January 15, 1931
I N D U S T R I A L A N D ENGINEERING CHEMISTRY
41
Ash and Electrical Conductivity of Refined Cane Sugars' F. W. Zerban and Louis Sattler N. Y. SUGARTRADELABORATORY, 80 SOUTHST., NEW YORIF,N, Y.
The percentage of ash (sulfated less 10 per cent) in HIS final chapter of our sulfated ash method was serefined cane sugars such as granulated and remelts, investigation on the relected by the writers as the containing less than 0.3 per cent ash, can be found by standard because it is affected lation between ash and dissolving 25 grams of the sugar in 100 ml. conductivity less by details in manipue l e c t r i c a l conductivity of water, determining the specific conductanee of the lation than any of the "carsugar cane products (3 to 9) solution at 20" C., and multiplying the result, after b o n a t e d " ash m e t h o d s . deals with the sugars made in correcting for the conductivity of the water, by the With the latter, the quanc a n e s u g a r refineries, and factor 530. To find the ash percentage in soft sugars, tities of chlorine, sulfur, either sold or r e t u r n e d to only 5 grams are used in 100 ml. solution, as in the case and perhaps p h o s p h o r u s process. of raw sugars. The appropriate factor, which varies which are volatilized during Work on similar products of from place to place, may then be determined for each the heating process may beet sugar refineries has been refinery, or else the general method described may be reported in Europe, especially vary widely with slight difemployed. The article concludes with practical recomby Lundrh ( I ) , and on Amerif e r e n c e s in p r o c e d u r e . mendations for equipment and methods to be used in F u r t h e r m o r e , L u n d h (1) can granulated beet sugars by routine work on all types of cane products. Nees (2). The last named has found that the sulfated author used a concentration ash method gives the most of 25 grams of sugar in 100 ml., and found that for granulated concordant figures when used as a basis for refinery conbeet sugars from three different states the ratio between the spe- trol. Yet it is after all an empirical method and yields ciiic conductance X lo6 and the per cent sulfated ash (less 10 discrepant results in the hands of different analysts. When per cent) averages 231.5 if the conductivity determinations are the ash content is very small, as in many of the samples remade a t 25"C. and corrected for the conductance of the water corded in Table I, the results even of the sulfated ash method used as a solvent. The concentration of 25 grams in 100 ml. are quite unreliable, because usually only a few milligrams was chosen because the specific conductance passes through or even less of ash are actually weighed, unless very large quantities of sugar are ashed, which is precluded in actual a maximum in the neighborhood of that point. practice. I n such cases the possible percentage error in the Granulated and Remelt Cane Sugars with Low Ash ash figure becomes enormous. The measurement of specific The first group of refined cane sugars taken up by the conductance, on the other hand, is well known to be most writers comprised granulated and remelt sugars with an ash precise, and for this reason alone the electrical ash method, content up to 0.3 per cent. Nees' concentration of 25 grams although admittedly empirical, is, nevertheless, to be prewas adopted for these low ash sugars, but the normal tem- ferred over the other empirical ash methods. I n addition perature for sugar laboratories, 20" C., has been adhered to. to this, it is much more rapid, and much more easily executed. The same equipment was used as in all previous work, and Table I-Ash a n d Conductivity of Unwashed a n d Washed Granulated all the solutions were Htered through a mat of filter paper a n d R e m e l t Sugars, w i t h Ash up to 0.3 Per C e n t and asbestos to exclude the effect of the ash contained in the SPECXFIC CHEMICAL CONDUCTIVITY K X insoluble portion of the sugar on the chemical ash determiX 108 (K) C-RATIO Av. C-Ratio SAMPLE ASH V" nation. The limit of 0.3 per cent ash was arbitrarily chosen 1 0,0069 11.'7 504 0.0062 because with sugars of high ash content our standard con16.1 478 0.0085 2 0.0077 19.0 449 0.0101 centration of 5 grams of sugar in 100 ml. can be used, as has 3 0.0088 22.6 420 0,0120 4 0.0095 been done in the case of raw sugars and also of soft sugars. 0.0087 5 0.0110 16.5 67 1 0.0087 16.6 679 6 0.0112 The results for 34 samples from four different refineries 0.0109 7 0.0128 20.0 621 are given in Table I, where the sugars are arranged in the 8 0.0153 31.8 497 0.0169 5 9 . 1 492 0.0313 9 0.0292 order of ascending ash content. The column headed "Chemi63.4 524 0.034 10 0.033 63.1 554 0.033 cal Ash" shows the sulfated ash, less 10 per cent, determined 11 0.035 77.6 503 0.041 12 0.039 in the usual manner on the filtered solution of the sample. 111.8 441 0,059 13 0.052 The next column shows K , the specific conductance X IO6, 0.066 14 0.071 124.4 57 1 0.071 15 0.073 134.3 544 of the solution at 20" C., corrected for the conductance of 147.9 534 16 0.079 0.078 0.094 178.4 465 17 0.083 the water. The figures in the succeeding column, headed 156.9 536 0.083 18 0.084 "C-Ratio," represent the quotient of the ash percentage di189.5 507 0.100 19 0.096 0.131 247.5 445 20 0.110 vided by the specific conductance itself (not X 106). The 204.5 558 0.108 21 0.114 181.3 651 0.096 last column gives the ash percentage calculated by multi22 0.118 0.109 23 0.124 206.4 602 plying the specific conductance with the average C-ratio 530, 0.124 24 0.130 233.9 , 556 or K with 0.000530. 0.134 25 0.134 253.1 530 0.155 293.3 498 26 0.146 For the proper interpretation of these results it must be 0.177 334.5 500 27 0.167 0 .170 28 0.169 319.9 528 kept in mind that the different chemical ash methods them0.189 357.4 481 29 0.172 selves are all entirely empirical and do not give concord0.166 314.0 567 30 0.175 0.184 31 0.177 346.9 510 ant results among each other. It will be recalled t h a t 4 h e 0.229 32 0.225 431.7 52 1
T
I _
1 Received September 18, 1930. Presented before the Division of Sugar Chemistry at the 80th Meeting of the American Chemical Society, Cincinnati, Ohio, September 8 to 12, 1930.
33 34 35
0.226 0.269 0.295
367.2 460.0 566.2
Av.
599 585 52 1 530
0.195 0.244 0.300
42
ANALYTICAL EDITION
One difficulty arises in the case of specially purified sucrose, and some refined sugars of the very highest grade. With sugars of this type the specific conductance of the solution may be less than the specific conductance of the water, owing to the depressing effect of sucrose on the conductivity of electrolytes. I n cases like this, specially purified water might be used, but even then the difficult question of correction would remain. With such sugars the ash content can be found only approximately, yet with greater precision than by the chemical method. It is interesting to inquire how the C-ratio of 530 found for refined cane sugars compares with the C-ratio of granulated beet sugars. At 25" C., the temperature used by Nees, the value 530 would be reduced to 470. Need divisor, 231.5 at 25" C., is equal to a C-ratio of 432. This confirms the statement of Nees that the ratio between ash and conductivity for cane sugars is probably different from that for beet sugars, because the latter contain a large proportion of highly ionizable alkali salts. This would involve a lower C-ratio for granulated beet sugars, in agreement with the facts. With this class of sugars it is obviously unnecessary to resort to the more complicated conductometric procedures of ash determination, developed by the writers for raw sugars and for sirups and molasses. Soft Sugars
The chemical ash in the samples of soft sugars received by the writers from three different refineries ranged from 0.18 to 2.31 per cent. The conductivity determinations were therefore run on solutions containing 5 grams of total sugar in every 100 ml. of solution, as in the case of raw sugars. Within the ash range up to 1 per cent, 5 grams of the soft sugar were used, and above 1 per cent, 2.5 grams of soft sugar plus 2.5 grams of sucrose; in the latter case the result of the conductivity determination was multiplied by 2. ParaIIel determinations were made in the presence of acid, 5 ml. of 0.25 N hydrochloric acid being added to 200 ml. of the 5-gram-per-100-ml. sugar solution, and measuring the specific conductance again, exactly as in the previous work. The results of the measurements are shown in Table 11. Columns 1 to 5 are the same as in Table I. The average Cratio was found to be 1580 which is lower than the value found previously for any group of refinery products, but this fact has little significance because it has been shown before that the C-ratio may vary within extremely wide limits. Column 6 gives the individual deviations of the electrical ash (in column 5) from the chemical ash. The values for K1, which is the specific conductance X loe of the acidified solution, are found in column 7. I n column 8 are shown the figures for the ash calculated by the simple conductometric expression developed previously (0.913 K 193.5 - 0.1 K1), multiplied by the factor 0.001695. This factor agrees closely with the average factor obtained for refinery sirups (8). The individual errors by the C-ratio method exceed 0.03 per cent in seven cases, amounting to 0.04 in two, 0.05 in one, 0.08 in two, and 0.12 in one. The total deviations for this method are -0.52 and 4-0.51, or 1.03 in all. The conductometric formula results in only two deviations of 0.04 per cent and two of 0.05 per cent; the total deviations are -0.30 and $0.41, or 0.71 altogether. The simple conductometric formula method is evidently more reliable than the C-ratio method, and still better results could probably be obtained by the general conductometric formula based on three conductivity determinations (Q), one on the solution itself, a second after addition of N orthophosphoric acid, and a third after addition of 0.25 N potassium hydroxide solution. But it is believed that this would have no prac-
+
Vol. 3, No. 1
tical advantage, and in the control of a single refinery even the C-ratio method will probably prove quite satisfactory for most purposes. Table 11-Ash a n d Conductivity of Soft Sugars CHEMIK X ASHCALCD. SAM- CAL CAv.CBY PLE Asa K RATIO RATIO ERROR K I FORMULAERROR r
%
%
1" 2a 3" 4" 5" 6 7 8 9 10 11" 125 135 14" 15" 16a 17 18" 19 20 21" 22 23" 24 25O 26 27" 28 29 30 31 32 33 34 35
%
%
1.30 829.6 1567 1.31 $0.01 1824 1.32 $0.02 1 . 4 3 900.2 1589 1.42 1776 1.45 -0.01 $0.02 1 . 5 3 983.4 1755 1.58 1556 1.55 $0.02 $0.05 1.84 1149.4 1601 1.82 -0.02 1717 1.85 $0.01 2.31 1385.8 1667 2.19 -0.12 1573 2.27 -0.04 0 . 4 3 280.5 1497 0.44 2143 0.40 +0.01 -0.03 0.46 308.3 1492 0.49 2184 0.44 $0.03 -0.02 0.60 399.4 1502 0.63 2098 0.59 $0.03 -0.01 0.79 506.2 2045 0.77 1561 0.80 $0.01 -0.02 0.89 563.4 1931 0.87 1580 0.89 0.00 -0.02 1 0 7 695.6 1538 1.10 $0.03 1945 1.07 0.00 I A A1 1.23 807.8 1523 1.28 1970 1.24 +0.05 1.26 813.0 1550 1.28 $0.02 1889 1.27 $0.01 1 . 5 0 963.8 1556 1.52 4-0.02 1821 1.53 $0.03 1.49 940.2 1585 1.49 0.00 1767 1.51 +0.02 1.63 1013.8 1608 1.60 -0.03 1756 1.63 0.00 0.27. 178.2 1515 0.28 +O.Ol 2077 0.25 $:.:, 1.47 892.0 1648 1.41 -0.06 1528 1.52 -, "."" 0.42 276.6 1518 0.44 +0.02 2020 0.41 -0.01 0.21 136.4 1540 0.22 +O.Ol 2067 0.19 -0.02 1.84 1110.6 1657 1.76 -0.08 1474 1.87 +0.03 0.80 509.4 1570 0.80 0.00 1770 0.82 +0.02 1.52 942.4 1613 1.49 -0.03 1633 1.56 +0.04 0.63 413.9 1522 0.85 $0.02 1946 0.64 +O.Ol 1.26 777.2 1621 1.23 -0.03 1770 1.26 0.00 0 . 8 3 541.9 +0.03 1898 0.84 1532 0.86 +O.Ol 1.72 1036.4 1660 1.64 -0.08 1613 1.71 -0.01 0.28 199.1 1406 0.32 $0.04 2113 0.28 0.00 0.19 126.8 1498 0.20 $0.01 2135 0.17 -0.02 0.45 299.4 1503 0.47 2054 0.44 -0.01 +0.02 0.22 167.7 1312 0.26 $0.04 2153 0.22 0.00 0.59 375.1 1573 0.59 0.00 2044 0.66 -0.03 0.18 132.7 1356 0.21 4-0.03 2150 0.17 -0.01 0.87 533.2 1632 0.84 -0.03 1795 0.85 -0.02 0.48 309.3 1552 0.49 +O.Ol 1942 0 . 4 8 ,O.,O,Q 36 0.60 387.6 1548 0.61 +0.01 1934 0.60 " 37 0.75 490.3 1550 0.77 $0.02 1855 0.77 $0.02 0.00 1748 0.91 38 1573 0.89 4-0.02 0.89 565.8 39'3 1.31 832.2 1574 1.31 0.00 1811 1.33 +0.02 $0.01 1825 1.31 405 1.29 824.6 1564 1.30 +0.02 41" 1.31 812.2 1613 1.28 -0.03 1815 1 . 3 0 -0.01 a The conductance determinations on these samples were made at a concentration of 2.5 grams sample plus 2.5 grams sucrose, and the results were multiplied by 2. T " . " L
.
Y"
High Ash Remelt Sugars
The samples collected by the writers included six remelt sugars with an ash content within and also above the soft sugar range. The conductivity determinations were therefore made a t the concentration adopted for soft sugarsthat is, on 5 grams sample in every 100 ml. up to an ash content of about 1 per cent; a t an ash content between 1 and 3 per cent, 2.5 grams sample plus 2.5 grams sucrose were taken, and when the ash exceeded 3 per cent, 0.5 gram sample plus 4.5 grams sucrose were used. The results are given in Table 111. Table 111-High SAMPLE
CHEMICAL
ASH
K
c-
K
x
RATIO 1580
ASHCALCD. BY
Error
K I FORMULA ERROR
%
% 245.1 0.39 375.3 0.66 1 . 3 5 814.2 2.05 1193.2 3.25 1985.0 4.63 2761.0
Ash R e m e l t Sugars
1591 1759 1658 1718 1637 1677
0.39 0.59 1.29 1.88 3.14 4.36
0.00 -0.07 -0.06 -0.17 -0.11 -0.27
1936 1723 1709 1443 1891 1734
%
%
0.38 0.62 1.34 2.01 3.15 4.61
-0.01 -0.04 -0.01 -0.04 -0.10 -0.02
The discrepancies found by the C-ratio method, with the average C-ratio of 1580 for soft sugars, are rather large, but, as has been explained above, without significance. The results calculated by the simple conductometric formula, with the soft sugar factor 1695, are very much better, considering that an error of 0.10 on 3.25 per cent ash is really onIy about 3 per cent of the total. Just as with the soft sugars, the general conductometric formula mentioned above would probably reduce the errors, but in practice it is unnecessary to go to such refinements.
January 15, 1931
INDUSTRIAL AND ENGINEERING CHEMISTRY
Summary of Recommendations for Routine Electrical Ash Determinations in Sugar Cane Products
43
procedure, with only one conductivity determination, based on actual comparisons of chemical ash and specific conductance of the various products. These should include not only the materials studied by the writers, but should be extended to the several types of juices. When samples are received from many different sources, such as in regulatory and similar work, the choice of the proper method will depend on the type of product analyzed. For granulated and other refined sugars of low ash content, the simple C-ratio method outlined in this paper is sufficiently accurate. For raw cane sugars and soft sugars the simple conductometric formula with two conductivity determinations should be used, the factor being 0.001757 for raw sugars (7), and 0.001695 for soft sugars. The same method, with the factor 0.01757, will also suffice for sirups and molasses known to have been produced without char treatment (8), but otherwise it is safest to resort to the general conductometric formula based on three conductivity determinations, one on the solution itself, one with the addition of phosphoric acid, and one with the addition of potassium hydroxide
EQUIPMENT-For routine conductivity measurements it is advisable to use a self-contained instrument with as little outside wiring as possible, to prevent current leaks and other inconveniences. If it is operated by a battery this should also be enclosed in the instrument case. With this type a telephone receiver is necessary as a null indicator. I n a noisy factory laboratory the telephone is practically useless, and if alternating line current is available or can be provided, it is better to use an instrument to be connected to the a. c. line with a galvanometer as null indicator. The only other outside connection should be with the conductivity cell. The instrument should be calibrated in terms of specific conductance a t 20" C.; this necessitates a compensator for variations in the cell constant. For cane products it is not advisable to have the scale calibrated directly in ash percentage, on account of the variations in the C-ratio, but an additional blank scale might be provided which could be calibrated by the individual worker for the C-ratio most frequently used. The instrument should also be provided (4). with a compensating device for variations in temperature. Acknowledgment Since the temperature coefficient itself varies to some extent as has been shown by the writers, especially when conducThe writers are indebted to various sugar refining comtivity determinations are made also in the presence of acid panies in the New York district for the samples used in and alkali, it is safest to keep the temperature of the solu- this investigation. tion as close as possible to the standard of 20" C. This is Literature Cited most readily accomplished by the use of the Lange type of cell provided with a water jacket, as employed by the writers. Lundbn, 2. Ver. deul. Zuckerind., 76, 763 (1925). This cell has the further advantage for routine work that the (1) (2) Nees, IND. END.CHEM.,19, 225 (1927). solution which has been tested can be run out rapidly and (3) Sattler and Zerban, F a d s about Sugar, 28, 686, 713 (1928). the next solution be filled in without delay. Dipping cells (4) Sattler and Zerban, IND.ENG.CHEM.,Anal. Ed., 8, 38 (1931). may also be used if preferred, but they are not as convenient (5) Zerban and Mull, Facts about SUEQY,21, 278 (1926). ( 6 ) Zerban and Sattler, I b z d . , 21, 1158 (1926). as the Lange type of cell. (7) Zerban and Sattler, I b i d . , 22, 990 (1927). METRoD--For the control work of individual factories it (8) Zerban and Sattler, IND.ENG.CHEM.,Anal Ed., 2, 32 (1930). is desirable and quite possible to use the ordinary C-ratio (9) Zerban and Sattler, Zbid., 2, 322 (1930).
The Plastometer'~z A New Instrument for Measuring Plastic Properties of Coal Joseph D. Davis U. S. BUREAUOF MINES,4800 FORBESST.,PITTSBURGH, PA.
B
ETWEEN certain limiting temperatures, depending on its rank and to some extent on its origin, a coking coal assumes a semi-fused or plastic state. Destructive distillation of the coal substance and of those constituents which fuse, begins as soon as or before fusion sets in and is greatly accelerated by rising temperature; the mass may assume a more or less plastic state before solidifying as coke. As the temperature rises to the limit of the plastic range (or state), most of the volatile matter is driven off and the mass sets into coke. Plasticity develops, however, only when a favorable heating rate, such as that prevailing in industrial coking practice, is chosen. Audibert (2) has shown, for example, that it is possible to choose a heating rate SO slow that the fusible matter is decomposed before it has actually fused. I n such a case the coal does not become plastic and coke is not formed. On the other hand, heating may be so rapid that, although fusion does take place, decompo1 Received September 19, 1930. Presented before the Division of Gas and Fuel Chemistry at the 80th Meeting of the American Chemical Society. Cincinnati, Ohio, September 8 to 12, 1930. (Xot 2 Printed by permission of the Director, U. S. Bureau of Mines. subject to copyright.)
sition is accelerated to such an extent that plasticity cannot be measured and a frothy coke results. The instrument to be described was designed in connection with the Bureau of Mines Survey of the Gas- and Coke-Making Properties of American Coals, for heating rates within the range of those prevailing in industrial practice under these conditions. Coke is invariably produced, provided that the coal is suitable for coke-making. Previous Methods for Studying Plastic State of Coal
The method devised by Foxwell (3) and modified by Layng and Hathorne (4), and that of Agde and von Lyncker (1) will serve as examples of experimental methods previously used for study of the plastic state of coal. Layng and Hathorne carbonize a standard column of sized coal at a suitable rate in an electric tube furnace while passing nitrogen through it. Sufficient nitrogen for the test is confined in a bottle connected to the tube containing the coal. This is caused to flow by water displacement a t constant head, so that resistance to its passage develops when the coal fuses. A manometer connected to the nitrogen
