2 PO
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 CHEMISTRY
i t became necessary to reduce the box tests carried out in winter t o barrel conditions. This was done by assuming that the ratios of the ordinates of the barrel curves t o the box curves, obtained in summer, would remain the same during the winter. I n the construction of the curves, the initial carbon dioxide, water a n d calcium oxide contents were taken as zero. This renders them more easily used; i t then becomes necessary in order to determine the analysis after “air-slaking” only to add the water a n d carbon dioxide percentages from the curves t o the corresponding initial percentages as found by analysis. Similarly, the calcium oxide decrease as found from the curves is subtracted from the initial calcium oxide content. Exposure in shipment is usually for a short time so the time of exposure is indicated only up t o 30 days.
FIG.
STUDIES ON THE PHENOLDISULFONIC ACID METHOD FOR DETERMINING NITRATES IN SOILS By CHARLES W. DAVIS Received March 27, 1916
-4ccording t o TiemannI5* the estimation of no substance has so constantly occupied the attention of analytical chemists (“literally ‘enchained’ them”) as the determination of nitric acid; and Gi1112 says, “ N O determination requires more care, or occasions more trouble in its execution, or is more unsatisfactory when finished, t h a n the one in question.” Three general methods are used: I-The Zinc-Iron Method. 11-The Tiemann-Schulze Method. 111-The Colorimetric Method. The last two are direct methods. Other direct methods t h a t have attracted attention are those of Schlb~sing-Reichardt,~~ Crum-Lunge,ls and m r x Trommsdorf.lg These methods are best suited only when relatively large amounts of nitrates are present, and in water analysis this would necessitate the evaporation of a large quantity of water. The phenoldisulfonic acid method is another direct method t h a t has received much attention from soil chemists and soil bacteriologists during the past ten years. It originated with Sprenge120 in 1863, then for some time fell into disuse, but in 1885 it was revived by Grandval and Lajoux.21 Afterwards articles appeared by Johnson123 Lind,24 Smith,26 Bartram,26and Hazen a n d Clark.*’ Hazen and Clark27 as well as the German chemists have criticized the method severely. On recommendation of the Association of the German Experiment Stations,28 the Halle Station, after a n investigation as to the most reliable method for the determination of nitrates in soils and fertilizers, selected t h e ZincIron Reduction Method as being the most accurate. S O U R C E S O F ERRORS M E N T I O N E D BY V A R I O U S
VII-EFFECT OF EXPOSURE ON CALCIUM OXIDECONT.%NT OF BULK LIMEIN WINTERAND IN SUMMER
I n addition to t h e curves for total and available calcium oxide, curves giving the decrease in available calcium oxide on the dry basis are added. The calculation of analyses on the dry basis, i . e . , assuming the only loss in availability as being due t o carbonation, is a method satisfactory t o both t h e consumer and manufacturer of lime. The consumer pays only for the weight of lime as it leaves the lime plant when it contains practically no water. If it absorbs water on the road, it is merely converted into the hydrate, giving the same amount of available alkali. This slaking is of little consequence in many industries as the lime must be slaked before use. However, the carbonation represents a distinct loss, but as indicated on the curves calculated on the dry basis, there is a relatively small decrease i n the available calcium oxide content due t o this cause. Total calcium oxide, calculated on the dry basis, will show almost no decrease; the decrease in this case is simply due to t h e additional weight of the material in consequence of the absorption of the small amount of carbon dioxide. BERKELEY LABORATORY SECURITY CEMENT AND LIMECOMPAKY WSST VIRGINIA MARTINSBURG.
Vol. 9, No. 3
INVESTIGATORS
Leeds,32 FOX,*^ and Gill12 have found losses of nitrates on the water bath. Chamot a n d Pratt‘ report losses small on a water bath except when chlorides are present. Many writers have found interference in determinations in the presence of organic matter due in part to the masking of the yellow tint, besides certain flocculents as carbon black, potash alum,2 aluminum cream, copper sulfate, etc., used t o precipitate clay and organic matter occasions considerable loss in nitrates. Gill12 and Weston83 found losses in the presence of carbonates, while Chamot and Pratt’ claim losses of nitrates insignificant except when the quantities of nitrates are low or the alkalinity of the solution very high. Lipman and Sharp12 and Kelly7 call attention t o great losses in the determination due to presence of sulfates either in the solutions, or when sulfates as potash alum are used as a flocculent. 1 Part of Thesis submitted in partial fulfillment of the requirement for the Degree of Doctor of Philosophy in Agronomy in the graduate school of the Iowa State College, 1916. Numbers refer to Bibliography at end of article.
*
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
Mar., 1917
Chlorides seem to be t h e greatest interfering salt as evidenced by the investigations of Gill,l* Stewart a n d Greaves,lO and Chamot a n d Pratt.' The latter investigators also point out t h e interference of chloroform when used in soil solution t o prevent denitrification. They also show t h a t the presence of iron produces a brown or red solution, thus affecting the desired yellow color of the nitrophenoldisulfonate. REAGENTS AND APPARATUS
I-All reagents were tested for purity before using. a-The standard nitrate solutions were m'ade u p according t o t h e U. S. Bureau of Soilsll a n d used in the determination of nitrates in the first eight tables of results shown herein. The standard solution for the remainder of determinations was made after Hill's procedure.'j 3-Throughout the whole work*Chamot and Pratt's' modified phenoldisulfonic acid reagent was used. g-.The color was always developed with a concentrated potassium hydroxide solution. 5-Colors were compared in the regulation comparing tubes. The Sargent-Kennicolt colorimeter was used occasionally as a check on t h e work. In obtaining results as shown in Tables XV and XVI, the writer used a colorimeter manufactured by Lena a n d Naumann, New York. Known amounts of nitrates were measured from standard potassium nitrate solution by means of pipettes. EFFECT OF AMMONIA FUMES ON THE DETERMINATION
It was thought advisable t o ascertain if ammonia fumes in t h e laboratory would affect the results in the evaporating process on the water bath. Shallow dishes containing ammonium hydroxide were placed in the hood. Here samples of known nitrate content were evaporated and compared with samples evaporated in the laboratory. T h e ammonia fumes did not affect the results. I n a second experiment ammonium hydroxide was boiled in the hood with other samples, so t h a t the fumes were given off profusely, a n d these samples were evaporated; nitrates were determined and compared with samples evaporated away from the presence of ammonia. I n this second experiment no loss of nitrates was obtained.
291
EFFECT OF LIGHT AND TIME O N COLOR MATERIAL
Three solutions were prepared and the color developed. No. I was read immediately. No. z was left on the laboratory desk for 24 hours. It was thus exposed t o light for about 1 2 hours. No. 3 was placed in the dark room for 2 4 hours. From the results (Table 11), we conclude t h a t readings should be made without delay after the color is developed. TABLEI1 No. 1 , 2.. 3..,
. . ......, .. ... .
Mg. Nitrates Added Found 0.0040 0.0040 0.0040 0.0025 0.0036 0.0040
TREATMENT
Immediate reading Left on laboratory desk 24 hours Left in dark room 24 hours
METHODS OF APPLYING THE ACID
The next experiment was planned for the purpose of finding the effect of method of applying the phenoldisulfonic acid t o the dry residue in the nitrate determination. T h e acid was applied t o the salt as follows: ( I ) without stirring; ( 2 ) while stirring with a glass rod; (3) while hot.' No variation was found in the results. EFFECT OF TEMPERATURE WHILE POTASSIUM HYDROXIDE I S BEING ADDED
At various times we observed that in the application of potassium hydroxide for the purpose of developing the color much heat was evolved a n d sometimes violent action occurred. A series of experiments was carried on t o find the influence of temperature during the time the alkali was being added, with the results -given in Table 111. TABLEI11
No. TREATMENT OF SOLUTION 1.. , Kept at room temperature 2.. Heated by reaction 3.. Heated to 80' C. 4.. Heated to 100' C. 5 . . ,, At freezing temperature (on ice)
... ........... . .... ...
Mg. Nitrates Added 0.010 0,010 0.010 0.010 0.010
Mg.
Nitrates Found 0.010 0.010 0.010 0.010 0.0096
EFFECT OF CONCENTRATED SOLUTION WHEN POTASSIUM HYDROXIDE I S ADDED
After the application of phenoldisulfonic acid, when the salt is taken up with water, if the solution is highly concentrated, a precipitate is sometimes formed on the addition of KOH. This phenomenon suggested a series t o find whether the concentration of the solution at this point affected the results. Table I V shows no variation in results whether the solution just before the addition of potassium hydroxide was dilute or concentrated. TABLEIV
EFFECT OF DELAY I N APPLICATION OF PHENOLDISULFONIC No.
ACID AFTER EVAPORATION
A series of nitrate solutions was evaporated t o dryness, and after a delay of 2 4 , 48 and 7 2 hours, the phenoldisulfonic acid was added. T h e results showed that the delay in the application of the phenoldisulfonic acid had no effect whatever. h second series was prepared a n d equal quantities of the acid were applied immediately after evaporation a n d left in contact unequal periods of time. Table I shows the results of this experiment:
............. . . .. ...
Time in Contact Nitrates Added (GJ.. Nitrates Found (G.)..
.. ...,, ..
TABLEI 10 min. 0.004 0.004
30 min. 0.004 0.004
1 hr. 0.004 0.0035
24 tu& 0.004 0.0035
....... ....... .. ... 4 . . . . .. . 1 2 3..
SOLUTION Concentrated Concentrated Dilute Dilute
Cc.
25 25 50 50
MR. Nitrates Added 0.025 0.025
Mg. Nitrates Found 0.025
0.025 0.025
0.025 0.025
0.025
EFFECT OF VARIOUS SALTS
The writer carried on experiments t o ascertain the effects of NaC1, Na2S04, NazCOa, and mixed alkali salts on the loss of nitrates. These results confirm in a general way the results of Lipman and Sharp' in experiments with these same salts. EFFECT OF NaCZH302 Since Lipman2 as well as the writer found the effect of chlorides, sulfates, and carbonates t o decrease in
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
292
the order mentioned, t h e latter producing slight loss, if any, it was believed a weak acid with a strong base might not occasion any loss whatever. From I t o 2 0 mg. of sodium acetate were used in a solution containing 0 . 0 2 5 mg., no loss of nitrates being noticed. E F F E C T OF VARYING AMOUNTS O F STANDARD N I T R A T E SOLUTION AND UNIFORM AMOUNTS OF P H E N O L DISULFONIC ACID
A series with a nitrate content from
0 . 0 1 2 5 to 0 . 2 0 0 mg. was now analyzed using uniform amounts of phenoldisulfonic acid (2 cc.) throughout and compared with standard of 0.02j mg. having been treated with 2 CC. of phenoldisulfonic acid. The loss here with the sample lowest in nitrates was 4 per cent; the sample highest in nitrates lost 30 per cent. (See Table V.)
TABLEV-2
cc. PHBNOLDISULFONIC ACID ADDEDIN EACHCASE
M g . Nitrates Added. M g . Nitrates Found..
EFFECTS
OF
.........
0.0125 0.0250 0.0500 0.0750 0,1000 0.2000 0.0120 0.0250 0.0446 0.0625 0.0832 0.1388
VARYING
AMOUNTS
OF
NITRATE
WITH
VARYING AMOUNTS OF P H E N O L D I S U L F O N I C ACID
It was then decided t o increase the amount of phenoldisulfonic acid in proportion t o the amount of nitrates used: z cc. of this acid were used for every 0.025 mg. of nitrate. I n this way a greater per cent of nitrates was recovered from the artificial solution. Here the maximum loss was only I O per cent as compared with a loss of 30 per cent in Table V. Cc. Disulfonic Acid M g . Nitrates Added.. M g . Nitrates Found..
UEANS
OF
.. .. ,. ..
TABLEV I 1 2 4 6 8 16 0.0125 0.0250 0.0500 0.0750 0.1000 0.2000 0.0125 0.0250 0.0500 0.0695 0.0892 0.1800
PREVENTING
LOSS
OF
NITRATES
BY
THE
P H E N O L D I S U L F O N I C ACID METHOD
The results of the last two experiments demonstrated the fact that when the nitrate solution approaches I O O parts per million, or more, the loss of nitrates is great even when there are no interfering salts present, such as chlorides, sulfates, etc. On further investigation the writer was convinced t h a t much loss took place on the water bath as had been suggested by Lipmana and others. Three things suggested dissociation of KN03 on t h e water bath: ( I ) Slight or no loss of nitrates when sodium carbonate was added before evaporation; (2) recovery of more nitrates in soil solution when CaO is used as a substitute for alum in precipitating the clay in a soil solution. Not only does the use of CaO prevent the loss occasioned by the SO4radical, as in the case when alum is used as a flocculent, but the fact t h a t CaO is a n alkali prevents the loss of nitrates when the K N 0 3 dissociates by uniting and forming Ca(N03)2. An excess of alkali prevents the formation of nitric acid; (3) a bit of blue litmus paper was placed in the KNOa solution and i t was noticed to have turned red just before the solution became dry. This was the first clue t h a t furnished a solution for the prevention of loss of nitrates on the water bath. E F F E C T OF ADDIIiG AMhfOPiIA TO T H E POTASSIUM NITRATE SOLUTION B E F O R E EVAPORATION
Since i t had already been found t h a t ammonia fumes did not affect the loss or gain of nitrates, a series
Vol. 9, No. 3
was run in which each sample was kept ammoniacal during evaporation. The results were as anticipated as will be seen in Table VII. TABLE VI1
Mg. Nitrates Added.. M g . Nitrates Found..
.. .. .. ........ 0.0125 0.0125
0.0250 0.0250
0.0500 0.0500
0.0750 0.0760
0.1000 0.1010
I n the last experiment the five samples were compared t o a standard containing 0 . 0 2 5 mg. of KNOa, to which no ammonia had been added before evaporation as in case with the samples above. EFFECT OF POTASH A L U M [K2A12(S04)4] It was desired, if possible, to prevent loss occasioned
by the use of potash alum as a flocculent i n preparing the soil solutions for analysis. Lipman and Sharp,2in speaking of the phenoldisulfonic acid method in determining nitrates, say: “So t h a t while we deem it unsafe in the presence of considerable quantities of salts containing chlorides and sulfates t o determine nitrates by the phenoldisulfonic acid method, and would therefore recommend the Street modification of the Ulsch method36 in such cases, it is likewise clear t h a t many of the nitrate determinations made in soil laboratories, as is especially the case in soil bacteriological work, would not be interfered with by salts. I n such cases the method can be safely depended upon if potash alum, aluminum cream and bone-black are not used t o coagulate the clay and organic matter, since they have been found in the researches above described t o be productive of very serious errors.” Since ammonia is highly volatile, potassium hydroxide was substituted in keeping the solution alkaline on the water bath. This prevented the loss of nitrates on the water bath, so t h a t we were able t o recover all nitrates when the samples contained from j t o ~ j omg. of potash alum before evaporation. Lipman and Sharp,2 however, lost as high as 38 per cent of nitrates when they used t h e same amounts of potash alum without the addition of alkali. Table VIII shows a comparison of the writer’s and Lipman and Sharp’s results. MG. KsAIs(SOa)4 ADDED Davis Lipman 5.0 ... 12.5 12.5 25.0 25.0 50.0 50.0 100.0 100.0 150.0 150.0
TABLE VIII
MG. NITRATESADDED Davis Lipman 0.050 0:Ijis 0.050 0.025 0.050 0.025 0.050 0.025 0.050 0.025 0.050
M G . NITRATESFOUND
Davis
0:Ijis 0.025 0.025 0.025 0.025
Lipman 0.040 0.036 0.033 0.031 0.034 0.040
I n the previous experiment we have shown conclusively t h a t potash alum may be used as a flocculent in preparing t h e soil solution without incurring any loss of nitrates; then, since potash alum is undoubtedly the best flocculent in precipitating clay and organic matter, soil chemists and soil bacteriologists may safely continue its use as a flocculent, provided the solution is kept alkaline on the water bath. E F F E C T OF POTASSIUM C H L O R I D E B Y i i E W METHOD
We now attempted t o recover all nitrates in the presence of the chlorine radical. A series was prepared using from I t o 20 mg. KC1 and evaporated down with excess of potassium hydroxide as in the previous experiment. Here equal amounts of phenol-
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 CHEMISTRY
Mar., 1917
disulfonic acid were applied, but rather violent action took place. Hydrochloric acid fumes were noticeable. The results as shown in Table I X were startling. TABLEI X Mg. KCl Added Mg. Nitrates Added.. Mg. Nitrates Found..
.........
.........
1
0.025 0.0125
5 0.025 0.100
10 0.025 0.0050
20 0.025 0.0035
This loss of nitrates, of course, did not take place on the water bath, b u t a t the time t h e phenoldisulfonic acid was added. There was a noticeably large residue of potassium salts since potassium hydroxide had been added t o keep t h e solution alkaline and potassium chloride had been added t o t h e series. This was responsible for t h e violent action, thus liberating much hydrochloric acid which in t u r n brought about losses of nitrates at this point. EFBECT
OF
Ca(OH)2
IN
PREVENTING
THE
OF
LOSS
NITRATES I N T H E P R E S E N C E OF CHLORIDES AT T H E P O I K T W H E N T H E P H E N O L D I S U L F O N I C ACID I S APPLIED
T o avoid t h e violent action when phenoldisulfonic acid is applied it was decided t o substitute saturated calcium hydroxide solution for potassium hydroxide before evaporation Potassium chloride was added in amounts as before. When t h e solutions went t o dryness the residues were found t o be small, and we hoped the difficulty had been overcome, b u t we were much disappointed as the results in Table X will show. TABLEX hfg. KC1 Added Mg. Sitrates Added.. Mg. Nitrates Found
......... ..........
1 0.025 0.0250
5 0.025 0.0220
10 0.025 0.0195
20 0.025 0.0140
Here Kith 2 0 mg. of KC1 we obtained a loss of 44 per cent. This was better t h a n in t h e previous experiment, yet t h e loss was still too great. I n t h e l a s t experiment t h e chemical action was slight, b u t HC1 fumes were still noticeable when the acid was applied. Another trial was carried out as previously, except t h a t the phenoldisulfonic acid was added, slowly, drop b y drop, i n a n effort t o reduce t h e actioh. The results were as follows: 'PABIG
Mg. KC1 Added Mg. Nitrates Added.. hlg. Nitrates Found..
.........
.........
XI
1 0.025 0.023
5
0.025 0.023
10 0,025 0.019
20 0.025 0 014
Still another trial was made. Kos. I , 2 , 3 , and the standard were treated as before, i. e., 4 cc. of phenoldisulfonic acid were applied t o each, but in No. 4 an excess of phenoldisulfonic acid was used (about 1 2 cc.), a n d instead of adding the acid slowly i t was flooded over the dry residue quickly. The results were as follows : TABLE XI1 KO.
Mg. KC1 Added M g . Nitrates Added.. Mg. Nitrates Found.. . . . . . . . . .
.........
1 1 0.025 0,0225
2 5 0.025 0.0220
E F F E C T OF SODIUM SULFATE B Y IiEW NETHOD
Kelly' made a study of the effects of sulfates on t h e determination of nitrates, using Na2S04, (NH4)2SO4, and CaS04. Since his greatest loss occurred in t h e presence of Na2S04we carried out a n experiment with this same salt b y our new method. A comparison of our results with those of Kelly's is given in Table XI'II below.
4
20 0.025 0.0250
The treatment of No. 4 in Table XI1 shows means of preventing loss of nitrates a t the time of application of phenoldisulfonic acid. We now decided t o apply treatment of No. 3 in the above table t o a whole series. This was done and gave results free from loss of nitrates.
TABLE XI11 Mo. NITRATESADDED Davis Kelly 0.025 0.275 0.025 0.275 0.025 0.275 0.025 0.275 0.275
Mo. NaaSO4 ADDED Davis Kelly 1 1 5 5 10 10 20 20 40
..
Mo. NITRATESFOUND Davis Kelly 0.025 0.275 0.025 0.265 0.025 0.225 0.025 0.180 0.140
...
...
The writer recovered all nitrates, while Kelly lost from o t o 3 2 per cent when 20 mg., and 48 per cent when 40 mg. of sodium sulfate mere used. SULFATE AS F L O C C U L E N T
BAER'S NETHOD-COPPER
Baer14 used copper sulfate as a flocculent in preparing soil solutions for nitrate determinations. After the solution was clarified with copper sulfate, aliquot parts were measured out into Erlenmeyer flasks and the copper removed b y adding one gram of manganese oxide. The flasks were stoppered and gently warmed, and then filtered and washed, the filtrate was evaporated t o dryness and t h e nitrates determined b y t h e ordinary method. While CuS04 is an excellent flocculent t h e writer has never been able t o recover all nitrates even by the modified method. Since potash alum can be used as a flocculent and all nitrates recovered regardless of what other salts may be present, it seems t h a t there is no use of attempting t o use copper sulfate since it is necessary t o remove t h e copper before t h e determination can be made. APPLYING
NEW
METHOD
TO
THE
DETERMINATIOK
OF
NITRATES I K SOILS
As lime, copper sulfate and alum are considered good flocculents, a comparison of these was made by t h e new method. Three 50-gram samples were prepared and placed in Mason jars with 240 cc. of distilled water. Ten cc. of normal solutions of CaO, CuSO4 and K2A12(S04)4 were added, respectively. The samples were placed in a shaker for 30 minutes and t h e determinations made by t h e modified method. TABLE XIV FLOCCULEXT No. USED 1 . . . . . . . . . CaO 2.. cuso4 3.. KZAlZ(SO4)4
....... .......
Mg. Nitrates Found in Soil Solution 0.1514 0.925 0.1514
Another sample of soil was taken and lime a n d alum were used as flocculents. The acid solution with the alum was tried both by new and old method. TABLEX V NO.
3 10 0.025 0.0200
293
....... ....... ........
1.. 2.. 3.
FLOCCULEXT USED CaO KzAIz(SO4)r (New Method) KzAlz(SO4)4 (Old Method)
hIg. Nitrates Found in Soil Solution 0.1543 0.1543 0.1025
It was now suggested t h a t a comparison of t h e old colorimetric and modified colorimetric method be tried on several soils of varied nitrate content. Alum was used as a flocculent in each case. Samples of soil were taken from t h e following plots: Corn, fallow, oat stubble and alfalfa. The results are found in Table XVI.
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
294
TABLEX V I NO.
l............. 2.. 3 4..
KINDOF SOIL Corn Fallow Oats Alfalfa
....
............... ................. ...............
Mg. Nitrates in 100 Grams of Soil Old New Color. Method Color. Method 1.1639 I . 3403 0.8798 1,1639 1.1060 1.1245 2.0382 2.0382
You will observe t h a t by t h e modified method greater amounts of nitrates were found with each soil except in case of t h a t from the alfalfa plot; here t h e results were the same. Perhaps a heavy application of lime t o t h e soil before seeding t h e alfalfa rendered this soil strongly alkaline a n d the presence of t h e alkali in the soil prevented loss of nitrates on t h e water bath. Since in the last experiment t h e highest amount of nitrates found in the soil was over z mg., we tested t h e reproducibility of t h e method in artificial solutions of known nitrate content, usicg samples from 0.55 mg. to over z mg. All nitrates were recovered. Many investigators have asserted t h a t the colorimetric method is unreliable when large amounts of nitrates are t o be determined. This objection prompted a n experiment t o find if as much as 4 mg. of nitrate could be recovered in artificial solutions. All nitrates were recovered, thus showing t h e reproducibility of results. APPLICATION
OB
THE
MODIFIED
PHENOLDISULFONIC
ACID METHOD TO SOIL BACTERIOLOGICAL WORK
Frequently large amounts of nitrates are obtained in the nitrification experiments in soil bacteriology. We decided t o test the applicability of the method t o work of this kind. NITRIFICATION EXPERIMENT
Soil samples were taken from the soil plots of the Iowa Experiment Station. The plots were as follows: Soil No. IOI from timothy sod. The timothy had just been cut. Soil No. 102, peat plot. Two and eight-tenths tons of peat had just been added a n d kept fallow. Soil No. 107, check plot which had also been kept fallow. Two hundred-gram samples of each soil were placed were in tumblers in duplicate: zoo mg. of (“&SO4 dissolved in 60 cc. water a n d added to each tumbler. The incubation was carried on for three weeks a t room temperature. The tumblers were weighed every six days, and t h e water lost by evaporation was restored. At the end of three weeks t h e nitrates were determined as follows: The samples were placed in shaker bottles with goo cc. of water. Alum was used as the flocculent. After the samples had been shaken 30 minutes, zs-cc. portions, in duplicate, were evaporated t o dryness with 15 cc. of saturated Ca(OH)2 solution. T h e samples were treated with 5 cc. portions of phenoldisulfonic acid a n d compared with standard. Table X V I I shows the large amounts of nitrate found. T h a t large amounts of nitrates can be determined by the phenoldisulfonic acid method is here demonstrated. I n Table XVII from 6 t o 15 times as much
Vol. 9 , No. 3
TIEL*XVII
Son No.
........... .......
101.. 102...... 107..
...........
PLOT Timothy Peat Check
Mg. N Found as Nitrate per 100 g. Soil Duplicates 62.774 58.250 66.086 57.564 35.786 29.016
nitrate was determined as in t h e preceding experiments where known amounts of nitrates were used, Should soils contain larger amounts of nitrates than those used in Table X V I I one need only t o reduce t h e amount of aliquot part of soil solution taken for t h e determination. SUMMARY I-STUDIES
ON THE OLD METHOD
I-Ammonia fumes in t h e laboratory do not affect the result in t h e determination of nitrates by the phenoldisulfonic acid method. z-Light affects t h e color material and readings should be made without delay. 3-Applying phenoldisulfonic acid without stirring, stirring with a rod, or applying while hot shows no difference in results. 4-The temperature of the solution a t the time alkali is added t o develop color shows no variation in results except a t freezing temperature when a loss of 4 parts per million is found in a Ioo-part-per-million solution. 5-In checking up Lipman and Sharp’s work, “Studies on the Phenoldisulfonic Acid Method for Determining Nitrates in Soils,” we found the loss of nitrates occasioned by t h e addition of various salts t o correspond with t h e results of these investigators, the maximum loss being caused by the chlorine radical, and decreasing with sulfates and carbonates-the latter producing no loss. The addition of a weak acid (sodium acetate) produced no loss of nitrates whatever. 6-Potassium chloride added just before and just after t h e developing of t h e color by potassium hydroxide produced no loss of nitrates. 7-When uniform amounts of phenoldisulfonic acid (z cc.) were used t h e maximum loss of nitrates was 30 per cent; when proportional amounts of phenoldisulfonic acid were used (i. e., z cc. for each 0 . 0 2 5 mg.), the maximum loss was reduced t o I O per cent. 11-PREVENTING
LOSS OF NITRATES
BY
A
MODIFIED
METHOD
I-LOSS of nitrates was found t o take place on the water bath, and this loss was prevented by keeping the solution alkaline during the process of evaporation. z-The addition of two drops of HC1 in a solution containing z 5 parts per million of nitrates caused a loss of all nitrates. 3-By the modified method we were able t o prevent the loss of nitrates in the presence of chlorides, sulfates and carbonates. 4-When chlorides were present, a loss of nitrates was found t o take place on the addition of the phenoldisulfonic acid. This loss was overcome by evaporating the solution t o dryness with excess of Ca(OH)2,
Mar., 1917
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
a n d flooding a n excess of phenoldisulfonic acid quickly over the salt. j-All nitrates in a soil solution can be recovered regardless of the salts present therein. &Potash alum may be used as a flocculent in preparing t h e soil solution without producing a loss of nitrates. By the old method the loss of nitrates in the presence of certain salts was often as high as 50 per cent. 7-Since potash alum is a n excellent flocculent, soil chemists and soil bacteriologists need not hesitate t o employ its use, provided they use the modified phenoldisulfonic acid method. BIBLIOGRAPHY Schreiner anc Failyer, “Colorimetric, Turbidity and Titration Methods Used in Soil Investigations,” Bureau of Soils, U. S. Dept. Agri., Bull. 1
31. f C. B. Lipman and L. T. Sharp, “Studies on the Phenoldisulphonic Acid Method for Determining Nitrates in Soils,” Unio. Cal. Pub. i n Agr. Sci., Vol. 1, No. 2. :E. M. Chamot and D. S. Pratt, “A Study of the Phenoldisulfonic Acid Method for the Determination of Nitrates in Water-The Composition of the Yellow Compound,” Jour. A m . Chem. Soc.. Vol. 32, pp. 630-637. 4 E. M. Chamot. D. S. Pratt and H. W. Redfield, “A Study on the Phenoldisulfonic Acid Method for the Determination of Nitrates in Waterthe Chief Sources of Error in the Method,” Jour. A m . Chem. SOC.,Vol. 83, pp. 366-381. I E. M. Chamot, D. S. P r a t t and H. W. Redfield. “A Study of the Phenoldisulfonic Acid Method for the Determination of Nitrates in Water-A Modified Phenoldisulfonic Acid Method,” Ibid., Vol. 33, pp. 38 1-384. 8 H. H. Hill, “The Determination of Nitrates in Soil and Soil Extracts,” Annual Reporl of lhe V a . E x g l . Sla., 1911-12, p. 133. W P. Kelly, “The Effects of Sulfates on the Determination of Nitrates,” Jour. A m . Chem. SOC.,36 (1913), 775. Robert Stewart, “The Occurrence of Potassium Nitrate in Western America.” Jour. A m . Chcm. SOC.,33 (1911). 1952. R. Stewart and J. E. Greaves, “The Influence of Chlorine on the Determination of Nitrates by the Phenoldisulfonic Acid Method,“ Jour. A m . Chem. Soc., 36 (1913). 579. 10 R. Stewart and J. E. Greaves, “The Influence of Chlorine upon the Determination of Nitric Nitrogen,” I b i d . , 34 (1910). 756. 11 E. M. Chamot and D. S. Pratt, “A Study of the Phenoldisulfonic ComposiAcid Method for the Determination of Nitrates i n Water-The tion of the Reagent and the Reaction Product,” Jour. A m . Chcm. SOC., 31 (1909). 922. 12 A. H. Gill, “ O n the Determination of Nitrates in Potable Water,“ Jour. A m . Chem. Soc., 16 (1894). 122. 18 King and Whitson. WIS.Agri. Exp Sta.. Bulls. 86 and 93. 1 4 Baer, Thesis (unpublished) for M.S.in Agriculture, Univ. of Wisconsin (1914). Tiemann-Gaertner “Wasseranalyse,“ 3rd Ed., p. 168. 11 Schulze-Tiemann, Ber. d . chem. Gcs , 6 , 1041. 17 Schl6ssing-Reichardt. Z . anal. Chem.. 9, p. 24. 1: Crum-Lunge. Phil. Mag.. [3] 30, 426. 1) Marx-Trommsdorf, 2. anal. Chem , 9, 171. 10 Sprengel, Pogg. Ann., 121, 188. (1 Grandval and Lajoux, Comfit. rend.. 10, 1, 62. I* Fox, Tech. Quart.. 1, 1. 1) Johnson,Chem. News, 61, 15. “Lind, Chem. News, 68, 1, 15, 28. Smith, Analyst. 10, 197. Bartram, Jour. Frank. I n s f . . March‘l7, 1891. Hazen and Clark, J . Anal. Appl. Chem., 6, 1. 1: E x p . Sto. Record, 6, 404. 2) Fox, Tech. Quart., 1, 54. 80 Andrews. Jour. A m . Chcm. Soc.. 26, 388. Montenari, Gazz. chim. ital., 32, 1, 87, 1902. I* Leeds, A m . Jour. Sci.. [3] 7 , 197. ‘1 Weston, t a b . Uhiv. of Ill, 1909. Mercille, A m . Chem. Anal., 14 (1909). 303. Ulsch, New Jersey E W . Sta. Rcpl., 1892,~188-193.
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T B N N I W SST~A~T I ~ ~ N O R Y ASCHOOL L MEMPHIS.TENNBSSRB
295
A NOTE ON THE DETECTION AND ESTIMATION OF SMALL AMOUNTS OF METHYL. ALCOHOL By ELIASELVOVE Received January 24. 1917
I n applying the DenigBsl test for methyl alcohol
t o its colorimetric estimation, Simmondsz recommends t h a t the solution be always made up t o contain I O per cent3 ethyl alcohol. I n studying this method with the view of applying it t o the detection and estimation of methyl alcohol vapor in air it was found, however, t h a t the test can be made more sensitive b y reducing the proportion of ethyl alcohol from I O t o 0.5 per cent. T h a t this is so may be seen from the following experiment:‘ T o 2 . 5 cc. of a n aqueous solution of methyl alcohol containing 0.3 mg. methyl alcohol (No. I), in a 5 0 cc. Erlenmeyer flask, there were added 2.5 cc. of a one per cent aqueous solution of ethyl alcohol. T o another equal volume of this methyl alcohol solution (No. z ) , there were added 2.5 cc. of a 2 0 per cent aqueous solution of ethyl alcohol. Each solution was then treated with 2.5 cc. of a 2 per cent potassium permanganate solution and 0.2 cc. concentrated sulfuric acid and allowed to stand 3 minutes T h e excess of the permanganate was then reduced by mixing each solution with 0.7 cc. of6 a 9.6 per cent6 oxalic acid solution. Each solution was then further acidified by mixing with one cc. 6f concentrated sulfuric acid, allowed to cool t o room temperature, and finally mixed with 5 cc. of Schiff’s reagent. After standing 40 minutes, they were compared in the narrow form jo cc. Nessler tubes a n d i t was found t h a t whereas No. I had developed a very decided color, No. 2 was almost completely colorless in comparison. After standing a n hour, this difference was even more pronounced, the color 1
Comfit. rend., 160 (1910), 832.
* Analysf. 37 (1912).
16. All percentages of ethyl alcohol mentioned in this paper refer to percentage by volume. 4 The details of this experiment also give the essentials of the procedure which was finally adopted. To apply this for estimating the methyl alcohol In its aqueous solution, such as may be obtained by suitably passing through water a definite volume of air carrying methyl alcohol vapors, proceed as follows: Ascertain by a preliminary experiment the approximate amount of methyl alcohol in the solution. If this shows t h a t 5 cc. of it contain more than 1 mg. of methyl alcohol, dilute so as t o bring it within this limit. Mix 4.5 CC. of this diluted solution with 0.5 cc. of 5 per cent ethyl alcohol. Similarly prepare several 5 cc. portions of methyl alcohol solutions by diluting the proper amounts of a 0.1 per cent (0.1 g. to 100 cc.) aqueous solution of methyl alcohol to 4.5 CC. with water and then adding 0.5 CC. of 5 per cent ethyl alcohol t o each. These standard methyl alcohol solutions are made t o vary by 0.1 mg. methyl alcohol and the limits are chosen so as t o bring the unknown within their range. The unknown and the standards are then subjected exactly alike, preferably in 50 cc. Erlenmeyer flasks, to the permanganate treatment and the subsequent mixing with Schiff’s reagent as described above. The solutions are finally transferred into the narrow form 50 cc. Nessler tubes and the resulting colors are compared after the solutions have stood 40 minutes. 6 Simmonds used 0 5 cc. of the oxalic acid solution but this amount was found insufiicient t o reduce readily the excess permanganate when the proportion of ethyl alcohol was reduced t o 0.5 per cent, and hence 0.7 cc. was used in each case in order to make them exactly comparable. That this slight difference in the amount of oxalic acid used was not an important factor was proven by making a similar comparison in which the two cases differed only in this respect, when there was no appreciable difference in the 8
result. This strength oxalic acid is used by Simmonds but it was found that a 10 per cent solution (10 g. t o 100 cc.) answers the purpose just as well and for the sake of simplicity appears preferable. Hence in all the subsequent work a 10 per cent oxalic acid solution was employed. In cool weather this solution may need a little warming to redissolve the crystals formed on standing.
