INDUSTRIAL Ah’D ENGINEERING CHBNISTRY
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Vol. 19, KO. 3
Manganese Deficiency in Soils and Fertilizers’ By Oswald Schreiner and Paul R. Dawson SOIL
FERTILITY INVESTIGATIONS, BUREAU O F PLANT INDUSTRY, WASHINGTON, D. C.
T
H E role of manganese in soil fertility has been a matter of more or less interest to agricultural investigators for many years. The possibility of its function as an oxidizing agent, catalyst, or actual plant nutrient led to attempts to determine its effect upon field crops and plants in the greenhouse under controlled culture conditions. These early experiments, which have been reviewed in a number of publications from this office and other sources, gave results that, while often contradictory or indifferent, furnished some indication of benefit from the application of manganese salts. More recently, however, the question has received increased attention and more light has been shed upon the relation of manganese compounds to the plant in its soil environment. Manganese in Relation to Soil Oxidation
Some years ago, in connection with investigations carried on in this laboratory on the oxidative processes in soils, the effect of compounds of manganese on such oxidation reactions was studied. It was demonstrated2 that soil oxidation, as shown by aloin and other indicators, mas increased by the addition of manganese; that, although containing similar amounts of the element, soils varied greatly in their oxidizing power; and that the oxidation depended upon the form of the manganese as well as the amount. The form of the organic matter of the soil was also found to influence its oxidizing power; the oxidative power of manganese salts was increased by some organic acids and decreased b y others. I n a study of soil catalysis3 similar conclusions were reached. Furthermore, no close relationship of the catalytic power to the manganese content was shown, although some degree of correlation was evident. Here likewise the form of the manganese rather than the absolute amount seemed to be the controlling factor, as well as the nature of the associated organic matter. Further extensive investigations4 were conducted upon the action of manganese in soils. I n pot cultures, using an unproductive sandy loam soil, manganese chloride, sulfate, nitrate, carbonate, and dioxide had a stimulating effect upon wheat, with the best results from the application of 5 to 50 parts per million of manganese. K i t h a productive loam soil, however, the various manganese salts had no stimulating effect. Experiments with treated aqueous extracts of soils demonstrated that with poor, unproductive soils the manganese salts increased oxidation and growth, especially in extremely poor soils, from one of which several harmful organic compounds had been isolated. I n productive soils oxidation was increased but growth was decreased, with the plants showing symptoms of excessive oxidation. It was suggested that the beneficial action of manganese may be due to its function of aiding and increasing the oxidation processes and other vital processes in the plant as well as soil, and by this means changing or destroying some noxious products detrimental to plant growth. A six years’ field test5 with wheat, rye, corn, cowpeas, 1 Presented hefore the Division of Fertilizer Chemistry at the 72nd Meeting of the American Chemical Society, Philadelphia, Pa , September 5 to 11, 1926 * Schreiner and Sullivan, C S Dept A g v , Bur Sods, Bull. 73 (1910). 8 Sullivan and Reid, Ibrd , Bull 86 (1912) 4 Skinner and Sullivan, G S Dept of Agr , Bull 4 1 (1914). 6 Skinner and Reid, I b t d , Bull 4 4 1 (1916)
and potatoes was conducted, where manganese sulfate was applied a t the rate of 50 pounds per acre to a silty clay-loam soil, of acid character, low in organic matter, and in rather poor physical condition. The effect of manganese each year was not beneficial to the crops grown and the oxidative processes, a t best not strong, were Iessened. On the other hand, where the same plots were kept neutralized (1780 to 2750 pounds of calcium carbonate per acre) for the three succeeding years, the productivity of the soil was increased by manganese under this neutral or slightly alkaline condition. With wheat, rye, timothy, beans, corn, and cowpeas the yields were increased, while with potatoes they were practically the same in the treated and check plots. The oxidative power of the neutralized soil was also increased by the manganese in accordance with the results of former investigations showing that oxidation of manganese salts is greater under slightly alkaline conditions. Table I shows a comparison of the effect of the manganese under acid and neutral conditions on wheat, rye, cowpeas, corn, and potatoes. Table I-Effect of Manganese under Acid and Neutral Conditions on Wheat, Rye, Cowpeas, Corn, a n d Potatoes (Manganese-treated plots compared with untreated plots as 100) CROP Wheat R”?
C;wPjzrain Corn Stover Potatoes
UNLIMED ACIDSOIL (Average, 1907-1912) 82 99 81 82 59 77
LIMEDTO NEUTRALITY (Average, 1914-1915) 123 151 124 112 112 94
Schreiner6 has pointed out that manganese salts under alkaline conditions absorb gaseous oxygen to a marked degree, forming more or less labile combinations which may act as soil oxidizers, and that these oxygenated manganese combinations, on again being subjected to acid conditions, readily give up the absorbed oxygen, which in the nascent state of liberation in a soil may become a strong oxidizing agent. Recent Experiments on the Relation of Manganese to Soil Fertility
Since the work just described, relating largely to soil oxidation, some progress has been made by other workers in the study of the manganese problem, although many of the experiments, like those of earlier date, h a l e led to indifferent or contradictory results. However, sufficient evidence has been accumulated to indicate that, whatever the fundamental function of manganese, as an oxidizing agent or catalyst or as an essential element like iron, there is the possibility of its exerting a profound influence on soil fertility indirectly through its effect on chemical and biological processes in the soil. Additional evidence of the almost universal presence of varying amounts of manganese in soils and plants has been forthcoming; the action of the element in stimulating the processes of nitrogen fixation and of ammonification and nitrification has been demonstrated; and a considerable volume of literature has accumulated in relation to the effects of manganese compounds in culture and field experiments. 8
J. A m
Soc A g r o n , 15, 275 (1923).
March, 1927
I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
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A Unique Soil Involving Manganese Deficiency The contradictory or indifferent results obtained in many of the culture and field experiments mentioned may probably The soil on which the following experiments were conbe attributed to variations in the manganese content and in the reaction of the soils involved. I n a soil even slightly ducted presents a striking combination of exceedingly low acid, where the availability of such manganese as is already manganese content with the highly calcareous and slightly present is likely to be sufficient, any addition is likely to alkaline condition which would tend t o render this negligible have a negative result or even to overstep the limit of toxicity. amount of the metal less available, but which would, on the Wherever neutral or slightly alkaline conditions have pre- other hand, be more likely to favor response to applications vailed, as with a high calcium carbonate content,, benefit of manganese salts. This soil consists of highly calcareous deposits occurring has generally resulted from the application of manganese compounds. Another factor leading to contradictory re- in glades bordering on the Everglades in Dade County, sults in culture experiments is the failure to exclude the Florida, southwest of Miami. I n connection with field possibility of the presence of small amounts of manganese, experiments on the possible influence of fertilizers on the occurring as impurities in the culture media and nutrient nail-head rust disease of the tomato, occurring in this region, salts used. carried on cooperatively between the U. S. Department of McHargue’ has demonstrated, apparently conclusively, Agriculture and the Florida Agricultural Experiment Station, that manganese is essential to the normal growth :and func- some of this glade soil was shipped to Kashington for labor a t o r y a n d greenhouse tion of plants. By exercisstudy. It is composed aling precautions to elimimost entirely of calcium nate traces of manganese A highly calcareous soil occurring in glades in Dade carbonate (89 to 92 per cent) from the solutions or sand County, Florida. and employed for the growing of and approximately 5 per u t i l i z e d for cultures and tomatoes, fails to produce a crop, even with heavy cent of organic matter, varyfrom the salts employed as applications of inorganic fertilizers, unless stable ing somewhat with the locanutrients, he has shown that manure is applied to the young plants. In experiments tion of the deposit and the in the absence of manganese on this soil striking results were obtained by the apagricultural treatment. As growth is retarded after the plication of 25 to 50 p. p. m . of manganese as sulfate in t o the other constituents, a very early s t a g e s , d u r i n g addition to a balanced inorganic fertilizer. In cont y p i c a l sample contained which the manganese controlled greenhouse experiments normal, vigorous 2.11 per cent silica, 0.26 per tent of the seeds appears growth and fruiting of tomato plants took place with cent magnesium, 0.15 per to be sufficient. The plants manganese-treated soil; while under the same concent phosphorous, 0.08 per manifested the usual sympditions, but in the absence of manganese, plants were cent iron, 0.33 per cent total toms accompanying such a greatly retarded in growth, failed to blossom, and denitrogen, 0.015 per cent nic o n d i t i o n of r e t a r d e d veloped a strikingly characteristic chlorosis, which, trate, 0.25 per cent soluble growth and in addition dehowever, rapidly disappeared upon subsequent applicasalts, and less than 0.001 veloped varying degrees of tion of manganese. Experiments under field conper cent manganese, tochlorosis. In the presence ditions led to equally marked increase in growth and gether with small amounts of manganese as carbonate the commercial yield of fruit. This case presents a of sodium, potassium, sulnormal growth to maturity striking example of the problems that may arise from fate, and chloride. The rewith normal color rewlted. the use of pure fertilizer compounds of modern manuaction is naturally slightly In the case of an acid soil facture on soils deficient in minor constituents essential alkaline, of approximately containing 0.1 per cent of to normal plant growth. pH 8. The soil undoubtedly manganese* the addition of represents an accumulation further amounts of the eleof w e a t h e r e d c o r a l or ment as sulfate caused decreases in growth, but the application of calcium carbonate similar residues together with organic residues of such vegetation as it has supported. This organic material to the same resulted in increases in growth after app!ication of manganese sulfate. He concludes that manganese in resembles that from certain peat deposits, but with a small concentrations is essential to a normal course of the rather high percentage of a complex misture of fatty and waxy material. photosynthetic process. Similarly, McLean and Gilbertg encountered a case of Within recent years these glade soils have been utilized marked chlorosis and retardation of growth of spinach to a considerable extent during the winter season for the on a completely fertilized and moderately manured soil. growing of tomatoes on a commercial scale, Dade County The condition was remedied with the restoration of normal alone utilizing upwards of 10,000 acres for this purpose. color and increases of yield, by the application to the soil During the summer the soil is more or less submerged in of a dilute manganese sulfate solution. Ferrous and other water. The rather unusual agricultural practice employed sulfates were inactive. hIore recent experimentst0in prog- consists in general of running shallow furrows corresponding ress a t the Rhode Island Station have indicated a beneficial to the rows of plants, as soon as the water has subsided effect from the application of manganese sulfate to various sufficiently to afford a footing, disturbing the lower soil crops in a soil limed to the point approaching neutrality. as little as possible, dropping the young plants into this Thus the more recent experiments have demonstrated , furrow, and covering the roots each with a handful of stable not only the indispensability of manganese to normal plant manure, the total application amounting t o about 1000 growth, but also the importance of the soil reaction in pounds per acre. The commercial fertilizer is applied favoring response to treatment with compounds of that to a limited area surrounding the plant, the first application, metal. small in amount, a t the time of planting, the rest a t subse7 THIS JOURNAL, 11, 332 (1919); J Am Chem. S o c , 44, 1592 (1922), quent intervals. Only in the presence of the manure has a Ferttliner Green Book, 6, 17 (1925), THIS JOURNAL, 18, 172 (1926). successful crop proved possible, no matter how heavy the 8 J . Agr Research, 24, 781 (1923). applications of inorganic fertilizers; an application of 3000 9 Science, 61, 636 (1925) lo Fertdrner Revreu, 1, No 7 , 9 (1926). pounds per acre of a complete fertilizer is generally made. I
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INDUSTRIAL A N D ENGINEERING CHEMISTRY
Other water-holding mulch materials, such as peat, have not proved satisfactory; any attempts a t working up the lower soil or intensive cultivation hare prored disastrous. The manure apparently carries with it some constituent essential t o normal vegetation or which has a remedial effect upon conditions or compounds in the soil deleterious to plant growth. Laboratory Experiments
The laboratory investiqation of the problem was initiated on the assumption of the possible presence in the soil of toxic organic substances, and it was attacked from this viewpoint. Preliminary experiments in the greenhouse indicated that slightly beneficial effects were obtained under conditions favoring oxidation, such as thorough preliminary drying and aeration of the soil.
1
I
of Manganese Sulfate o n Growth of Tomato Plants i n Glade Soil Left: Untreated soil Center: Soil with addition of fertilizer b u t no manganese Right: Soil with addition of ferti!izer a n d 50 p. p. m. of manganese
Figure 1-Effect
K i t h this clue the application of small amounts of manganese salts to favor oxidation suggested itself. Tomato plants in pots of the soil, untreated except for t,he admixture of 25 to 100 p. p. ni. of manganese as the sulfate, shon-ed considerable improvement in growth and color. Manganese dioxide in corresponding concentrations n-as not effective. Likewise ferrous sulfate, while promoting very slightly greater growth, failed to prevent yellowing of the foliage. With these results as a basis more comprehensive experiments were carried out, with and without the presence of added nutrient salts, using one-gallon glazed earthemvare crocks holding approximately 4 kg. of moist soil. A number of pots were left untreated as checks; others were treated with 10 to 100 p. p. m. of manganese as MnSO4.H20 (specially purified to eliminate iron); still others with amounts of sodium nitrate, calcium acid phosphate, and potassium sulfate equivalent to 3000 pounds per acre of a 4:8:8 mixture; and finally other pots received applications of both the fertilizer salts and 25 and 50 p. p. m. of manganese. The added ingredients were thoroughly mixed with the soil, which was then repotted. The pots were watered to a moisture content slightly in excess of the optimum to simulate the field conditions-i. e., to about 30 to 35 per cent of the total weight-and were planted 77ith Mar-Globe tomato seedlings approximately 2 inches in height. The results were unexpectedly striking. I n the absence of fertilizer or manganese growth was greatly retarded, with characterist'ie symptoms, such as a purplish cast to the under sides of the leaves and stems. Eventually slow, spindling growth took place accompanied by the development of the chlorosis to be described below. In the pots
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receiving manganese without fertilizer, growth, although retarded for several weeks, ultimately progressed slowly but more or less normally, with a healthy green color of foliage. The plants finally equaled in size those receiving heavy applications of nutrients without manganese, blossomed, and formed fruit, while those not receiving manganese did not. With fertilizer alone, and with fertilizer and manganese, growth progressed from the beginning of the experiment and was about equal in the two cases for the first two weeks. Those with fertilizer alone, however, soon began to fall behind and developed a striking form of chlorosis. This chlorosis manifests itself a t first as a lightening of the green color, turning to yellow, in the leaf areas farthest from the major veins. As the condition progresses the yellow becomes more marked and extensive, the veins still remaining green, gil-ing a characteristic mottled appearance to the leaf. Eventually the foliage may become completely yellow; and in many cases, especially on the untreated soil, a necrosis sets in, appearing at first as tiny brown pin points centering in the yellow areas farthest from the veins and expanding t o larger dead areas indicating complete breakdown of the tissue. lleanwhile the growth. while continuing, becomes more and more spindling, little or no blossoming takes place, and no fruit is formed. On the other hand, the plants receiving manganese as well as fertilizer manifest a luxuriant growth from the start with normal green color and continue so until the effects of pot confinement exert an influence. Profuse blossoniing takes place and considerable fruit is formed and matured. It appears obvious that the retardation of growth and the chlorosis are indicative of a failure of normal leaf function caused by inadequate chlorophyl synthesis. The appearance of the chlorosis indicates that it is due to a deficiency of some normal plant constituent, since it appears first in the areas farthest from the 7-eins while the latter remain green. 15'hatever the actual function of the manganese it is the controlling factor. This was clearly demonstrated by the remarkable results obtained froni the application of a solution of manganese sulfate equivalent t o about 25 p. p. ni. of manganese to pots containing plants which had developed a marked mottling but in which the condition had not progressed to the point where necrosis or cessation of growth occurred. TTithin a few days the upper leares, still in a vegetative condition, showed a greener color in the center areas gradually spreading to the tips until normal color was fully restored. The new growth when it occurred was normal in color and luxuriant, eo that the upper portions of the plants resembled those treated from the start with manganese, while the lower portion with its older leaves still showed the original chlorosis and retarded growth in stem and leaf. Later experiments yielded practically identical results. Some recently conducted in larger pots holding about 13 kg. of soil and kept under outdoor conditions have furnished even more striking contrasts between plants with and without manganese applications. At least 10 p. p. m. of added manganese were essential for improvement, and the best results were obtained from 25 to 50 p. p. m . The application of corresponding amounts of ferrous sulfate alone or with the manganese had no effect. Analyses of leaves from plants treated with manganese shovied a manganese content of 0.0026 per cent of the dry weight; thoqe from plants receiving no manganese contained but 0.00087 per cent. The soil itself contains such a small amount of manganese, less than 0.001 per cent total, that it is without doubt practically unavailable under the slightly alkaline conditions produced by the large amount of calcium carbonate. It
ISDUSTRIAL .4SD EAVGI,2'EERISG CHEMISTRY
March, 1927
is entirely probable that the manganese content of the manure applied in the field is sufficient t o meet, a t least in part, this deficiency, especially since the manure is concentrated around the young plant. I n a pot experiment where 300 grams of n-ell-rotted manure, in addition to the inorganic fertilizer mixture, were applied to the surface of the soil around plants grown in 13 kg. of soil, normal growth and color resulted. which even surpassed that of thoie treated with fertilizer and manganese. Even better results followed such an application together with 50 p. p. m. of manganese; 300 grams of the particular manure used c0ntaint.d 58 mg. of total manganese. Field Experiments
I n conjunction n i t h their field experiments wit11 tomatoes on the glade soils during the past winter, J. J. Skinner, of this office, and R. T\-, Ruprecht, of the Florida Agricultural Experiment Station, included some experiments with nianganese sulfate and ferrous sulfate along with the general fertilizer study. The results of this test in the field on the condition and yield of the crop are of interest and significance as bearing out the laboratory results in a practical may. The manganese sulfate, or ferrous sulfate, vias distributed over areas one foot from the plants in two applications, the first a t the time of setting and the second 2 weeks later. The total amount was equivalent to a broadcast application of about 150 pounds per acre. The inorganic fertilizer, altogether 3000 pounds of a 4.8:8 niixture per acre, wa3 included in all cases, with a light application a t the time of setting and the rest in several subsequent applications. I n Table I1 the results where manganese or iron \pas present together with 2000 pounds of manure per acre are compared with those from the use of 1500 pounds and 3000 pounds of manure without manganese or iron. Included also are the results of manganese or iron applications TT here 1000 pounds of peat, which alone is not successful, nc:re substituted for the manure. Table 11-Yields of Tomatoes per Acre on Glade Soil a t Homestead a n d Cutler, Florida, w i t h Different Treatments of Manure, Peat, Manganese, and Iron APPLICATION
Pounds (manure)
(peat 1 a
FERTILIZER HOMESTEAD FIELD Pounds 3000
3000
C!UTLER FIELD
Cratesa
Crates .~
363 426 465
418 440
3SO 321
498
242 256
520 362 243 270
Crates hold 50 pounds
The addition of manganese with 2000 pounds of manure per acre gave increases in yields over those from 1500 pounds of manure without manganese, amounting to 32 and 24 per cent, respectively, for h - 0 separate fields; the increases in yields, over those from 3000 pounds of manure without manganese, were 9 and 18 per cent, respectively. Khere 1000 pounds of peat per acre were substituted for manure the yields, on addition of manganese. exceeded those from the same amount of peat without manganese by 48 and 84 per cent, respectively. Furthermore, they surpassed those from 1500 pounds of manure without manganese by 8 and 19 per cent; and, as compared with those from 3000 pounds of manure but no manganese, while there was a decrease of 12 per cent in the one case, there 1%-asan increasc of 13 per cent in the other. At the same time superior growth of plants and color of foliage was noted in all cases where manganese was present. Ferrous sulfate applications resulted in yields slightly lower than those from the corresponding check plots. The results of the laboratory experiments are thus essen-
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tially corroborated under practical field conditions. The manure as now generally applied seems to carry sufficient manganese to compensate, in part a t least, for the deficiency existing in the soil. Peat can apparently take its place as a mulch material provided manganese sulfate is applied at the same time. As indicated by the laboratory experiments and further demonstrated here, the iron of the soil is sufficient for the plant requirements, even under these alkaline conditions. Discussion
These experiments demonstrate beyond doubt that, whatever the fundamental function of manganese, the element is indispensable t o the normal growth of the tomato plant under the conditions prwailing in this glade soil. Although the soil is of n unique type, owing to its esceedingly high calcium carbonate content, and is exceptional in possessing a negligible manganese coiitent as compared with the general run of American soils, it nevertheless furnishes a striking illustration of a kind of problem that may arise more frequently in the future, with the more intensil e cultivation of old and the development of new agricultural areas, together with the utilization of modern pure fertilizer materials of chemical TIlanufacture. I n the first place, h p r e v a i l i n g conditions are stimulating the exploitation for agricultural purposes of lands whose natural fertility has not hitherto warranted such development. Unquestionably, many of these areas, as is the case with the glade soils, may owe their lack of fertility, in part, to deficiencies in such inorganic constitusmall amounts present, I _.._7 brought about by peculiar physical or chemical conditions. Further, the may Figure 2-Leaf from Plant Grown in b e e x t e n d e d t o in- Glade Soil Treated with Fertilizer b u t No Manganese, Showing Characteristic e l u d e s u c h elements Ch]orosis as zinc, copper, nickel, boron, etc., the relation of nhich to plant growth is not yet fully known. I n the second place, modern trend in regard to fertilizer materials may give rise to problems of a similar nature. The older fertilizers, consisting of, or derived from, plant and animal by-products or offal, and even the inorganic fertilizer salts originating in natural deposits and containing greater or less amounts of accompanying impurities, are being supplanted, and will in the future be supplanted to a greater extent, by manufactured products of a high degree of purity, especially the air-derived nitrogen product>. The application of these chemical fertilizer substances t o the general run of soils containing sufficient reserves of the lesser inorganic constituents is not likely to inrolve any problem of deficiency from that source. On the other hand, under conditions where these constituents may be deficient or unavailable, or may in time become so, the results of such deficiency \vi11 probably be encountered; with the cruder fertilizer materials sufficient amounts of the necessary elements might be supplied as impurities. I n the probleiii
described above the heavy a~iplicatioiisof inorganic fert.ilizers, while furnistiing an adequate supply of the inajor nutrients, could not meet the deficioiicy of iiinnganeso iii tlie soil. However, bhe manure apparently carried sufficient manganese to supply the dcmiinds of the plaiit,. Hence future fertilizer practice must take indo coiwidimition t,he role of manganese and other elenrents which may be prorcd indispensable to pltirit growtli and fnnction;
provision must be niade for determining deficiencies where they occur and meeting thein through appropriate suppleinents to the fertilizers applied. At t.be same time it should be emphasized t,liat the amounts of the constituents required are exceedingly sniall and t,irat precautions must bc excreised to prevent risk of toxic effects from excessive applications or from applicatioiis to soils and addition to fertilizers already supplying amounts sufficient, for plant. requirements.
Interchangeable Unit Laboratory Furniture' O M E features of t.lic l:iborrit,ory fiiriiitnre ilesigmd by the staff of tlic Ikpnrtmaiit of (',liwuii~:allhgiiiceritig of t,lic 1:nirersity of Michigan 11:iw prorod of siiffioioot valuc duriiig tlic tlircc years of opcratiim to rvarrttnt tlieir descriptioii. Prior exjx:ri(:nrt! li:irl tniiglrt, that the type of funiitiire iriost ncrrled iii :L given Idiomtory would vary froni ye:w to yenr, ii1111 t,li:it l ~ w v yfixed ~ fnniitnre was undesir:iblc. It w a i lit r tu kccp the cost of iiew furnit,uro lo\\-, iiiiii it irnblc to taka ndv3ntngc of hhe ecoiiornici rcsiilting FS prodi~r~tim or st;iialardizetl nnitrj. Tlic icatures described liere are not :LIIn w e l , hiit it is iiclicved that the resultatit furniture is iliffmmt from that iii any otlrer laboratory. A11 uriits-~ial,~irat~iry desks, sinks, lroods, apparatus cases-were iiiade of sta unit of its kind could lx?placed next to a ~ i o t l s or r siilistitutcil for onot,licr.
S
Desks
The niost iiistiiictive features arc seen i n Figurw 1 and 2, which show two riews of the end units of ii r1oul)le row of laboratory desks. Icignre 1 shows norn~;d nppcarnnce of the assembled units and Fieiire 2 m s tlic siiiiii: eiiiiiij-
dnits. The sinks are carried oii indepeiident pipe frames and the iead waste pilies discharge vcrticniiy into it leadliiied wooden trongh wlrich lias B iliwliarge at. one end through :L lead pipe iuto a n iron soil pipe susycndcd from the ceiling of the rou~rihelow. Tlie pip nd sinks were instdied while there was entire freedom for t,lie workmeii to nse tlieir tank on bot,li d e s of the rack. \Vhen the pipe work was completed the beneli units were pushcd into plaoe and the desk was conlplete. If are needed tire piping system becomes completely .ibk by prilling away the bench units. li:aoh bench 5 feet long, 21 inches wide, and 40 inahes high. Ench pipe rack is also 5 feet long, 64 inches high, and 9 inches vc.iilc. An exception is to he noted in t.lie pipe racks w-liicli carry the flues for down-draft hoods where tlie width of the r x k is increased to 12 inr:hes. T h e constroclion for single desks to stand against the wall is similar. The desk units theniselves are identical, but tlie sinks for the single units are shorter. A corner of n single nnit with its sink is shown i n Figure 3, wliich also shows the lead pipe from the sink and the iron waste pipe from the iiood uniting i n a cast-iron soil pipe tee. Castused for all waste lines after leaving tlie
Fieure I - LahoraIory ~ Ilcsks. Complete Assembly
Pleurs 2 --Laborrrcory Desks, Bench Unirs Removed
nient wit,lr tire bench units piilled i r i i t US tlie way tu perniit access to the piping. All pipes are carried on a wooden pipe rack which stands between the two tables. The pipe rack shown in Figure 2 carries a soctiini flue for downdraft desk hoods, pipes for steam, waterr gas, and compressed air, a lead-lined trough for waste water, and elect,rical con-
tables, the favorable experience of fiftceri years i n the Chemistry Building having shown that acid-proof iron was unnecessary for our purposes. The value of this design has been proved not only when repairs or alterations have had to be made to the piping or wiring system, but also vhen it has been desirable to convert a laboratory to different uses. Single units have been
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Received Novemher 8, 1926.
