ANALYTICAL EDITION
March 15, 1935
93
TABLEIX. FACTORS TO CONVERT FISCHER LOW-TEMPERATURE ASSAY YIELDSTO BUREAUOF MINES-AMERICAN GAS ASSOCIATIONCARBONIZATION RESULTS COAL No.
500° C."
1W 2 3 4 5
6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 Mean Deviation
COKE
600' C.a
%
%
1.054 1.072 1.056 1.015 1.022 1.027 1.038 1.025 1.041 1.007
1.004 0.997 0.974 0.966 0.967 0.964 0.985 0.965 0.984 0.958 0.971 0.976 0.969 0.966 0.971 0.983 0.968 0.969 0.972 0.971 0.970 0.969 0.960 0.967 0.962 0.951 0.954 0.951 0.968 0.967 0.970
d d
1.031 1.024 1.025 1.018 1.028 1.030 1.029 1.033 1.036 1.035 0.991
1.019 1,009 0.992 1,002 1.012 1.027 1.024 1.026
500' C. % 0.63 0.59 0.56 0.43 0.44 0.56 0.52 0.52 0.71 0.67 d d
0.74 0.71 0.71 0.73 0.69 0.66 0.72 0.75 0.63 0.72 0.53 0.66 0.72 0.66 0.69 0.76 0.71 0.75 0.65
TAR
600" C.
WATER(LIQUOR) 600' C.
500' C.
%
%
%
0.69 0.61 0.54 0.63 0.61 0.64 0.71 0.72 0.79 0.67 0.73 0.74 0.76 0.71 0.64 0.73 0.76 0.74 0.63 0.77 0.61 0.76 0.53 0.70 0.75 0.68 0.80 0.78 0.73 0.74 0.70
1.31 1.41 1.24 1.22 1.29 1.25 0.78 1.40 1.22 1.13
1.33 1.18 1.54 1.65 1.65 1.64 1.14 1.51 1.26 1.20 1.24 1.34 1.09 1.20 1.30 1.40 1.27 1.20 1.13 1.22 1.02 1.11 1.55 1.44 1.12 1.58 1.36 1.43 1.40 1.46 1.33
0.15 0.32
d d
0.99 1.02 1.15 1.15 1.07 1.07 1.04 0.98 0.98 0.88 1.18 0.93 0.98 1.27 0.89 1.20 1.21 1.11 1.12
500' C. cu. f t . / t .
..
GAab 600' C. cu. ft./t.
..
..
LIGHTOILb'C 500' C. 600' C. GaZ./t.
Gal&
.. ..
..
d
..
.. .. .. .. .. .. ..
1.14 1.14 1.18 1.25 1.15 1.24 1.28 1.33 1.28 1.29 1.24 1.24 1.30 1.28 1.44 1.36 1.28 1.39 1.27
1.86 2.26 2.14 2.00 2.14 2.05 2.15 2.19 2.26 2.41 2.33 2.10 2.38 2.02 2.30 2.54 2.51 2.28 2.10 2.34 2.22
0.86 0.93 1.22 0.88 1.04 0.76 0.92 1.01 0.96 1.15 0.65 1.18 0.78 0.55 0.60 0.90 1.10 1.16 0.92
1.20 1.23 0.97 1.03 1.29 1.09 1.26 0.85 1.00 1.14 0.96 1.25 0.83 1.33 1.00 0.97 1.24 0.96 1.06 1.21 1.09
0.06 0.17
0.14 0.36
0.16 0.37
0.13 0.26
d
d
d
from
b 0
d
Mean Av. 0.012 0.008 0.08 0.06 0.13 0.034 0.22 0.17 0.34 Max. 0.046 BM-AGA carbonization temperature. Light oil not scrubbed from gas in Fischer, test for coals 1 to 10,inclusive. Light oil from gas plus fraction of tar distilling below 170' C. in BM-AGA test. Not determined by BM-AGA test.
(3) Fieldner, A. C., Davis, J. D., Thiessen, R., Kester, E . B., and Selvig, W. A,, Bur. Mines, Bull. 344 (1931). (4) Fieldner, A. C., Jones, G. W., and Holbrook, W. F., Bur. Mines, Tech. Paper 320 (1925). (5) Fischer, F., a n d Schrader, H., 2. anoew. Chem., 33,172 (1920). (6) King, J. G., a n d Edgecombe, L. J., Dept. Sei. I n d . Research, Fuel Research Tech. Paper 24 (1930). (7) King, J. G., Tasker, C., and Edgecombe, L. J., Ibid., 21, 29 (1929).
(8) United States Steel Corp. Chemists' Committee, "Sampling and Analysis of Coal, Coke, a n d By-Products," 3rd ed., p. 130, Pittsburgh, P a . , Bureau of Technical Instruction, Carnegie Steel Co., 1929.
RECEIVED November 13,1934. Presented before the Division of Gas and Fuel Chemistry a t the 88th Meeting of the American Chemical Society, Cleveland, Ohio, September 10 to 14, 1934. Published by permission of the Director, U. 8. Bureau of Mines. (Not subject to copyright.)
A Rapid Test for Chlorate Ion A Qualitative and Approximately Quantitative Test Especially Suitable for Work with Plant Extracts H. R. OFFORD,Bureau of Plant Industry, U. S. Department of Agriculture, Berkeley, Calif.
A
RAPID and convenient test for chlorates has been devised that is especially suitable for work with plant extracts. The method has been developed in connection with studies on the toxic action of sodium chlorate on Ribes L., currants, and gooseberries, and should be of value to other workers for the rapid determination of small amounts of chlorates. No clarification is necessary and only a single drop of the unknown solution is needed. The use of the proposed method permits the rapid examination of a large number of samples of plant material with a minimum of laboratory equipment and labor. The method depends upon the oxidation of ammonium thiocyanate in specially prepared test paper by the chlorate, with the production of a pale lemon-yellow to cadmiumyellow mixture of oxidation products of sulfocyanic acid. The characteristic color is rapidly developed when the test paper is heated in a drying oven a t 95" to 105" C. for 5 or more minutes. Poch (4) has previously reported this reac-
tion as a suitable qualitative test for chlorate. He added 1 cc. of 0.5 N ammonium thiocyanate to 1 cc. of the chlorate solution, evaporated to dryness, and heated to 140" to 150" C., confirming the presence of chlorate by the appearance of an orange-red coloration. If a constant quantity of ammonium t h i o c y a n a t e 4 e., segments of prepared test paper-is used under approximately equivalent temperatures, the intensity and shade of yellow a t equilibrium depend upon the concentration of the chlorate ion. This procedure, therefore, can be made roughly quantitative by comparing the color of the unknown against a set of known standards. ANALYTICAL PROCEDURE PREPARATION OF THIOCYANATE TEST PAPERS.Immerse Whatman No. 1 filter paper of convenient size in 3 N ammonium thiocyanate solution made up from c. P. chemical and distilled water. Remove the papers as soon as they are thoroughly impregnated with the thiocyanate and dry them on a cord sus-
INDUSTRIAL AND ENGINEERING CHEMISTRY
94
pended above a steam radiator] taking care to keep them out of contact with any metal surface. Turn the papers from time to time t o prevent uneven distribution of the thiocyanate. It is important to dry the papers with maximum air circulation at a temperature not exceeding 70" C. When dry place test papers in a clean envelope. If protected from light and dust they may be used for qualitative work for several months. It is not necessary t o keep the test papers in a desiccator, provided they are dried prior to we. TESTFOR CHLORATE.Dry the test paper at 60" C. for 10 minutes. Cut from this pa er a number of small strips which show no discoloration. To tiese duplicate test strips add one or more drops of the unknown solution. Place the strips of test paper on a clean watch glass and leave for 5 t o 30 minutes in a drying oven operating at any temperature over the range 95" to 105' C. A pale lemon-yellow to cadmium-yeIlow color s'hows the presence of chlorate. This color is produced over that area of the paper dampened by the drop of unknown solution. (The color nomenclature used in this paper is that of Ridgeway, 6.) CHEMICAL REACTIONS. It is well known that thiocyanate can be readily oxidized or reduced and that chlorate, particularly in acid solution, is an active oxidizing agent. The reduction of chlorate takes place in different steps and at various rates depending upon the reducing agent, temperature] p H of the medium, and light conditions. Essentially, however, the various steps in the reduction of chlorate may be summarized as: 2c103- +c d 302 (1)
+
Thus, in the reduction of chlorate ion, both chlorine and oxygen may be available as active oxidizing agents. In the present test, the heat decomposition reaction with ammonium thiocyanate proceeds as follows: 2NaC103 + NHhCNS ----f 2NaClf NH3 -b HCNS
+ 302 (2)
The thiocyanic acid rapidly forms polymers which in turn are converted to the mixture of yellow oxidation products. The composition of this mixture of yellow colored oxidation products depends on the concentration of the solutions employed, temperature] the p H of the medium, and the presence of other constituents.
Vol. 7, No. 2
SENSITIVITY OF TESTS The results given in Table I show that the method gives a definite test for as Iittle as 0.01 mg. per cc. of sodium chlorate, potassium chlorate, or calcium chlorate. Extracts or solutions containing more than 10 mg. per cc. of chlorate are apt to char the test paper if the oven temperature is greater than 95" C.; such solutions should, therefore] be diluted and an aliquot taken for analysis. With concentrations of 1 mg. or more per cc. the entire area of filter paper covered by the drop of test solution is usually a homogeneous color. In concentrations below 1 mg. per cc. the pale yellow color is most noticeable along the circular margin of the drop. The color produced by 1 mg. per cc. is apparent to ocular observation in diffused daylight. For smaller quantities the color may not be apparent to the naked eye unless the paper is held up before a bright light (preferably a bright sky) and viewed by transmitted light. The color produced varies from a pale lemon yellow (0.01 to 1mg. per cc.) through a lemon chrome (1to 10 mg. per cc.) to an orange or cadmium yellow (10 mg. per cc. or over). I n making quantitative tests the best gradation of color is obtained over the range of 0.1 to 10.0 mg. per cc. Between 0.1 and 1 mg. per cc. the presence of an additional 0.2 mg. makes an appreciable difference in the intensity of the coloration. Heating should be continued until no further intensification of the color takes place. Table I1 presents data covering experiments with Nitella expressed sap and extracts of R. petiolare leaves. Fresh Nitella cells were crushed and the expressed sap was freed of suspended solid organic material by filtration. The pale lemon-yellow color of the filtered sap did not prevent the ready detection of sodium chlorate in concentration as low as 0.05 mg. per cc. Tests were run on the Nitella-chlorate mixture at 24-hour intervals to note the disappearance] if any, of ohlorate. At the end of 7 days the color test commenced to be indefinite in the 0.05 mg. solution. The color of the hot sodium hydroxide extract of the R. petiolare leaves definitely
TABLEI. SENSITIVITY OF THIOCYANATE TESTPAPERS FOR QUALITATIVE DETERMINATION OF AQUEOUSCHLORATES SOLUTION TESTIUD Sodium chlorate Potassium chlorate Calcium chlorate Distilled water a
CONCN. OB CHLORATE SOLUTION Mg./cc. 0.01,Q0.10, 0.12, 0.16,0 . 2 5 0.50, 1.00 10.00,100.00 0.01,~0.10,1.00 10.00 0.01,'0.10 1 . 0 0
1o.od
Control Control Smallest quantity detectable in aqueow solution.
OVEN TEMP.
c.
98
103
105 98 103 98 103 98,100 103,105
The products formed on the filter paper consisted chiefly of canarine (HeCgNsS70) and pseudothiocyanic acid (HCSNgSs). Tests were also secured showing the presence of small amounts of isoperthiocyanic acid (H2CZNtSg) and hydropseudothiocyanic acid (H.GN&O). Temperatures below 100" C. and a large excess of the thiocyanate favored the formation of canarine, the true dyestuff (soluble in alkalies and alkali borates), a t the expense of the other pulverulent orange-yellow nondye (insoluble in alkali). Higher temperatures and a slight excess of thiocyanate favored the production of the nondyes a t the expense of canarine. Poch (4) worked with aqueous solutions a t temperatures of 140' to 150" C. in conducting his test for chlorate] and reported that the orange-red substance was pseudothiocyanic acid. Isoperthiocyanic acid was identified by tests described by Stokes and Cain (7) canarine and pseudothiocyanic acid by data of Goldberg (I), and hydropseudothiocyanic acid following a report by Melis (2).
PERIOD IN OVEN Min. 85
RESULTOB T ~ S T Pale lemon yellow to cadmium yellow.
15
Positive in all cases
5 Same as sodium ohlorate
30
5 30 5 85,30 15, 5
Same a0 sodium chlorate ,
No color No color
interfered with the detection of chlorate in concentration below 0.5 mg. per cc. On diluting this dark brown extract with ten volumes of water, a light amber-colored solution was obtained which permitted the detection of chlorate in concentration of 0.05 mg. per cc. Different combinations of oven temperature (95" to 105" C.) and periods of heating (5 to 240 minutes) were used in the tests reported in Tables I and 11. Thus, it was found that an oven temperature of 98" to 100" C. with 30 minutes or more of heating represented more favorable conditions for the determination of l mg. or less of sodium chlorate than high temperatures and shorter exposure. If chlorate is present in amounts greater than 1 mg. per cc., 5 minutes in the oven a t 103" to 105" C. brings out the color most satisfactorily. In subsequent experiments positive tests for chlorate were obtained from unfiltered and unclarified cold-water extracts of 1-gram samples of roots, stems, leaves, and petioles of R. petiolare. These plants had been allowed to stand for vary-
March 15, 1935
ANALYTICAL EDITION
Y5
ing periods in dilute sodium chlorate solutions. Extracts same lot of ammonium thiocyanate and to use extracts of made from untreated plants showed no coloration which, control plants to which known amounts of sodium chlorate have been added. might have been confused with the chlorate color. OF THIOCYANATE TESTPAPERSFOR QUALITATIVE DETERMINATION OF AQUEOUSCHLORATE IN MIXTURE TABLE 11. SENSITIVITY WITH PLANTEXTRACTS
NATUREOF TESTSOLUTION Nitella expressed sap.
SODIUM CHLORATE ADDEDTO TIWTSOLUTION MQ./cc.
(Six series a t 24-hour intervals)
R. petiolure leaves macerated in cold water. Filtrate
R. petiolure leaves macerated in cold NaOH (6 N). Filtrate R. petiolare leaves macerated in cold HC1 (6 N ) . Filtrate
0 0 5 , O 0 50, 5 . 0 0
Control 0 05,“0.50, 1.00, 10.00, 100.00 Control 1.00,10.00 100.00 Cont;ol 1.00,10.00 100.00 contrh
R. petdolure leaves boiled in NaOH (6 N ) . Filtrate
0.05 0.50
5.00,50.00
Control
R. petiolare leaves boiled in NaOH (6 N),filtrate diluted with 10 volumes of distilled water
0.005 0.05O
0.50 5.00 Codtrol a
RESULTOF
TEST
Pale lemon yellow to lemon chrome. Positive in all cases No color Palelemon yellow to cadmium yellow. Positive No color Buff yellow to antimony yellow. Positive Pale pinkish buff. No yellow tinge Pale lemon yellow to cadmium yellow. Positive No color Pinkish buff. Indefinite Cream buff. Fair Buff yellow to antimony yellow. Positive Cinnamon buff. No yellow tinge Pale cinnamon ink. No yellow tinge Cream buff. &ir Pale lemon ellow to lemon chrome. Positive Pinkish b u g No yellow tinge
Smallest amount detectable in light green or light brown plant sap.
EFFECTOF OTHERCHEMICALS ON TEST. I n the present procedure, yellow colorations, somewhat similar to those described for chlorates, are produced on the test paper by bromates, iodates, peroxides, persulfates, hypohalites, and halogens. Perborates and borates do not interfere. Colored substances such as permanganates and dichromates mask the color of the chlorate test, while salts of iron, cobalt, copper, and molybdenum produce characteristic colors. For example, copper sulfate produces a green-yellow color, cobaltous chloride a pale cerulean blue, and sodium molybdate a magenta which changes in a few hours to a cedar green. A satisfactory test for 0.1 mg. of chlorate per cc. may be made in sulfuric, nitric, acetic, oxalic, or sodium hydroxide solutions as strong as 0.1 N . The test is unsatisfactory, of course, in any solution that is corrosive enough to injure the test paper. Since chlorides are frequently used as diluents of the sodium chlorate sold for weed-killing purposes, the sensitivity of the procedure was tested for acid and alkaline mixtures of sodium chloride and sodium chlorate. It was found that chlorate in concentration of 0.1 mg. per cc. could be readily detected in acid or alkaline solutions containing 100 mg. per cc. of sodium chloride. I n testing the applicability of the method for the determination of chlorate in mixture with the ingredients of typical nutrient water cultures comprising nitrate, phosphate, and sulfate, it was found that a definite color was obtained for 0.2 mg. of chlorate. I n neutral or nearly neutral medium 0.1 mg. of chlorate per cc. is the limit of sensitivity in the presence of equal or double the amount of cyanide, thiosulfate, and sulfite. Large excesses of thiosulfate and sulfite (10 times) definitely interfered with the detection of 0.1 mg. per cc. The presence of any appreciable quantity of free iron will tend to mask the light yellow color produced by low concentrations of chlorate. However, extracts made from plants which had been grown on nutrient solution containing iron tartrate did not exhibit this interference. A c. P. grade of ammonium thiocyanate usually contains about 0.0001 per cent of iron. This is sufficient iron to discolor test papers left exposed to the air, but it does not impair their sensitivity, since the pink coloration always disappears when the papers are heated. Indeed, it has been observed that this slight trace of iron accelerates the oxidation of thiocyanate by chlorate. Sharma (6) and Patten and Smith (3) have made similar observations regarding the role of iron in the oxidation of ammonium thiocyanate. In quantitative work it is advisable to prepare standards from test papers made from the
SUMMARY
A method has been devised for the detection of small amounts of chlorate which is especially suitable for work with plant extracts. Ammonium thiocyanate in test paper is oxidized by the chlorate compound with the production of yellow oxidation products of thiocyanic acid. The yellow coloration can be made roughly quantitative as well as qualitative by comparing the color of the unknown against the color of standard test papers. Under the conditions of the test the oxidation products consist largely of canarine and pseudothiocyanic acid, with small amounts of hydropseudothiocyanic acid and isoperthiocyanic acid. The sensitivity of the test and the influence of other constituents on the accuracy of the method are also discussed. Halogens, bromate, and iodate, hypohalites, persulfates, peroxides, and cupric salts give somewhat the same coloration of the thiocyanate test paper as the chlorates. LITERATURE CITED (1) Goldberg,A., J . prakt. Chem., 63,465 (1901): 64,439 (1901). (2) Melis. €3.. Ann. chim. amlicata. 17.74 (1927). (3j Patten, C. G., and Smith, H. D.,’TraAs. Roy. SOC.Can., (3), 22, 111,221 (1928). (4) Pooh, P., Anales 8oc. espaa. @s. qu‘im., 20, 662 (1922). (5) Ridgeway, R., “Color Standards and Color Nomenclature,” Washington, D. C., 1912. (6) Sharma, B. S., Z. anorg. allgem. Chenz., 187,237 (1930). (7) Stokes, H. N., and Cain, J. R., Bull. U.S. Bur. Standards, 3, No. 1 (1907). RECEIVED September 5 , 1934. The work has been made possible through the cooperation of the College of Agriculture (specifically the Forestry Division), University of California, with the Division of Blister Ruat Control. Effective December 1, 1933, this activity was transferred to the Bureau of Entomology and Plant Quarantine.
CORRECTIONS. In the paper on “Double-Acid Method of Optical Analysis of Beet Products” [IND.ENQ. CHEM.,Anal. Ed., 6, 193 (1934)l the following errors occurred: On page 197 in the last paragraph, sixth line from the bottom, and on page 199, in the fourth line of the next t o last paragraph, the density of the hydrochloric acid should be stated as “1.1029” instead of as “1.029.” On page 196, in line 6 of the paragraph following Table IV, the specific conductance of the sugar should be stated as “0.26 X 10-6 at 25” C. in a solution containing 25 grams per 100 ml.” instead of “0.26.” S. J. OSBORN J. H. ZISCH
