INDUSTRIAL AND ENGINEERING CHEMISTRY
Julv 15. 1929
145
Modification of Parr's Total Carbon Determination in Coal' R. E. Brewer and E. P. Harding DIVISION OF TECHNOLOGICAL CHEMISTRY, UNIVERSITYOF MINNESOTA, MINNEAPOLIS, MI".
HE A. S. T. M. method ( I ) * for determining carbon in
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coal and coke is time-consuming and rather difficult for the beginning student to carry out. Parr (2) proposed a gas volumetric method for determining carbon from the residue obtained by fusing the coal sample with sodium peroxide and potassium chlorate. The residue consists largely of sodium carbonate and sodium peroxide. This is dissolved in water, treated with concentrated hydrochloric acid, and the evolved carbon dioxide is measured under known conditions of temperature and pressure. As a substitute for the A. S. T. 111. standard method, Parr's peroxide fusion method for total carbon has been found t o be more convenient and sufficiently accurate for the requirements of the engineer in boiler testing computations. Ten years' experience in the laboratory a t the University of Minnesota has justified the use of this rapid method. Modified Apparatus
The total carbon apparatus designed by Parr has been changed in several minor respects and used under slightly different conditions in the Minnesota laboratory. These changes have resulted in an easier control of the temperature, have eliminated the need of compressed air, and have made possible a higher accuracy of results due to a better control of the experimental conditions. Figure 1 shows the modified apparatus. Water at room temperature from an overhead storage tank, such as is used with a continuous-flow gas calorimeter, enters the tube W a t the top, flows downward to the bottom of the jacketing tube, J , fills this, and leaves through the overflow tube, D. By proper adjustment of the flow of water through the apparatus, a uniform temperature can be maintained throughout a determination. The temperature of the gas in the 200-ml. buret is obtained by means of a thermometer suspended in the water jacket, J . The leveling tube, L, is filled with a 20 per cent solution of sodium sulfate to which 5 per cent by volume of concentrated sulfuric acid has been added. This confining solution minimizes the absorption of carbon dioxide. Sufficient methyl orange indicator is added to give a deep red color which facilitates the buret readings.
opened, and the material clinging to the cover is washed with prepared water into a 250-ml. beaker. (All distilled water used in this determination has been recently boiled for 10 minutes t o remove dissolved gases.) The cup containing the fused material is placed on its side in the bottom of the beaker and two-thirds covered with hot prepared water (about 60" (2.). The beaker is covered with a watch glass. (These precautions minimize contamination with carbon dioxide from the water used and from the air.) By gently moving the beaker, the fusion cup will rotate sufficiently to expose all parts of the fusion to the action of the water and the solution of the material will be completed in a short time. Water a t too high a temperature causes too rapid solution of the residue and often results in loss by spattering or by flowing out of the beaker. The solvent action of water a t a temperature much under 50-60" C. is so slow that contact with air is unduly prolonged. When the fusion is dissolved, the cup is removed, rinsed well with prepared water, and the washings together with the main portion of liquid in the beaker are poured into the 300-ml. Florence flask, B. The beaker is washed thoroughly with prepared hot water and the washings are added t o the main portion in flask B. II
Modified Procedure
The procedure described by Parr (5) as here rewritten includes the changes in procedure and manipulations. The residue from a fusion of the sample with sodium peroxide and potassium chlorate or perchlorate, as accelerator, is used in the carbon dioxide determination. One-half gram of coal is placed in the fusion cup and mixed with 1 gram of the accelerator by rotating the cup a t an angle of about 45 degrees. One measure full-about 14 grams-of sodium peroxide is added to this mixture, the temporary cover put in place, and the ingredients thoroughly mixed by shaking. The permanent cover with the firing wire attached is then fastened in place, with the wire just dipping into the charge. The bomb is next placed in a beaker of water and submerged to the stem. The charge is then fired with a current of about 2 to 4 amperes. When cool, the bomb is wiped dry, 1
Received March 28, 1929
* Italic numbers in parenthesis refer t o literature cited at end of article.
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Figure 1-Parr's
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Total Carbon Apparatus Modified
The large double pipet, P, is a little more than half filled with a 40 per cent solution of caustic potash or such other. strength as is ordinarily used for the absorption of carbon dioxide gas. Sodium hydroxide may be used, but is less satisfactory on account of the lower solubility of the sodium bicarbonate formed. The three-way cock, T, is turned so as to connect the pipet P with the buret G. The leveling tube, L, is lowered so that the liquid in P is raised to the mark R on the capillary limb. The cock T is now closed to the
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from the apparatus as previously described until the capacity of the buret is nearly reached. This volume is now measured and passed into the absorption pipet as previously described. The pipet is then gently shaken so as to aid in the absorption of the carbon dioxide. The air in the pipet is next drawn back into the buret and measured. The difference between the combined vol-
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Deqrees Cen fiqrade Figure 2-Average
of Graphs for Pressures in Table I
Two or three milliliters of bromocresol green indicator (0.04 per cent solution) are placed in the funnel and about 30 ml. of concentrated hydrochloric acid added. The bromocresol g e e n changes from bluish green in an alkaline solution to reddish yellow in an acid solution and indicates when sufficient hydrochloric acid has been added to the contents of flask B, a point difficult t o determine when no suitable indicator is used. The flask is connected to the funnel tube, A, and the condenser, C, as shown in Figure 1. The ring support with the gauze in place is brought up into position under flask B. The leveling tube L is lowered and acid is gradually admitted to flask B from the funnel and the tlyee-way cock T so manipulated as t o allow gas to pass into the buret, but no confining liquid to flow from the buret into flask B. (Care must be exercised in controlling the opening of cock T t o the tube connecting flask B until sufficient gas has been generated to equalize the pressure.) Cock T is then left opened to the buret G. When the gas generated shows a volume of about 160 ml. in the buret the acid is shut off and shortly afterward cock T is closed. The gas in the buret is then carefully read after the liquid in the leveling tube and buret have been brought exactly t o the same level. The temperature of the jacketing water and the barometric pressure are taken for this volume of gas. The cock T is now opened to the absorption pipet and the gas in the buret is forced quickly into pipet P by bringing the liquid in buret G to the zero point. Cock T is then closed and the gas is deft in the pipet for the complete absorption of the carbon dioxide. The procedure of generating, measuring, and absorbing the carbon dioxide is repeated until no more of this gas is generated. Care should be exercised during the addition of the acid so that there will be no more than a slight excess a t any time. This may be accomplished by an occasional shaking of the flask.
measurea gives the amount of carbon dioxide absorbed. If during the collection of gas while boiling the contents of flask B there is a slight increase in the temperature of the jacket water, the final buret reading should not be taken until the cooling water flows through the jacket long enough to cool the gas t o the temperature of the volumes previously measured. Corrections for COZin Reagents and in Inorganic Combination in Coal
The sodium peroxide reagent usually contains some carbonate. This evolves carbon dioxide when the fusion is treated with hydrochloric acid. The total volume of carbon dioxide evolved during a determination should be corrected for that coming from the carbonate impurity in the sodium peroxide by running a blank on one measure of the sodium peroxide in the same manner as for the fusion. Some coals contain an appreciable amount of carbon in inorganic combination as carbonates-e. g., calcium carbonate. Carbon in this form furnishes no heat when the coal is burned. For many purposes the data for carbon are desired in terms of the combustible or organic carbon. The total carbon in the coal may be corrected for the carbon present in inorganic combination by running a blank for this carbon. To do this 5 grams of the coal sample are placed in the flask B and treated precisely as for the residue from a fusion. It is usually best to add some water to the sample before adding the hydrochloric acid. The amount of inorganic carbon subtracted from the total carbon in the coal gives the combustible or organic carbon in the coal. Computation of Results
The net volume of carbon dioxide produced from the fuel sample is found by subtracting from the sum of the several measured volumes of carbon dioxide and air the sum of the total volume of air finally measured in the buret and the volume of carbon dioxide coming from one measure of the peroxide. If the net volume of carbon dioxide from the
July 15, 1929
INDUSTRIAL AND ENGINEERING CHEMISTRY
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combustible carbon of the fuel sample is desired, there should be a further deduction for the carbon dioxide from the inorganic carbonates in the same weight of fuel sample. By reference to Table I there is found a t the observed temperature and pressure the weight in milligrams of carbon in 1 ml. of carbon dioxide gas. The product of this factor and the corresponding net volume of carbon dioxide in milliliters represents the weight in milligrams of combustible carbon in the coal sample. The percentage of carbon is found by multiplying the weight of carbon expressed as grams by 100 and dividing by the weight in grams of coal sample taken. The general method of computing results as given above is easily applied when both the observed temperature and pressure correspond exactly with milligram values for carbon in carbon dioxide given in Table I. These data, however, more often fall between the values directly given in the table. The writers have noticed repeatedly that many
E 5 view of sim'plifying the computations, Tables I1 and I11 ~ ~b b ~ (bD $ N U $ I$ W $ O W b UbI ~ ~ ~b W b ~ W b ~b W 6 ~ ~~O ~ 5 N ~ U I~ ~ P W t ~ N P& t ~ t ~ ~ Figure 2 were constructed. and rOWmmWOmWwUIrmCUI0PWNmWNUIWrP 02 00000000000000000000000000
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Table 11-Temperature Correction Values.
TENTHS OF
1' C.
22 2.2 4.4 6.6 8.8 11.0 13.2 15.4 17.6 19.8
23 2.3 4.6 6.9 9.2 11.5 13.8 16.1 18.4 20.7
24 2.4 4.8 7.2 9.6 12.0 14.4 16.8 19.2 21.6
25 2.5 5.0 7.5 10.0 12.5 15.0 17.5 20.0 22.5
26 2.6 5.2 7.8 10.4 13.0 15.6 18.2 20.8 23.4
Table 111-Pressure Correction Values.
TWENTIETHS OF^
MM.
1 2 3 4 5 6
7
a
9 10
12 0.6 1.2 1.8 2.4 3.0 3.6 4.2 4.8 5.4 6.0
13 0.65 1.3 1.95 2.6 3.25 3.90 4.55 5.2 5.85 6.5
14 0.7 1.4 2.1 2.8 3.5 4.2 4.9 5.6 6.3 7.0
Proportional Parts
27 2.7 5.4 8.1 10.8 13.5 16.2 18.9 21.6 24.3
28 2.8 5.6 8.4 11.2 14.0 16.8 19.6 22.4 25.2
29 2.9 5.8 8.7 11.6 14.5 17.4 20.3 23.2 26.1
30 3.0 6.0 9.0 12.0 15.0 18.0 21.0 24.0 27.0
Proportional Parts
TWENTIETHS OF 2 MM.
11 12 13 14 15 16 17 18 19
12 13 14 7.15 7.7 6.6 7.2 7.8 8.4 7.8 8.45 9.1 8.4 9.1 9.8 9.0 9 . 7 5 10.5 11.2 9.6 10.4 1 0 . 2 11.05 1 1 . 9 1 0 . 8 11.7 12.6 1 1 . 4 12.35 1 3 . 3
Inspection of Table I shows that the differences between the factors, for each degree Centigrade and constant pressure, range from 0.0022 to 0.0030, while for each 2 mm. pressure and constant temperature the differences are 0.0012, 0.0013, or 0.0014. Table I1 is a proportional parts table showing the corrections corresp6nding to tenths of 1" C. and Table I11 a similar table showing corrections corresponding t o twentieths of 2 mm. (0.1 mm.) to be applied to the factor a t or nearest to the next lower temperature and lower pressure than the observed data. The graph in Figure 2 represents the mean of a family of graphs for the different pressures mg. The recorded in Table I and is accurate to =+=0.0001 differences between the factors-i. e., from 0.0022 to 0.0030are plotted as ordinates, while the temperatures from 10" to 35" C. are plotted as abscissas. An example of the method of double interpolation will make clear the computations: Given 20.6" C. and 741.7 mm. Find the correct factor in milligrams per milliliter of carbon dioxide gas under these conditions. From Figure 2 the "difference" per degree Centigrade for the temperature interval 20-21" C. is observed to be 0.0025 mg. Referring to Table I1 we find that 0.6 of 0.0025 is 0.0015, as the correction for temperature. The correction for pressure (Table 111) is 17/20 of 0.0014 or 0.00119. The corrected factor in milligrams per milliliter of carbon dioxide is then 0.4749 0.0025 0.0012 = 0.4736. This method of double interpolation is accurate to *O.OOOl.
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ANALYTICAL EDITION
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It should be noted that the correction for temperature should always be subtracted while the correction for Pressure should always be added when applied to the factor a t or nearest to the next lower temperature and lower pressure as is recommended for simplicity in the use of the corrections. The general principle of this method of double interpolation may be applied in any caSe of double interpolation from tabulated data.
Vol. 1, No. 3 Acknowledgment
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The writers wish to acknowledge their thanks to N. Taylor for suggestions in devising the method used for making the double interpolations, Literature Cited (1) Am. Soc. Testing Materials, Standards, 1927, D271-27, p. 535. (2) Parr, University of Illinois Bulletin, Vol. 1, No. 20 (1924); J . A m . Chem. Soc., 26, 294 (1904). (3) Parr, “Analysis of Fuel, Gas, Water, and Lubricants,” 3rd ed., p. 179.
Specific Heats of Mineral Oils’ Determined by a New Method L. M. Henderson, S. W. Ferris, and J. M. McIlvain THE ATLANTIC REFININQ COMPANY, PHILADELPHIA, PA.
ECENT developments in distillation equipment have increased the need for dependable data on specific heats of mineral oils a t elevated temperatures. It is in this region of elevated temperatures that the present available data disagree. Cragoe has expressed his results by means of the formula A
R
(1)
Presented under the title “Specific Heats 1 Received April 19, 1929. of Mineral Oils” before the Division of Petroleum Chemistry at the 77th Meeting of the American Chemical Society, Columbus, Ohio, April 29 to May 3, 1929. * Italic numbers in parenthesis refer t o literature cited at end of article.
where d = density, t = temperature in constants
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which shows a smaller increase in specific heat with rise in temperature than that allowed by the expression presented by Fortsch and Whitman (2) (t
+ 670)(2.10 - sp. gr.600
Specific heat = where t = temperature in
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(2)
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F. Because of the industrial importance of these equations, the results of an investigation employing an experimental method differing materially from that reported by previous investigators are here presented. The data derived from this work, which was initiated some four years ago, show the same temperature gradient for the specific heat of oils as that given in Equation 2. The actual values of the specific heat vary, however, with the source of the crude oils. This agrees with the findings of Cragoe. For a given temperature and specific gravity, the paraffinic oils show a greater specific heat than the naphthenic oils. O
Apparatus
A diagram of the calorimeter used in this investigation is shown in Figure 1. It consisted of A , a brass calorimeter
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