492
ANALYTICAL CHEMISTRY
Table 11.
Sample No. 51 52 53 54 55 56 57 58 59
Specific Gravity of Foreign and Domestic Oil Shales Source South .Ifrica
Australia
60
61 62 63 64 65
Brazil Manchuria
66
67 68 69 70 71 72 73 74 75 76 77 78 79
80
81 82 83 84 85 86 87 88
Modified Fischer Oil Yield, Gal./Ton 33.3 45.0 45.6 68.8 99.8 28.2 82.9 114.7 135.9 147.2 31.3 33.6 26.1 26.3 38.6 18.1 55.9
Indiana
Kansas Kentucky Nevada Ohio Tennessee Texas Wyoming
56.8 4.8 8.6 9.7 12.4 14.3 10.9 8.1 5.6
11.5 16.4 10.2 22.8 7.1 9.8 14.7 52.8 3.7 7.3 7.4 39.8
Specific Gravity 600/600‘ i. 1.645 1.599 1,627 1. 5 1R
1.376 2,072 1 ,633 1.301 1, 2 3 1 1,258
1 . Flfi?
2.01li 1 .YO3 1.Yl.i I , j3!1
1.687 1.570 1.533
2,536
2.183 2.216 2.148 2.212 2,133 2.207 2.387 2.232 2.114 2.356 2.072 2.490 2.382 2.222 1.520 2.359 2.332 2.354 1.969
Table 11 gives the oil yields and specific gravities of 38 oil s l ~ n l tfrom ~ s four foreign countrit,s and eight states other than Colo-
rado. These data show that the numerical value of the oil yieldspecific gravity relationship for the specified Colorado oil shales is not applicable to all oil shales; however, they indicate that similar relationships may be obtained for oil shales from other specific areas. Furthermore, this rapid method of estimating the oil yield of shale may be useful for routine control purposes where time and equipment will not allow the determination of oil yields by the modified Fischer assay. SUMMARY
The relationship betwren the oil yield by the modified Fischer :may and the specific gravity of certain Colorado oil shales provides a practical means of estimating the oil yields of other oil shales from the same area. The oil yields estimated from the specific gravities of samples from the Green River formation in the Bureau of Mines oil-shale mine, Rifle, Colo., differed from the actual oil yields of the shales by a maximum of 3.0 gallons of oil per ton and by an average of 1.2 gallons of oil per ton of shale. The numerical value of the oil yield-specific gravity relationship for these Colorado oil shales was not applicable to all oil shales. However, it indicated that similar relationships may be obtained for oil shales from other specific areas, and this method‘of estimating the oil yield of oil shale may be adapted to rapid routine testing of oil shales where time and equipment will not allow assays to be made by the more reliable modified Fischer-retort assay method. This report represents the results of work done under a cooperative agreement between the Bureau of Mines, United States Department of the Interior, and the University of Wyoming. LITERATURE CITED
(1) Am. SOC. Testing Materials, Standards, Part 11,pp. 323-4, Designation C 135-40, 1946. (2) Engelhardt, D. von, Brennstof-Chem., 13, 10 (1932). (3) Gardner, E. D., Bur. Mines, Rept. Invest. 4269 (4pril 1948). (4) Stanfield, K. E., and Frost, I. C.. Ibid., 3977 (October 1946) ; 4477 (June 1949).
RECEIVED April 12, 1949.
Acid-Bleached Fuchsin Solution as Analytical Reagent ALBERT STEIGMANS 21 Manison St., Stoneham, Mass. [LUTED solutions of basic fuchsin, which are decolorized with sulfuric acid and to which formaldehyde is added after bleaching, have been recommended as a quantitative reagent for sulfur dioxide and thiols. The reagent is much less sensitive for thiosulfate. Other substances than thiols interfere with the sulfur dioxide reaction. Their reactions are less sensitive and slower for comparable concentrations than those of the thiols, but they are also more difficult to mask. The masking of thiols or thiosulfate can be achieved with mercuric chloride or with the chlorides of platinum and palladium( 11). The mercury-precipitated thiols and thiosulfates must be removed by filtration or centrifugation before the sulfur dioxide test is carried out; otherwise the sulfur dioxide reagent will react with the precipitate. The mercuric thiosulfate precipitate is even more reactive than thiosulfate itself, whereak the platinum and palladium precipitates are not reactive or much less so. Grant ( 1 ) was the first to point out unknown substances which interfere with the sulfur dioxide reaction and which, unlike the thiols, cannot be removed by masking with mercuric chloride. He removed the mercuric thiol precipitates by centrifugation before adding the sulfur dioxide reagent, which can be kept for a long time by working with two stock solutions.
Stock Solution I is made from 228 ml. of water, 22 ml. of concentrated sulfuric acid, 4 ml. of basic fuchsin (3% alcoholic solution), or 8 ml. of fuchsin in the case of Grant’s quantitative rocedure. The solution is made up with water to 400 ml. a n f a g e d 3 days. The precipitate which forms is decanted or filtered off, or, better still, the fresh solution is shaken with 150ml. of carbon tetrachloride, when the colloidal precipitate goes into the interface. This purification procedure with the aid of a separation funnel is useful under all similar circumstances. Stock Solution I1 is made by adding 5 ml. of 40y0 formaldehyde, to water to make 100 ml. Reagent. Before use, 10 parts of I are mixed with 1 part of 11. A sensitive reagent for ascorbic acid is obtained by taking 6 parts of 11. Grant ( 1 ) makes the interesting statement that the blanks of the tissues which he tested for sulfur dioxide give a slightly positive color reaction, although “it seems unlikely that it represents any naturally occurring sulfur dioxide.” The author’s experiments with gelatin, for which he introduced the test, have also shoiin interference by gelatin, even in the case of Eastman electrodialyzed gelatin and other gelatins that contained no sulfur dioxide. The interfering gelatin reaction is, however, much less sensitive and much slower than the reaction with sulfur dioxide. It could be still further subdued and almost inhibited by plati-
493
V O L U M E 2 2 , NO. 3 M A R C H 1950 num chloride, and although no amino acids present in gelatin were found to give the interfering reaction, cysteine and tryptophan were recorded as interfering with the sulfur dioxide test. The tryptophan trace reaction is, however, very slow. Enediols like ascorbic acid and reductone and o-dihydroxybenzenes like adrenalin, catechol, and ethyl hydrocaffeate, were found to give strong but slow to very slow color reactions with the reagent. These reactions, unlike the quick but fading thiol reaction of cysteine, are not inhibited by mercuric or platinum chloride, and it can therefore be assumed that untreated fruit juices or proteins which give the color reaction very distinctly, even in the presence of platinum or mercuric chloride, contain ascorbic acid,
an enediol, or o-dihydroxybenzene derivatives. The reaction with proteins needs further investigation. The presence of anionic wetting agents can also interfere nrith all the reactions which are given by acid-bleached fuchsinformaldehyde (sulfur dioxide, thiols, enediols, o-dihydroxybenzenes, sulfinic acids), but the anionic wetting agents are easily detected because they react slowly with Stock Solution I, and do not depend on the presence of formaldehyde. , LITERATURE CITED
(1) Grant, w. M., AX.41.. C H E Y . , 19, 346 (1947).
RECEIVED April 21, 1949.
Microdetermination of Iodine in Plant Material FORREST G. HOUSTON K e n t u c k y Agricultural E x p e r i m e n t S t a t i o n , I;exin,g:lort, Ii?.,
IIE simplicity inherent in the spectrophotometric procedure rused by Gross, Wood, and McHargue (1) for the determination of iodine in biological materials makes it well suited for the routine examination of agricultural crops. However, certain modifications which make it possible to determine smaller amounts of iodine extend greatly the usefulness of this procedure. 7
Table I.
Determination of Iodine Yo Transmittance
Iodine, 7 / 5 Ml. 0.10 0.25 0.50 1.00 2.50 5 00
a t 575 mp 96.7 92.0 84 0 70.0 41.0 li.O
E X P E R I Vw v r . k L
l3y decreasing the final volume from 50 to 5 ml., 0.1 micrograiii of iodine can easily be detected when a Model DU Beckman quartz spectrophotometer is used n-ith standard Corex cells having a 1-em. light path. However, the color developed is not suitably stable if the concentrations of the reagents are maintained a t the level used by Gross, Wood, and McHargue. The chief tlifficulty appears to be associated with a slow decomposition of tlir: potassium iodide, resulting in a gradual increase in the amount of starch-iodide chromogen formed. This difficulty is partially overcome by greatly decreasing thc amount of potassium iodide used. Further improvement is obtained by substituting phosphoric acid for sulfuric acid in order to maintain the pH of the solution at approximately 2.5. These changes do not significantly decrease the. sensitivity of the starch to iodine and the peak of maximum light absorption remains a t 575 mp. The color is stable for an indiifiriite time if the solution is kept in a bath of ice water until transriiittitiice readings are ready to be made. Cooling also increases the sensitivity of the starch iodide reaction, especially a t thc l o w r concentrations of iodine. Potato starch appears to be slightly bettc.1. than arrowroot starch, because the sol is less opalescent.
Collect the distillate in a 50-ml. Pyrex beaker containing 1 ml. of 0.2 A; sodium hydroxide. Five milliliters of 30oJ,phosphorus acid are sufficient to reduce the excess chromium trioxide completely and ensure recovery of the iodine present. Collect exactly 35 ml. of distillate. After the distillate has been evaporated to 5 or 10 ml., prepare a reference solution in another 50-ml. Pyrex beaker by adding 1 ml. of 0.2 N sodium hydroxide and 5 to 10 ml. of water. Oxidize the iodides as described by Gross, but use 1 or 2 drops of 0.2 AI potassium permanganate followed by 3 drops of 28% phosphoric acid, and continue the evaporation to a final volume of 2 or 3 ml. Transfer the contents of the beakers to small graduated cylinders or test tubes marked a t 5 ml. Immerse them in a beaker of ice water for 2 minutes. Add one drop of 5% potassium iodide, mix, and add 10 drops of 0.25% potato starch. Mix thoroughly, dilute to the 5-ml. mark, mix again, and immerse in the ice water. illlow the tubes to remain in the ice water a t least 2 minutes before reading the transmittance of the unknown against the reference solution. Make readings a t 575 mM in a cell having a 1-cm. light path. A curve prepared in the following manner indicates that the starch-iodide chromogen follows Beer’s law over the range of 0.1 to 5.0 micrograms of iodine. Standard solutions of potassium iodate containing from 0.10 to 5.00 micrograms of iodine and 1 ml. of 0.2 N sodium hydroxide are treated as described above for an unknown, except that distillation and the treatments prior t o distillation are omitted. When the micrograms of iodine per 5 ml. are plotted against the logarithm of the per cent transmittance a straight line is obtained which passes through 100% transmittance a t zero microgram of iodine. Table I shows the results obtained in this laboratory with a Model DU Beckman spectrophotometer.
Table 11. Kecoberj and Keproducibility Tests .\faterial Standard iodine solution Standard iodine solution 10 ml. of 10 h’ CrOs 30 ml. of 10 M CrOs Wheat straw I , 5-gram sample Wheat straw I , 1-gram sample Wheat straw 11, 1-gram sample
Knon n Iodine Content
I.ound by Thls Metllod
Y
Y
P.p.m
0.25 0.50
0.24 0.4(1 0.18 0.55 1.32 0.25 2.85
...
..
.. .. ..
... ,..
0:264 0.250 2.850
PROCEDURE
.I sample of dry plant material weighing 1 gram will be sufficient i n most cases. Oxidize the sample in the usual manner, using 10
ml. of 10 M chromium trioxide solution and 50 ml. of concentrated sulfuric acid. After cooling the digestion mixture add 50 ml. of distilled water and 2 or 3 large chips of porous tile or alundum.
If commercial chromium trioxide is used in this procedure, it is necessary to make a blank correction or to prepare 8, reference curve by carrying the standard iodine solutions through the same
