560
ANALYTICAL CHEMISTRY REFERWCES
Table VI.
Results Obtained with Calcium Acetate and Lead Method
Type of Paper Schleicher and Schiill No. llOlL Macherey, Nagel No. 613 Oxidized Whatman No. 1
Table VII.
Carboxyl Content, hleq./Gram Calcium acetate Lead acetate 0.08 0.10 0.65
0.046
0.064 0 420
Carboxyl Content of Some Filter Papers
Type of Paper Whatman N o . 1 Methylester of Whatman KO.1 Oxidized Whatman No. 1 Methylester of oxidized Whatman No. 1 Whatman No. 4
Carboxyl Content, Meq./Gram 0,008 0.002 0.420
0.017 0.007
0.007 0.035 0,046 0.064
Davidson, G. F., J . Teztile Inst., 39, T 6 5 (1948). Ibid., p. T87. Ibid., p. T93. Farrar, J., Neale, S. Ll., and Williamson, G. R., A’ature, 168, 566 (1951). Foreiati, F. H., Rowen, J. R., and Plyler, E. K., J . Research Nail. B u r . Standards, 4 6 , 4 (1950).
Francis, C. V.,ANAL. CHEM.,2 5 , 941 (1953). Geiger, E., and Kuneler, P., Helu. Chim. Acta, 28, 283 (1945). Haller, R., and Lorenz, F., Melliand Tertzlber., 14, 449 (1933); 1 2 , 2 5 7 (1931).
Heymann, E., and Rabinov, G., J . P h y s . Chem., 4 5 , 1 1 5 2 (1941). Hirsch, P., Rec. trav. chim., 71, 525 (1952). Kaye, 11.A. G., and Kent, P. W., J . Chem. SOC.,1953, 79. Kullgren, C., Svensk Papperstidn., 51, 47 (1948). Kunin, R., and Barry, R. E., I n d . Eng. Chem., 41, 1269 (1949). Lautsch, W.,llanecke, G., and Broser, W.,2. Saturforsch., 8b, 232 (1953).
Liidtke, M., Biochem. Z., 233, 25 (1931); 268, 372 (1934); 285, 78 (1936): Z . anuew. Chem.. 4 8 . 650 (1935).
nitrogen dioxide-oxidized paper showed a faint color and the methyl esters of these papers colored strongly. It is evident that oxidized cellulose contains a certain quantity of lactone groups which are readily split open. Such groups can also occur in native cellulose; therefore, no conclusions should be drawn regarding the acid value of the ionizable groups by extrapolation of titration curves (33). I n titrations with an excess of alkali the splitting of lactone is probably not the principal reaction involving the liberation of extra carboxyl groups. Carbonyl groups can, in an alkaline medium, be subject to conversions resulting in the formation of carboxyl groups. Furthermore, cellulose is very sensitive to oxidation a t a high p H value. Apart from difficulties arising a t very high lactone concentrations, the chromatographic determination of carboxyl groups carried out by means of lead ions seems to be a rapid and reliable method for determining the carboxyl content of filter paper. ACKNOWLEDGMENT
The authors express their sincere thanks to G. J. Schuringa for his encouragement, to J. R. H. van Nouhuys, director of the Vezelinstituut T.S.O.(Fiber Research Institute T.X.O.), for his permission to publish the results of this investigation, and t o R . C. Blume and G. S. Milford for discussing and-correcting the manuscript.
AIcGee, P.’A., Fowler, W.F., Jr.; and‘Kenyon, W.O., J . A m . Chem. SOC.,6 9 , 3 4 7 (1947).
Kabar, G. hl., and Padmanabhan, C. V., Proc. Indaan Bcad. Sci., 31.4,371 (1950).
Neale, S . >I., and Stringfellow, W. A.. Trans. Faradav S O C . 31, , 1718 (1936);33,881 (1937).
Nevell, T. P., J . TertiZeInst., 42, T91 (1951). Roudier, A . , Assoc. tech. i n d . papetihre, Bull., 4 , 118 (1953). Rowen, J. W., and Plyler, E. K., J . Research NatZ. B u r . Standards, 4 4 , 3 1 3 (1950).
Sarkar, P. B., Chatterjee, H.. hIaeundar, A. K., and Pal, K. B., J . SOC.Dyers Colourists, 63, 229 (1947).
Schdnfeld, T., and Broda, E., Mikrochemie aer. Mikrochini. Acta, 3 6 / 3 7 . 5 3 7 (1951).
Schute, J. B.; thesis, University Leiden, p. 90, 1953; S a t u r e , 171,839 (1953).
Sookne, A. AI., Fugitt, C. H.. and Steinhardt, J., J . Research S a t l . B u r . Standards, 2 5 , 61 (1940).
Sookne, A. >I., and Harris, AI., Ibid., 25, 47 (1940). Ibid., 2 6 , 2 0 5 (1941). Weber, 0. H., 2. prakt. Chem., (K.F.),158, 33 (1941). Whistler, R. L., llartin, -4.R., and Harris, M.,J . Rescarch S a t l . B u r . Standards, 2 4 , 13 (1940). Whittaker, V. P., and Wijesundera, S., Biochem. J . , 51, 348 (1952).
Wieland, Th., and Berg, A , , Angew. Chem., 6 4 , 4 1 8 (1952). Wilson, K., Srensk Papperstzdn., 5 1 , 4 5 (1948). Rijk, A. J. A. van der, and Studer, ll.,Helv. Chim. Acta, 32, 1698 (1949).
Yackel, E. C., and Kenyon, W. O., J . A m . Chem. S O C . ,64, 121 (1942).
RECEIVED for review April 28, 1954. .4ccepted October 25,
1954.
Rapid Determination of Water in Silicate Rocks LEONARD SHAPIRO and W. W. BRANNOCK
U. S.
Geological Survey, Agricultural Research Center, Beltsv;lle,
A rapid and simple method for the determination of total water in silicate rocks has been developed by modifying the Penfield procedure. In this method, the time required for a single determination has been reduced to less than 10 minutes. Comparison of the data obtained by this modification and the Penfield method indicates the same degree of accuracy.
T
H E value obtained for total water in a rock analysis includes water of crystallization, water held uncombined in the grains or on their surfaces, and water formed, as the result of heating, from hydrogen or hydroxyl groups present in regular atomic arrangement in molecular or crystal structure. The determination of water in rocks invariably involves initial
Md.
ignition of the powdered sample, either by itself or with a flux, and subsequent measurement of the expelled water. The expelled water can be measured in several ways. It can be absorbed in a desiccant in a preweighed tube (I), condensed and determined by measurement of volume (S), or measured as in the method of Penfield ( 4 ) , which is more widely used than any other method. In the Penfield method the upper part of the glass tube, containing the condensed water expelled from the sample powder, is separated by fusion from the lower part of the glass tube, containing the powder. T h e part containing the water must be allowed t o reach thermal and moisture equilibrium with the laboratory air before weighing. A second time-consuming heating and equilibration step is necessary in getting the final or “dry tube” weight to subtract from the initial weight to obtain the amount of water in the sample. Because of these time-consuming steps, the
V O L U M E 2 7 , NO. 4, A P R I L 1 9 5 5 Penfield method, though it takes less time and is simpler than other methods, usually requires 30 to 40 minutes for a single determination. -4value for water can also be obtained by determination of loss on ignition. Values so obtained vary in accuracy from good to poor depending upon the composition of the samples. The U. S. Geological Survey has need for analyses of many rock samples and hap described rapid methods for the determination of the major constituents of silicate rocks ( 6 ) . I n this described analysis an “ignition loss” determination is used in lieu of a water determination. For samples in n hich carbonate and ferrous iron concentrations are low, values based on ignition loss determination are entirely adequate. When the samples contain appreciable carbonate or appreciable ferrous iron or both, direct determination of mater is desirable. The method described-a modification of the Penfield procedure-requires less than 10 minutes per sample and was developed to meet the need for a rapid method for the determination, I t consists of expelling the uater from the sample in a test tube, absorbing the a a t e r on a preLwighed strip of filter paper placed inside the tube, and subsequently reweighing the paper. The difference in the weight of the paper before and after absorption of the water is then used, after correction for water lost in handling, to calculate per cent water in the sample.
561
Table 1.
Relationship betw6en Water in Sample, Absorbed and Computed Waters Error, hlg.
I n sample
Water, Mg. Absorbed
4.0 L O
3.2 4.8 7.4 9.0 12.2
8.0
10.0 13.4
20.0 26.8 40.2 50.0
67.0 80.0
100.0 134.2
18.5 25.5 39.0 48.0 65.9
78.2 98.2 132.1 147.2
Computed a 3.5 5.0 8.1
9.9
13.4 20.5 27.5 41.0 50.0
67.9 80.2
100.2 134.1 149.2
Experimental -0.8 -0.4 -0.6 -1.0 -1.2
-1.5 -1.3
-1.2 -2.0 -1.1
-1.8
-1.8 -2.1 -2.8 -2.3
After correction -0.5 0.0
+o.
1 -0.1 0.0 +0.5
+0.7 C0.8 0.0 +0.9 +o 2 +0.2 -0.1
-0.8 -0.3 167.2 lfi5.2 a Correction rule applied. For range 0.0 to 20.0 mg. of absorbed water a d d 10% of the amount obtained; above this value add 2.0 mg. to t h e amount obtained. 150.0
167.5
WET PIPER FOR C O K I N G ,
HOLE
APPARATUS AND REAGENTS
Test tube for ignition, 18 X 150 mm., borosilicate glass. Test tube for weighing paper, 18 X 65 mm. Rubber stopper for ignition tubes, one-holeJ S o . 1. Filter paper strips, 2 inches square cut from any grade of paper except hardened types. Funnel for transfer of sample to bottom of ignition tube. Analytical balance. Finger stalls or rubber gloves for covering the tips of the fingers of one hand. Support to hold the test tube during ignition. Burner, Fisher type. Anhydrous sodium tungstate for use with samples containing sulfur. Fuse several hundred grams of reagent sodium tungstate dihydrate (Na2WO4.2H20). Cool and grind to a fine powder and store in a bottle with a tight sealing cap.
WIRE --TUBE SUP PORT
BURNER
1
PROCEDURE
Transfer 1.000 gram of sample powder to a dry 18 X 150-mm. borosilicate glass test tube by means of a funnel. (For samples containing an appreciable amount of sulfur it is advisable to mix 3 grams of anhydrous sodium tungstate with the sample powder prior to ignition to prevent high results.) Cover the fingers of the hand with finger stalls or a rubber glove. Roll a piece of filter paper (2 inches square) into a cylinder and slip it into the 18 X 65mm. weighing tube; stopper the tube with a solid stopper and weigh. (To avoid abEOrptiOn of moisture from the fingers, the paper should be handled only with covered fingers.) Quickly transfer the paper cylinder from the weighing tube to the upper part of the 18 X 150-mm. test tube, which contains the sample powder and stopper with a one-hole stopper. Next, place a piece of wet paper (2 X 3 inches) around the outside of the upper portion of the ignition tube to cool the tube. Then place the tube in a horizontal position in a holder a t a height t h a t will allow the tube to get maximum heat from a Fisher burner (Figure 1). Heat the closed end of the tube gently a t first, then a t full heat of the burner for 5 minutes. The flame should then be played along the tube below the filter paper for 1 or 2 seconds to drive the water into the upper part of the tube. ,4110~the tube t o cool for a t least a minute. Remove the stopper, and, with the aid of a rod or narrow spatula, quickly 77-ipe the walls of the tube surrounding the paper by gently pressing and rotating the filter-paper cylinder for one full rotation. With the fingers covered quickly transfer the paper from the test tube to the weighing tube, stopper, and weigh the tube. The increase in weight represents the water caught by the filter-paper strip. d small amount of the expelled water is not condensed and caught by the filter-paper strip. Part is driven out of the tube and part remains as unabsorbed vapor in the tube. To take care of these losses a simple correction is applied, based on an empirically determined rule. If the amount of water absorbed.on the filter paper is 20 mg. or less, increase the value obtained by 10%. If the absorbed water is over 20 mg., add 2 mg. to the weight of
Figure 1. Apparatus for determination of water water absorbed. The result obtained after the correction is applied is equal to the weight of water in the sample. EXPERIMENTAL DATA
Effect of Handling Filter Paper with Bare Fingers. A 2 X 2-inch piece of filter paper, an 18 X 65-mm. weighing tube, and a stopper were placed on the pan of the balance with the bare fingers and weighed. K i t h the bare fingers the paper from the balance pan was rolled into a cylinder and inserted into the weighing tube. The tube was stoppered and weighed. An increase in weight of about 3 mg. vas observed. The experiment was repeated but with the fingers covered by rubber finger covers. K O change in weight n-as observed. Each experiment was repeated three times, with no change in results. These experiments indicate the desirability of avoiding contact of the bare fingers with the filter-paper absorber. small part of the water Correction for Unabsorbed Water. expelled from the rock samples fails to be absorbed on the filterpaper strip. A part of the unabsorbed water is driven out of the tube as a result of the expansion of the air in the tube Tvhen the tube is heated. An additional small amount remains unabsorbed as vapor in the tube. A series of tests Tw,s made to relate the amount of water absorbed to the amount of water actually present in the samples
’
ANALYTICAL CHEMISTRY
562 in the concentration range anticipated for rock samples. Different amounts of National Bureau of Standards Standard Sample No. 97 (clay) were carried through the procedure. I n Table I the amounts of water absorbed are tabulated against the amounts of water contained in the several sample weights. The results obtained by two analysts have been used in the preparation of the table. I n each case, the amount of water absorbed is a little less than that originally in the sample portions. Inspection of the data shows that a simple rule can be used to correct for the deficiency in the amount of water absorbed. On samples for which the water absorbed is 20 mg. or less the value should be increased by IO%, and on samples for which the water absorbed is 20 to 160 mg. the value should be increased by 2 mg. Table I also shows the result of applying this rule to the set of data.
Table 11. Precision Sample Water, %
9a
loa
11 b 7.9 7.7 7.9 7.8 7.8 7.7
0.23 1.9 0.28 1.9 0.28 1.9 0.29 1.9 0.29 1.9 0.30 1.9 Average 0.28 1.9 7.8 Determined b y Leonard Shapiro. 6 Determined by Harry F. Phillips, U. S. Geological Survey.
12 b 13.2 13.4 13.4 13.2 13.2 13.2 13.3
RESULTS
Precision of the method has been tested by running samples six times a t each of four concentration levels. The results are shown in Table 11. Results obtained by the rapid method for total water in eight rock samples by two analysts are compared in Table I11 with results obtained by a third analyst who used the
Table 111. Comparison of Results by Rapid and Penfield Methods Water, yo Rapid
Penficeld Sample 4a Bb C W-ld 0.61 0.59 0.59 G-ld 0.19 0.34 0.30 1 0.54 0.50 0.58 2 0.40 0.35 0.36 1.0 0.94 3 1 .o 4 2.1 2.2 2.1 2.4 2.2 5 2.3 6 2.3 2.1 2.2 7 7.8 7.7 7.8 13.2 8 13.4 13.4 Determinations by Leonard Shapiro. b Determinations by Harry F. Phillips, U.S. Geological Survey. C Determinations by Paul W. Scott, U. S. Geological Survey. d Two carefully prepared rocks for collaborative study ( 8 ) .
conventional Penfield procedure. The values are in close agreement. A collaborative study of silicate rock analysis (2) reports the results of water determinations by the Penfield method and aome of its modifications. The reported values varied by 0.3 to 0.4% a t the 0.5% level of water. The rapid method gives values well within the range indicated by this collaborative study. LITERATURE CITED (1) Dittrich, M., and Eitel, W., 2.anorg. Chem., 75,373 (1912). (2) Fairbairn, H. W., and coworkers, U. S. Geol. Survey, Bull. 980 (1951). (3) Federov, A. A., Zaoodskaya Lab., 1 1 , 3 5 4 (1945). (4) Penfield. S. L., Am. J . Sci., 3rd sei-., 48, 31 (1894). (5) Shapiro, L., and Brannock, W. W.. U. S. Geol. Survey, C i t c . 165 (1952).
RECEIVEDfor review October 23, 1954. Accepted December 16, 1954. Publication authorized b y the director,
U.S. Geological Survey.
Polarographic Determination of Sulfite DONALD 6. AULENBACH and JEAN L. BALMAT Department of Sanitation, Rutgerr University, N e w Brunrwick,
A method was needed for determining sulfite in the presence of other reduced compounds, in order to study the transformation of sulfur compounds in biological sewage treatment. The use of the polarograph is satisfactory for determining sulfite in concentrations of 1 to 250 p.p.m. as sulfur. Themethod involves the deaeration of the sample in neutral or alkaline conditions, acidification of the sample to convert all the sulfite to sulfur dioxide, determination of the height of the anodic wave produced by the sulfur dioxide, desorption of the sulfur dioxide, and determination of the height of the wave at the same applied potential in the absence of the sulfur dioxide. The difference between the two determinations is directly proportional to the concentration of sulfite originally present.
A
Tu' ACCURATE method for the determination of sulfite
in the range of 0 to 250 p.p.m. was needed for the study of sulfur transformations occurring in waste treatment processes. The two methods more frequently used for determining sulfite in low concentrations, oxidation and subsequent determination as sulfate ( 4 ) and oxidation with iodine ( 5 ) , are subject to interferences from other inorganic sulfur compounds and other oxidizing or reducing compounds, which occur in sewage and industrial wastes. Therefore, a method had to be found which was sufficiently
N. 1.
sensitive and accurate to measure low concentrations of sulfite in highly heterogeneous mixtures, such as wastes. Kolthoff and Miller ( 8 ) showed that sulfite in 0 . 1 s nitric acid produced a polarographic wave in pure solutions of sodium sulfite having concentrations of approximately 5 X 10-4M (15 p.p.m. as sulfur). This indicated that the polarographic method was sufficiently sensitive; however, it had to be proved that this method would give accurate results when used to analyze waste samples of a highly complex nature. APPARATUS
The apparatus used was the Fisher Elecdropode. The scale of the galvanometer was calibrated and it was found that each division of the scale a t the 1X sensitivity was equivalent to 0.0186 Ma. The temperature of the samples was maintained a t 25" C. by immersing the polarographic cell in a constant temperature water bath. \Tater-pumped nitrogen was used for deaeration of the samples. EXPERIMENTAL
Effect of pH. The nitric acid supporting electrolyte used by Kolthoff and Miller was tried. However, the deoxygenation of the sample prior to polarographic analysis resulted in the desorption of the sulfite, present as sulfur dioxide in such acid conditions.. Although the loss of sulfur dioxide from the sample initially appeared to be detrimental, it later served as the basis for the method of sulfite determination described in this paper.
