304
T H E JOGRLYAL OF I S D C S T R I A L A S D ENGIATEERISG CHE,I.IISTRY.
rails with carbon about o 69 with the phosphorus under o 03. These were intended for a range of ductility of 12 to 18 per cent. for use under highspeed trains where the temperature in winter falls IO to 30 degrees F. below zero. Rails of similar composition have been in service three and four years with comparatively few fractures. Correlation of the Equiknzent and the Trucb 9.
The equipment and track are of necessity so intimately correlated that for high-speed trains of heas >loads the wheels need tires of higher physical properties and maintenance than formerly required. The tires under the heavy wheel loads do not all wear uniformly the entire circumference of the tread, soft spots developing in a portion and the wheels become eccentric, increasing the dynamic shocks upon the rails each revolution. The metal in tires under the heavy loads and high-speed trains is more se\ erely strained and abraded than in the past, and it will require as thorough consideration of the comparative methods of manufacture as has been exercised for rails. The tonnage upon the tread of a tire accumulates with great rapidity. The 36-inch wheel makes 5Go 2 revolutions per mile, therefore, every portion of the metal of bearing surface of the tread is subjected to its static lcad 560 2 times per mile, and for a static load of five tons it would be equivalent to 2,801 tons per mile, beside the generated wheel effects. The accumulated tonnage exclusive of the generated wheel effects for a static load of five tons per wheel in a trip from Boston to Chicago would be 2,865,423 tons; New York to Chicago, 2,700,164 tons; New York to St. Louis, 3,243,558 tons; New York to Cincinnati, 2,478,885 tons. X tender wheel with a n average static load of nine tons, or 5,041 8 tons per mile, the tonnage for a trip of 150 miles would be 756,270 tons and run in about three hours and fifteen minutes. The generated wheel effects would be from 2 0 to 50 per cent. additional in all cases, depending upon how smooth or even the treads maintained their circumference, speed, and also the smoothness of the track. A tender wheel became eccentric for a space of about ten inches in the tread after it had run zg,ooo miles and its total tonnage approximated 146,000,000 tons in about six months’ service. Some tires become eccentric after running 10,ooo to 15,ooo miles. The tires are subject to greater tonnage than rails in a given length of time. Years are required for the rails to carry as heavy tonnage as the tires do in a few months, the latter being returned for further duty. It requires a metal of high elastic limits of the steel t o sustain the treads without undue wear. CONCLUSIONS. I.
The illustrations of the elongation and ductility
J u ~ J - ,1910
tests indicate the possibility that from a well studied chemical composition for steel rails with good fabrication a range of ductility in reference to great toughness can be prescribed for the different sections to meet conditions of service as girders for high speeds, or with more hardness but less ductility, to resist curve abrasion and wear a t slow speeds. 2 . Rails which are to be used in low temperatures under high-speed trains the toughness and ductility of the metals must have preference over hardness, particularly of that high in phosphorus, as the latter limits the amount of carbon which can be used to resist abrasion and wear, and still be safe as girders. 3. The carbon in basic open-hearth rails should be below the eutectic mixture of the chemical composition for high-speed trains, as otherwise the toughness and ductility may be reduced to a condition of brittleness in many rails. 4. The average ductility in Bessemer rails of 0 . j o carbon and o 095 in phosphorus has been raised two or three per cent. by the use of ferro-titanium in the steel as practically shown by one and two winters’ service, and is considered worthy of further trials. Ferro-titanium has a direct action upon the purification of the metal and setting of the ingots, and must, therefore, be used with a knowledge of what is desired, to secure the best results. j. The problems of rail-making for service in the United States are now upon a better basis than ever before, owing to the cooperation of the railroad companies and the manufacturers to secure rails which are suitable for the present traffic. This arises from a more general knowledge of what is required than was understood a few years since.
[COSTKIBUTION
FROM
PITTSBUKC LABORATORY, TECHNOLOGIC BRAXCH,
UNITEDSTATES GEOLOGICAL SURVEY]
SOME VARIATIONS IN THE OFFICIAL METHOD FOR THE DETERMINATION OF VOLATILE MATTER IN COAL. B y A. C. FIELDNER AND J D . D A V I S . ~
Received May 13, 1910
In view of the proposed revision of the officiaI methods of coal analysis, it may be of interest to present certain experimental data bearing on the present official method for the determination of volatile matter in coal. These experiments were conducted in the Pittsburg and Washington laboratories of the U. S. Geological Survey, primarily to ascertain the difference in volatile matter produced by using a 2 0 cm. natural gas flame as compared with the 20 cm. coal gas flame. After starting the work i t was found desirable t o investigate the influence of other factors such as gas pressure, type of burner, and surface condition of 1
Presented by permission of the Director, U. S. Geological Survey
, F I E L D - Y E R A h D D A L-IS 0-j- l.OL.4TILE -1fLlilTTER I S COAL. platinum crucible, i. e . , dull gray or polished. ,In order to eliminate influence of variation in size and . shape, three go-gram platinum crucibles of practically the same capacity and weight with closely-fitting coyers were used in all the experiments, it having been demonstrated by actual trial that each one of the three crucibles gave the same results. As these crucibles had been regularly used for volatile determinations, both inner and outer surfaces had the dull gray appearance which platinum assumes when heated several times in the natural gas flame. To protect the flame from air currents, the platinum triangle supporting the crucible was enclosed in a cylindrical sheet metal shield, lined with asbestos, 15 cm. long and 7 cm. in diameter, the platinum triangle being placed 3 cm. below the top of the shield; the bottom of the crucible was exactly 8 cm. above the mouth of the burner. The temperature measurements were taken on a parallel test, using the same crucible with the regular cover replaced by one of nickel; the thermocouple, inserted through a small opening in the cover, was placed z mm. above the bottom of the crucible; the opening around the thermocouple leads was closed with a cement of barium sulphate and sodium silicate. The description of coals tested is given in the following table : TABLEI. Coal S o .
Type.
Locality.
Semibituminous
Pocahontas, W.
Bituminous
Pennsi-lvania
1 2 3 10
va.
11
12 4 5 6
8.
Temperature during volatile determination o n coal h-o. 1 with varying pressures. (Time in minutes.) Pressure in 3 3.5 4 4.5 5 6 7 inches 0 . 5 1 1.5 2 2.5 w a t e r . ° C . o C . 'C. O C . 'C. OC.OC. 'C. O C . ' C . OC. ' C . 1 150 450 590 670 725 i 4 5 750 755 760 760 760 760 3 185 440 590 670 740 760 770 780 7 5 0 780 780 780 180 450 605 710 765 790 800 SO3 803 802 800 800 5 9 220 480 635 720 775 805 815 820 820 823 823 823 13 320 550 690 780 825 840 548 848 848 848 847 845
The maximum temperature varies from 760 to Coal No. 6, a bituminous coal, gives practically the same yield of volatile matter throughout the series. The semi-bituminous coals, Nos. I and 3, are more sensitive to variations in temperature, the extremes being nearly 2 per cent. The maximum pressure, 13 inches, was used in all subsequent work with natural gas. It has frequently been noted by the writers that during the early part of the 7-minute volatile process, the coke swells or puffs up to the lid of the crucible, oftentimes raising i t slightly. On comparing such determinations with duplicates that did not swell, they were invariably found to be one to two per cent. lower in volatile matter. This peculiar swelling has been noticed only in the case of semi-bituminous coals. It is more apt to happen at the lower temperatures, and when the coal is kept perfectly level in the bottom of the crucible. The swelling can be prevented by simply tapping the crucible on one side so as to settle the coal in an inclined position across one corner of the bottom of the crucible, thus preventing the formation of a film of fused coal across the crucible. Comparative results are given in the following table : 8 4 5 O C.
TABLEIII.--VARIATIONS DUE TO SWELLING OR PUFFIXG CP O F COKE
Inpzwme of Chaizge i?z Gas Pressawe.-Coal gas can be burned efficiently at low pressures, two to three inches of water being sufficient; natural gas, owing to the much larger proportion of air required, must be supplied to the burner at higher pressures. Table I1 gives results obtained by varying the pressure from I to 13 inches of water:
Coal S o .
Coke residue in compact lump in bottom of crucible.
1
16.7 17 2 1i.l
TABLE1 1 . - I N F L U E N C E O F GAS P R E S S U R E O N V O L A T I L E Natural gas; Tyrell burner; 20 cm. flame.
1
2 3 4 5 6 8 9
12 13
MaxP e r cent. volatile matter. imum temperCoal Coal Coal ature. S o . 1. S o . 3. No. 6. O ' C . 15.4 15.8 32.4 760 15.2 16.7 ....... 15.4 16.7 32.3 550 16.3 . . . . 32.7 16.7 16.5 32.6 800 ... 17.2 16.7 33.0 16.7 .... 3 2 . 7 17.2 825 17.2 16.9 32.7 17.1 17.1 32.5 S45
Arerage.
...
....
....
... ...
Kind of flame. Yellow tipped
........ ..........
Faint yellow- tip Tellow t i p just removed Long inner cone
.......... ..........
17.0 17 .O
16.0
15.4
sw-elled u p to cover. 15.3 14.5 15.2 15.1
15.7 15.6 15.3 15.4
I$uevice of T y P e of Burner.-It is reasonable to expect some lack of uniformity in volatile results where widely different types of Bunsen burners are used. A burner with a large bore will give a larger flame volume, with a correspondingly increased heating effect. Determinations were made with the following types of burners on both natural and coal gas : (a) The simple Bunsen burner, bore 9 mm. ( b ) The Tyrell' burner, bore 9 mm. (cj The Fletcher, No. 5g.l burner. bore 12 mm.
Well defined inner cone Sharp, greenish, inner cone
16.2 16.8 16.0 15.5 15.7
Coke residue
16.9
MATTER
-
....
Cuke residue swelled half i i a y to COYer.
.... 2
----
IN
CRUCIBLE.
'
Anthracite
Gas pressurein inches [it' water.
305
1
Eimer & Amend catalog, p. 80.
B
T H E J O U R N A L OF INDUSTRIAL A N D ENGINEERING C H E M I S T R Y .
306
The results are given in Table IV. TABLE IV.-~NFLUENCE OF DIFFERENT TYPESOF BURNERS.
The coal gas' analyzed:
............ ...................... ............................
Unsaturated hydrocarbons. Carbon dioxide.. Oxygen.. Carbon monoxide.. Methane Hydrogen Nitrogen..
Difference. 7
Per cent. volatile. 7
Coal
1
2 6
4 S
I
No. Fletcher. Tyrell. Bunsen. ( a ) Natural gas. 17.2 17 .O 15.7 17.0 16.8 15.8 32.8 32.6 32.6 31.8 31.3 31.2 31.5 31.5
....
-
850°
Fletcher and Bunsen.
-1.5 -1.2 4 . 2 4.6
-0.2 -0.2 -0.2 -0.5 0.0
4 . 8
TABLE VI.-DIFFERENCE DUE TO USINGNATURALOR COALGAS.
. I .
... ...
... ...
Average,
------
Per cent. volatile.
4 . 7
...
...
....
.... .... .... .... .... ....
Coal No.
1 2 6 4
-1.1 4 . 8 4 . 3 -0.3 4 . 3 4 . 6
5
-
1 6 4 5 7
-0.6
TABLE~.-TEMPERATURE MEASUREXENTS. ("'2.) 20 cm. flame; natural gas a t 13 inches wates pressure. Time in minutes, 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 6 Fletcher b u r n e r. coa1,No. l... 280 590 710 788 830 845 850 850 850 850 850 Tyrell burner, coal No.1 250 530 670 780 825 840 850 850 850 850 850 Bunsen burner, coal S o . l... ......... 250 580 700 760 780 785 785 785 790 790 790 Pittsburg coal gas a t 2.5 in. pressure; 20 cm. flame. Tyrell burner. coal N o . 1 ............ 260 540 680 760 810 835 850 855 855 855 855 Washington illuminating gas a t 2 ,5in. pressure; 20 cm. flame. Fletcher b u r n e r. CoalNo. 1 . . . . . . . . . . . 630 . . . 910 ... 975 . . . 975 970 970
............
850 790
855
970
The Fletcher burner gives slightly higher volatile matter than the Tyrell with practically the same maximum temperature. The larger flame volume of the Fletcher burner, heats up the crucible more rapidly, which increases the gas yield slightly. With the use of natural gas, the maximum temperature of the Bunsen burner is 60' less than either the Fletcher or Tyrell; this produces a marked difference in volatile matter in the case of the semi-bituminous coals. Evidently a burner like the Flefcher or Tyrell, admitting of both gas and air regulation, is preferable to the simple Bunsen. Injluence of Composition of: Gas.-In order to determine the influence of composition of fuel gas, determinations were made over 2 0 cm. coal gas flame and 2 0 cm. natural gas flame, each gas being supplied to the burner a t its proper pressure. The natural gas analyzed as follows :
100.00
+0.2 4 . 1 4 . 2 +0.3 4 . 2
0.0
t0.3 +0.3 -0.3 +0.1 -0.2
__
Average, 8500
Temperature 'C.. 855'
850
...................... 0.1 ................ 98.6 ........................... 1.3
Difference.
( b ) Tyrell burner. 16.7 17.0 32.3 32.6 31.6 31.3 31.4 31.5 4.5 4.3
7
....
...
Coal gas, Natural gas, 2.5 in. pressure. 13 in. pressure. ( a ) Fletcher hurner. 17.0 17.2 17 .O 17.1 33 .O 32.8 31 .5 31.8 31.7 31.5 Average,
Temp. 'C. 970'
Carbon dioxide.. Paraf6n hydrocarbons. Nitrogen..
-
Both series of volatile determinations were made by the same analyst, using the same apparatus, the only difference being in the fuel gas used. The results are shown in Table VI :
850'
....
7.5 1.5 0.2 8.9 44.8 33.7 3.4
100.00
... -
-
Average, -0.2 790' ( 6 ) Coal gas (Pittsburg). 1 17 .O 16.7 16.3 4 . 3 6 33.0 32.3 4 . 7 5 31.7 31.4 -0.3 Average, -0.4 Temp. O C 855" 810° (a) Carburetted water gas (Washington). 1 18.3 17 2 17.8 11 18.6 12 18.0 17.7 18.4 10 18.9 18.5 ... 3 18.8 17.6 2 18 2
Temp. 'C.
................... ............................. ............................ ...........................
7
Fletcher and Tyrell.
July, 1910
+0.04
The temperatures are practically the same and the variations in volatile matter average zero. It should be noted, however, that the natural gas was supplied to a carefully regulated burner a t 13 inches pressure. If the comparisons were made at the lower pressures usually found in laboratories, the results by natural gas would be decidedly lower. Table VI1 gives a comparison of volatile matter obtained on the same samples of coal, in two different laboratories of the Geological Survey. The Pittsburg laboratory used natural gas a t 13 inches water pressure with .a Tyrell burner ; the Washington laboratory used illuminating gas a t 2 inches pressure with the Fletcher burner. The height of flame was 2 0 cm. in each case: TABLEVII.-COMPARISON
OF
RESULTS OBTAINED
IN
DIFFERENT'LABORA-
TORIES.
Per cent. volatile matter
Coal N o . 1 2 3 4 5 6 7 10
Pittsburg. Natural gas. 13 in. pressure. Tyrell burner. 17.0 16.8 17 .O 31.3 31.5 32.6 4.3 17.7
Washington. Illuminating gas, 2 . 5 in. pressure. Fletcher burner. 18.3 18.2 18.8 32.5 32.6 33.4 5.3 18.7 Average.
Difference. f1.3 1.4 +1.8 +1.2 +1.1
+
+0.8
+1.1 +1.0
--
f1.2
970 C. Temperature 850' C. 1 Coal gas taken from the mains of the gas company that supplies artificial gas, in Pittsburg, Pa.
F I E L D S E R A,VD D.4VIS O S 1 - O L A T I L E M A T T E R I N COAL. From the previous experiment on natural and coal gas, closely agreeing results would be expected. Such, however, was not the case. As shown in the table, the Washington series averaged I . 2 per cent. higher than the Pittsburg. The maximum temperature of 970' C., noted in the Washington laboratory, was 120' higher than noted with either coal or natural gas a t the Pittsburg laboratory. It had been supposed that the Washington illuminating gas was of a similar composition to that of the Pittsburg coal gas. This assumption, however, proved to be erroneous, as shown by the following analysis: TABLE\ ~ I I I . - - A N . ~ L Y ~ OF I S\VASHINGTON I L L U M I N ~ T GAS INC Per cent. Carbon dioxide. ....................... 3 .0 Unsaturated hydrocarbons. , 10.4 Oxygen .............................. 1.0 Carbon monoxide. .................... 27.6 Methane. . . . . . . . . . . 19.0 Hydrogen ............................ 33.1 ~ i t r o g e ............................. n 5.9
___
Temperature measurements. Time in minutes.
0.5
1
1.5
2
2.5
3
307 ("C.) 3.5
4
4.5
5
6
7
Before polishing, coal No. 1 . 250 530 670 780 825 840 848 850 850 850 850 850 320 550 690 780 825 840 848 848 848 848 847 845 After polishing. coal 5-0,1 . . . . . . . . . . 240 590 750 840 880 890 890 890 890 890 890 890
...........
TABLE X.-\'OLATILE MATTER BY DISTILLATION.
Test Time in No. minutes. 1 30 2 45 3 45 4 45 5 40 6 45
7 8 9
7 7 i
Per cent. volatile moisVacuum. ture. 3/4-in. Hg 18.3 3/4-in. Hg 18.7 19.4 3/4-in. H g . 3/4-in H g 18.2 4-in. HzO 18.8 Atmospheric pressure 1 8 . 7
Retort weighed. Coke weighed. Coke weighed. Coke weighed. Coke weighed. Gradual heat.
Average, Atmosphere of COz Atmosphere of CO2 Atmosphere of COz
30-gram platinum a u cible heat treatment as in official method.
18.7 18.5 18.3 18.6
-
Average,
18.5
Official method,
19.3
Remarks.
100 . o
The Washington gas consists entirely of carburetted water gas. It contains 26 per cent. less methane and 19 per cent. more carbon monoxide than coal gas. The replacement of methane by carbon monoxide decreases the flame volume very materially, and since the height of flame is the same in both cases, the heating effect of a low methane gas is, under ordinary laboratory conditions, considerably greater. Chikashiga and Matsumatol call attention to the disadvantages of uncarburetted water gas as a laboratory fuel on account of the high temperature of the flame produced. They state that "comparatively thick copper wire and sheet, and even thin platinum wire, are easily melted and hard glass easily worked in its flame." Another factor that may have contributed to the difference in temperature noted in the two laboratories is the surface condition of the platinum crucible. Constam, in a paperz communicated to the Seventh International Congress of Applied Chemistry, mentions " t h a t the slower rise and the lower final temperature in dull platinum crucibles caused the yield of coke in them to be greater than in polished platinum crucibles." As the crucibles used in all the experiments a t the Pittsburg laboratory were very dull and tarnished in appearance, i t was decided to polish them and then run some determinations to check Constam's conclusions. The results are given in Table I X : TABLEIX.-COXIPARISON OF VOLATILE MATTER PRODUCED I N THE SAME CRUCIBLE BEFORE ASD AFTER POLISHING. Per cent. volatile. Coal No. Before. After. 10 17 . O 18.1 3 17 . O 18.1 6 32.6 33.3 Temperature "C. 84.5' 890' .To?rr. SOC.Chem. Ifid.. 23 (1904). Jan. 30, p. 50. J o i i r . f U T Gasbel. (1909), Oct. 9, p . 889.
Difference. 1.1 1.1 0.7
450
I n tests Kos. I to 6, inclusive, a sample of Pocahontas coal was subjected to destructive distillation in an iron retort, made from a piece of I-in. gas pipe, capped a t one end and tubulated a t the other. The retort was heated by means of a train of Bunsen burners to a bright red heat, in a furnace of asbestos board. A 20-gram charge was used. Tests Kos. 7 to 9, inclusive were made in a 30gram platinum crucible with a tubulated cover; carbon dioxide was kept passing through during the determination ; the heat treatment was exactly the same as in the official method. Both retort and crucible tests give results somewhat lower than the official method, although not materially. SUMMARY.
The results of these experiments may be briefly summarized as follows : Two laboratories are likely to vary 2 per cent. in volatile matter, both using the official method. The percentage of volatile matter obtained from the same sample of coal varies with the temperature and rate of heating. This is not sufficiently defined by height of flame. Temperatures ranging from 760' C. to 890' C. may be attained with a 2 0 cm. natural gas flame, when the gas pressure is varied from I to 1 3 inches of water; variations of 2 per cent. volatile matter are thus produced. Difference in type and size of burner influence results from 0 . 3 to I . 5 per cent. Polished crucibles become hotter and yield about I per cent. more volatile matter than dull gray ones. Laboratories using natural gas are apt to get results on volatile matter that are considerably lower than those using coal gas, unless the following precautions are observed : (I) Gas should be supplied to the burner a t a pressure of not less than I O inches of water.
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 .
308
(2) Natural gas burners admitting an ample supply of air should be used. (3) Gas and air should be regulated so that a flame ‘ with a short, well-defined inner cone is produced. (4) The crucibles should be supported on platinum triangles and kept in well-polished condition.
LABORATORY METHODS FOR ORGANIC NITROGEN AVAILABILITY. By C. H.
JONES.
Received February 17, 1910.
There is a n extensive demand for nitrogen in a form suitable for plant food. This demand has been mainly supplied in the past by nitrate of soda, sulphate of ammonia, and the animal and vegetable ammoniates, including dried blood, various tankages, fish scrap, bone meal and cottonseed-meal. These constitute a class which furnish nitrogen t o the growing plant in a readily available form. As a supplement to these high-grade manures there has gradually come into use another group of nitrogen-containing materials including raw and treated leather, peat, tartar pomace, garbage tankage, mora meal, beet and gas-house refuse, and others. Their nitrogen availability is supposed to be considerably less than obtains with the so-called standard ammoniates, the nitrogen being so “ locked up,” “fixed,” “ embalmed” or “inert that decomposition in the soil is a long, slow process. Most fertilizer laws legislate against materials in this class, prohibiting their use unless statement of their presence is made. It does not follow that because a popular classification puts a material in the inert class, that the material may not, by suitable treatment, be so changed as t o merit a place in the readily available nitrogen group. The personal equation must be eliminated and each material allowed to stand on its own merits as measured by careful field and pot experiments. In other words, the true availability of any source of nitrogen for plant food must be eventually determined by the growing plant. It happens, unfortunately, that field and pot experiments cannot be conducted without extensive equipment, that they are time-consuming, and that the great variation in results under seemingly uniform conditions, with different crops, soils, etc., necessitates repetition if anything like true availability averages are t o be secured. This has led to the formulation of short laboratory methods designed to differentiate between ammoniates of high and low crop producing power. A history of suggested methods is beyond the scope of this paper and would be out of place here.l I wish to describe a t this time first the alkaline 1
Vt. Station, Reg., 11, 1897, page 160.
July, 1 9 1 0
permanganate method and second the pepsin digestion method as employed in the Vermont Experiment Station laboratory and submit results obtained by their use on fifty-one samples representing many socalled high- and low-grade animal and vegetable ammoniates now on the market. The Alkaline Permanganate Method.-Weigh out an amount of sample containing 0.045 gram of organic nitrogen and transfer to a 600 cc. distillation flask. Add IOO cc. of alkaline permanganate solution (16 grams of pure potassium permanganate and 150 gfsdms sodium hydroxide dissolved in water and made to volume of I liter), connect with a condenser to which a receiver containing standard acid has been attached, and digest below the boiling point for 30 minutes. Then boil until 85 cc. of the distillate are obtained. If the material shows a tendency to adhere to the sides of the flask, an occasional gentle rotation is necessary during distillation. Peksin Digestion Method.-Weigh out an amount of sample containing o 0 2 5 gram of organic nitrogen. With raw materials transfer to a suitable 150-200 cc. flask and add IOO cc. of a pepsin-hydrochloric acid solution. Digest for 24 hours in a water bath a t a constant temperature of 40° C., keeping flasks loosely corked. At the end of the 2nd, 5th, 8th, and 11th hours, add 2 cc. of I O per cent. hydrochloric acid solution. Shake well after each acid addition. After the digestion filter the contents of the flask through single filters and wash until filtrate amounts to 400 cc. Dry and determine nitrogen in the residue by the Kjeldahl or Gunning method. With commercial fertilizers weigh the required amount on a filter, wash with about 2 0 0 cc. water, and treat residue as already described. The pepsin-hydrochloric acid solution is prepared by dissolving 5 grams of the -4rmour & Co. soluble scale pepsin ( I : 3000 U. S. P.) in 1000 cc. of twotenths per cent. hydrochloric acid. In using this permanganate method with commercial fertilizers it is necessary that the nitrogen present as ammonia and as organic nitrogen be first determined. The amount of material taken is based on the percentage of organic nitrogen present. Nitrates are unaffected by the treatment, and any ammonia orginally present in the sample is deducted from the result obtained before calculating the organic availability. Both nitrates and ammonia are given due credit under the total availability column. I n testing the availability of commercial fertilizers, particularly when ammonia salts are present, it is recommended that the water-insoluble organic nitrogen be determined. An amount of material equivalent to 0.045 gram of water-insoluble organic nitrogen is then weighed onto a hardened filter, washed with about 200 cc. of water (small portions a t a time), the residue dried a t about goo C. and transferred from the filter
