are as listed in column 4. Assume also that concentration costs $5 per ton, and that the cost of processing 8 slime concentrate is $150, or 20 per cent more than for an ore. If milling gives 83 per cent recovery a t a concentration ratio of 3, other costs being fixed as in columns 3 and 4, the cost per milligram of radium will be $53 (column 5 ) . At 75 per cent recovery and a concentration ratio of 4 the still lower cost of $49.25 is obtained (column 6). Assuming development, mining, and milling costs for 0.75 per cent ore to be $3, $20, and $5, respectively, 73 per cent recovery and concentration ratio of 5 shows a cost of $54.20 per milligram (column 7). These ratios of concentration and recoveries are based upon tests which will be described. It should be emphasized that the figures in Table I, with the exception of columns 1 and 2, are not to be taken as representing actual costs, which obviously will vary for different deposits and methods of operation. They merely illustrate the relations between grade of ore, cost of mining, and cost of radium, rand especially the possibilities in concentration of low-grade ores. These possibilities have been somewhat neglected because of filtration difficulties, higher costs, and lower recoveries, when processing a dust concentrate by the usual methods of treating an ore.
zontal shafts revolving in opposite directions. The roasted ore was fed continuously into one end of the machine through a sealed hopper and subjected to the action of the paddles which tossed it about. .Jets of compressed air in the bottom of the trough blew off the dust which was collected in the usual arrangement of cyclone dust collector and bags. The clean scoured sand was discharged through a sealed overflow at the end of the trough opposite the feed hopper. This equipment and procedure gave much better results than had been previously attained. The ratios of concentration and recoveries used in Table I, columns 5, 6, and 7, are representative of these tests.
Concentration Methods
I. Dissolution of the radium by an acid, with or without a preliminary treatment. 11. Chemical disintegration of the gangue and its removal by leaching or volatilization, leaving the radium concentrated in a small residue. 111. A sulfating treatment (fusion with niter cake or digestion with sulfuric acid) followed by leaching to dissolve the soluble sulfates, and then a separation of the sand, slime, and solution by classification (or decanting) and filtration (or settling), and fmally the recovery of radium from the slime by some method covered by I or 11. This procedure cannot be applied to a dust concentrate because the sandy portion of the ore has already been eliminated.
Carnotite ore is a sandstone that has been impregnated with carnotite and related minerals. Organic matter such as the remains of trees often caused deposition of “bug holed’ of nearly pure mineral, but as a rule the carnotite forms incrustations on the sand grains on exposed faces. in joints and fractures of the rock, and less abundantly as individual grains. As the carnotite is relatively soft, most ores are easily crushed to the size of the sand grains. These ores are concentrated by a mechanical separation of the dust from the coarser sand grains. This may be accomplished either wet or dry. Wet methods are more effective, but scarcity of water in the carnotite areas makes the use of wet methods impractical in most cases. By the dry method the dry, crushed ore is agitated in a current of air to separate the dust from the sand. For good results the sand grains must be scoured clean from adhering mineral, with the minimum crushing of the barren grains. Ordinary crushing or grinding equipment is not well adapted to this operation, because it is designed to crush or pulverize but not for scouring through attrition. The impact or beater mill used in the Bureau of Mines work (4) is probably the best standard type for this purpose. Early in 1921 the author completed semicommercial tests on the dry concentration of low-grade carbonaceous ores from the Temple Mountain area near Green River, Utah. Because of the large amount of organic material present, these ores are among the most difficult to treat by either mechanical or chemical methods. Much of the organic substance resembles a tough asphalt and is so closely associated with the valuable minerals that both mechanical and chemical disintegration are obstructed. It was found that the di5culty could be overcome by roasting, a procedure which was later patented by another worker (9). Roasting not only removes all organic matter and moisture, but it also causes chemical changes which disintegrate the physical structure of the valuable minerals, reducing their powers of cohesion rand adhesion so that they are more easily reduced to a dust. A special machine was designed and constructed to scour the sand and separate the dust. It consisted of a long metal trough provided with a tight hood and had a double row of agitating paddles. The latter were mounted on parallel, hori-
Extraction of R a d i u m f r o m Concentrates
Mechanical concentration of the ore before shipment appears to be the most promising means of lowering costs. As previously noted, it is more difficult to extract radium from a concentrate than from an ore, and little has been published upon this problem. The various methods of treating an ore have been adequately discussed in the references already given. Therefore, only the application of these methods to a concentrate will be considered. The methods of extracting radium from carnotite ore may be classified as follows:
Extraction w i t h Acids
SULFURIC ACID-Hot concentrated sulfuric acid has been used to extract radium from a slime concentrate (obtained by method 111),but the large amount of acid required (two or three times the weight of ore slime) and the difficulties in handling the acid (especially filtration) have made this method unattractive. As applied to a dust concentrate from a low-grade ore, the amount of acid used per milligram of radium recovered would be much larger. However, the consumption of acid might be reduced to little more than that required to react with the ore by distilling the excess acid from the acid filtrate. From this filtrate or residue a high-grade radium-barium sulfate is precipitated by dilution and boiling, and the other valuable constituents of the ore may be recovered from the solution. Recovery of the excess acid, together with improved methods and equipment, might make this method economical. HYDROCHLORIC Acm-Most ores require a preliminary treatment before a satisfactory extraction of the radium can be obtained with hydrochloric acid. The usual procedure is to boil or autoclave the ore with a solution of sodium carbonate (plus caustic), then filter and wash thoroughly. By this treatment the radium is converted to the acid-soluble carbonate, and soluble sulfates, which might cause premature precipitation and loss, are removed. The average ore requires its own weight of 20 per cent acid and 40 per cent of its weight of soda ash. A dust concentrate will consume and require much more reagent than an ore, and filtrations are more difficult. These disadvantages are reduced by a preliminary roast. NITRICAcID-since even radium sulfate is quite soluble in hot 38 per cent nitric acid, a direct treatment with this
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INDUSTRIAL A N D ENGINEERING CHEMISTRY
reagent will obtain a high extraction of radium from most ores. By regeneration of nitric acid from the sodium nitrate recovered as a by-product, the acid cost is as low as or lower than that for hydrochloric acid (7). The limitations of this method as applied by the National Radium Institute are as follows: (1) It is not effective on ores containing considerable gypsum or carbonaceous matter. ( 2 ) The recovery of vanadium is very poor. (3) Handling and filtration of hot 38 per cent nitric acid are difficult and expensive. (4) Slow filtration may cause precipitation and excessive loss of both radium and vanadium. This difficulty makes the treatment of a dust concentrate by this method very unsatisfactory. Preliminary Roasting
Although certain types of carnotite have in the past been roasted as a preliminary to the usual methods of treatment, some important results which may be obtained by roasting have not been recognized. As applied to the nitric acid process, roasting followed by a wash with sodium carbonate solution as described in a Bureau of Mines report (2) makes possible the following benefits: (1) Exceptionally high recoveries of both radium and vanadium are obtained, even from the most refractory ores. (2) Roasting eliminates carbonaceous material which otherwise would consume nitric acid, cause excessive frothing and slow filtration, and prevent dissolution of occluded minerals. Acid which reacts with inorganic minerals is finally recovered as sodium nitrate, but the acid reduced by organic material is destroyed and unrecoverable. (3) Roasting converts the iron content of the ore to an insoluble oxide, thus reducing the amount of acid required to leach the ore. Eliminating most of the iron with the insoluble residue greatly simplifies subsequent recovery of uranium and vanadium, reducing costs and increasing recoveries. (4) Roasting changes the physical and chemical condition of the ore so that subsequent filtrations are speeded up. This action is very important, especially in the case of dust or slime concentrates, which are very difficult to treat unless roasted. (5) I n general, a carefully controlled roast makes possible the extraction of a large part of the vanadium by a sodium carbonate leach previous t o the acid treatment. This soda leach also removes soluble sulfates which would otherwise cause reprecipitation of radium during the acid leach. After the ore has been conditioned by these two operations, the nitric acid exerts its full strength as a solvent for radium and the residue of vanadium; there is slight possibility of loss through re-precipitation.
I n many cases roasting appears to reduce the solubility of the radium, both as to rate of solution and the total extraction. Experiments demonstrate that this effect is due to inclusion of radium in agglomerated particles, consisting of, or coated with, insoluble iron oxide, and that the dissolution of radium is rapid and nearly complete if the agglomerates are thoroughly disintegrated by light grinding or attrition. Chemical Dissolution of Silica
Reduction of the gangue material, which consists principally of silica, may be accomplished by fusing the ore with an excess of caustic soda (or soda ash) and leaching the soluble silicate from the melt with hot water. The practically complete recovery of radium by this method has made possible its commercial application to relatively highgrade slime concentrates produced by sliming a sulfated ore, but the cost of chemicals is prohibitive for direct treatment of an ore or even a dust concentrate from a low-grade ore. Volatilization of Silica
The use of hydrofluoric acid to remove silica from a slime concentrate was patented by McCoy (6). More recently Fleck and Haldane (3) have patented the use of a soluble
VOl. 22, No. 2
fluoride (NHIHF~)and sulfuric acid, with subsequent regeneration of the fluoride. The following is an abstract of their process: A slime concentrate, ammonium hydrofluoride, and sulfuric acid are mixed in the proper proportions and slowly heated t o volatilize the silicon fluoride,.which is collected in a tower. The residue is digested in very dllute sulfuric acid and filtered; the filter cake contains the radium as a high-grade sulfate. Slaked lime is added to the filtrate, from which ammonia is then distilled and used to regenerate fluoride from the tower liquor. The lime precipitate from the ammonia retort contains the vanadium and uranium.
The chief merits of the above method are the substantially complete recovery of all the valuable constituents of the ore and the regeneration of the fluoride reagent. The design and operation of a plant using this process may involve considerable expense. The reactions require about twice as much 65’ BB. acid as the weight of material treated and also its chemical equivalent in quicklime for regenerating the ammonia. From these considerations it appears that, though the process may be the best treatment for a rich slime concentrate, its application to a dust concentrate from low-grade ore is more doubtful. Recovery of V a n a d i u m a n d U r a n i u m
It is not difficult to obtain a good recovery of uranium and vanadium as by-products from the treatment of carnotite by any of the usual methods of extracting radium. Methods of recovering these by-products have been adequately described and will not be reviewed here. The market for uranium products is limited, but there is ample demand for vanadium. According to Hess (8), “In 1922 with highgrade ferrovanadium selling a t $4.50 to $5.00, iron vanadate carrying 32 per cent Vz05 was sold at 36 to 75 cents per pound and fused vanadium oxide carrying 75 per cent Vz05 was sold for $1.40 per pound of material.” At the present price of ferro (about $3.50) a good grade of Vz05 should bring about $1 per pound. This figure leaves a wide margin of profit when vanadium is a by-product in the recovery of radium from carnotite. At the present t8ime,however, with the decreasing amount of South American vanadium available, our metallurgical industries are again turning toward the carnotite deposits. Vanadium is again the chief product sought and radium is not even recovered as a by-product on account of the Belgian competition. This situation is deplorable when the limited resources of this most valuable of all elements are considered. The usual, and probably the best, method of recovering vanadium from the vanadiferous sandstones (roscoelite and carnotite) is to roast the ore with about 10 per cent of common salt and 2.5 per cent of soda ash. The calcine is first leached with water and then with dilute sulfuric acid and vanadic acid or ferroas vanadate is precipitated from the extracted solutions. Any radium present in the ore will be left as a fine precipitate in the tailings. If these tailings are discarded, the water used to flush them out and subsequent weathering will disperse the radium beyond all possibility of recovery. If, however, the tailings are deslimed, and the slimes are dewatered and stored, the radium will be saved in a concentrated form a t a cost which is an insignificant fraction of its potential value, provided the original ore contains as much as 1 per cent UaOs. If such low-grade ores can be produced in sufficient quantity to permit efficient countercurrent leaching operations on a large scale, it is probable that treatment costs could be considerably lowered. However, until it is certain that such operations would not break the present price of radium, the large investment required for such an enterprise would not be justified.
February, 1930
I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y Literature Cited
(1) Barker, University of Missouri, B d l . S4, No. 26 (1923). (2) Doerner, Bur. Mines, Repls. of Iwestigations SETS (1928). (8) Fleck and Haldane, U. S. Patent 1,577,217 (1926). (4) Kithil and Davis, Bur. Mines, Bull. 10s (1917).
189
(5) Kunkle, Eng. Mining J . Press, 114, 503 (1922). ( 6 ) McCoy, U. S. Patent, 1,154,230 (1915). (7) Parsons, Moore, Lind, and Schaefer, Bur. Mines, Bull. 104 (1916). (8) Spun and Wormser, “Marketing of Metals and Minerals,” New York, 1925. (9) Vogt, U. S. Patent 1,429,550.
Pollution Studies of the Upper Mississippi River’ F. L. Woodward MIXNESOTA DEPARTMENT O F HEALTII, ?IlIKNEAPOLIS,
Mlh‘S.
This paper covers briefly the activities of the Minneing Minneapolis is fairly well HE pollution of the upper Mississippi River, sota State Board of Health and cooperating departrecovered from any great particularly the section ments in studying the pollution problem of the Misl o a d s of pollution. Soon sissippi River from Minneapolis and St. Paul, Minn., after entering the Twin City below the Twin Cities, has to La Crosse, Wis., a distance of about 160 miles. It a r e a t h e r i v e r shows t h e longbeena subject of discuswas found that conditions of pollution are evident effects of the sewage and insion and complaint, but not until recently has it been during the winter time as far down stream as the outlet dustrial wastes discharged &le to make any comprehenof Lake Pepin, a distance of about 100 miles. Under into it. Visible evidence of summer conditions the pollution is quite pronounced this pollution may be found sive study of the situation. for a distance of 50 miles or During the period from June, at the head of Lake Pepin 70 miles below Minneapolis, but recovery is practically complete at the outlet of more down the river. Other 1926, to August, 1927, H. R. Crohurst, sanitary engineer the lake. The changes in the oxygen balance at various evidences of the extent of points in the stream at different seasons are illustrated pollution are odors produced of the U. S. public Health by means of charts. During the summer, odors are by the d e c o m p o s i t i o n of Service, conductedan investiproduced by the decomposition of organic matter in sewage and wastes and the gation of the pollution of the the pool above the Twin City Lock and Dam. Another absence of fish life in the secMississippi River and its dam is being constructed at Hastings 30 miles downtion of the river immediately tributaries from Minneapolis stream, which is expected to bring about similar condibelow the Twin Cities. to Winone, a distance of a p p r o x i m a t e l y 137 miles. tions in the river through St. Paul and South St. Paul. T h e Mississippi River A tentative classification, from a pollution standpoint, enters Minneapolis a t CamDuring the same period a study of fish life in that of the river below Minneapolis is given. den a t an elevation of about section of the river was made 802 feet above s e a level. by A. H. Wiebe, biologist of the U. S. Bureau of Fisheries. Near the business center of Minneapolis the river passes over It is fortunate that this work was done a t a time when St. Anthony Falls, dropping about 70 feet t o an elevation the discharge of the river was less than it had been for of 728. About 6 miles below St. Anthony Falls is located many years and conditions of pollution were consequently the Twin City Lock and Dam, where the river again drops more pronounced than they are during ordinary stages of the 33 feet to an elevation of 690. This dam has created a pool river. of relatively foul water extending about 5 miles upstream. The Metropolitan Drainage Commission of Minneapolis All but one of the sewers of the Minneapolis system and and St. Paul was created by an act of the Minnesota Legis- eleven of those of the St. Paul system discharge into the river lature in 1927. The commission immediately began its work above this dam. As a result, large quantities of suspended of studying the subject of sewage disposal for the Twin Cities. material are deposited in the pool. These deposits give In order that the commission might have a basis for its pro- rise to unsatisfactory conditions, especially in the summer gram, the Minnesota State Board of Health was asked to when the river discharge is low and the water temperature make a classification of the river below the Twin Cities. is high. Mr. Crohurst states in the preliminary report of This necessitated the collection of additional information his work on the Mississippi that indications of septic conbefore such a classification could be made. Therefore, the ditions are likely to be found in the pool above the Twin Minnesota State Board of Health in collaboration with the City Lock and Dam during the summer whenever the flow Minnesota Department of Conservation, the Wisconsin State of the river is less than 5000 cubic feet per second. This Board of Health, and the Metropolitan Drainage Commission, statement is corroborated by observations made in 1928. conducted an investigation during 1928 covering the MissisA few miles below the Twin City Lock and Dam the Mississippi River from Minneapolis to the southern boundary of sippi is joined by the Minnesota, a river which, because of its Minnesota, treating the various phases of the pollution low summer discharge, does little to relieve conditions in the problem. Mississippi. Below this point the river receives additional sewage and industrial wastes from St. Paul, South St. Paul, Pollution Conditions between Twin Cities and La Crosse and Newport. At Hastings, about 30 miles below the Twin The Mississippi River rises among the lakes of northern City Lock and Dam, another dam is being constructed as an Minnesota and flows a distance of about 530 miles before aid to navigation. This dam will create a pool extending upentering the Twin City area. The cities and towns discharg- stream to the Twin City Lock and Dam, and it is expected ing sewage and wastes into this stretch of the river are rela- that the conditions found in the pool above the present dam tively small and far apart, so that the water in the river enter- will be duplicated in the pool through - St. Paul and South St. Paul. 1 Received October 12, 1929. Presented before the Division of Water, A short distance below Hastings the St. Croix River enters Sewage, and Sanitation Chemistry at the 78th Meeting of the American Chemical Society, Minneapolis, Minn., September 9 to 13, 1929. the Mississippi. This is a relatively clean stream and,the
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