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beet pectin, or 18 per cent on the dried beet pulp, the mucic acid being derived partly from galactose and partly from galacturonic acid. Mucic acid is now being made commercially from the wood of Lariz occidentalis for use in the manufacture of baking powder. This wood contains only 10 per cent of galactan and accordingly yields not over 7 or 8 per cent of mucic acid. From the standpoint of yield the pectincontaining substances have a decided advantage over the larch as a source of mucic acid. While many new uses will probably be suggested by studies on the constitution of pectin and its reactions as an organic substance, other valuable applications may be expected as a result of researches upon its colloidal properties. Apparently very little has been done in that direction.
PECTIN IN OTHER FIELDS The reactions of pectin enter into the preparation oi certain of the fibers used for textiles, notably flax, hemp, ramie, etc. The separation of the celIulose fibers from their incrusting substances depends upon breaking down the pectin substances which act as the cementing agent. The processes, thenwhether enzymic or bacterial, as in the natura! rsfii-g pmeess, or strictly chemical-are primarily concerned with the degradation of pectin. A knowledge of its decomposition reactions will accordingly find application here. The produc-
Vol. 16, No. 10
tion of wood pulp for paper-making is a different problem, since in this case lignin, not pectin, is the cementing agent. The pectin content of wood is apparently very small. Pectin plays an important role in the life processes of plants. For that reason the solution of some of the problems in plant physiology and the application of these to practical agriculture will be materially aided by a more complete understanding of pectin chemistry.
BIBLIOGRAPHY l-ElLis, “Country Housewife’s Family Companion,” James Hodges and B. Collins, London. 2-Ann. chim. phys., 28, 173 (1825); through Czapek, “Bichemie der Pflanzen,” 1905, p 546. 3-J. pharm. ch?m., 26, 368 (1840). 4-Ber., 1, 58 (1868); 6, 612 (1873). Zentr., 62, 618 (1891). 5-Chem. 285, 278, 292 (1895). 6-Ann., 7 - p ~ a review of early work on pectin, see von Fellenberg, Biochem. Z.,85, 118 (1918), or Czapek, loc. cit. 8-von Fellenberg, loc. cit. 9-Chem. Zlg , 41, 197 (1917). 10-Biochem. J., 15, 494 (1921); 17, 83 (1923). 11-J. Am. Chem. Soc., 46, 145 (1924). J . , 17, 510 (1923). 12-Biochem. 13-J. Assoc. Oficial Agr. Chem., 7 , 57 (1923). 14-U. S. Dept. A g r . , Dept. Bull. 1166, 5 (19231 15-Ibid., p. 34. 16-Chem. A g e (N.Y . ) , 80, 433 (1922).
Potash from Cement Dust’” Concentration by Elutriation By E. J. Fox and C. W. Whittaker BUREAUOF SOILS, WASHINGTON, D. C .
Fractions of cement dusts, the potash contents of which are a p contrary, it Was assumed E M E K T dust has proximately double those of the original materials, were obtained by that the two were PreciPibeen shown to be air separation. I n no instance was all the potash obtained in One tated independently, and Potentially a very might therefore be sepaimportant Source of Amerifraction of the material, regardless of the size of the fraction. r a t e d by Some Physical can p ~ t a s hbut , ~ production I n all fractions of a giuen sample the potash content decreased as means. Because of the difcosts Published to date inthe size of the particles increased. ficulties attending any wet dicate that the technic of The potash is apparently present on the surface of the dust particles method of separation, it is recovery of Potash thereand the disfribufionof the potash ouer all surfaces is apparently egual. believed that any successful from has not yet been deThe concentration of potash obtained was apparently due to the veloped to a satisfactory increase in the aggregate surface obtained in the finer fractions. method for the recovery of degree. Researches have potash from cement kilns been inaugurated, theremust be on some basis fore, to investigate this phase of the potash problem to de- other than water as a means of separation. The advantermine if more efficient methods of recovery can be devised. tages would be manifold. Both the dust and the potash The results and tentative conclusions reached from a study salts would be obtained in a dry state. KO elaborate equipof one phase of the problem are presented briefly in the fol- ment, for treating the dust with water would be required, which would eliminate all evaporating and crystallizing problowing paragraphs. The potash volatilized in cement kilns escapes from the lems incident thereto; and at the same time the one overcharge as a vapor, and as such is carried along with the gas whelming difficulty with calcium sulfate precipitating in water stream issuing from the kiln until the temperature of the gases pipes and spray nozzles would be avoided. To accomplish this, elutriation in media that would not drops to a point where the potash condenses. The potash or the dust was undertaken. then exists as minute particles of potash salts in a highly react with the . potash dispersed state. The dust, on the-other hand, consists of DESCRIPTION OF ELUTRIATOR relativelv large, solid Darticles which are blown from the kiln. ’Cinderzhe influence of the electric precipitator all the The elutriator employed consists of a lower reaction of 2l/4dust particles and a greater part of the potash fume are inch brass pipe, 16 inches long, surmounted by a 4-inch brought down together. I n the absence of evidence to the section, 30 inches long. The two sections are joined by a frustum Of a 60” cone, and are securely soldered 1 Received April 1, 1924. Presented under the title “Elutriation as a Means of Concentrating Potash in Cement Dust” before the Division of together. Industrial and Engineering Chemistry a t the 67th Meeting of the American is attached to the bottom of the lower A 60-degree glass Chemical Society, Washington, D. C., April 21 to 26, 1924. section by means of a brass collar or yoke screwed to the bot2 Published with the permission of the Secretary of Agriculture. tom of the section, making an airtight joint by means of rubber 3 U. S. Dept. A g r . , Bull 672.
C
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INDUSTRIAL A N D ENGINEERING CHEiUISTRY
October, 1.924
gaskets, which also act as cushions for the glass cone. The locities below 25 cm. to effect a clean separation in the entire glass cone is easily removed, in order that the sample may be sample. The potash content of the fraction carried off bereadily placed in it. I n practice, the cone is weighed with the tween 25 and 43 cm. is so small that higher velocities would sample, thereby doing away with the necessity of transferring offer no additional advantages. In other words, the potash content of the residue is so small that the concentration obthe sample from one receptacle to another. A l/s-inch copper tube passes through the wall of the lower tained at velocities greater than 25 cm. would not be worth section of the stack about 4 inches from the bottom, and ex- while, especially since it tends to cut down the percentage of tends at a downward angle to the center of the stack, where it potash in the fines rather sharply. The results of the analyses are given in Table I. is bent straight downward and extends along the axis of the The effect of increasing the velocity from 25 to 43 cm. is stack to :I, point just below its bottom rim. To this tube a nozzle is w ttached, which extends to about 1inch from the apex more clearly indicated by Table 11, which shows the potash of the glass cone when it is in place. This feature is employed content of the fraction of dust blown off between the two vein order that nozzles of various sized openings may be attached locities. The fraction blown off below 25 cm. is also included for comparison. depending on the air velocity desired. Air under pressure is forced into the apparatus through the 11-EFFECT O F I N C R E A S I N G AIR V E L O C I T Y O N C O N C E N T R A T I O N OF nozzle, which directs it downward and with such force that the TABLE POTASH IN CEMGNT DUST Per Ratio dust in the bottom of the cone is lifted and forced upward cent of of KzO total in one through the stack. The velocity of the air through the stack Air ve- Weight Per Per K20 size t o is controlled by the air pressure and the size of the opening in locity o f f r a c - cent cent per 1 that Cm./ tion of total KzO in fraction of total per cent next the nozzle. The particles of dust small enough to be carried Fraction min. Grams dust Grams Per cent KzO of dust above along by the air velocity employed are carried on over the top B-A 0-25 4.10 41.0 0.5306 12.95 84.40 2.05 5.130 C - B 25-43 1.76 17.6 0.0434 2.47 6.90 0.39 .. of the stack and caught in a dust collector placed about the opening. Those that are too heavy to be lifted by the air DUSTFROM SECURITY CEMENT & LIMECOMPAXY current in the top section fall back into the lower section and into the cone. A better example of the nature and sizes of the dust partiThe dust collector is a cage 10 inches in diameter and 18 cles in the average run of dust is furnished by that from the inches high. Its top is a cone with its apex downward and Security Cement & Lime Co., Hagerstown, Md., which has extending a short distance into the top of the stack so that the not been previously concentrated in any may as is the case with dust par;icles will be deflected outward. The bottom is a that from the Riverside Company. copper pan 2 inches deep, in the center of which is a 4-inch This plant uses coal as fuel, and its dust is very unlike that opening and a collar that fits snugly about the top of the stack. obtained from an oil-burning plant,. Considerable quantiThe side:, are of cloth stretched over a skeleton frame so that ties of coal dust and ashes are present in the dust, which, air may pass freely through it but the dust will be retained. according t o several investigators,4 modifies to a large extent The top, sides, and bottom are made separately that they may the nature of the potash contained therein. Certain it is be readily taken apart for the removal of the dust. that the percentage of total potash that is water-soluble is A mechanical knocking device is attached to the side of the much less than in dust from oil-burning plants. stack to jar loose any dust that might otherwise adhere to the There is present’,however, a considerable quantity of potash walls. The apparatus has proved very satisfactory in opera- that is readily soluble in dilute hydrochloric acid, but not soltion and has occasioned no mechanical trouble. uble in water as determined by the Methods of the Association of Official Agricultural Chemists. It may be rendered waterDUST FROM RIVERSIDEPORTLAKD CEMEXTCOMPANY soluble, however, by a simple heat treatment of the dust, or by heating with steam under pressures of from 50 to 100 The Riverside Portland Cement Co., Riverside, Calif., uses pounds. It is generally considered as available potash, and it oil as fuel and the dust obtained is free from carbon. The has been demonstrated that it does dissolve in hot water potash in the dust is practically all water-soluble. The system under prolonged treatment. In fact, during the war period, for catching the dust employed by this company consists of a when cement dust was used in fertilizer mixes, this portion, precipitakor with four hoppers arranged in series. The dust though not paid for as water-soluble potash, 7.va.ssold on that from these is graduated according to size (and also incidentally basis, because the acid nature of the mixture immediately according to its potash content). The larger the size of the rendered it water-soluble. particles the smaller is its potash content, and vice versa. I n this manner, it will be noted, they have effected considera- T A B ~111-CONCESTRATION E OF WATER-SOLUBLE POTASH IN CEXENTDUST Ratio ble concentration of potash in a portion of the dust. KzO in ‘ ~ A D L EI-CONCENTRATION OF
Air yeW t . of lociresities due Sample Cm./min. Grams A (Originalmaterial) 10.00 B 25 5.90 C
43
4.14
POTASH IN CENENTDUST
Ratio KzO in fines Wt. of T n Kz0 in residue fines K1O in fines resiPer cent Grams Grams Grams Per cent due 6.23 1.67 1.33
0.629 0 0,0986 4.10 0.0551 5.86
0 0.5305 0.5739
0 12.95 9.80
0 7.75 7.36
The dust used in the following experiment was from Hopper 4, which contains the finest dust particles and the highest percentage of potash. The entire sample consisted of such fine and extremely light particles that there was difficulty in obtaining a separation a t all, especially a t lower velocities. Two satisfactory separations were obtained, one at a velocity of 25 cm. per minute and the other at 43 cm. per minute. The material in the cone could not be sufficiently agitated at ve-
Air ve- W t . of locity residue KzO in Sample Cm./min. Grams Per cent A (Original material) 10.00 4 . 4 0 B 17.0 8.77 3 . 7 4 C 25.0 6.87 2.93 D 43.0 5.04 2.18 E 56.0 3.64 1.50
fines W t . of residue fines K20 in fines Kz0 in Grams Grams Grams Per cent residue 0.440 0.328 0,200 0.110 0.035
0 1.23 3.13 4.96 6.36
0 0.112 0.240 0.330 0.3S5
0 9.10 7.67 6.66 6.06
0 2.43 2.62 3.06 4.04
Table I11 gives the results of several fractional separations of the dust with their water-soluble potash content. The water-soluble potash in this case refers to that extracted by boiling with water for one-half hour. Analyzing these figures in the same manner as those for the Riverside dust, for the potash content of the various fractions of additional material blown off by increasing the air velocity, the results shown in Table IV are obtained. 4 Potter and Cheesman, THISJ O U R N A L , 10, 109 (1918); Anderson and Nestell, Ibzd 10, 1030 (1918), Merz and Ross, I b z d , 11, 39 (1919).
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TABLEIV-EFFECT OF INCREASING AIR VELOCITY ON CONCENTRATION OF WATER-SOLUBLE POTASH IN CEMENTDUST Per Ratio cent of of KzO KsO in one Wt. of Per Per per 1 size to Air vefrac- cent cent per that locity tion of total Rz0 in fraction of total cent of next Fraction Cm./min. Grams dust Grams Per cent Kz0 dust above B-A O t o 1 7 . 7 1 . 2 3 1 2 . 3 0.112 9 . 1 0 2 5 . 4 2.06 1.35 C-B 1 7 . 7 to 25 1.90 19.0 0.128 6 . 7 4 29.1 1.53 1.36 D-C 25to43 1.83 18.3 0,090 4.92 20.5 1.12 1.26 E D 43to56 1.40 14.0 0.055 3.93 12.5 0.89
..
The available potash as determined by solution in dilute hydrochloric acid gives higher results throughout. Inasmuch as some very interesting deductions may be made therefrom, the results of the analyses for potash by this method are given. The acid-soluble potash, as given in Table V, was determined in the same residue as the water-soluble potash. They are therefore strictly comparable throughout. TABLE V-CONCENTRATIONO F ACID-SOLUBLE POTASH Air ve- Wt. of locity residue Sample Cm./min. Grams A (Originalmaterial)lO.OO B 17.7 8.77 6.87 C 25 D 43 5.04 3.64 E 56
CEMENT DUST Ratio Kz0 in fines Wt. of Ka0 in residue fines Wt. of KzO fines Kz0 in Per cent Grams Grams Grams Per cent residue 7 . 6 2 0.762 0 0 0 0 12.78 1 . 8 5 6 . 9 0 0.605 1 . 2 3 0.157 10.83 1.76 6 . 1 5 0.423 3.13 0.339 9.96 1.87 5.32 0.268 4 . 9 6 0 . 4 9 4 9.21 1.91 0.176 6 . 3 6 0 . 5 8 6 4.83 IN
-
A comparison of the water-soluble potash, and the acidsoluble potash in the residues and fines obtained a t various velocities is shown in Table VI.
-
TABLE VI-COMPARISON
OF WATER-S0LUBI.E AND ACID-SOLUBLE POTASH IN CEMENT DUST Ws water-soluble potash; AS = acid-soluble potash ,------FINES---RESIDUERatio Ratio WS ws AS ws ws AS Sample Per cent Per cent A S Per cent Per cent AS A 4.40 7.62 0.578 0 0 0 B 3.74 6.92 0.542 9.10 12.78 0.712 10.83 0.707 C 2.93 6.15 0.476 7.67 D 2.18 5.32 0.410 6.66 9.96 0.669 E 1.50 4.83 0.310 6.06 9.21 0.658
-.
-
A very s i w c a n t fact to be observed from Table VI is that the ratio between the water-soluble and acid-soluble potash falls off in both the residues and fines as the sizes of the particles in the two fractions increase. By analyzing the results in Table V, for the effect of increasing velocities, the data in Table VI1 are obtained. TABLE VII-EFFECT
INCREASING THE AIR VELOCITY ON THE CONCENTRAACID-SOLUBLE POTASH IN CEMENT DUST Per c e X o f Ratio total KzO in Kz0 one size to Per per 1 Wt. of Per that cent of per frac- cent of next tion total KzO in fraction total cent of above Grams Per cent KaO dust Grams dust 1.338 1 . 2 3 1 2 . 3 0.157 1 2 . 7 8 20.60 1 . 6 8 1.130 9 . 5 8 23.89 1.26 1.90 19.0 0.182 1.29 1 . 8 3 18.3 0.155 8 . 4 7 20.34 1 . 1 1 .. 1 . 4 0 1 4 . 0 0 , 0 9 2 6 . 5 7 12.07 0 . 8 6 OF
TION O F
Air velocity Fraction Cm./min. B-A 0 t o 1 7 . 7 C-B 1 7 . 7 t o 2 5 D-C 25to43 E-U 43to56
Table VI11 gives a comparison of the water-soluble and acid-soluble potash contained in the fractions lying between the various velocities. TABLE VIII-COMPARISON
OF WATER-SOLUBLE AND .%CID-SOLUBLE POTASH CEMENT DUST B Y FRACTIONS Ratio Acid-soluble Water-soluble Per Cent water-soluble Per cent Per cent Per cent acid-soluble 12.78 9.10 0.712 9.58 6.74 0.703 8.47 4.92 0.581 6.57 3.93 0.597 IN
Fraction B-A C-B D-C ' E-D
SURFACE AS THE DETERMINING FACTORFOR POTASH IN CEMENTDUST It has been observed that the potash content invariably decreases as the size of the particles in the dust increases.
Vol. 16, No. 10
Evidence will be adduced to show that this relationship apparently is a surface phenomenon. Before attempting to show the relationship between potash and surface, it will be necessary to show the connection between surface and the velocity of the air in the elutriator a t which the separations were made. From Stokes' law, the size of the particles that will be carried by an upward air current varies directly as the square root of the air velocity, other factors remaining constant. The relation of surface to the size of the particles in a unit mass in terms of air velocity is given by the following equation:
and since r varies as l/Z. S
1
a = kv'vel. -=
where S is the total surface in a given mass, M ; A is the number of particles in the mass; s, m, 0,and r are the surface, mass, volume, and radius of a particle, respectively; and d is the density which is assumed to be constant for all siees. If the potash is equally distributed over the surface of the particles, then the amount contained in a given mam Q€ the dust will vary inversely as the square root of the velocity a t which those particles will be blown off. The percentage of potash contained in the fractions obtained at various velocities, divided by the reciprocal of the square root of the velocity a t which the fraction was obtained, should then equal a constant, K . Table I X shows this to be the case. TABLEIX-RATIO KaO TO SURFACE IN CEMENT DUST Wt. of KzO Deviation Air Wt. of from Percent Fraction velocity Sample K average deviation R-A 17.7 0.2370 0.1278 0.540 -I-0.023 f4.46 C-B 25 0.2000 0.0958 0.479 -0.038 -7.8b D-C 43 0.1525 0.0847 0.556 +0.039 +7.64 E-D 56 0.1335 0,0657 0.493 -0.024 -4.64
-
z.
The conclusion to be drawn from this evidence is that, the potash fume is deposited on the dust particles, rather than simply mixed with the dust. I n regard to the water-insoluble, but acid-soluble potash contained in the dusts from coal-burning kilns, it appears that, since the acid-soluble including the water-soluble potash, and not the water-soluble alone, conforms more closely to the surface phenomenon, it is probable that there is no real difference between the two other than q portion of the potash is adsorbed by the carbon residues present in such dusts. Since the carbon particles are derived from coal dust that has been subject to sufficiently high temperatures to drive off its volatile constituents, they must be porous, if not actually activated, and therefore offer a relatively greater proportion of surface than do the other dust particles. Potash fume is doubtless deposited in the pores, and becomes practically inaccessible to water. Acid, however, will dissolve certain of the water-insoluble compounds, which may coat the carbon particles and thereby expose the potash contained therein. Further justification of this view is found in the fact that those dusts containing the higher percentages of carbon also contain relatively greater proportions of water-insoluble, but acidsoluble potash. Igniting the dusts t o burn off the carbon renders this potash water-~oluble.~ ACKNOWLEDGMENT Grateful acknowledgment is made to J. W. Turrentine, of the Bureau of Soils, under whose direction this work was done, and W. H. Ross and A. R. Merz for their suggestions and criticisms. Merz, THIS JOURNAL, 10, 106 (1918).
