INDUSTRIAL AND ENGINEERING CHEMISTRY
766
halide in the mass of the calcium silicate of the slag and the extensive surface afforded by the liberated calcium fluoride when the calcium silicate framework of the slag is dissolved by the citrate solution. The reaction between the more basic phosphates and calcium fluoride induced experimentally in the solid mixtures, in aqueous suspensions, in carbonated water suspensions, and in ammonium citrate solution-suspensions, gave a persistent citrate insolubility not found for the basic phosphatic mixtures devoid of fluorides. Component calcium fluoride may therefore be considered as a potent factor in the development of citrate insolubility in ammoniated superphosphates and in those with which liming materials are incorporated. It should be stressed that the increases in citrate insolubility may develop in commercially processed superphosphates not only during the curing period, but also during the actual analysis of the finished product. The citrate insolubility that develops during curing of superphosphates rendered nonacid forming, or those ammoniated, may be considered an inescapable incident of manufacture. It is not equitable, however, that the manufacturer be charged with citrate insolubility that is developed during the imposition of analytical technic. Conditions imposed by the analytical technic should not cause a diminution of available Pz06 during the actual analysis. Apparently, however, citrate digestions cause such a diminution when used for the analysis of processed superphosphates
VOL. 29, NO. 7
that contain fluorides and considerable proportions of basic phosphates.
Literature Cited (1) Assoo. Official Agr, Chem., Methods of Analysis, 1930. (2) Jacob, K. D., Rader, L. F., Marshall, H. L., and Beeson, K. C., IND.ENQ.CHEY.,Anal. Ed., 4, 25 (1932). (3) Jacob, K. D., Rader, L. F., and Tremearne, T. H., J . Assoc. Oficial Agr. Chern., 19, 449 (1936). (4) Jacob, K. D., and Ross, W. H., S. Am. SOC.Agron., 23, 771 (1931). (5) Karandeeff, B., 2. anorg. Chem., 68, 188 (1910). (6) Keenen, F. G . , IND.ENQ.CREM.,22, 1378 (1930). (7) Ibid., 29, 197 (1937). (8) MacIntire, W. H., U.5. Patent 2,067,538 (1937). (9) MacIntire, W. H., and Hardin, L. J., J . Assoc. Oficial Agr. Chem., 18, 297 (1935). (IO) MacIntire, W. H., Hardin, L. J., and Oldham, F. D., IND.ENQ. CHEM.,28, 48 (1936). (11) Ibid., 28, 711 (1936). (12) Maohtire, W. H., Jones, R. M., and Hardin, L. J., J. Assoo. Oficial Agr. Chern., 18, 301 (1935). (13) MacIntire, W. H., and Shaw, W. M., IND. ENG. CHEM.,24, 1401 (1932). (14) MacIntire, W. H., and Shaw, W. M., J. Am. SOC.Agron., 26, 656 (1934). (15) MacIntire, W. H., and Shuey, G . A., IND.ENO.CHEM.,24, 933 (1932). (16) Willard, H. H., and Winter, 0. B., IND.ENG.CHEM.,Anal. Ed., 5, 7 (1933). RECEIVEDMarch 1, 1937.
Fertilizer from Rock Phosphate' Conversion by Fusion and Treatment with Water Vapor
F
HARRY A- CURTIS, RAYMOND L-COPSON, ture required is just below that OR some time it has been EARL H. BROWN, AND GORDON R. POLE at which the phosphate fuses. k n o w n t h a t when fmely ground rock phosphate is T~~~~~~~~ valleyAuthority, wilson D ~~ ~1 ~, I n. c i p i e n t fusion gives rise to heated in an oxidizing atmosm e c h a n i c a l difficulties in hanphere and i n t h e p r e s e n c e of dling the pasty mass. Fbck phossufficient silica and water vapor, fluorine is volatilized from phates have a softening rangerather than a sharp melting the material. Under suitable conditions the fluorine content point, and they vary considerably in fusing temperature, depending on the proportions of the several impurities present. may be reduced from an initial value of over 3.0 per cent to Consequently the temperature must be under very close cona final value of less than 0.1 per cent. When the defluotrol by the operator a t all times. rinated product is quickly cooled, the phosphate is nearly all I n the investigation a number of attempts were made a t available as plant food. first to calcine rock phosphate in an experimental oil-fied Jacob and hi co-workers in the United States Bureau of rotary kiln, approximately 15 inches inside diameter and 20 feet Chemistry and Soils studied this process on a small scale (3, long. The combustion of the oil was relied upon to produce 4, 6, 6). With rock phosphate containing 4 t o 12 per the water vapor necessary for the reaction. However, the cent silica, they found that upwards of 95 per cent of the results were not equal to those obtained in small-scale work. fluorine was volatilized and 80 per cent or more of the phosFor example, when a rock phosphate containing 6 to 9 per cent phate was converted into the citrate-soluble condition by heatsilica was calcined a t a maximum temperature of 1400" to ing small charges of 40-mesh material in the presence of water 1450" C. and a t a feed rate such that the total time in the vapor for 30 minutes a t approximately 1400' C. These inkiln was approximately one hour, the fluorine volatilization vestigators demonstrated that water vapor and silica together varied from 50 to 70 per cent, and the conversion to citratepromote the defluorination of rock phosphate. soluble phosphate varied from 20 to 40 per cent. Even when Attempts are being made, both in this country and abroad, the time in the kiln was doubled, either by decreasing the rate to develop practical means of using the calcination process on of feed or by putting the product back through the kiIn a a larger scale ( 1 , 7 ) . There are several difficulties to be oversecond time, the fluorine volatilization did not exceed 75 per come. One of the worst arises from the fact that the temperacent, and the conversion to citrate-soluble phosphate did not The term "rock phosphate" is used to distinguish the amorphous phosexceed 50 per cent. I n these experiments the rock phosphate phates, such as occur in the deposits in Tennessee and Florida, from the was ground to pass a 40-mesh sieve and was moistened with "mineral phosphates" of definite chemical compositions, such as fluorapawater and fed to the kiln as a stif€mud, to avoid dust losses. tite, phosphorite, etc.
JULY, 1937
INDUSTRIAL AND ENGINEERING CHEMISTRY
The experimental conditions were varied considerably from those just stated, without improvement in the results. When coarser material was used, the reaction was much slower. When temperatures within the softening range were used, the material became plastic and formed rings in the kiln. The use of steam to atomize the oil, or the addition of small quantities of superheated steam to the atmosphere in the kiln, did not improve the results noticeably.
Preliminary Fusion Experiments
767
indirect electric arc furnace was adopted for small-scale experiments. The furnace was a Detroit rocking electric furnace type GM. The furnace was modified as shown in Figure 1. A pipe manifold w&smounted on the furnace, through which steam or gas could be forced into the molten material. The furnace was operated at 20 to 25 kw., using 1.5inch graphite electrodes. A 20-pound charge of rock phosphate could
Because of practical difficulties encountered in attempt-
During the experiments on calcinaing to defluorinate rock phosphate by treatment with water tion in the rots,y kiln, a few samples of vapor at temperatures below the fusion range of the rock, fused material were obtained. The product from one run at approximately the possibility of defluorinating fused rock phosphate was 1450' C. contained rounded particles investigated. Small-scale experiments indicated that fluorine about l/g inch in diameter, which apcould be removed from rock phosphate at temperatures 50" to parently had been fused. These were 170" C. above its melting point, that contact with water separated by hand; on analysis it was vapor was necessary for rapid defluorination, and that comfound that the sample contained only 0.5 per cent fluorine, and that 74 per bustion gases from hydrocarbon fuels might be used to supply cent of the PZOSwas citrate soluble. the water vapor. Products containing approximately 0.1 Another sample of fused material colper cent fluorine, 30 per cent total PZOs, and 26 per cent lected from the wall of the kiln was citrate-soluble PZO6 were obtained. found to contain only 0.14 per cent Three different semiworks furnaces, oil-fired, were built fluorine. In one set of preliminary experiand operated to determine necessary conditions, fuel conments, finely ground rock phosphate sumption, life of refractories, and character of product. was mixed with water, molded into rods Results obtained in the small-scale tests and in the semiapproximately 6 / ~ inch in diameter, works furnaces are summarized in this paper. and dried. The rods were held in the flame of an oxyhydrogen torch, and the molten mat'erial was allowed to droD directly into water. The products co& tained 0.2 per cent fluorine or less, corresponding to over 93 per be fused in about one hour, starting with a cold furnace. In cent volatilization, and 86 per cent of the PzO6 was citrate all of the experiments described here, the indirect-arc furnace was lined with a silica refractory. The normal operation of soluble. This result was surprising, in view of the short time the furnace was as follows : during which the phosphate was in afused condition. Apparently the reaction was very rapid a t the high temperature and A charge of lump rock phosphate was dumped into the hot a t the highwater vapor concentration of the oxyhydrogenflame. furnace, and the arc started. During the period of fusing the Other preliminary experiments were made in which rock charge, the openings from the gas manifold were kept above the charge. After fusion was complete and the desired temperature phosphate was fused in refractory crucibles and also in a reached, steam or other gas was started through the manifold small cylindrical furnace having a capacity of about 5.5 and the furnace rotated so as to bring the gas openings to the pounds. Oxygen-hydrocarbon gas flames were used in these bottom of the molten charge. The gas was forced through the experiments. The temperatures varied from 1500" to molten rock for the predetermined time. In order to prevent the melt from solidifying around the o enings from the gas 1600" C., and the time of fusion from 20 to 60 minutes. The manifold, and thus cutting off the gas 8 w , it was customary products contained from 0.5 to 0.03 per cent fluorine, and 72 to heat the molten rock to a temperature 100" C. or more above t o 86 per cent of the Pz06 was citrate soluble. its fusion point. The furnace was then rotated so as to bring the openings above the melt, the gas flow interrupted and the Small-Scale Fusions in Indirect- Arc Furnace melt poured out. The melt was either blown into ehets by a blast of air or was quenched in water. An opticafpyrometer I n order to investigate the conditions necessary for rapid was used to measure the temperature in the furnace at intervals and the temperature of the fused product as it was poured from volatilization of fluorine from fused rock phosphate, a small the furnace. The arc was shut off during the measurement of temperature within the furnace. PEFRACTORY
FIQURE1.
INDIRECT-ARC FURNACE
The composition of the rock phosphates used in the experiments is shown in Table I. Sample 1 is representative of the material fused in the indirect-arc furnace. The products were analyzed for total Pa05, citrate-insoluble PzOs,and fluorine. F l u o r i n e was determined in all samples by the Willard and Winter method. The citrate-insoluble PzOs was determined by the official n e u t r a l a m monium citrate method, using 1.0 gram of sample to 100 cc. of citrate solution, and with t h e a d d i t i o n of filter paper pulp (2). All s a m p l e s for analysis were ground to pass an 80-mesh sieve. It was necessary to adopt a standard fineness, since it was found that the
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INDUSTRIAL AND ENGINEERING CHEMISTRY
VOL. 29, NO. 7
citrate solubility of the PsOc determined by the indicated Since the rotary kiln was available in which the calcination procedure, varied with the fineness of the sample, and that experiments bad been made as described, i t was decided to try the finer the sample, the greater was the citrate solubility. to fuse rock phosphate in this kiln. The kiln wss lined When rock phosphate was fused for 60 minutes in the inwith silica refractory brick and was fired with 28"to 32"A. P. I. direct-arc furnace, with no control of the furnace atmosphere, gas oil atomized with compressed air. The rock phosphate the product contained about 1.9 per cent fluorine. When fed to the kiln was sized to pass a 2-mesh and he retained on nitrogen saturated with water vapor was introduced over the a 20-mesh sieve. With material of this size there wits little melt in the furnace, the fluorine removal was only slightly imtrouble with formation of rings in thekiln. Themoltenprodp r o v e d , since the uct was niinnched p r o d u c t s contained i n w a t e r , and the a b o u t 1.2 per cent quenching apparatus fluorine, after treatwas arranged so that ment for 60 minutes. the steam generated Likewise, bubbling a was drawn hack into rapid stream of dry the kiln. a i r or n i t r o g e n A test run lasting through the melt for 18 days was made in I5 to 20 minutes rethe rotary kiln. The sulted in unsatisfacaverage composition tory removal of fluoof the feed is given as rine, theproductsconsample 2 in Table I. tainingfrom 1.8t02.2 The average composiper cent fluorine. tion of the product is However, whendry shown in Table 111, steam was b u b b l e d where the results of A . 0.14 pr cent ~ u ~ ~ iB. 0.42 ~ ~oent fluorine t h r o u g h the molten this run are summaFIGURE 2. PHOT~XRAPR OF THIN SECTIONS OF FUSEDPNOSPH~TE TAKEN rized. On the averphosphate at such a WITH TRANSMITTED LIGHT AND CnOSsED NIcoLs ( X 75) rate BJ to a e i t a t e age, 92 per cent of the themelt violently, fluorine was volatilthereby giving good contact, volatilization of most of the ized, and 83 per cent of the P20swas converted to the citratefluorine was accomplished readily. During the steam blow, soluhle condition. The oil consumption averaged 5.7 pounds acrid fumes were emitted from the charge. per pound of available P,O, produced; this figure was excesTable I1 gives the results of several experiments in which sive since the heat losses from the kiln were large and since no steam was blown through the molten phosphate; the data in atdempt was made to recover heat from the flue gases. each ease are the average of two duplicate experiments. The Sfter 18 days it was necessary to stop operation because the fluorine in the products varied from 0.30 to 0.12 per cent, silica brick lining of the kiln had been badly attacked by the and the citrate solubility of the P,O, from 84 to 87 per cent. molten phosphate, and the steel shell of the kiln had become No appreciable volatilization of PIOswas observed during the so hot that there was &anger of serious warping. experiments. The fact that the total PzOsin theproductswas lower thanin the rock phosphate charged was evidently due to Tilting Converter Furnace solut.ion of some of the silica refractory by the molten charge. A semiworks furnace was built in which superheated steam It was found possible to blow the molten product into small could be blown through the molten phosphate, as shown in pellets by means of an air blast, as the melt was poured from Figure 3. This furnace was similar to the small, indirectthe furnace. 'I'he size oi the pellets could be varied within arc furnace except that it was oil-fmd. The chamher of the wide limits by regulating the pressure of the air blast. The furnace was cylindrical, and it was mounted on trunnions so fluorine content and the citrate solubility of the PzOs were that it could be rotated about its horizontal axis. A single about the same, whether the melt was blon-n with air or was opening in the furnace shell was used both for charging and quenched in water. When air-blown, the product consisted of small, dark green, glassy spheres; when quenched in water, it disintegrated into pieces approximately 1s,' inch in size. TABLE I. ANALYSEBOF ROCKPHOSPHATES USED Photomicrographs of thin sections of the defliiorinated phosphate are shown in Figure 2. The sample of Figure 2A Analysis, %Sample Ignition contained 0.14 per cent fluorine, and 83 per cent of the Ps05 No. Msterisl PIO. F CaO Sios F*Oa AIaO. lam was citrate soluble. The major constituent was identified by 1 Tenn.Orornioek 30.7 3.3 41.8 14.3 2.4 1 . 4 5.6 2 32.9 3.5 46.1 9.5 2 . 9 1.3 4.1 its optical properties as a-tricalcium phosphate (S), crystal:3 3 0 . 7 5 . 3 4 2 . 7 9.9 3.5 3.5 3.4 lized in random orientation. A small amount of a glassy 4 Tenn. white rock 29.6 3.3 42.1 13.5 2.8 2 . 3 3.1 5 2 0 . 6 3.3 44.0 13.0 3.1 1.6 4.7 material, with a refractive index close to that of the u-tricalcium phosphate (1.58 to 1.59), was also present: it %'as apparently a calcium-aluminum-iron silicate glass. The sample of Figure 2B contained 0.42 per cent fluorine, and only 72 per Length -Analysis of Prodnot. vola. Cit. Of Citrstetiharate cent of the P20,was citrate soluble. In this case the crystals Steam Total id. tion of sol. "f of tricalcium phosphate were smaller and were interspersed Temp. Blowri PSOI PIOs Si08 F Fluorine P%06 C. Min. % 70 % % % % with fibrous crystals which apparently were fluorapatite. 1660 1s 28.7 26.1 24.0 0.30 sn 84 isan 17 28.3 24.6 26.1 0.18 94 sr
.-
Rotary Kiln
These experiments demonstrated that fluorine may be volatilized rapidly from molten rock phosphate when intimate contact with water vapor is provided.
15 30.4 30.7 25.8 0.12 96 1630 17 30.6 20.4 26.5 0.12 96 The quantity of dry steam blown through the molten charge mated st from 0.4 t~ 0.8 w x n d per pound of rook !Aoaphate. 6 Calculated from total P.0. in charge and in product. 1610
85 87
WBB
=ti-
INDUSTRIAL AND ENGINEERING CHEMISTRY
JULY, 1937
TABLE 111. AVERAGERESULTSOBTAINED I N Rock Phosphate No. 2
3
4 5
Type of Furnace Rotary kiln Convertera Hearth Hearth
Duration of TemType of Charging Test perature Day8 O C. Continuous Batch Batch Continuous
18 9
8 8
1510 1520 1540 1540
Production Rate Per Per hour batch Lb. Lb.
65 80 110
191
...
640 715
...
769
SEMIWORKS FURN.4CES
of Product-
-----Analysis
Citrate soly. of PzOs
Total P?Os
Si01
%
%
%
yo
30.8 29.8 31.5 30.2
19.2 17.5 14 8 17.0
0.25 0.34 0.19 0.47
83
F
80
85 70
-Oila Per hour
Lb. 94 90 108
80
ConsumptionPer lb. Per l b of of availuble product PzOs
Lb.
Lb.
1.45 1.12 0.98 0.42
5.7 4 7c 3.7 2.0
Gas oil, 28O t o 32' A. P. I. b Superheated steam blown through melt for 5 minutes during each %hour cycle; quantity of steam estimated a t 0.06 pound per pound of rock phosphate. C Does not include oil for superheater.
0
for pouring out the molten product by tilting the furnace. X pipe manifold was mounted along the side of the furnace, t b o u g h which superheated steam could be introduced. The openings from this manifold were maintained above the level of the melt during charging and fusing, and the furnace was rotated so as to bring them a t the bottom of the bath during the steam blow. The furnace was heated by two oil burners, located a t opposite ends of the combustion chamber, and two regenerators were provided for recovering part of the heat from the flue gases. The burners were used alternately; the hot flue gases passed through one regenerator and the air for combustion was preheated in the other, in the usual manner for such furnaces. An oil-fired superheater was provided for superheating the steam. Flexible pipe connections were used between the superheater and the fusion furnace. The furnace was lined throughout with silica refractory, with the exception of the pouring spout which was lined with zircon brick. The regenerators were constructed of highgrade fire clay refractories. This furnace could produce 1.0 to 1.7 tons of fused rock phosphate per day, when charging 1-inch lump rock. On the average, over 90 per cent of the fluorine was volatilized, in the product was citrate soluble, and 80 per cent of the PzOs when the melt was blown with superheated steam for 5 minutes. However, the time required for fusing the charge was excessively long, indicating low rates of heat transfer. It was also necessary to reheat the charge after the steam blow to make it sufficiently fluid for pouring. Thus the steam blow occupied only 5 minutes out of an average operating cycle of 8 hours. Although it is probable that the operation can be improved, the results so far obtained indicate an excessively high oil consumption in this type of furnace. The average results of a 9-day run are given in Table 111.
1
FIGURE 4. HEARTH FURNACE
The life of refractories in the converter furnace was found to be very short. Thus, a 9-inch silica refractory lining had a life of only 14 days of continuous operation. The attack of the molten phosphate on the refractory lining probably was increased as a result of the agitation of the charge - in this type of furnace.
Hearth Furnace
FIGURE 3. CONVERTEE~ FURNACE
The third type of furnace was a regenerative, oil-fired furnace, having two hearths on which the charge was melted. This furnace is shown in Figure 4. Silica refractories were used for the crown and side walls. The hearths were constructed of tamped ganister, on a firebrick base. The furnace was heated by two oil burners located a t opposite ends of the combustion chamber. The burners were used alternately, the hot flue gases passing through one regenerator and the air for combustion being preheated in the other, as in the converter furnace. The regenerators are not shown in the drawing. Rock phosphate was supplied to the furnace through the hoppers shown in Figure 4. The feed was between 1 and inch in size. As the rock phosphate fused, it flowed into the central trough of the furnace in which it collected and from
770
INDUSTRIAL AND ENGINEERING CHEMISTRY
which it was tapped a t intervals. The fused phosphate was quenched by means of a high-pressure water jet and sprays. The furnace was operated with both continuous and batch charging. In the first case the hoppers were maintained full of rock phosphate which descended continuously into the furnace as the material on the hearths melted. The fused product was tapped from the furnace a t intervals of about 5 hours. In the second case a batch was charged into the furnace, and wai melted and tapped before a second charge was introduced. With batch charging the interval between taps averaged about 6.5 hours. The results obtained with each type of operation are summarized in Table 111; the data are the average for an 8-day run in each case. The fluorine content of the product was lower with batch charging, but the rate of production was higher and the oil consumption lower with continuous charging. The oil consumption per pound of available Pzo5 was much lower in the hearth furnace than in the rotary kiln or in the converter furnace. However, the air for combustion was not carefully controlled, and it is believed that the oil consumption can be considerably decreased over the figures reported here. To heat one pound of rock phosphate to 1550" C. requires 540 B. t. u., and additional heat is required for fusion. The total quantity of heat can be supplied by the combustion of 0.04 pound of fuel oil. Thus, eventhe lowest oil consumption reported in Table I11 corresponds to a low thermal efficiency. The hearth furnace was operated for a total of 50 days, and about 70 tons of fused rock phosphate were produced. During part of the time a limited amount of water vapor was introduced into the furnace atmosphere, in addition to that supplied by combustion of the oil. No difference in results was observed. Examination of the refractories after 50-day operation showed that the silica refractory lining was deeply corroded a t the flux line. The ganister hearth had been dissolved to a depth of 2 to 3 inches. The top two courses of brick in the regenerator checkers were glazed, owing to dust carried over from the combustion chamber. Otherwise the refractories were in good condition. It was evident that the same kind of refractory gave much better service in the hearth furnace than in the converter furnace.
Conclusions 1. Fluorine was volatilized readily from fused rock phosphate a t temperatures above 1500" C. and in the presence of
VOL. 29, NO. 7
water vapor. When dry steam was bubbled through the molten phosphate, from 5 to 15 minutes were sufficient for volatilization of over 90 per cent of the fluorine, and for conversion of over 80 per cent of the Pz05 to the citrate-soluble condition. No addition of silica over that present in the rock phosphate was required. 2. Rock phosphate was fused and defluorinated in an oilfired furnace in which water vapor was supplied only by combustion of the oil. In the hearth furnace the time required for fusion and defluorination was approximately 5 to 6.5 hours. 3. Refractories were severely attacked by molten rock phosphate. Most of the experience so far has been with silica refractory, and this has not given satisfactory length of service. The attack on the refractories was much less in the hearth furnace than in the rotary kiln or the converter furnace; in the latter, corrosion of the refractories prpbably was increased by the agitation of the molten charge. 4. If the refractory problem can be solved, either by use of better refractories or by improvements in furnace design, it appears probable that available phosphate can be produced cheaply by fusion and treatment by water vapor. The lowest oil consumption was 2.0 pounds per pound of available P205 produced, and a considerably lower figure should be possible.
Acknowledgment The authors are indebted to other members of the staff of the T. V. A. Chemical Engineering Laboratorv a t Wilson Dam assistance in obtainink the data presentea in this paper.
Literature Cited Caldwell, U. S. Patent 1,902,832(March 28, 1933). Jacob, Rader, and Tremearne, J. Assoc. Oficial Agr. Chem., 19, 449-70 (1936). Marshall, Reynolds, Jacob, and Rader, IND.ENG. CHEM.,27, 205-9 (1935). Reynolds, Jacob, Marshall, and Rader, Ibid., 27, 87-91 (1935). Reynolds, Jacob, and Rader, Ibid., 26,406-12 (1934). Reynolds, Marshall, Jacob, and Rader, Ibid., 28, 678-82 (1936). St. Jacques, IND. ENG.CHEM.,News Ed., 15, 29-30 (1937). Schneiderhohn, Mitt. Kaiser-WilheEm Inst. Eisenforsch. DGsseEdorf, 14,34-6 (1932). R E C E I V ~April D 17, 1937. Presented before the Division of Agricultural and Food Chemistry a t the 93rd Meeting of the American Chemical Society, Chapel Hill, N. C., April 12 t o 16, 1937.
Removal of Undesirable Constituents from Tobacco Smoke R. E. DERR, A. H. RIESMEYER, AND R. B. UNANGST
on the practicability of minimizing this or any other undesirable compound. Because of the lack of this information the work to be described was undertaken. It had the primary object of employing the adsorptive properties of activated alumina for this purpose by placing this highly adsorptive material in the stem of pipe and cigaret holders. (Activated alumina is a highly adsorptive granular aluminum oxide produced by Aluminum Company of America.) Other sorptive materials were investigated also, and as a result the conclusion which will be developed is: A fresh cigaret of any commercial brand is the most practicable eliminator of undesirable constituents of tobacco smoke.
A l u m i n u m Research Laboratories, A l u m i n u m Company of Ame.ica, New Kensington, Pa.
ANY investigators have studied the constituents of smoke which pass from a cigaret or pipe into the smoker's respiratory system. From this work i t is well known that tobacco smoke contains nicotine, carbon dioxide, carbon monoxide, ammonia, aldehydes, and a number of organic tarry compounds. Although there has been disagreement as to the degree of harm resulting from the assirnilation of these constituents into the body, it is generally conceded that nicotine, ammonia, and tarry matter are present in amounts which could be irritating or which would have the greatest physiological effects. Most invcstigat.ions ha,ve been concerned with the nicotine conknt of tire smoke, but substantially no data are available
M
Puffing Device A review of the literature shows considerable variations in the quantity of nicotine present in tobacco smoke, and this is undoubtedly caused by differences in the smoking procedures. Therefore, the first problem was the selection of a puffing device with which normal smoking could be simulated and which would pernit consistent duplication of results. The use of a partial vacuum as a means of drawing the puff and a mechanically rotated valve for controlling the duration of was rejected puff, as employed by Jensen and Haley (4, because of insufieient control of volume and volocity. Obviously, the effects of these important items would be accentuated by the slightly increased resistance introduced by a sorptive smoke filter. The smoking device selected was constrncted substantially as shown in Figure 2 of the article by Bradford, Harlan, and Hanmer @): This devicc permits the drawing of a definite volume of air at a uniform rate and in a definite period. The volume is controlled by a meamred quantity of water flowing from a buret. The PIS
= water leveler K = adjustable top sapnoit for leveler bulb L = bottom auppoit for leveler bulb
J
771
