I
WILLIAM W. WINSHIP The Thermal Syndicate, Ltd., New York, N. Y.
Vitreous s i l i c a has been used and specified by many workers in the field of organic (chlorination) and inorganic (chloridizing) reactions with chlorine. Indifference to severe temperature conditions, to chlorine even in its nascent condition, and to chlorinated organic compounds and most metallic chlorides, together with noncatalytic properties and, in the trans-
HEMICAL reactions utilizing chlorine and its compounds on the production scale entail somewhat unusual problems, often involving considerations of photochemistry and catalysis in addition to the more frequent factors of temperature and chemical resistance. In many of these operations metals and alloys lack the required resistance to wet chlorine and hydrochloric acid a t high temperatures, and most ceramics are deficient with respect to homogeneity, purity, or resistance to thermal shock. Phosgene is a useful source of chlorine for both chlorina tion and chloridizing reactions and has been found especially efficient in the latter field. The chloridizing of mineral materials in admixture with carbon probably involves the reversible reaction CO Clg = COCL. The reducing action of carbon monoxide liberated during the decomposition may serve a useful purpose in such chloridizing technique
since the maximum was reached a t the temperature where the latter dissociated. Von Ktigelgen and Seward (48) stated that when silica is mixed with carbon, a 2-hour treatment at 900" C. chlorinates only 1 per cent of the silica present. The surface resistance of fused silica apparatus under similar circumstances will greatly exceed the resistance to chemical attack of finely powdered material; furthermore, reaction on powdered materials may be due to the presence of impurities. Nascent chlorine as liberated during the decomposition of phosgene is the most reactive form of this element. The complete indifference of silica to chlorine is strikingly demonstrated in the following table by Chauvenet reproduced by Dyson (18) which shows the reaction temperatures of carbonyl chloride with various metallic oxides and indicates the resulting anhydrous chlorides:
+
~~~~~~~~~~~~~
ob"
~~~~~~~~~
parent variety, high transmission of actinic light, provide a chemical engineering material valuable for reactor construction and for equipment required in hydrogen chloride, hydrochloric acid, and chloride recovery. An extension of the use of fused silica and quartz glass on an industrial scale is suggested along lines of application which have already proved their value.
Silica
Oxide Tungstio Vanadio Iron Tantalic Titanio Ziroonia Tin A 1umi n a Magnesia, Zinc Beryllia
Judged by the criteria of chemical, thermal, catalytic, and optical requirements, vitreous silica combines the desired properties in an unusual degree. The transparent variety (quartz glass) and the translucent and opaque grades (fused silica) are identical in homogeneity and chemical properties and similar in thermal, catalytic, and most other physical characteristics. The clear variety is unusually transparent to ultraviolet light (a characteristic lacking in the translucent and opaque grades), transmitting down to about 2000 A. It is also highly transparent in the visible and infrared ranges. CHEMICALRESISTANCE.In chlorination and chloridizing practice, chlorine and its compounds generally have no effect on vitreous silica up to its useful temperature limit (1000llOOo C.). Some alkali metal chlorides are an exception; for example, Maier (60) reported that fused lithium chloride is rather active in dissolving silica. Fink and de Marchi (28) investigated the effect of certain chloridizing reactions on fused silica at about 900' C. and found i t apparently due to the presence of sulfur compounds,
Temp., O C.
Chloride
Oxide Manganese Uranium Barium Nickel Chromium Cerium Yttria Lanthanum Thoria Silioa
Tzmp., C. Chloride 460 MnClr 450 UC14 600 BaCln 560 NiClr 600 CrClr 600 CeCL 600 YC4 600 LsCL 650 ThCh
Nore-
aotion
....
While investigating the thermal decomposition of phosgene, Ingelson (86) found that glass was attacked by the chlorine set free; therefore, vitreous silica had to be used as a container for the gas. THERMAL RESISTANCE.Vitreous silica apparatus can be used continuously without loss of strength a t temperatures up to its crystallization point, 1000-1100' C. The upper limit is favored by the absence of strongly reducing gases, while the lower limit may be depressed by certain substances (for example, sodium tungstate, vanadic acid, or sodium and potassium chlorides) which tend to accelerate this so-called devitrification. On the other hand, in a favorable chemical environment 143
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vitreous silica equipment will withstand operating temperatures up to 1400" C. if it is not allowed to fall below the low-temperature transition point a t 300" C.
n
n
Vol. 33, No. 2
OPTICALCHARACTERISTICS. I n appearance similar to a high-quality colorless glass, quartz glass analyzing (like all vitreous silica products of high quality) about 99.8 per cent SiOz possesses high optical transmission up to its crystallization point, from the long infrared range through the short ultraviolet. It is therefore particularly useful where actinic light is employed to accelerate reactions or to supply visibility under temperature conditions impossible with glass. On account of its high electrical resistance a t elevated temperatures, vitreous silica offers special advantages for insulating current leads, arcs, and other elements in processes utilizing electrical forces in the conversion of hydrocarbon compounds by chlorination. The low expansion of vitreous silica, which is much less than that of metals or alloys, demands special care when assembling silica apparatus with other chemical plant details.
Lacy (46) showed a chlorinator comprising cylindrical iron shells with cylindrical silica linings, the spaces between being filled with finely ground flint (Figure 1). Ground fused silica might be substituted for the flint to give the low expansion characteristic of fused silica equipment. Groll and Hearne (29) mentioned four methods of accelerating hydrocarbon chlorination reactions: radiation by actinic light, presence of a catalyst, induction by simultaneous chlorine addition, and heat. The reacting gases may be preheated before mixing, or the mixed gas may be passed through a heated tube. Egloff said that actinic light, heat, and catalysts have been extensively used to accelerate the chlorination of the paraffin hydrocarbons (19) but posed a question as to the actual wave lengths of Iight which are effective. He calls attention to the zero catalytic effect of fused silica in these reactions.
SILICACHLORINATOR ASSEMBLY FIGURE 1. FUSED The thermal conductivity of vitreous silica (0.0035 calorie/ second/cm./sq. cm./" C. for the transparent grade and 0.0025 for the nontransparent) is excellent and, in general, increases with rising temperature. But the thermal property of outstanding technical importance is its exceptionally low expansion and contraction with temperature change, which ensures immunity to thermal shock in a degree possessed by no other ceramic material. Not only is the linear coefficient of 0.00000054 per " C. smaller than that of any other manufactured product, but it is practically constant and gives a straight-line curve up to about 1100" C. Vitreous silica can accordingly be employed over this entire temperature range without thermal strains due to critical temperature zones. CATALYTIC CHARACTERISTICS.Vitreous silica is chemically inert and homogeneous and lacks the property of a practical adsorbent owing to its low retentivity (56). While various porous forms of silica have been recommended as catalysts in Chlorination processes, especially when preheated to high temperatures (48), the value of vitreous silica in such operations is rather as a catalyst carrier, because of its catalytic, chemical, and thermal inertness. The essentially noncatalytic character of vitreous silica apparatus, combined with its resistance to chemical attack, is of the highest importance in safeguarding against secondary reactions involved in organic chemical operations generally.
I
-
I
FIGURE2. FUSEDSILICAS-BENDREACTION SYSTEY FOR COUNTERCURRENT LIQUID-PHASE CHLORINATIONS
Chlorination reactions are often highly exothermic (5'4) and require reactors capable of resisting sudden cooling; or the chlorinating vessels may have to be heated in order t o bring about the reaction (19, 46). Vitreous silica reaction vessels may be air- or water-cooled, or may be heated externally by fuel gases; and tubular reactors may be wound with resistance wire for electrical heating in continuous flow
February, 1941
operations, temperature gradients being maintained by varying the winding on the same tubular vessel. Chlorination processes may require that the chlorine gas be preheated and mixed with the hydrocarbon vapor, and that the mixed vapors be passed through a heated zone where their temperature is gradually increased (21). Fused silica tubes with separate windings of resistance wire offer obvious advantages for such operations, and vitreous silica equipment will also provide for collecting and absorbing the separated hydrogen chloride. Wiezevich and Vesterdal (71) suggested the use of glass vessels in the absence of iron to obtain the best yields in chlorinating various petroleum products. Obviously the use of fused silica would permit the employment of larger individual units, under more severe temperature conditions. I n countercurrent chlorinations of organic liquids, vitreous silica packed towers may be water-cooled to remove reaction heat. A more efficient type of apparatus for such operations is the flattened S-bend absorber (Figure 2). Organic chlorinations may utilize the direct action of chlorine gas, or use hydrogen chloride or phosgene as the chlorinating agent. Groggins and Newton noted that vapor-phase reactions, especially those employing light as an accelerant, require equipment very different from that used for liquidphase chlorinations (28) and mentioned fused silica as a suitable material of construction for the former. Wet hydrochloric acid gas has always presented a difficult engineering problem in developing vapor-phase chlorination processes. Roka (61) pointed out that silica vessels enable the chlorination of methane to be effected a t high temperatures with moist reaction gases. Moisture was also claimed by Lacy to be advantageous in manufacturing methyl chloride (@), and he mentions the use of vitreous silica equipment. Vapor-phase reactions calling for accurate temperature control in continuous operations may well be conducted in vitreous silica tubeswound with electrical resistance wire for direct heating. A f l i n g of ground fused silica between tubing of the same material and metal enclosing cylinders offers possibilities of an assembly for high-pressure hightemperature endothermic reactions. Carter and Coxe (12) mentioned the use of tubular chlorinators, which may be made of fused silica and maintained a t 400-650' C. by any suitable means, for producing chloro derivatives of methane. I n the production of chlorinated hydrocarbon derivatives, Jackson, Wainwright, and Hailes (37) speciFIGURE 3. VITREOUS fied an electrically heated silica IMSILICA ELECTRIC tube through which the reacting MERSION HEATER vapors pass a t 700" C. Heated vitreous silica reaction vessels were also suggested by Lacy for manufacturing organic halogen products (46),including ethyl chloride (44). The reaction of hydrocarbon gases with chlorine may be promoted by passing the hot mixed gases through porous plates of sintered fused silica (16). Such plates have recently been offered for commercial use. Vitreous silica electric immersion heaters (Figure 3) are particularly convenient for internally heating chlorination equipment in either gas- or liquid-phase reactions.
145
I n certain chlorination processes, notably the manufacture of rubber hydrochloride (65), pure dry hydrogen chloride rather than chlorine is used as the halogenating agent. Saturated hydrocarbons (42)may be chlorinated by reaction with hydrochloric acid and oxygen a t temperatures up to 650" C. Hydrogen chloride is also the reacting agent, with oxygen, in producing chlorobenzene from benzene (67); and in some modifications of the Friedel and Crafts reaction (go), aluminum chloride, reacting with hydrocarbons, yields hydrogen chloride which takes part in further reactions. The presence of the latter also appears to be essential to the reaction of certain hydrocarbons with aluminum chloride. Hydrogen chloride hydrolysis may be applied to organic compounds and hydrogen chloride as a hydrolyzer, and as a by-product of hydrolysis may present a considerable engineering problem (2%). With larger sizes of vitreous silica equipment now available i t should be possible to extend the use of this material on the plant scale. Hydrogen chloride for the production of lower alkyl chlorides must be of extreme purity, and special precautions are necessary to obtain the gas as free as possible from admixture with chlorine and other permanent gases. A patent describes the production of such gas and its use with a suitFIGURE4. FUSED able catalytic agent (39). One SILICABURNERFOR COMBUSTION OF of the most important requireCHLORINE IN HYDROments in chlorinating rubber is GEN a supply of anhydrous hydrogen chloride, which may be dried over sulfuric acid or anhydrous calcium chloride (63). About 5 per cent of hydrogen chloride contained in the spent acid is usually recoverable. Large volumes of hydrogen chloride gas are evolved in industrial Friedel and Crafts reactions, and the corrosion problem is always present (41). I n rubber chlorination, boiling vessels must be employed (69) to remove hydrogen chloride and free chlorine. Egloff (20) stated: "In many of the reactions of pure hydrocarbons in the presence of aluminum chloride, hydrogen chloride is a highly important component of the system. It may be added to the reaction or may be present as a result of hydrolysis of the aluminum chloride by water, or may arise as a product of the hydrocarbon reaction." Hydrocarbon halides in the presence of steam and catalysts may decompose to give hydrochloric acid and water vapors (48). Hydrochloric acid may be formed in the thermal purification of chlorinated hydrocarbons containing similar compounds, in the presence of suitable dehydrogenation catalysts (8). Methane will produce hydrogen chloride (IO) by a highly endothermic reaction with sodium chloride, and calcium, lithium, and potassium chlorides can be used similarly. A tubular reactor with excess of water vapor should be employed a t 700-800" C. (64) in the synthesis of hydrochloric acid by reaction of methane, water vapor, and chlorine. Conditions of economy as well as sound engineering practice require that the loss of chlorine as hydrogen chloride from hydrocarbon halogenations be kept to the minimum, and hydrochloric recovery systems are standard features of most halogenation processes. Hydrogen chloride liberated in hydro-
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carbon halogenations might profitably be decomposed and the chlorine recirculated for further use. Patents (49, 66) cover methods for effecting this recovery. Here the conditions of corrosion are severe, and proper choice of equipment material is essential.
4i'
SILICA ROTATING FURNACD FOR ANEIYDROUS FIGURE 5. FUSED METALLICCHLORIDE PRODUCTION
High-quality hydrochloric acid of 20" BB. strength suitable for marketing is usually obtainable from the chlorination of hydrocarbons. In some chlorination processes the liberated hydrogen chloride may be recirculated with the gaseous mixture through the reaction chamber (66); where hydrogen chloride is the original reacting agent, this is especially practicable (67). A patent issued to Ayres (2) illustrates a typical vitreous silica absorption system used in recovering hydrogen chloride from chlorinated solvent manufacture. Water is particularly suitable as an absorbent for recovering hydrogen chloride from chlorination processes, not only on account of the high solubility of hydrogen chloride in it, but because of its substantial immiscibility with most halogenated organic products (22). Its high heat capacity and latent heat make it an effective cooling agent when used in small quantities to avoid excessive dilution of the hydrochloric acid formed. Methods have been devised for preventing the formation of organic films on the absorbent ( I ) , and for rectifying the liquid mixture of chlorinated products and hydrochloric acid to produce anhydrous hydrogen chloride (16). Fused silica condensers arranged on the reflux principle enable water cooling to be employed a t temperatures impossible with glass or stoneware equipment. Hydrochloric acid separated in chlorination processes is often obtained free from arsenic and sulfur compounds (9) and may be anhydrous (63). In gas-phase reactions, washing with water is often sufficient to separate the hydrogen chloride from residual organic gases (44). Hydrogen chloride produced in liquid-phase reactions may be scrubbed with the make-up hydrocarbon compound entering the process before absorption in water (14). Baxter suggested the separation of by-product hydrogen chloride from admixed organic vapors by scrubbing in a tower containing boiling water, the heat of reaction maintaining the scrubbing solution a t about 110" C. (6). He claimed that 20 per cent hydrochloric acid can be so obtained. Thomas (68) described the separation of hydrochloric acid from the chlorination of pentane and its absorption in a countercurrent fused-silica system, giving hydrochloric acid of 20" BB. strength for sale. In the production of hydrogen chloride for chlorination and chloridizing processes, the combination of chlorine and hydrogen by combustion gives gas of high purity and high strength. With gas supplies adjusted in proper ratio and adequate cooling, a plant of this type will operate continuously with the minimum of supervision.
Vol, 33, No. 2
Figure 4 shows a standard fused silica burner employed for the combustion of chlorine in hydrogen, an excess of the latter gas flowing through the outer tube. A vertical combustion chamber and cooling equipment of the same material are followed by absorbers if liquid hydrochloric acid is required. ~~~~~~~~~~~~~~~~
gf raor[ynEliu:)
JpqPlreraricPera
Apparatus for chloridizing must ordinarily withstand temperatures considerably higher than those encountered in organic chlorinations; the production of aluminum chloride, for example, necessitates resistance to chlorine a t 1000" C. (41), that of beryllium chloride involves a temperature of 800" C. (72), while zinc chloride can be formed from its elements a t 600-700" C. (60). Selective separation of metal chlorides by heating ores and similar materials in the presence of chlorine has been carried out a t 1100" C. in separating chromium, nickel, and iron values (SI),a t 1050" for separating niobium and tantalum (64), a t 900" in the case of chromite (87), a t 900" for obtaining aluminum chloride from clay or bauxite (@), a t 700-900" for separating iron and nickel (SO), and a t 400" for lead vanadates (6). Such processes may be made continuous, employing fused silica apparatus. It may be advantageous in chloridizing operations to introduce the chlorine through a small fused silica tube directly into the boat containing the charge in a larger tube of vitreous silica ( 3 ) . Electrically heated vitreous silica retorts are suitable for preparing beryllium chloride from beryl and carbon in a stream of carbon tetrachloride and chlorine a t 800" C. (7B). Phosgene undergoes extensive decomposition a t temperatures above 300' (18) and is also decomposed in radiation of wave length 2750-3050 b. On the other hand, it may be formed by the photochemical union of its elements (36). In producing anhydrous aluminum chloride from either aluminum oxide or metallic aluminum and chlorine gas, the apparatus must be capable of withstanding chlorine a t 1000" C. Intimate contact of the reacting materials is required for efficient results (41). FIGURE6. VITREIn preparing aluminum chloride, it OUS SILICARDACshould be kept in mind that molten TION CHAMBER AND CONDENSER FOR aluminum readily attacks vitCONTINUOUSCornreous silica equipment. The latTIRCURREINT CHLOter has, however, been successRIDIZATION fully used for purifying aluminum chloride bv admixture with aluminum powder and resubliming (68). Carl (11) described in detail an electrically heated fused silica rotary furnace for making anhydrous aluminum chloride, and Wohlers (73) applied similar equipment to the production of anhydrous metallic chlorides in general (Figure 5 ) . Baughman (6) used a rotating fused silica cylinder, 13 inches (33 cm.) in diameter, 60 inches (152 cm.) long, heated by an electrical resistance coil, in the chloride volatilization of Black Butte ores and in separating the mixed oxides by volatilization. Baskerville (3) recommended vitreous silica tubing for chloridizing thorium oxide mixed with carbon.
~
CHLaRINATidN
Fused silica equipment is very suitable for u88 as condensers or mbliming chamber8 in chloridizing operatiom where sudden cooling under severe cbemical conditions is required. Such condenser chambers, like the chloridizenr, may be provided with eeveral independent electrical windings for murate temperature control (60). Maier (61) specised a vitrabu. silica reaction chamber and condenser for the continuous countercurrent chloridisation of ores. As Figme 6 shows, the temperature conditions here are unusually wvere, the pteheating and chlorination mes being maintained a t about 900' C. by electrioal resiatom while water cooling is employed a t the lower end of both mwtion chamher and condenser. The d u e n t gsses may contain hydrochloric acid and water vapor. Richsrdson (SO) claimed that s h u n assist% materially in chloridizing metals or metallic compounds, and recommended a tubular silica furnaoe maintained a t !3GtMooOo C. for prcduaing anhydrous chlorides. In chloridbing operations a mixture of gwous hydrogen chloride and steam (70)wae recommendedfor treatingoxide o m aontsining smallamounta of nickel and large amounta of iron, and a mixture of hydrogen chloride gas and chlorine may be employed (17) in refining mixtures of the platinum group metals. Chlorides may also be formed by renetion between the oxide and a mixture of hydrogen chloride gas, hydrogen, and steam; a rotmy siliaa tube furnaca is conveniently employed (86). Carrying chloridixing resctions further, metallic chlorides treated with hydrogen and steam at a high temperature are in aome c a w converted into the corresponding oxides and hydrogen chloride (86). Hydrogen chloride is also a frequent by-product of inorganic chloridiaing processes (69) and may besepsratedfromthemixedgasesandrecoveredforre-use(70). Phosgene (26)rescta readily with most metallic oxides to giw the chloride of the metal and carbon dioxide. Resistancewire-wound fused silica tubes are a convenient form of reactor. Bsskerville (4) e m p h w i d the simplicity of the prcoedure-merely heating the pulverised material in a silica tube in a stream of &aseous phmgene. Hulett (33)employed this reaction for purifying inorganic m a t e d contsining iron, including silica ssnd intended for optical glass manufacture. Metallic anhides treated with phosgene give the ohloride of the metal and carbon oxysulfide (36). By hydrolpi8 p h w gene yields hydrogen chloride and carbon dioxide. The preparation of very pure metallic chlorides often involves ae a 6nal step the fusion or dehydration of the d t in a current of hydrogen chloride, the material being contained in a vitreous &ca boat inside a heated tube of the same matarial (60).
Photoehemioal A p p l i ~ a t i o ~ Actinic light has long been employed to promote chlorination processes. It ha! been claimed that under the influence of ultraviolet light a molecular rearrangement d t a during the ohlorination of hydrocarbons, very liMe hydrogen dorids being liberated (67). Payne and Montgomery (66) demiba a procam involving the expoeure of gaseous hydrooarbons to ultraviolet light after treatment with chlorine in amtact with a catalyst formed by the chlorination of a liquid hydmcarbon. In chlorinating rubber, ultraviolet rays may be used in preparing the rubber solution in order to increasa ita cancenhtion, to p m o t a halogemtion, and to s t a b the finished product (13, 84). Ultraviolet rays are also olsimed to he valuable in promoting the reaction of chlorinatedhydroosrbons with sulfur dioxide and chlorine for tho production of organic h a I o g e n 4 o n i c acid chlorides (38). The exact reqnirementa in this field are not definitely known, and it has been suggested that various parta of the ultraviolet range below 3132 A. may have specifio action re-
,147
sulting in ditrerent products from the same raw materiala (86). Where light of extremely short wave length is required, the low-pressure mercury vapor lamp in quarts (operating mostly in the 2536 A. region) may der advantagen in same c~se8on account of ita low temperature. On the other hand, the heat contributed by the high-pressure quartz mewuryvapor lamp may in some instance be advantageous in promoting an endothermic reaction (68). While glass equipment is photOchemicaUy suitable for chlorinations employing tho longer rays of the ultraviolet spectrum,fused quarts is necessary as an apparatus material whem the full actinic power of quarts mercury-vapor l a m p is desired. In d d e equipment tubular reaction ahamhem of nontransparent f d silica may have inteersuJr fused-in sections of transparent quarts glass where required for ultraviolet irradiation. Large-ade equipment may be provided with quarts glass details for internal irradiation and reaction v d of other materials may be fitted with windows of quarts glass in suitable packing glands. The least expensive type of quartz glass apparatus for carrsing out photochemical chlorinations is an arrangement of Btrsight quartz tu& through which the gam or liquids paes while expoeed to the actinic light source. A coil of quarts glass tubing surrounding the ultraviolet light is more &cient. Various forms of quartz glsss equipment have been deviaed for bringing reacting m a t e d into intimate contact with the actinic rays in continuous photochemical chlorinations in the liquid or vapor phase. Typical arrmgement.9 of this kind are shown in Various patents (7,30,40,47,74).
Literature Cited (1) An-, E.E..Jr. (to B. A. 8. Co.). U. 8. Patent 1,631,474(Nov. 10,1931). (2) .. Avrea. . E. E.. Jr. (to Shamlea 8olvents Co.). IM..1,836,201 (Deo. 8,1931). (3) Btwkerville. C.,J . Am. C h . Soc.. 28,92242 (ISM). (4)B.skemiUe. C.,Seianca. 50, 443 (1919). (6) Bsulrhman.. W.. . TmM. Am. Ek&&em. Scc.. 43, 281-316 (lG23). Barter. J. P. (to Imperial Chemioal Industden, Ltd.). U. 8. Patent 2,047,611 (July 14,1986). Britton. E. C.. Coleman. 0. H..and Hadler. B. C.. U. 8. Patent
>an,G. H.,and Zemba, J. W. (to Don Chemid Co.). Ibid.. 2,084,937(June 22, 1937). Brook. B. T.,and Pndmtt, F. W.. U. 8. Patent 1,320,831 (March 21. l917L , C&&, C.,'Ma.~&rc&?mMioirr39,1139 (July 16, 1LW) .Carl. B. E., U. 8. Patent 1,862,298(June 7. 1932). Carter. C. B.. and Coxe. A. E.,IW.. 1,572,613(Feb 91, 1926). chcrmiaohe Fabrik BuOLSu. Frenoh Patent 788.167 (Aur. 1. 1934). C o w , G. H.. and Moore. GI. V. (to DonChemical Co.). U.8. Patent 2,174.737 (Oot. 3, 1939). h e . 0. O., Jr. (to Carbide & Carbon chemi& Co.). Ibid., 1,4aa&38 (Juk 18.1922). Daohlsuar, IC., end 89hnitalsr. E. (to I. 0. Farbrmindlutrie). Ibid., 2,156,039(April ab. 1939). Deutwhe Gold- und 8ililbemcJcheidesmtalt VORD. Rneedler, Fnmch Patent 841.W (May 18,1939). Dyson, Q. M., C h . Rn..4,1 G 3 4 3 (1927). Ed&. Gu~tav,Sohand, R. E., end Lowry, C. D., Jr.. Ibid.. 8, 1-80 (1931). (ZO) E&S, Quatav, W h n , E., HUUS. 0.. Van A d 4 P. M.. IW., 20,346411 (1937). (21) EUio, C. (to Cbsdsloid Chemical Co.), U. 8. Patent 1,aOZprO (Oot. 24, 1916). (22) Enpa, W..and Redmond, A. (to Shell Development Co.). IW.. 2,077,882 (ApdI20, 1937). (28) Fink, C. 0.. d de Marehi. V. 8.. Tmtu. Ebdmrbn. &e., 74 (lueprint) (1W). (24) Flaresoo, W.. Frenoh Pstsnt 788,632 (Aug. 10,1934). (ab) Gibbs. H. D. (to ssldsn Co,). Brit. Patent 123,341 (Oat. 2% 1917). (26) Gibb.. W. E., Rept. Tin and Tungaten B o d (Brit.), 1922.
.
INDUSTRIAL A N D ENGINEERING CHEMISTRY
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(27) Great Western Electroohemiad Co.. Brit. Patent 609.368 (July 14, 1939). (28) Gro-a, P. H., "Unit Pmeessas in Or-c Byntheaia". and d., 1938. h l l . E. P.. and H e m e , G.. ID. ENQ.Carnu.. 31,1684-7 (1939). Hart. C.. U. 8. Patent 2,030,867 (Feb. 18.1936). Ibid., 2.030.868 (Feb. 18, 1038). Bolt. L. C.. and Daudt. E. W. (to E. I. du Pont de Nemoun 6. Co.. ho.).lbid.. 2.091.986 ( b t . 7. 1937). H i & . G.'A.. U.8.'Pat&t 1;3&,38e web. 16. 1921). 1. G. Farbenindukie, Brit. Patent 283.106 (Dea. 6,1928). I n g e h , H. J.. J . Chem. 800.. 1927.2244-64. Jackmu. K.E., J . C h . Education. 10,622-6 (1838). J a b . K. 8.. Waioaripht. 0 . E.. and Hail-. E. R. (to Imwrid 'chermiod Indun&. Ltd.).Brit. Psterk 438,Wk (Oot. ?. 1936). (38) Johnmn, G. W. (to I. 0. FarbenindustriB). IW.. 616,214 (July
z&
1.a3'1.662 ( A U ~21,1917). . Elipstein, E.E., C h . Mark&, 25.6936 (1029). Kmw. %oh, and R 6 b , K. (to Hohverkohlwmr-hdmtrie) U. 8.Patent 1,664,821 (Jan.3.1928). Kgelgen, F. von, and & w d , 0 . 0. (to VirSinia Lsb. Co.). bid., 1.147.83a (J* 27,1916). Lacy. B. 8.. U.8. Patent 1,242,208 (Oot.9.1917). L w . B. 8. (to Roesaler & Edsoher Chemical CO.), Ibid.. i.iii,84a (&pt. ag. 1914). Ibid., 1,263,wW (April 23,1918). , F.. U. 8. Pateut 1,459,777 (June 26. 1933). (48)Lloyd, ~~~. 8. J., and Kennedy, A. M., IW., 1,849,844 (March 16, 1932). (40) Low. F. 8. (& Wedtvaco Chlorine Fmducta Co.), Ibid., 1,746,-2 m h . 11. 8Ml).. - 1..__, (€4) Maim. C. G., U. 8. Bur. Mined. T d .Paper 360 (1826). (61) Maier. C. G.. U.8.Patent 2,183,987 (Oot. as. 1938). (62) Msier, C. G. (to Glad Weatem Eleotroohemioal Ca.), Ibid.. 2 . 1 4 a . e ~(J-. a. 1 ~ 9 ) .
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vol. 33, NO.
a
(63) Moffett, E. W., Winkelmann, H. A. and Willisma. F. E. (to
~ a r b o uCOW.).IW.. 2,138,ma (Deo. 6, i9as). (64)Padrovmi, C.. D e Bartholomasis, E., snd 8inirsmed. C., Ani X" cam.idem Aim., 41,6143 (1939). (66) . . Palmer. W.0 . . and Clark. R. E. D.. ploe. Rar. 800. (London). .. Al49,'3& (1984). . (66) Payne. E. E., and Montgomery, 8. A. [to Standard Oil Co. (Id.)]. U. 8. Patent 1,463,766 (May I. 192.3). (67l Prshl. W., and Mathen, W. (to F. Raaohig. Q.m.b.H.), W.. 2,Oa6,917 (March 31, 1936). (68) Ralaton, 0. C.. U. 8. Bur. Mines, T d .Papa 321 (1923). (69) Raalin Corp., Brit. Patent 489,964 (Aug. 6. 1938). (60) Riohsrdmn, H. A., Ibid.. 621,976 (June 6. 1940). 631) Rob. K. (to EohverLohI-Indwtriatrie Akt.&.). IW.. 14, 1921). U.6. Patent 1,383,366 (Dee. 14. 1920). (64) 8oaYt6 Sen&& m6tallur(pque de Eobokeu, Brit. Patent €47.124 (68) Bsunders, H. F., and Butherland. L. T. (to Glyain Corn.). I1.321pI
(66) 8ooi66 intemationds des industried ohimiques et d6riv&a,8. A. Holding. h o b Patent 834,124 (Nov. 14, 1938). (66) &ell, J., and Runkel, C. (to I. Q. Farbenindustrie), U. 8. Patent 1.880.167 (Nov. 28,1932). (67) Teichmaoo. C. F.. Klein, H., and Rathemsaher. 0. P.. U. 8. Patent 2,016,044 (8ept. 17. 1936). (68) Thomaa.C.A.."Scienoeof Petmleum",Vbl.4.pp.a7862801.Oxford univ. Praaa. 1938. (69) W-uht, R.. C h . F&. 1923.121-2. (70) Wesoott. E. W., U. 8. Patent 2,036,684 CApd 7, 1936). (71) Wiwevich. P. J., and Vederdel. H. Q., C h . Rea.. 19, 101-17
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and Yntema, L. F.. Tram. Am. &I&&.
-I EQUIPMENT M. A. KNIGHT, J R ~ Maurice A. Knight, h. Ohio
TRICTLY speaking, chlorination involves the substitution of chlorine atoms for other atoms in molwules of a substance. In a broader sema it may be conaidered ea any pmoeas or chemical d o n involving chlorine itself or one of ita compounds in whioh substitution or addition
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of chlorine atoms occura. The aotivity of chlorine with nearly every metal in the presence of water, the temperatures reached in some meas, the organic solvent nature of many of the compounds p r o d , and the frequent praeenoe of hydrochloric acid rule out all forms of equipment except ceramicware or g l m . Definition of Chemical Stoneware Bow is chemicsl stoneware M e r e n t from pottery, porcelab, clay building tile, or m e r pipe since they are all made from day?' Brielly, the above forms are essentially aluminum silicates plus minor amounts of other materials. Chins
and poroelain are white, dense, often translucent ceramic bcdies that are fuUy vitrified and acidpmf. Highly p u m raw m~terialssre used to en%unr whiteness, and the body is highly fluxed to obtain maximum denaity. This last oharaoteristio pub definite Dse limitations on true porcelain articles. Pottery such as flower v ~ s e sand mme d i m a r e is not alwap v i W and depends on an applied glase for service. Elementa added for coloring and for manufacturing eaee would lesoh out in acid Service. Mechanical strength is comparatively low. Building brick and sewer tile generally take raw clay from local murcea, and it is formed m d fired without puriscation to mske a earviceable prcduot. The premnce of iron permits lower firing temperah snd imparts the familiar red color. The raw clays are too impure to be used for other ceramic purposes. Chemical stoneware, in addition to being acidpmof, must meet phyeical requhmenta ea to stmngth, tempersture,'pamsify, snd dimenDona in a variety of &apes which am much larger than
