INDUSTRIAL AiYD ENGINEERING CHEMISTRY
860
paint has been obtained these superior qualities may have been due largely to the type of vehicle used. Literature Cited ( 1 ) Browne, Proc., Wood Painting Conference, Madison, Wis., September
13 and 14, 1929.
Vol. 22, No. 8
(2) Hartwig, Am. Paint Varnish Xffrs. Assocn., Circ. 866 (August, 1929). (3) Nelson, Proc. A m . SOL. Testing M a t e r i a l s , 22, Pt. 11, 485 (1922). (4) Nelson and Schmutz, Ibid., 24, Pt. 11, 923 (1924). ( 5 ) Nelson and Schmutz, I N D . ENC. CHEM.,18, 1222 (1926). (6) Nelson, Schmutz, and Gamble, Pror. 4 m. SOL. T e s t i n g M a l e r i a l s , 26, Pt. 11, 565 (1926).
Gases Produced b y the Decomposition of Nitrocellulose and Cellulose Acetate
Photographic Films'
John C. Olsen, Austin S . Brunjes, and Victor J. Sabetta T H E POLYTECHAIC INSTITUTEBROOKLYN, N. Y.
H E great loss of life resulting from the Cleveland hospital fire, reported to be due to the poisonous gases given off by the decomposition of the x-ray films, indicated the desirability of undertaking a thorough investigation of the nature and quantity of the gases given off by the decomposition of such films. As the investigation also included the explosive limits of the gases evolved when mixed with known amounts of air, it should be possible to establish rules for safe storage of cellulose films. It was anticipated that the character of the gases would be influenced by the presence or absence of air. For this reason the decomposition was effected in the entire absence of oxygen and in the presence of sufficient air to give a reasonable excess of oxygen. Decomposition Procedure
T
The apparatus employed consisted of a 140-cc. Lunge nitrometer. Weighed amounts of the samples being investigated were placed in small flasks and decomposition effected by heating the flask by means of a Bunsen burner. For the experiments in which absence of oxygen was desired, a 20cc. flask filled with nitrogen was employed. The nitrocellulose films decomposed very rapidly when heated to the decomposition temperature (about 154' C.), leaving a small oily or carbonaceous residue. This was further heated with the Bunsen burner in order to obtain decomposition as nearly complete as possible under such conditions as would prevail during the decomposition of large quantities of the material when high temperatures prevailed. After the flask had cooled to room temperature, the volume of the gas, as well as the temperature and pressure, was read. From these data the volumes of the gases a t standard conditions given off per gram of material could be calculated. On cooling the gases evolved from the acetate films and newspaper, a small amount (1 or 2 cc.) of condensate was obtained. It consisted of water and p-poligneous matter. A small amount of the soluble gases such as nitrogen peroxide and carbon dioxide was no doubt absorbed, but the error from this source could not be very large. The condensate from the nitro films was so small as to be negligible. Varying per'centages of air were then added to the gas and the mixture passed into a Hempel explosion pipet and ignited with an electric spark. I n this way the minimum amoust of air, as well as of gas, which would form an explosive mixture a t atmospheric pressure was determined. The method described for decomposition of the films in nitrogen proved satisfactory for both nitrocellulose and 1 Received March 3, 1930. Presented before the Division of Cellulose Chemistry at the 79th Meeting of the American Chemical Society, Atlanta, Ca., April 7 to 11, 1930.
cellulose acetate films. The behavior of the two types of films under these conditions differed considerably. The nitrocellulose films decomposed rapidly, leaving some residue. The cellulose acetate films melted a t low temperatures and decomposed gradually on being heated, leaving finally a considerable carbonaceous residue. A large quantity of distillate was obtained consisting of water, pyroligneous acid, and tarry matter. As the gases were allowed to cool before being measured or analyzed, the composition found is somewhat different from the composition of the hot gases, which would contain considerable amounts of the condensate in the vapor state. The decomposition of the films in the presence of excess air was carried out without difficulty in the case of the nitrocellulose product. A weighed quantity of the film was introduced into a 250-cc. flask, which was then connected to the nitrometer. As the decomposition of this product is very rapid, the heating was conducted so that a portion only of the sample was decomposed, after which on further heating the remainder decomposed. Under these conditions the first portion of the gas in the flask mixed with the air would be ignited in the flask by the heat developed by the decomposition of the second portion of the sample. I n some cases explosions occurred in the flask which were so violent as to cause loss of the sample. Undoubtedly under these or similar conditions a more or less violent explosion would undoubtedly result when larger quantities of the nitro film were decomposed. It was found impossible to produce an explosion in the Hempel pipet of any mixture of air and the gases obtained by decomposition of the nitrocellulose films in nitrogen. As the nitrogen would dilute the gas and reduce its explosibility, the experiment was repeated with gas produced by decompositions of the film in a flask filled with the gas produced by a previous decomposition. It was also found impossible to explode this gas. This behavior of the gas is undoubtedly due to the presence of the large volume of nitric oxide. When this gas was removed the residue exploded easily. When the cellulose nitrate film was heated in a test tube, it was not difficult to obtain ignition of the gases issuing from the mouth of the test tube. The temperature of the gas produced in this manner was high enough to produce ignition on contact of the gases with the air. It is evident that a t high temperatures these gases will burn in the air and that the temperature is high enough to produce ignition. Undoubtedly explosions would also be produced in this manner. The failure of the attempts to obtain an explosive mixture of these gases a t ordinary temperatures is undoubtedly due
August, 1930
IJVDUSTRIAL A N D ENGINEERING CHEMISTRY
to the fact that nitric oxide absorbs oxygen a t ordinary temperatures, producing N20R or KO*. So much oxygen was taken up by this reaction that a sufficient amount would not remain for the explosion of the carbon monoxide and the methane or other combustible gases present. At elevated temperatures this reaction does not take place so that the oxygen would be available for producing explosion. As the gases were only slightly colored when oxygen was absent, it is believed that only NO was present. When free oxygen was present the gas was undoubtedly largely N203or K204 a t room temperature. The cellulose nitrate film was also decomposed in a flask of 1000 cc. capacity, 0.2 gram of the film being used. This experiment was carried out in order to compare the results with those obtained on the decomposition of the acetate films when a much larger excess of air was required for the combustion. The marked difference between the nitrocellulose and acetate film in this respect is due to the fact that the cellulose nitrate film contained a considerable amount of combined oxygen which is not present in the acetate films. It was found impossible to burn the acetate films in a flask with excess air so that the oxygen would react with the cellulose acetate or the gases produced. I n thin films this material will not burn in the air when ignited. I n order to obtain samples of the gases evolved when this material burns, it is necessary t o keep the material a t a high temperature during combustion. This was accomplished by introducing the weighed sample in a porcelain boat into a hot combustion tube and passing a stream of air through the tube during the decomposition and combustion. Under these conditions the acetate film burned readily and the gases produced were collected without difficulty. Determination of Gases Produced
The commonly occurring gases, such as carbon dioxide, carbon monoxide, and oxygen, were determined by absorption in the well-known reagents. The hydrogen and methane were determined by explosion, the diminution in volume and the amount of carbon dioxide produced being noted. The nitric oxide was determined by absorption in a saturated solution of potassium dichromate to 5 volumes of which 1 volume of concentrated sulfuric acid had been added. Although the complete absorption of the nitric oxide was somewhat slow, this method proved entirely satisfactory and gave accurate results. Gases containing nitric oxides were measured over mercury to avoid the error due to absorption by water. Hydrocyanic acid was determined by passing the gas to be tested through a solution made up of equal volunies of a 10 per cent solution of ferrous sulfate, and a solution of caustic potash consisting of 1 part of caustic potash and 2 parts of water. The ferrocyanide formed was converted into Prussian blue and determined by comparison with the color obtained in the same manner from a standard cyanide solution. Chlorine and bromine were determined by passing the gas through a 10 per cent potassium iodide solution and titrating the iodine liberated by means of standard sodium thiosulfate solution. The flash and fire point of the samples were determined by placing 1gram of the material in a metal crucible immersed in an oil bath and covered with an asbestos cover having an opening of '/4 to inch (6.4 to 9.5 mm.) diameter. The oil was heated a t an approximate rate of 5" C. per minute. During the heating, tests were made about once a minute with a small flame and the flash or burning of the vapors was noted. The temperature was indicated by a thermometer in the oil bath. The crucible had a capacity of 50 cc., and was 30 mm. wide and 45 mm. high.
861
Composition of Samples Tested
The samples tested had the following composition: (1) Nitrocellulose and camphor with small amounts of urea and solvents such as butyl and ethyl alcohol and acetone. ( 2 ) Cellulose acetate and triphenyl phosphate and diethyl phthalate with small amounts of the solvents such as acetone and ethyl alcohol. (3) Cellulose acetate, monochloronaphthalene, a small amount of a nitrogenous compound, and small amounts of solvents, acetone, and ethyl alcohol. (4) Same material as (3) coated with photographic ,emulsion consisting of gelatin, silver bromide, and a small amount of silver iodide. ( 5 ) For comparison with ordinary cellulose material the gases evolved from ordinary newspaper were also analyzed.
Results
The results are given in the accompanying tables. Note-In the tables the figures given for total gases, in the case of films decomposed in an atmosphere of nitrogen, do not include the nitrogen initially present in t h e flask, but in the case of the films decomposed in excess of air the figures do include the air in which the film was burned.
Film Uncoated
S a m p l e 1-Kitrocellulose
DECOMPOSED IN ATMOSPHEREOF GAS FROM A PREVIOUS EXPERIMENT (0.350 gram in 50 cc.) A B C D Av.
Total gases: Cc. per gram Cubic feet per pound
372
%
%
%
%
%
Carbon dioxide Carbon monoxide Hydrogen Nitrous fumes (NO) Hydrocyanic acid Methane Nitrogen
12.0 32.4 0.0 42.4 0.22 1.6 11.4
17.1 29.8 0.0 37.2 0.12 2.3 13.5
14.8 35.2
13.5 39.0 1.3 33.2 0.31 3.4 9.3
14.8 34.1 0.4 38 0.23 2.4 10.7
B
Av.
% .14.2 7.0 0.7 0.6 3.5 0.96 73.7
640 10.31 % 14.8 8.8 0.04 1.2 3.4 0.6 71.2
368
385
390
0.1
39.0 0.25 2.3 8.4
a t room temperature. EXCESSAIR (0.250 gram in 250 cc. air) 7 1 7-11A A B
379 6.07
Explosive range-non-explosive
BURNEDIN
Total gases: Cc. per gram Cubic feet per pound
635
646
? I ? 7 " ,15.0 15.6 10.0 10.8 0.1 0.0 2.0 1.5 3.6 2.6 0.5 0.4 69.4 68.5 ,I
Carbon dioxide Carbon monoxide Hydrogen Nitrous fumes (NOz or N203) Oxygen Methane Xitrogen
% .14.4 7.4 0.0 0.6 4.0 0.5 73.1
Flash point O Ignition poi;lt,'.C.
154 154 BURXEDIS Excess AIR (0.2 in 1000 cc. of air) ---I-
A
Total gases: Cc. per gram Cubic feet Der pound
B
--11A
5409 86.6
Carbon dioxide Carbon monoxide Nitrous fumes (NOz or Nz03) Oxygen Unsaturated hydrocarbons Nitrogen
B
5440 87.3
Av.
5425 87.0
%
%
%
%
%
7.6 5.8 0.2 8.6 0.3 77.5
7.2 6.0
7.8 4.6 0.6 9.0
7.6 5.0 0.4 9.0 1.8 76.2
7.6 5.3 0.3 9.0 1.0 76.8
0.1
9.2 0.4 77.1
1.6
76.4
S a m p l e 2-Cellulose Acetate Film Uncoated DECOMPOSED IX ATMOSPHERE OF PI'ITROGES (3.00 grams in 20 cc. nitrogen) A B C D E A v . Total gases: 3 6 . 8 36.75 36.4 38.0 38.0 36.79 Cc. per gram Der uound 0 . 5 9 0 . 5 9 0 . 5 8 0 . 6 1 0.57 0.59 Cubic feet . .
7 Carbon dioxide Carbon monoxide Hydrogen Hydrocyanic acid Acids-acetic Explosive range: Max. per cent gas hlin. per cent gas
44.4 49.1 4.1
0
%
;:; 5.8
50 35
%
44.4 49.1 4.2 2.4 50 35
INDUSTRIAL A N D ENGINEERING CHEMISTRY
862
Total gases: Cc. per gram Cubic feet per pound
S a m p l e 2 ' (Concluded) BURNED IN EXCESS OP AIR (0.20-gram sample used) A B 5000 80.1
Carbon dioxide Carbon monoxide Oxygen Nitrogen Unsaturated hydrocarbons
Av. 5000 80.1
5000 80.1
%
%
%
6.8 4.8 10.0 77.8 0.6
7.0 5.8 8.2 78.6 0.4
6.9 5.3 9.1 78.2 0.5 212
Flash point, O C. Ignition point, C.
226
S a m p l e +Cellulose Acetate Film Uncoated DECOMPOSED I N ATMOSPHER8 OF NITROGEN (2.00-gram sample in 20 cc. nitrogen) A B C D Total gases: Cc. per gram 57.8 64.2 62.6 61.0 Cubic feet Der Dound 9.26 10.3 10.0 9.77 Carbon dioxide Carbon monoxide Hydrogen Halogens (Cl-) Hydrocyanic acid Acids-acetic Methane Explosive range: Max. per cent gas Min. per cent gas
%
%
%
42.4 44.2 3.16 0.13 0.43 2.4 7.12
43.7 40.3 8.8 0.06 0.38 2.6 4.6
41.5 41.6
%
Total gases: Cc. per gram Cubic feet per pound Carbon dioxide Carbon monoxlde Oxygen Nitrogen Unsaturated hydrocarbons
%
:i : :t9
6.6
0.40 2.50 6.4
7.4
37.2 37.2 38 35.0 35.0 35.0 BURNED IN EXCESS OF AIR (0.20-gram sample)
37.5 34.0
30
5000 80.1
5000 80.1
%
%
%
7.0 7.8 2.4 82.2 0.6
7.2
8.0 3.0 81.4 0.4
71 1 7.9 2.7 81.8 0.5
206 289
200 283
Flash point, O C. Ignition point, C.
5000 80.1
208 286
Acetate Film Coated DECOMPOSED I N ATMOSPHERE OF NITROGEN A B
Sample 4-Cellulose Total gases: Cc. per gram Cubic feet per pound
Av.
60 0.96
63 1.01
%
%
%
Carbon dioxide Carbon monoxide Hydrogen Halogens (Cl-) Hydrocyanic acid Acids-acetic Methane
42.3 35.1 8.5 0.08 0.83 2.55 10.6
41.5 33.7 7.7 0.14 0.68 2.62 13.6
41.9 34.4 8.1 0.11 0.75 2.58 12.10
Explosive range: Max. per cent gas Min. per cent gas
39 30
61.5 0.98
39 30
Carbon dioxide Carbon monoxide Oxygen Nitrogen Unsaturated hydrocarbons Flash point, ' C,. Ignition point, C.
5000 80.1
5000 80.1
5000 80.1
%
%
%
5.4 7.0 5.8 81.4 0.4
5.8 7.4 6.4 80.2 0.2
5.6 7.2 6.1 80.8 0.3
225 287
231 293
228 290
Discussion of Results
This investigation has shown that there are three highly toxic gases which may be present in the gases produced by the decomposition of cellulose films. These are carbon monoxide, nitrous fumes, and hydrocyanic acid. Less toxic gases which are produced include acetic acid fumes and hydrocarbons. Acetic acid fumes were evolved in moderate quantity from the acetate films and these fumes are irritating to the nose, throat, and eyes, but not highly toxic.
Av.
Total gases: c c . per gram Cubic feet per pound
55 0.88
%
%
%
%
Carbon dioxide Carbon monoxide Hydrogen Hydrocyanic acid Acids-acetic Methane Unsaturated hydrocarbons
49.4 36.5 4.4 0.0 1.6 8.1 0.0
43.2 41.5 0.0 0.0 1.6 11.5 2.2
44.7 37.1 10.1
47.2 37.1 7.1 0.0 1.6 5.4 1.6
46.1 38.1 5.4 0.0 1.6 7.6 1.4
45 38
46 38
Explosive range: Max. per cent gas Min. per cent gas
58 0.93
56 0.90
59 0.94
0.0
1.6 4.9 1.7
45 47 35 40 BURNEDIN EXCESSOF AIR (0.20-gram sample) 7 1 -II-A B A
Total gases: Cc. per gram Cubic feet per pound
5000 80.1
Carbon dioxide Carbon monoxide Hydrogen Oxygen Methane Nitrogen Unsaturated hydrocarbons
57 0.91
%
B
5000 80.1
Av. 5000 80.1
%
%
%
%
%
6.6 6.2 0.0 8.6 0.0 76.8 1.8
6.4 6.8 0.0 8.0 0.0 77.0 1.8
8.2 6.0 0.0 6.8 0.0 78.4 0.6
8.2 6.8 0.0 7.2 0.0 78.2 0.6
7.0 6.2 0.0 7.7 0.0 77.6 1.2
Flash point, O C. Ignition point, C.
265 285
S u m m a r y of Analyses SAMPLESAMPLES A M P L E SAMPLE S A M P L E 1 2 3 4 5 DECOMPOSED I N ATMOSPHERE OF NITROG8N
Total gases: Cc. per gram Cubic feet per pound
379 6.07
Carbon dioxide Carbon monoxide Hydrogen Nitrous fumes (NO) Halogens (Cl-) Hydrocyanic acid Acids-acetic Methane Nitrogen Unsaturated hydrocarbons
Total gases: Cc. per gram Cubic feet .~ per pound
36.79 0.59
61.4 9.83
57 0.91
%
%
%
%
44.4 49.1 4.2 0 0 0 2.4 0
%
42.5 42.0
41.9 34.4 8.1 0 0.11 0.75 2.58 12.10 ..,
46.1 38.1 5.4 0
37.5 34.0
39 30
46 38
5000 80.1
5000 80.1
5000 80.1
2.4 10.7
..
6.2 0 0.09 0.40 2.50 6.4
...
...
50 35
BURNEDIN
Carbon dioxide Carbon monoxide Nitrous fumes (NO) Oxygen Unsaturated hydrocarbons Nitrogen
61.5 0.98
14.8 34.1 0.4 38 0 0.23
Explosive range: Max. per cent gas Min. per cent gas
Flash point, C. Ignition point, O C.
BURNED IN EXCESS OF A I R (0.20-gram sample) Total gases: Cc. per gram Cubic feet . per . pound
Sample S N e w s p a p e r DECOMPOSED IN ATMOSPHERE OF NITROGEN (2.5-gram sample in 20 cc.) A B C D
Av. 61.4 9.83
Vol. 22, No. 8
1.6 7.5 1.4
..
EXCESSAIR
5425 87.0
5000 80.1
%
%
7.6 5.3 0.3 9.0 1.0 76.8
6.9 5.3 0 9.1 0.5 78.2
154 154
0 0.0
212 226
%
%
%
7.1 7.9 0 2.7 0,5 81.8
5.6 7.2
7.6 6.2
208 286
0 6.1 0.3 80.8
7 7 1.2 77.6
228 290
Carbon monoxide was given off in quantities ranging from 30 to 40 per cent by all of these films when decomposed in the absence of oxygen. The quantity of carbon monoxide produced from newspaper, which is fairly representative of wood and cellulose products generally, was approximately the same as from the films, so that, so far as this gas is concerned, the health hazard would be no greater than that arising from the decomposition of other cellulose materials. The nitrous fumes were given off in very large quantity from nitrocellulose films. This is a highly toxic gas and in the concentration produced might easily cause fatal results. This gas is wholly absent from the decomposition products of acetate films, and to this extent the health hazard from the acetate films is very much less. Both the concentration and the total amount of the nitrous gas are very much reduced when the nitrocellulose film is decomposed in excess of air. Hydrocyanic acid was produced from the nitrocellulose
August, 1930
INDUSTRIAL A N D ENGIXEERING CHEMISTRY
films as well as acetate films 3 and 4, the largest quantity being produced from sample 4. No hydrocyanic acid was found in the gases from film 2. As this is a highly toxic gas, the quantity produced would be a very serious health hazard. The gases from film 2 are therefore the least toxic and from sample 1, the nitrocellulose film, the most, dangerous gases are produced. The source of the hydrocyanic acid found in the gases from sample 4 is undoubtedly the gelatin used in the coating material. As gelatin is universally used in the coating of photographic films, it would appear that all types of films are liable to produce hydrocyanic gas when decomposed in the absence of air. The exact amount of hydrocyanic acid which would be obtained in a given case could be ascertained only by carrying out the test on a coated film. A small amount of nitrogenous material was also present) in film 3. By the Kjeldahl method 0.34 per cent of nitrogen was found. Other organic matJerial containing nitrogen would undoubtedly also give off hydrocyanic acid when decomposed in the absence of oxygen. Tests made in this manner on woolen clothing gave gases containing 1.5 per cent of this gas. When the films are burned in excess of air, the concentration of all the toxic gases is very greatly reduced. The percentage of carbon monoxide obtained in the absence of air varied from 34 to 49 per cent, while when excess of air was present this percentage dropped to from 5 to 8 per cent. On the other hand, the total amount of carbon monoxide increased very greatly when excess of air was used, as the volumes of gas produced per gram of material were much greater. For this reason the health hazard from carbon monoxide when excess of air is present was no doubt greatly increased. As both the concentration and total amount of the nitrous gases are very much reduced, the health hazard from this gas is very greatly reduced by the presence of excess of air. Hydrocyanic acid is absent from the gases of all the films when excess of air is present. The fire hazard from the acetate films is very much less than that from the nitro films and less than that from newsprint paper. This is due not only to the fact that the flash
863
and ignition point of these films is substantially higher than that of the nitro films, but also to the fact that the acetate films do not readily support combustion. As the acetate films will burn only when combustible matter is present, so that the temperature is maintained at the ignition point, these films furnish even less fire hazard than many other combustible materials. The gases developed from all the acetate films in the absence of air were explosive when mixed with air. Although there is some difference in the explosive range, the variation is not great enough to give a very great difference in explosive hazard from the gases. The gases produced from the nitrocellulose films in the absence of air contain enough gas such as carbon monoxide and methane to produce an explosive mixture, but the nitrous fumes which are present take up so much oxygen at ordinary temperature that it is impossible to explode these gases when mixed with air. It is well known that these gases will produce explosions when this film is decomposed, but this occurs only when the temperature of the gases is above the point a t which 30 absorbs oxygen to produce Nz03 or KO2. This temperature varies somewhat with conditions, but may be taken as between 150" to 200" C., so that if a large amount of the nitrocellulose film became ignited, the hot gases when mixed with air would undoubtedly explode. As might be anticipated, when these films decompose or burn in the presence of excess air, the gases produced are not explosive. It is obvious from these results that the most dangerous conditions of storage for these films is in confined, unventilated spaces, where the gases are not free to escape and where access to air is prevented. This is particularly true of the nitrocellulose films. As the acetate films do not readily burn, there would be no hazard unless these films were stored near other combustible material. The films should not be stored where they can become heated to the ignition point. This precaution is particularly necessary with the nitrocellulose films, which have a relatively low ignition point.
Nitrite Production in Soils' G. S. Fraps and A. J. Sterges TEXASAGRICIJLTURAL EXPERIMENT STATION, COLLEGE STATION, TEXAS
HE store of nitrogen in the soils, one of the most
T
important plant foods, is chiefly in organic compounds, from which plants cannot secure nitrogen. The organic compounds must first be decomposed, and the organic nitrogen changed to ammonia and nitrates, before it can be assimilated by plants. This fact has been known for a long time, and the process by which the nitrogen is rendered available has been given extensive study. It has been known that the change is effected by bacteria and that the nitrogen in the organic matter is first changed to ammonia, then to nitrites, and then to nitrates. It has generally been believed that the nitrite stage is temporary, and that the nitrites change quickly to nitrates, so that very little nitrites occur in the soil or in nitrification experiments. The writers have not found any notice of such occurrence in the literature, and little attention has been paid to nitrites. They shared this belief in regard to 1 Received April 26, 1930. Scientific Paper 104, Texas Agricultural Experiment Station. Presented before the Central Texas Section of the American Chemical Society, April 19, 1930.
nitrites and did not test for their presence, until recently they have found them to occur in relative large quantities in some experiments. Experimental
The nitrites were first detected in the course of some experiments planned to find the reason for the failure of certain soils to nitrify ammonium sulfate. These soils received 1 per cent calcium carbonate and 500 p. p. m. of nitrogen in the form of sulfate of ammonia. They had water equal to 50 per cent of their water capacity and were incubated a t 35" C. for 4 weeks. Some of these soils did not produce any nitrates from the ammonium sulfate, but they formed from 42 to 226 p. p. m. of nitrous nitrogen. The standard soil, which had a high nitrifying power, did not produce nitrites from the ammonium sulfate, but many of the soils produced both nitrites and nitrates. Portions of the soils which received carbonate of lime but no ammonium sulfate produced 6 to 98 p. p. m. of nitrous nitrogen. Thus both the original soil and the soil with
864
INDUSTRIAL A N D ESGINEERING CHEMISTRY
ammonium sulfate formed remarkably high amounts of nitrites. Several of the samples which produced nitrites were subsoils, but nitrites were produced in the surface soil of such important types as the Lake Charles clay loam (Harris County), Lake Charles clay (Harris County), and the Norfolk fine sand, of Camp County. A study of the rate of oxidation showed a rapid production of nitrites during the third and fourth weeks. A test on different quantities of water indicated that 50 per cent of the water capacity was more favorable to the production of nitrites and nitrates than 25, 35, or 80 per cent. Carbonate of lime increased the production of nitrites, just as it does nitrates, on some soils. The nitrites seemed to be quite stable in some of the soils studied. After 6 weeks there was an increase in nitrites in some soils and a decrease in others, but the soils still retained 29 to 360 p. p. m. of nitrite nitrogen. The nitrates and nitrites were extracted with water con-
Vol. 22, KO.8
taining calcium hydroxide. At first the analyses were made a t once, but experiments showed the solutions to be stable. After 7 days the solutions still contained practically the same quantities of nitrites. Conclusion
The work shows that nitrites may be present in considerable amounts in nitrification experiments. They also occur in field soils. The importance of this matter remains to be determined, in relation to nitrification work previously done, in relation to oxidized nitrogen in field soils, and in relation to plant nutrition. Both the scientific and the practical aspects of the occurrence of nitrites require investigation. Nitrites may be present in field soils, may be formed from fertilizers, may be of extensive occurrence, and may have influence upon plant growth. On the other hand, their occurrence may be restricted to special soils or under particular conditions. The matter is under active investigation a t the Texas Agricultural Experiment Station.
Effectiveness of Iodine in the Control of Smut on Oats‘ George M. Karns2 MELLON INSTITUTE OF INDUSTRIAL RESEARCH,
AYRE ( I ) has reported the successful control of smut on oats by the use of a dust treatment with iodine in fuller’s earth. Fuller’s earth, by its adsorptive action, holds iodine in a fairly stable state of combination over the entire dust surface, thereby aiding in the efficient distribution of the small amount of iodine used. It would seem, however, that the treatment might be more efficient if it mere possible to distribute iodine effectively without the use of any adsorbing material that might make it unavailable to even a slight degree to the treated grain and smut spores. With this consideration in mind, a treatment was devised in which the free iodine was brought into contact with seeds and smut spores with nothing present which would interfere with contact either by adsorbing the free iodine or by combining with it chemically. The treating material used was iodine in solution in carbon disulfide. Experimental Work
S
Seed infected with loose and covered smut was treated with a 10 per cent solution of iodine (resublimed crystals of Merck & Company) in carbon disulfide (U. S. P.). The treatments were applied by placing the sample in a large bottle and adding the desired amount of iodine solution directly from a pipet. The seed was then thoroughly mixed with the solution by rotating the bottle end over end for 5 minutes. After that time the color of the seed was uniform and the solvent had vaporized, leaving the grain in good condition to pass through a seed drill. During the treatment, which was made at room temperature, the igdine volatilized sufficiently to give a deep purple color. The iodine vapor so formed effected intimate contact comparable with that with a dust treatment of, say, molecular fineness. The seed, after mixing, was placed in paper bags and allowed to stand for a period of 48 hours. The treatments used varied from 0.07 to 1.0 ounce of iodine per bushel. In addition t o the iodine-treated samples, one sample was tumbled without treatment and another received the recomf
’Received April 30, 1930. Senior Industrial Fellow, Mellon Institute of Industrial Research.
UXIVERSITY OF PITTSBURGH, PITTSBURGH,
PA.
mended treatment of 3 ounces per bushel of a dust containing as its active disinfecting agent 1.6 per cent ethyl mercuric chloride. The tests were made on rod rows replicated ten times containing about 250 plants per row. Discussion of Results
The final smut counts revealed the smut infestation of the untreated seed to be quite low-about 1 per cent. After seed treatments of over 0.25 ounce of iodine per bushel, the smut infestation diminished markedly. With treatments of about 0.5 ounce of iodine per bushel smut infestation occurred to a degree which was approximately equal to that obtained after the standard treatment with ethyl mercuric chloride (about 0.3 per cent). Treatments of 1 ounce per bushel permitted only 0.04 per cent smut infestation. The similarity in effectiveness and cost of the treatment with 0.5 ounce of iodine and that with ethyl mercuric chloride indicate that further investigation of the iodine treatment is advisable. This report is a preliminary one, presenting observations from one year’s tests for the information of investigators in this field. The method of applying the treatment is applicable t o any solid disinfecting agent that is soluble in a suitable solvent. Conclusions
Iodine can be used effectively in the control of some forms of seed-borne smut, as has already been reported in the litera-
ture. Iodine can be applied easily and conveniently in the usual seed-treating apparatus by using a concentrated solution of this element in carbon disulfide. The treatment is of sufficient promise to justify more extensive trials against oat smut as well as other seed-borne plant diseases. Literature Cited (1) Sayre, Ohio Agr. Expt. Sta., B i n o n f h l y Bull. 13, 19 (1928)
