-4pr., 1921
T H E JOURiVAL OF I N D U S T R I A L A N D ENGINEERING CIIEMISTRY
305
Rapid Dry Combustion Method for the Simultaneous Determination of Soil Organic Matter and Organic Carbon‘ By J. W. Read DEPARTMENT OF AGRICULTURAL CHEMISTRY, A R K A N S AEXPERIMENT ~ STATION, FAYETTEVILLE. ARKANSAS
T h e results reported by Rather indicate t h a t t h e I n order t o carry out certain investigations on t h e quantitative relations of soil organic matter it became amount of organic carbon lost in t h e filtrate from t h e necessary t o devise a n accurate and suitable procedure acid treatment is negligible, falling within t h e limit of for determining t h e percentage of carbon in t h e organic error in most cases a t least matter in a large number of representative soils selected A P P .?.RAT U S A N D R E A G E N T S from nearly every Experiment Station in t h e United The combustions were made in a 100-cm. silica tube, States for t h e purpose of making a more exact study having a n internal bore of 23 mm., and with one-half of t h e percentage relationship of t h e organic carbon its length made of transparent silica so t h a t t h e process t o t h e total organic matter. The methods in general of combustion and t h e manipulation of t h e boat were use for t h e total organic matter determination are (1) under observation a t all times. A 3-unit electric furt h e loss on ignition, and (2) t h e organic carbon method. nace was used, and t h e combustion tube was charged T h e latter involves t h e use of a conventional conversion as shown in Fig. 1. factor. C E R I U M OXIDE ASBESTOS’ A N D PusirIcE-The asbestos A scheme which would make it possible t o determine catalyst was prepared by suspending highly purified, t h e organic matter and t h e organic carbon simultanemedium fibered asbestos in a saturated solution of ously, thereby reducing t h e labor t o about one-third, chemically pure cerium nitrate and evaporating praca t t h e same time securing t h e highest accuracy, was t h e tically t o dryness on a boiling water bath. The aschief object sought. The method described below met bestos was t h e n heated in a glass tube in a stream of these requirements t h e most satisfactorily. By its oxygen, t h e escaping vapors being absorbed in dilute use t h e writer was able t o complete twelve combustions, alkali. The cerium dioxide pumice, 12 mesh, recomtwenty-four determinations, in an ordinary day’s work, mended by Fisher a n d WrightZ as more desirable t h a n including all t h e necessary preliminary and final asbestos because of t h e tendency of asbestos t o crumble weighings, and employing only one combustion furnace. and “sag,” was similarly prepared. Reimer3 also had With t h e exception of several modifications and t h e previously called attention t o certain difficulties due introduction of a new feature in t h e t y p e of combustion t o t h e crumbling of t h e asbestos impregnated with boat, t h e rapid organic combustion method as modified t h e cerium dioxide. However, no such difficulty arose and used b y Levene and Bieber2 formed t h e basis of with t h e asbestos used in this work. On t h e other t h e procedure adopted. The success of determining hand, i t remained throughout long service in t h e very on t h e same sample of soil both t h e organic matter desirable granulated condition which it assumed in t h e a n d t h e organic carbon simultaneously is due in t h e process of preparation. main t o t h e use of a special perforated-bottom comL E A D PEROXIDE-It is very important t h a t strictly bustion boat3 and a specially constructed filter f ~ n n e l , ~ pure peroxide be used for absorbing t h e nitrogen prodtvhich made i t possible t o filter b y suction in t h e same ucts. Considerable trouble was experienced a t t h e manner as with t h e ordinary Gooch crucible. T h e beginning with a supposedly high-grade reagent.4 boat possessed suitable dimensions (97 mm. long, Previous t o using, t h e peroxide was digested three 18 mm. wide, 13 mm. deep) for handling t h e quantity times with boiling water, filtered, washed, and dried of materials required. on a Buchner funnel in a n electric oven. I n charging One-gram samples of soil (1-mm. sieve) were pret h e t u b e alternate layers of peroxide a n d peroxide pared for combustion by removing t h e carbonates and asbestos were lightly tamped into a fine copper gauze hydrated minerals in accordance with Method B decontainer. The peroxide asbestos was prepared by scribed b y Rather.5 This preliminary preparation intimately mixing about equal volumes of the two may be briefly stated as follows: substances. A I-g. sample of soil is weighed into a platinum evaporating P U R I F Y I N G APPARATUS-This consisted of two 8-in. dish and given six successive digestions, 5 min. each, on a boiling Peligot tubes filled as indicated in Fig. 1. Obviously, water bath, with 30 cc. of water and 10 cc. each of 2.5 per cent a purifying train filled in this manner will serve for a hydrochloric and hydrofluoric acids. After each digestion the large number of combustions. The use of t h e phossupernatant liquid is carefully decanted through the combustion boat on to an asbestos mat. After the sixth digestion the entire phoric anhydride as t h e dehydrating agent is unnecessary unless accurate determinations of hydrogen are sample is transferred to the boat with a rubber policeman. wanted. ’ Presented before the Division of Agricultural and Food Chemistry a t the 59th Meeting of the American Chemical Society, St. Louis, Mo , A B S O R P T I O ? ; APPARATUS-Accuracy and speed were April 12 t o 16, 1920. t h e principal advantages gained in t h e absorption ap2 J . A m Chem. S o c , 40 (1918), 460. 3 Made especially by the Coors Porcelain Co , Golden, Colorado. The wiiter sincerely thanks the company for the valuable cooperation given him and for the care and pains taken t o produce a satisfactory boat. 4 Grateful acknowledgment is made t o Eimer and Amend for their construction of the special filter funnel used with the boat. (See Flg. 3.) 5 Arkansas Experiment Station, Technzcal Bullelin 140 (1917) ; THIS JOURNAL. 10 (19181, 439.
J . A m . Chem Soc , 40 (19181, 462 Ibzd., 40 (19181, 869. a I b i d . , 37 (1915), 1637. 4 The author is greatly indebted t o Dr. W. D. Collins, U. S. Bureau of Chemistry, for furnishing him with a satisfactory peroxide manufactured by E. R. Squibb and Sons. The Bureau’s analysis of Squibb’s reagent gave 0.15 per cent soluble matter and 0.60 per cent sulfate. 1
2
306
18-30-mesh
T H E JOURhTAL O F 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
centage of organic matter present in t h e soil. All t h e combustions were made in a rapid current of air. The bubbling was severa1 tinies faster than c o u l d b e
26-Palladious chloride solution soda lime Tubes A and B are Elled alike
PALLADIOUS CHLORIDE soLvTIoN-Palladious chloride solution,’ prepared b y adding 1 cc. of a 5 per cent solution t o 200 cc. of distilled water, was used t o detect a n y carbon monoxide resulting from imperfect combustion. N o difficulty a t all was experienced in this respect. FILTERING-Filtration through t h e boat was ac-
Vol. 13, KO.4
~
Apr., 1921
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
min. were required t o burn t h e sample, and 8 t o 11 min. more were used t o sweep out t h e tube, during which time t h e t w o hot units cooled sufficiently t o introduce another sample. T h e temperature of Unit 3, used for heating t h e lead peroxide, was kept between 300" and 320" C. by means of a long stem thermometer with i t s bulb placed in t h e center of t h e peroxide charge N u c h above 320" C. decomposition of t h e absorption products formed with t h e nitrogen compounds took place. T h e absorption bulbs were always handled i n duplicate under t h e same conditions t o facilitate weighing. They were protected from t h e furnace heat by a thick shield of asbestos. T h e absorption of t h e carbon dioxide from t h e soil combustions never produced a n y perceptible change i n t h e temperature of t h e bulb taking i t up. Upon detaching t h e bulbs for weighing they were very carefully wiped with lens cloth and weighed after standing a very few minutes or just before their use another time. Two sets of bulbs were kept in use. DATA
T h e d a t a presented herewith are quite typical of t h e several hundred combustions made without recharging t h e combustion t u b e or either t h e purifying or absorption trains. T h e determinations are given i n
307
duplicate. T h e furnace was checked on a standard sample of sucrose received from t h e Bureau of Standards, with t h e followingresults i n percentages of carbon, -42.06, 42.13, 41.99. Theoretical = 42.08.
-
RegisDepth tration of Per cent OrNnmSample anic Matterber Type of Soil Inches (17 (2) Av. 0-20 2654 Lamour silty clay loam 20-36 2655 Subsoil t o 2654 2656 Webster silty clay loam 0-15 2657 Subsoil to 2656 15-36 2658 0-20 2659 20-36 2672 0-10 2673. 10-20 2674 20-36 2675 Grundy silty loam 0-12 2676 Subsurface soil t o 2675 12-18 2677 Subsoil t o 2675 18-36 0-24 2792 Diablo clay24- 72 2793 Subsoil t o 2i92
Per cent Carbon in Or-ganic Matter(1) (2) Av.
SU M M A R Y
T h e simultaneous determination of t h e organic matter and t h e organic carbon b y t h e above method effects a saving in time of approximately 60 per cent. I t is believed t h a t t h e d a t a secured on t h e many soils which have been investigated are more accurate t h a n could have been obtained by a n y previously described method, and t h a t t h e magnitude of error is reduced t o a minimum.
Studies on the Nitrotoluenes. VI-The Three-Component System: o-Nitrotoluene, p-Nitrotoluene, 1,2,4-Dinitrotol~ene~~~ By James M. Bell and Edward B. Cordon UNIVERSITY O F NORTH CAROLINA,CHAPELHILL, N. C.
In a previous paper of this series by Bell and H e r t ~ t h e cooling-curve method of obtaining t h e freezing points of various three-component mixtures has been described. The present paper contains t h e results ONT-4.45'
MNT513'
2650'
D NT 635-5'
obtained by t h e same method for another threecomponent system of t h e nitrotoluenes. We shall not repeat the details of t h e method or t h e methods of preparation of t h e pure components, b u t shall Received December 21, 1920. This paper is t h e sixth of a series dealing with t h e freezing points and thermal properties of the nitrotoluenes, the investigation having been undertaken a t the request of the Division of Chemistry and Chemical Technology of the h-ational Research Council. 8 Tnis JOURNAL, 11 (1919), 1128. 1 2
, refer ~ t o some of t h e features of this system. A foregoing paper1 has shown t h e existence of two forms of O N T , and therefore there should be two charts for this present study: One where t h e component, O X T , is i n its stable form, and one where i t is in its metastable form. These two charts would be identical except in t h e portion of t h e diagram where O K T is t h e solid phase. Reference. t o t h e foregoing paper DNT 80 70 70 60 60 60 50 50 50 50 40 40 40 40 40 30 30 30 30 30 .30 20
Per cent by Weight MNT
10 50 40 30 20
10
60 50 40 30 20
10
70 60 50 40 30 20
20 20 20 20 20
10
80 70 60 50
10
10 10 10
10 10 10 10
Tms
c.
10
20 10 30 20 10 40 30 20
20
1
Freezing Point
ONT
40
30 20 10 JOURNAL,
13 (1921), 59.
.
56.01 47.85 47.75 38.82 38.66 38.01 27.52 26.98 26.47 27.47 12.08 10.55 9.84 13.84 21.82 2.45 -4.19 -1 .50 9.74 20.15 29.39 -13.20
....
-3.89 8.48 19.10 27.83 35.69 -11.82 -15.65 -5.95 7.64 17.55 27.08 34.25 41.32
.
