June, 1916
T H E J O C R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
degree, or fraction of a degree, whereas, t h e thermoslide permits constant observation of t h e starch. T h e water b a t h method requires more t i h e for each test a n d t h e gelatinizing point cannot be determined with t h e same accuracy as b y t h e proposed method. Noreover, t h e total time necessary is very much shorter, as numerous determinations have been made b y t h e thermo-slide method, which required less t h a n five minutes t o complete each test. OKLAHOMAAGRICULTURAL EXPERIMENT STATION OKLAHOMA STILLWATER.
NOTE ON THE DETERMINATION OF PHOSPHORUS IN PLANT MATERIALS B y A. W.
CHRISTIE
Received February 14, 1916
I n t h e course of certain investigations in this laboratory, it became desirable t o find a quick a n d accurate method of oxidizing plant materials in order t o deA review of the termine t h e total phosphorus. literature suggested t h e following methods as being adaptable t o this purpose. Fusion with sodium peroxide’ can be used in t h e determination of phosphorus as well as of sulfur b u t t h e care a n d time required by this method makes i t undesirable. Neumann’s method is known t o give accurate results. A modification,2 consisting of digestion with sulfuric acid, I g. of potassium sulfate a n d a drop of mercury, gave fairly rapid oxidation b u t t h e subsequent precipitation with molybdate required standing over night t o be complete. Digestion with hot fuming nitric acid also suggested itself as a possible method. Ignition with magnesium nitrate3 was found t o be impossible in t h e case of m a n y plant materials due t o excessive deflagration. The method of ignition with magnesium oxide4 has been in use in this laboratory for t h e oxidation of organic matter i n t h e analysis of phosphorus-containing fertilizers. Hibbard6 describes this method b u t suggests “ t h a t some phosphorus m a y be lost from volatile organic substances containing it, when ignited with magnesia.” This method is believed t o be t h e quickest a n d most convenient of those suggested a n d hence t h e following experiment was performed t o deAv. MIDDLINGS CASEIN LECITHIN Lecithin
Ignition with magnesium oxide
(0.56
j 0.56
,0.57 0.57 Fusion with sodium peroxide.. 0.58 0.57 1 0 5; Modified Neumann method.. 0.58 0.56
Fuming nitric a c i d . , , . ,
.. .. ., . , .
,
0.87 0.86 0 86 0.87 0.87 0.86 0.85 0.85 0.88
: 2;
3.56
1
3.58
3”:;; 3.62
3.64
3.65’ 3.66 3.51 I
3.61
termine t h e accuracy of t h e magnesium oxide method as compared with t h e modified Neumann a n d peroxide fusion methods. Three samples. representing substances relatively high in their organic phosphorus content (Merck’s Bur. of Chem., Bull. 101, p . 13. 2. landw Versuchw., 13, 795-802. 8 Bur. of Chem., Bull. 107, p . 2 4 Z.physiol. Chem , 16, 426-32. 3 THISJOURNAL, 5 (1913). 998. 1
2
j I 1
casein, Merck’s lecithin a n d finely ground wheat middlings), were analyzed for total phosphorus b y t h e methods mentioned above. After t h e preliminary digestion, t h e phosphorus was precipitated from t h e solution in t h e usual manner as ammonium phosphomolybdate a n d finally weighed as magnesium pyrophosphate. T h e accompanying table gives t h e percentages of phosphorus obtained. T h e above figures show t h a t ignition with magnesium oxide gives substantially t h e same results for total phosphorus in t h e materials analyzed as fusion with sodium peroxide or digestion y i t h sulfuric acid, I g. of potassium sulfate a n d a drop of mercury. The sodium peroxide method has t h e advantage of furnishing a solution which can also be used for t h e determination of total sulfur. The modified Neumann method m a y also be used €or t h e determination of total nitrogen. The use of fuming nitric acid alone is found t o be unsatisfactory. coNcLusIoN-Ignition with magnesium oxide is a quick a n d accurate method of oxidizing plant materials for t h e determination of total phosphorus. nIVISION OF
AGRICULTURAL CHEMISTRY
AGRICULTURAL EXPERIMENT STATION U N I V E R S I T Y OF C A L I F O R N I A ,
BERKELEY
SOME EFFECTS OF LITTER ON THE FERMENTATION OF MANURE‘ B y W. E. TOTTTNGHAM Received February 14, 1916
Within recent years t h e increased use of shavings as litter in stables has raised questions regarding t h e possible effects of such practice upon t h e value of t h e manure. One of t h e most important of these questions concerns t h e extent of t h e loss of nitrogen from t h e manure. Others concern t h e rate of oxidation of t h e organic matter a n d related changes. This paper presents t h e results of a n investigation concerning some of these questions. I t is a report of t h e results of certain chemical changes in a fermenting mixture of manure a n d shavings as compared with straw-littered manure a n d unlittered manure. EXPERIMENTAL
METHODS--A
basal manure was prepared by mixing one p a r t b y weight of fresh horse manure with t w o parts of fresh cow manure, each manure having been freed f r o m litter. Four lots of this manure of z j lbs. weight each were placed in galvanized iron pails with loosely fitting covers. The weighings at this point a n d subsequently were made on a Fairbanks pjatform scale sensitive t o ‘/4 lb., or t o within a possible error of 1 . 0 per cent for t h e weights involved. Litters were prepared b y sifting finely cut oat straw, oak shavings, a n d shavings of Georgia pine t o uniform size, reserving t h e material which passed through a sieve of 5/16-in. square mesh, b u t was retained b y a similar sieve of ’/s-in. mesh. The manure was t h e n treated as follows: Lot I was left untreated t o serve as a control. Lot 2 was thoroughly mixed with 2 lbs. of pine shavings. Lot 3 was mixed with 2 Ibs. of oak shavings 1 Published with the permission of the Director of the Wisconsin Experiment Station.
512
T H E JOCRiZ'AL O F I N D C S T R I A L ALTD E;VGI-VEERITG C H E M I S T R Y
v01. 8 . KO.6
/
FIG.~--~\IANuRE ALONE
a n d Lot 4 n-as mixed with z lbs. of oat stran-. A t t h e beginning of t h e experiment on AIarch 25th) a n d at two, four, eight. a n d twelve weeks thereafter t h e several lots of manure were thorougly mixed a n d sampled for chemical analysis a n d bacterial counts.1 By weighing t h e pails before a n d after sampling i t was possible t o determine t h e losses of organic m a t t e r a n d of nitrogen due t o fermentation. T h e chemical analyses were conducted as follows: DRY MATTER-one hundred grams of sample were dried to constant weight a t a temperature of about 9 8 " C. TOTAL ASH-The residue from the determination of dry matter was charred, extracted with hot water and the insoluble residue thoroughly ignited. Extract and residue were combined, evaporated and heated in the usual manner. TOTAL ORGANIC A S D VOLATILE MATTER was computed by deducting the per cent of total ash from the per cent of dry matter. TOTAL XITROGES was determined by the Gunning modification of the Kjeldahl method, employing I O g. of the moist manure. WATER-SOLUBLE NITROGEN was determined by the Gunning modification of the Kjeldahl method, employing zoo cc. of the extract prepared for the determination of total water-soluble matter as subsequently described. AMMOSIA NITROGEX-Five grams of magnesium oxide were added to zoo cc. of the extract employed for determining the total water-soluble matter, and distillation was conducted in the usual manner. TOTAL WVATER-SOLCBLE SfATTER-One hundred grams Of moist manure were shaken with one liter cf distilled water in a motordriven machine for five hours at room temperature. The extract was then rapidly filtered by suction through a thick layer of paper pulp in a Buchner funnel. After washing the residue with ten portions of distilled water of 7 5 cc. each the extract and washings were added and made to a volume of two liters. One hundred cc. of the final solution were eyaporated and dried to constant weight at about 98' C. ~~ATER-SOLUBLE ASH-The dried residue from the determination of total water-soluble matter was carefully ignited in a platinum dish heated to dull redness. 1 For t h e bacterial counts, \rhich were made upon lactose agar plate cultures, t h e writer is indebted t o Mr. E. E. Eldredge, formerly a member of t h e staff a t this Experiment Station.
FIG 2--I?IASURE -k
PINE SHAVISCS
WATER-SOLUBLE ORGANIC AND rOLATILE MATTER was computed by deducting the per cent of water-soluble ash from the per cent of total water-soluble matter. HnMus-Fifty grams of manure were drained by suction on a layer of asbestos in a Buchner funnel, washed with I .o per cent HCI until no more calcium was extracted and finally washed free from HCl by water. The moist residue was digested for 36 hours with 4 . 0 per cent solution of "*OH, employing 5 0 cc. of solution per gram of original dry matter of the manure. The ammoniacal extract was filtered and its humus content determined by evaporating and igniting in the usual manner. HUMUS N I T R O G E X - h extract of the manure was prepared as in the determination of humus, but with the substitution of 4 ,o per cent solution of NaOH for the NHsOH solution. Nitrogen was determined by the Gunning modification of the Kjeldah1 method, employing IOO cc. of the filtered extract. RESULTS-The results of t h e analyses are presented i n Table I , each 1-alue being t h e average derived from duplicate determinations. Attention m a y be called to t h e enormous number of bacteria in t h e strawlittered manure a t t h e third analysis; at this stage i t mas possible only t o estimate t h e number of organisms: only in this lot of manure mas there evidence of t h e predominance of special types of bacteria. At t h e third examination an acid-producing organism was especially a b u n d a n t while a t ' t h e later stages streptot h r i x formed one-fifth t o one-third oE t h e total colonies developed in cultures f r o m t h e s t r a w l i t t e r e d manure. I n order t o facilitate comparison of t h e extent of t h e various changes followed i n t h e different lots of manure t h e percentages of t h e total organic matter, total ash, a n d total nitrogen which existed in various forms h a r e been calculated from t h e d a t a of Table I a n d are given in Table 11. It seems probable t h a t t h e percentages of organic m a t t e r i n mater-soluble a n d humus forms here bear definite relations t o t h e relatire susceptibility of t h e manures t o decomposition i n t h e soil. Similarly, t h e soluble ash a n d t h e uarious forms of nitrogen m a y bear direct relations t o t h e relative fertilizing values of t h e manures.
J u n e , 1916
T H E J O U R N A L OF I N D U S T R I A L A N D ENGINEERING C H E M I S T R Y
FIG. 3-MANURE
+ O A K SHbVINGS
T h e progressive losses of total organic matter in these manures during t h e four periods covered b y t h e investigation are also presented in Table 11. Each value is computed on t h e basis of t h e total organic m a t t e r present at t h e beginning of t h e respective period. I n a similar manner t h e gains or losses of nitrogen for each period of fermentation have been calculated as percentages of the tot21 amounts of nitrogen pres-
FIG.+-MANURE
513
+ O A T STRAW
e n t a t t h e beginning of t h e respective periods. These d a t a occupy t h e last column in Table 11. Assigning a value of I O O each t o t h e total organic m a t t e r , total ash a n d .total nitrogen of each manure a t t h e beginning of this investigation t h e relative values of all t h e other d a t a in Table I1 have been computed. The resulting values, which express t h e fluctuations in absolute amounts of t h e various constituents considered, have been plotted t o form t h e
TABLE I-COMPOSITION OF FERMETTING MANURES ~ C O ~ l P O S I T I O OFTDRY MATTER-RESULTS I N PERCENTAGES OF DRYMATTER-Total BACTERIA TIME D R Y Organic Total Organic Millions Weeks MATTER and Solids Matter Ash Soluble per Gram LOT ADDITIOS after Per Volatile Total soluble soluble soluble Total in Hz0 Humus of D r y No. TO MANURE starting cent Matter Ash in Hz0 in Ha0 in Ha0 N N .U as NHa Humus N Matter 0.90 660.0 11.76 15.98 11.44 4.54 1.69 0.81 0.020 13.68 20.37 88.24 0 1 None 12.80 12.89 8.23 4.66 1.97 0.64 0.130 13.59 0.88 210.0 18.92 87.20 2 14.41 15.79 9.77 6.02 2.24 0.46 0.036 14.74 0.94 25.0 17.12 85.59 4 16.01 13.69 8.21 5.48 2.04 0.39 0.028 67.0 16.20 83.99 15.86 1.00 8 16.64 10.94 6.00 4.94 2.22 0.25 0.020 15.72 83.36 1.13 4.1 12 14.73 9.19 3.28 1.26 0.61 0.011 8.18 12.47 0.65 212.5 0 25.97 91.82 10.78 2 Pine shavings. . . . 8.99 8.01 5.02 24.12 91.11 2.99 1.50 0.66 250.0 2 0.35 0.045 10.26 21.52 89.34 10.66 9.48 5.41 4.07 1.85 0.74 61.5 0.22 0.030 10.49 4 11.93 7.11 3.90 21.00 88.07 3.21 1.57 0.80 57.0 0.15 0.012 11.68 8 8.55 4.66 21.62 87.91 12.09 3.89 1.53 0.83 4.7 12 0.09 0,011 10.38 8.69 9.20 26.00 91.31 12.46 3.26 1.26 3 Oak shavings 0 0.59 0.011 0.59 272.5 10.27 9.33 8.33 5.23 24.45 90.6i 3.10 1.42 2 0.36 0.047 10.74 0.68 460.0 10.76 8.21 5.22 21.55 89.24 2.99 1.72 0.69 112.5 0.29 0.008 11.11 4 13.01 6.53 3.36 18.87 86.99 3.17 1.66 0.81 37.0 8 0.14 0,019 12.82 12 13.20 ,6.39 2.87 18.85 86.80 3.52 1.76 0.10 0.011 10.48 0.90 3,; 4 Oat straw. . . . . . . . 0 25.25 10.97 13.56 9.07 89.03 4.49 1.36 0.77 530.0 0.56 0.010 12.23 2 23.22 87.70 12.50 7.40 12.30 5.10 1.75 0.42 0.028 12.95 0.85 38.5 19.52 84.77 15.23 12.91 7.37 5.54 4 2.28 0.23 0.057 14.00 1.01 10,00O(a) 16.65 80.76 19.24 8 12.66 6.77 5.89 2.42 0.29 1.19 30.0 0.052 17.15 12 16.50 80.10 11.99 5.93 6.06 0.23 0.016 19.90 2.39 1.28 12.7 14.37 (a) See text. TABLE11-ANALYSES OF DATAIN TABLEI PERCENTAGES OF TOTALS PRESENT IN VARIOUSFORMS PERCENTAGE CHANGES TIME ORGANIC MATTER ASH -ATITRoGEN--DURING FERMENTATION ADDITION Weeks after Soluble As Soluble Soluble As As Humus Organic LOTh-0. TO MANURE Starting in Hz0 Humus in HrO in HrO NHs Nitrogen Matter Nitrogen 1 Sone.. . . . . ... 0 12.97 15.50 38.61 47.93 1.18 53.25 ... .... .... 7 9.44 15.58 36.41 32.49 6.60 44.67 - 9.1 6.9 4 11.41 17.22 41.78 20.31 1.61 41.96 -12.9 0.9 8 9.77 18.88 34.23 18.53 1.37 49.02 -12.2 -18 5 12 7.20 17.67 29.69 12.12 0.90 50.90 4.4 5.1 2 Pine shavings. . . . . . . . . . . . . . 0 10.01 11.74 40.10 48.41 0.87 51.90 .... .... 2 5.51 11.26 33.26 23.33 3.00 44.00 - 8.9 9.4 4 6.06 11.74 38.18 11.90 1.62 39.73 -17.3 4.0 8 4.43 13.26 26.91 9.36 0.76 50.76 -12.5 -23.0 12 5.30 11.81 32.18 5.67 0.72 54.25 - 1.5 - 3.9 3 Oak shavings.. . . . . . . . . . . . 0 10.08 11.25 37.51 47.06 0.87 46,75 .... .... 2 5.76 11.84 33.23 25.28 3.31 46.97 7.6 4.8 4 5.85 12.45 27.79 17.14 0.47 40.00 -14.6 5.6 8 3.86 14.74 24.35 8.25 1.14 48.61 -19.4 -20.5 12 3.31 12.07 26.67 5.91 0.63 50.97 - 1.9 3.8 4 Oat straw. . . . . . . . . . . . . . . . 0 10.18 13.74 40.93 41.40 0.74 56.76 .... .... 2 8.44 14.77 23.89 41.46 1.60 48.29 -12.4 +14.8 4 8.69 16.52 36.38 9.87 2.50 44.47 -22.1 4.9 8 8.38 21.24 30.61 12.02 2.15 49.26 -24.5 -16.0 12 7.40 17.94 30.45 9.50 0.67 53.72 - 4.0 - 4.2
-
-
++ + ++
++ + +
T H E J O U R N A L O F I N D U S T R I A L AAVD E N G I N E E R I - V G C H E M I S T R Y graphs of Figs. I t o 4 inclusive. These graphs indicate, therefore, t h e relative changes in t h e actual a m o u n t of each constituent in t h e different manures as fermentation progressed. S U 41$1 AR IT
T h e results expressed in t h e accompanying tables and figures m a y be summarized as follows: I-The loss of total organic m a t t e r during twelve weeks of fermentation ranged from 33 t o 51 per cent. I t was most rapid a n d greatest in t h e straw-littered manure, where bacteria were most numerous, 2-The water-soluble organic matter ranged from t o 13 per cent of t h e total organic m a t t e r in t h e fresh manures. I t decreased continuously during twelve weeks of fermentation with t h e loss of from 60 t o 80 per cent of the original amount. I n all cases t,he loss of this constituent was most rapid during t h e first two weeks. IO
3-Humus ranged from I I . 3 to I j,j per cent of t h e total organic matter in t h e fresh manures. This constituent decreased continuously, b u t more gradually t h a n t h e water-soluble organic m a t t e r . During twelve weeks it decreased from 26 t o 3 j per cent. T h e losses from t h e littered manures were nearly equal and about one-third greater, t h a n from t h e control manure. 4-The water-soluble ash ranged from 3 7 . j t o 4 0 . 9 per cent of t h e total ash in t h e fresh manures. This constituent decreased gradually in all of t h e manures during *twelve weeks of fermentation. T h e decrease ranged from 1 4 t o 30 per cent of t h e amount originally soluble. being less in t h e straw-littered manure t h a n in t h e other lots. j--The t o t a l nitrogen increased in all of t h e manures until the fourth week of fermentation, t h e grains ranging from 8 per cent of t h e original amount in t h e control manure t o 2 0 per cent in t h e straw-littered manure. More or less rapid loss of nitrogen occurred from t h e f o u r t h t o t h e eighth week of fermentation. After twelve weeks a net loss of nitrogen obtained in all of t h e manures. This net loss ranged from 3 t o 13 per cent of t h e original amount of nitrogen. being less in t h e straw-littered manure t h a n in t h e other manures. 6-The water-soluble nitrogen decreased rapidly in all of t h e manures during t h e first four weeks. I t suffered greater loss t h a n a n y other constituent investigated, i t s curve being quite similar t o t h a t of t h e total organic matter. This constituent formed from 4 1 . 4 t o 4 8 . 4 per cent of t h e total nitrogen a t t h e beginning of t h e investigation. Losses of t h e watersoluble nitrogen ranged from 7 7 t o 9 0 per cent of t h e original amounts a n d were somewhat greater in t h e shavings-littered manures t h a n in t h e other lots. 7-Humus nitrogen formed from 4 6 . 8 t o j 6 . 8 per cent of t h e t o t a l nitrogen in t h e fresh manures. Losses of this constituent ranged from 2 t o I O per cent of t h e original amounts, being greatest in t h e control manure. T h e fluctuation was similar in all of t h e manures, t h e humus nitrogen decreasing I O t o 2 0 per cent during the
Vol. 8 , NO.6
first four t o eight weeks of fermentation and then gradually increasing, 8-Ammoniacal nitrogen formed only 0 . 7 t o I . 2 per cent of t h e total nitrogen a t t h e beginning of t h e experiment. I t rose t o a maximum value in t h e control a n d shavings-littered manures during t h e first two weeks of fermentation, thereafter rapidly decreasing t o a b o u t t h e original value after four weeks. I n t h e straw-littered manure, on the other h a n d , t h e maximum production of ammonia was attained and passed gradually at a b o u t t h e fourth week. Ammoniacal nitrogen reached its greatest value in t h e control manure. I n all cases, however, its values, ranging from 0 . j t o 6 . 6 per cent of t h e total nitrogen, were t o o low t o allow t h e placing of great importance on its fluctuations. coscLusIos
Undoubtedly t h e gain of nitrogen during t h e early stages of fermentation is t h e most important change indicated b y t h e d a t a of this paper. Whether so extensiz-e gains are common is unceltain, b u t t h a t gains occur has been definitely proved by further work which appears elsewhere.' I n this work t h e writer showed t h a t gains of nitrogen occurred in manure treated with wheat straw litter a n d demonstrated t h e presence of nitrogen-fixing organisms in t h e manures. D a t a from field plots were also presented which showed greater gains from a fermented mixt u t e of manure a n d straw t h a n from a similar application of fresh manure. For purposes of comparison t h e latter d a t a are presented in Table 111, together with d a t a from shavings-littered manures. T h e crops referred t o were grown on plots of 1 / 2 ~ acre in size arranged in three sections f o r a three-course rotation of corn, barley a n d clover. Manuring preceded t h e entrance of t h e corn crop into t h e rotation. T h e writer is indebted t o Prof. E. B. H a r t of this d e p a r t m e n t for t h e privilege of using this d a t a . T h e control yield is t h e average f r o m t w o unfertilized plots. D a t a are averaged from six crops of corn, seven crops of barley a n d four crops of clover. TABLE111-COXPARATIVE YIELDSOF CROPSFROM FRESIIA X D FERMENTED 31XNURE9 WITH LITTERS MANURE STALLMAXURE UNFER- FRESH with with TILI ZED CONTROLStraw Shavings Straw Shavings CROP 111 100 106 106 Corn-grain., , , . . , , . . , , 100 114 104 109 106 stover , . . . . . . . . . . . , . 100 100 100 * 100 100 Barley-grain. . . , , . . . . , 100 98 97 100 99 straw , . , . , . , . . . . . 100 96 92 100 101 Cloverhay . . . , . , , . . . . . 100
.
h survey of t h e d a t a in Table I11 shows t h a t t h e effects of t h e manure are exhausted upon t h e first crop of t h e rotation. I n t h e year of application t h e fresh manure gave t h e same results whether littered with straw or with shavings. I t is only with t h e stall manure t h a t different effects appear from the use of t h e different litters. T h e stall manure was prepared from amounts of t h e fresh manure equivalent t o t h e direct applications of t h e latter, b u t had been given opportunity t o ferment t o a limited extent while stored in covered boxes during t h e winter. T h e d a t a show a decided gain in efficiency of t h e 1 W. E. Tottingham. "Increase of Nitrogen in Fermenting Manures." J . Biol. Chem., 24 (1916). 221-225.
June, 1916
T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
straw-littered manure b y this process, while t h e shavings-littered manure shows a n actual decrease of efficiency, a s compared with t h e fresh manures. For t h e values in rounded figures as given here t h e strawlittered, fermented manure produced about 10 per cent grain and stovert h a n did greateryield ?f b o t h t h e corresponding shavings .littered manure. hi^ difference is in harmony with t h e greater gain a n d
51.5
smaller net loss of total nitrogen in t h e straw-littered manure t h a n in t h e shavings-littered manures, as shown b y t h e analytical d a t a a n d graphs of this PaperThe results here presented Seem t o have opened for f u r t h e r investigation questions regarding t h e comparative value of different litters a n d t h e benefits t o be derived from controlled fermentation of manure. LABORATORY OF AGRICULTURAL CHEMISTRY EXPERIMENT STATION,
LABORATORY AND PLANT FLOW OF HEAT FROM SOLIDS TO AIR
Electrical measurements were made with carefully standardized voltmeter a n d ammeter, a n d t h e t e m peratures along t h e pipes were measured with t h e J. W. Richards1 makes t h e s t a t e m e n t t h a t t h e thermal-couples a n d a Leeds & Northrup Potentiomcoefficient of heat transfer from solids t o air is pro- eter Indicator, carefully standardized against metals portional t o t h e square root of t h e gas velocity, while of known purity. Each run, either blank or constant Irving Langmuirz states t h a t it is proportional t o t h e velocity, was. continued until thermal equilibrium cube root of t h e velocity. Since these statements was reached. T h e d a t a obtained are given in Table conflict, a n d since t h e experimental d a t a on which I, where t h e column marked Head is t h e differential t h e y are based are not given in either case, t h e following pressure i n inches of water or mercury, as indicated investigation was undertaken: a t t h e orifice, t h e diameter of which is given in t h e A known weight of air was blown at constant velocity column marked Orifice. through a n electrically heated tube. The temperaT h e volts 2nd amperes are those read, a n d are cort u r e of t h e t u b e was measured, a n d t h e heat picked rected in Table 11. T2,T8,Td, a n d T5 are t h e temperau p b y t h e gas was calculated b y subtracting from t h e tures measured b y t h e thermal-couples, a n d TI a n d Ta total electrical input t h e heat necessary t o maintain. are t h e temperatures of t h e water b a t h at opposite t h e same temperature in t h e t u b e when no gas was ends of t h e furnace. passing through it. T h e average temperature of t h e furnace for a given T h e a p p a r a t u s is shown diagrammatically in Fig. I . run was found b y plotting t h e temperature gradient A blower, A , delivers air through a CaClz drying against t h e length of t h e furnace a n d determining t h e average temperature difference b y means of a planimeter. For each series of runs a t constant velocity t h e power input was plotted against t h e average temperature difference between pipe a n d air. By subtracting t h e power input for t h e blank runs t h e net energy taken u p b y t h e gas was obtained. T h e values of K were t h e n calculated a n d tabulated in Table 111, which, however, includes only runs a t a velocity of 0.01 lb. per second. T h e values of K a t other velocities were calculated in an exactly similar way. The values of K for each velocity were tower, B , t o a n orifice, C, where t h e gas is measured. plotted against t h e temperature of t h e furnace, b u t F r o m C t h e air passes t o t h e furnace D . i t was found t h a t all these curves were practically T h e furnace consists of a brass pipe, in. inside horizontal straight lines, i. e . . t h e value of K was indein. X I'/* in. pendent of t h e temperature of t h e furnace. The diameter, 2 7 in. long, fitted with reducing elbows into which short pipes for air connec- values of K were then plotted against velocity; this tions are screwed. Four Iron-Ideal thermal-couples plot is shown in Fig. 2 . Points were p u t on this are attached symmetrically along t h e pipe, which is plot for furnace temperatures of I jo. z 50, a n d 3 jo" C. covered with insulating asbestos paper, a n d wound and these points as indicated were practically coincident with No. 19 resistance wire, t h e winding being closer except for a velocity of 0.Ooj. The discrepancy a t this together near t h e ends, t o even t h e temperature point is probably experimental. We m a y therefore conthrough t h e pipe. I t is covered with magnesia in- clude t h 2 t t h e value of K u p t o t h e temperature emsulation t o a diameter of j in. a n d the whole device ployed is independent of t h e temperature a n d a funcenclosed in a galvanized iron can, with suitable open- tion of t h e velocity alone. The equation of this curve is ings for lead a n d thermal-couple wires. T h e whole K = 39'6v wherein K is t h e coefficient of heat furnace was immersed in a water b a t h of measured V 3.67' temperature. transfer from solid t o air in B. t. u. per sq. ft. of By E. E.
C. S. ROBINSON AND W. K. LEWIS Received May 2, 1916
SNYDER,
+
1
J. W. Richards, "Metallurgical Calculations," McGraw Publishing
Co., New York, 1906, p. 179. f
Irving Langmuir, Phys. Reo.. 84 (1912). 401.
heating surface per O F . difference in temperature per hour, a n d V is t h e pounds of air per second flowing
