CALEB DAVIES, JR. Pittsburgh Coal Carbonization Company, Pittburgh, Penna. thoroughly agitated coal; the heating speed is the same for a14 of the coal and is controlled independently of the carbonizing temperature, considerable amounts of pitch vapor or pitch fog are contacted with the coal feed below carbonizing temperature, and partial combustion of by-products occurs within the retort, the coal having first been subjected to controlled heat treatment usually including some partial oxidation. I n spite of these differences (most of which are necessary t o make homogeneously excellent domestic coke from certain coals), the general by-product trend of Table 11 corresponds roughly t o that of Table I; the lower carbonizing temperature results in less gas, no ammonia, more tar, and, especially, more and higher boiling tar acids. The gas yield of the Disco process is low as compared with high-temperature processes, but it can all be made available, as the heating system can be readily adapted to the use of producer gas or suitable coal stokers; only one flame is required for one of our units which preheats and carbonizes daily about 184 tons of total feed, consisting of coal and recirculated breeze. This compares with perhaps 170 flames for the same throughput in high-temperature ovens. Larger single Disco units are contemplated. The light oil from the Disco process, although comparatively high in nonaromatics and low in benzene, contains a The most important by-product of coal carconsiderable amount of toluene, Since our operation is bonization by the Disco process is tar. Alhardly large enough to justify installation of light oil recovery though this tar differs considerably from equipment, the light oil data is based solely on small-scale the better known coal tars in many respects, investigation of the gas. The Disco gas liquor also is not commercialized. It conthe products properly made from it have tains some carboxylic acids, probably mostly acetic acid, and been found satisfactory in most branches of thus exhibits some slight analogy between low-temperature the tar industry and in some cases to have coal carbonization and by-product charcoal production from certain advantages. A distinctive feature wood, as noted in some of the old literature. A small daily of Disco tar is the large amount of contained addition of lime t o the gas liquor is sufficient to avoid corrosion of steel piping. The liquor also contains small amounts tar acids which can be utilized in plastics of other soluble organic compounds, mostly present in much by taking advantage of recent important larger amount in the tar, such as the lower-boiling phenols development. and some dihydric phenols. Some of this complex organic material acts as an indicator of alkalinity. The liquor is normally yellow and after dilution is almost water-white. Upon gradual addition of alkali to this dilute solution, it turns a muddy blue or greenish blue, then muddy purple, and plant and the other in the Disco low-temperature carbonizafinally clear deep red. Gradual addition of acid reverses tion plant. The low-temperature carbonization in Tablc I these changes. is not strictly comparable to the Disco process. Table I is Tar is the principal by-product of the Disco process, and based on batch heating of quiet masses of coal; different its characteristics and utilization will be described later. portions of the charge are heated at different speeds, the Before leaving the general discussion of low-temperature average heating speeds vary considerably with the carbonby-products, it should be noted that, if the Disco (low-temizing temperature, little or no pitch vapor or pitch fog conperature coke) were t o be further heated with exclusion of air denses on the coal before it reaches carbonizing temperature, in a separate operation so as to reduce the volatile content to and the process involves no partial combustion of distillation that of high-temperature coke, the principal by-product of products within the retort and no preliminary partial oxidasuch additional devolatilizing would be gas containing a very tion or high-temperature pretreatment of the coal. On the large proportion of hydrogen. This is consistent with the other hand, the Disco process continuously heats a stream of fact that Disco is much more smokeless than coal of the same 860
RACTICAE commercial results have been obtained throughout a period of more than seven years in connection with operations in the low-temperature carbonization of coal by the Disco process (4) a t Champion, Penna. During a considerable part of this period, Disco tar production has been in the neighborhood of 1.5 million gallons per year. Within a radius of fifty miles of this plant, the quantity of coal tar and tar products normally burned as fuel is perhaps greater than in any other equal area in the world. Although Disco tar and its products are not in the liquid fuel market, the inventory is generally low a t the end of each year. The relation between carbonizing temperatures and byproduct results is indicated approximately in Tables I and 11. Table I (3) shows by-products for each of a series of carbonization tests of a certain Alabama coal in an experimental retort which was held a t a different constant temperature throughout each test. Table I1 gives typical by-product results obtained from two rather similar but not identical Pittsburgh seam coals, one in a high-temperature by-product coke
P
. July, 1941
INDUSTRIAL A N D ENGINEERING CHEMISTRY
volatile content, and no less smokeless than some nonhomogeneous cokes containing much less volatile matter. Recent commercial trends for coal by-products show: Coal gas is suffering from increasing competition of natural and oil refinery gases and of water gas from low-grade oils; light oil is undergoing increasing competition from improved petroleum products and processes; by-product ammonia is affected by severe competition from synthetic ammonia whose plant capacity is now being greatly expanded for defense; but the demand for the large-tonnage types of tar products is fairly stable, and the use of certain coal tar specialties is increasing rapidly. A peculiarity of the tar business, however, is its abnormal relation t o general business conditions. There is a tendency for oversupply and surpluses in prosperous times when the country requires unusually large amounts of pig iron and coke. On the other hand, in times of general depression when coke production is low, there is usually a relatively good demand for certain important tar products such as road tars and export briquet pitch.
Properties of Disco Tar I n comparison with high-temperature coke-oven tar, Disco
tar is characterized by low specific gravity, high viscosity, high softening point of distillation residue, high tar acid content, and low total-bitumen content. On the other hand, it is similar to high-temperature coke-oven tars in weather resistance of its pitches, temperature susceptibility of pitches, viscosity index of liquid tars, tendency to form inverted emulsions with small amounts of water, and frictional characteristics of tarred surfaces in contact with wet rubber. Although Disco tar and its pitches are black, finely ground Disco tar pitches have a brownish color similar to many watergas tar products. Thin smears of filtered Disco tar on bright surfaces show a dark brownish-red color, but the same tar unfiltered makes a greenish smear. Benzene solutions of filtered Disco tar are fluorescent. Disco tar resists water, acids, and alkalies, with the exception that alkali hydroxides (but not carbonates) will combine with the phenolic bodies present. Disco tar tends to impart a red color to water with which it is in contact, especially in the presence of air and absence of acid. This has no practical significance and is due to the presence of small amounts of soluble dihydric phenols which take up oxygen from the air and form red compounds of great coloring power. The insoluble matter in Disco tar is largely, but not entirely coal dust. The determination of total bitumen in Disco tar by the standard method (solubility in carbon disulfide) shows considerably more insoluble matter than is found by filtering the tar and then washing the filter with hot benzene. Ap-
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much as carbon disulfide. Upon adding a large amount of benzene to the clear creosote-oil tar filtrate, a small amount of solid matter is precipitated. This pronounced difference between these three solvents has been observed with tars made in experiments with lower rank coals in a Disco pilot plant, as well as with our regular product made from Pittsburgh seam coal in the full size units. Experiments with hot tar in a good centrifuge resulted in a satisfactory reduction of the ash content of the tar without a corresponding reduction of the percentage insoluble in carbon diI
TABLE11. TYPICAL BY-PRODUCT RESULTSWITH DISCOCARBONIZERS AND HIGH-TEMPERATURE COKEOVENS ON SIMILAR PITTBBURGH COALS Carbonizing Process
n. t. U. Heat value/cu. ft B. t. U. 8p. gr. compared 't'o air Nitrogen content, vol. % LNH4)&04 obtainablehon dry coal, Ib. u g n t 011 Gal. obtainable/ton dry coal Toluene obtainable/ton dr coal, gal Unsulfonated residue in li& oil, vol: %
Disco
High-Temp.
3640 546 1510
11000 5800 5500
226 415 0.95 50
0
2900 500 0.38 5 25
1.4 0.2 65
3.3 0.6 4
Gal. msde/ton dry coal Commercial tar acids/ton dry coal, total gal. Crude tar sp. gr.,.25°[250 C. Dehydrated tar viscosity a! 50' C., a Eng!er Total bitumen (sol. in CSz) in crude tar, weight
14.75 1.22 1.14 85
11 0.31 1.18 38
Softening point of residue from standard road tar distn. to 300' C., C.
81.5
94.2
82
47
T- I o .r
%
sulfide. The percentage of the same centrifuged tar insoluble in cresote oil followed by benzene was so low that the ash content of the insoluble material so determined was as high as would be expected for very fine coal dust. Evidently the centrifuge removed all but a small amount of the very finest of the coal dust from the tar; and the creosote oil dissolved all the tar except this small amount of remaining coal dust, but the carbon disulfide precipitated several times as much solid material from the tar as the centrifuge left in it. This effect may be related to the fact that when the clarain and vitrain of coal are dissolved in hot pitch from high-temperature tar, the solution of coal in pitch readily forms a gel upon addition of benzene or carbon disulfide but not so readily upon addition of creosote oil. Perhaps some of the coal dust dissolves in pitch fog particles i n the by-product gas before these particles leave the carbonizer and are incorporated into the tar. Tar bases are present in Disco tar in small amount. They are mostly of a complex type, practically no simple pyridine being present. Some of them are combined with other comTABLE I. BY-PRODUCTS FOR VARIOUS CARBONIZING TEMPERA- pounds so that they cannot be removed completely from TURES FOR THE SAME COAL(5) crude distillates of Disco tar merely by washing with dilute Carbonizing temp C. 500 600 700 800 1000 sulfuric acid. After removal of tar acids by treatment with cu ft as/ton coA 2250 4250 7000 8750 11750 Lb: (NJ%zBO~/ton coal 3.0 12.5 26.0 23.0 16.0 caustic soda solution, the separated alkali-washed oil will then Gal li h t oil/ton coal 1.3 1.5 1.5 2.0 2.5 give up its tar bases almost completely to a sulfuric acid soluGal:to?ueneinliehtoil/toncoal 0.078 0.135 0.345 0.610 0.412 Gal. tar/ton coai 18.5 19.4 16.0 14.2 10.1 tion i,n the usual way. We have not commercialized these Gal. tar acids/ton coal 3.14 3.10 2.42 1.29 0.25 0 tar acids in tar 17.0 16.0 15.1 9.1 2.5 tar bases as such. They show some effectiveness as pickling p. gr. of tar 1.00 1.04 1-10 1.15 1.19 inhibitors and also in accelerating the action between formaldehyde and low-temperature tar acids. Tar acids in Disco tar distillates are more plentiful and more parently a large volume of carbon disulfide precipitates or complex than in high-temperature coke-oven tar distillates, flocculates solids out of the tar. A still smaller amount of especially in the higher boiling ranges. Roughly speaking, insoluble material will be found in the tar if it is first dissolved within the boiling range of the generally salable tar acids, the in hot creosote oil (made from Disco tar) and filtered, and the Disco tar contains about one and a quarter times as much tar filter and insoluble matter are then washed with hot acids as a typical high-temperature coke-oven tar. Our labobenzene. Apparently benzene also flocculates some of the ratory, by including higher boiling material, has made appartar constituents much more than creosote oil, but not so ently satisfactory phenol-formaldehyde resins from about
x
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INDUSTRIAL AND ENGINEERING CHEMISTRY
three to three and one-half times as much tar acids per gallon of t a r as is usual in the commercial utilization of high-temperature tars. By including still higher boiling distillates, a gallon of Disco tar will yield a total quantity of tar acids amounting to more than six times the quantity of tar acids usually extracted for sale from a gallon of high-temperature tar. (The high-temperature tars also include high-boiling tar acids which are not commercialized, but these are present in comparatively unimportant amount.) Even within the boiling range of phenol, the cresols, and the xylenols, the Disco tar acids show a more irregular boiling point curve than the high-temperature tar acids. There are three principal fields for phenol-formaldehyde resin-molding, laminating, and varnish or lacquer. Our laboratory has investigated Discotype formaldehyde resins for laminated products more thoroughly than for other uses, even a rather complex natural mixture of Disco tar acids giving good results. Cert'ain large and readily separated portions of the Disco tar acids make heat-advancing formaldehyde resins which can be cooked with linseed oil and therefore seem to be suitable for use in varnish manufacture. The separation and purification of certain of the Disco tar acids for use in light-colored and fast'curing forrnaldehydc resins for molding has not yet been t'lioroughly investigated by our laborat,ory, although promising results have been obtained from a portion of the material. Tne investigation of the very high-boiling Disco tar acids is also still incomplete. When working with Disco-type tar. distillates and tar acids and sodium cresylate solutions quantitatively in the laboratory, it should be noted that water is soluble in free tar acids and in alkali-washed and cresylate-washed tar oils to a considerable and variable extent, depending on v-hich tar acids are involved and other factors. I n general, thc water solubility of Disco-type tar acids decreases with increasing boiling points. I n this connection, a sample of rather high-residue Disco-type creosote oil was topped to a temperature of 315" C. (thermometer near liquid as in American Wood-Preservers' Association standard distillation). The distillate and the topped residue were then separately subjected to severe leaching tests, including agitation with large amounts of hot water. The lower boiling portion (which ~ r o u l dlargely evaporate out of vood in the first few years of service) showed a considerable decrease in tar acid content, but the topped material (which is more permanent in service) shon-ed only a slight decrease in tar acid content. The phenol coefficient of Disco-type t,ar acids for disinfect,ant use increases with increasing boiling point up to about 250" C. and then decreases with still higher boiling points! probably as a result of decreasing solubility. Dihydric phenols are found in Disco-type tar distillates, as described in the literature for typical low-temperature tar products. These compounds should be removed to prevent deterioration of Disco tar distillates in storage (especially in the presence of alkali, air, heat, or iron) as well as to prevent imparting a red color to products or a pink color to dilute emulsions made from such oils. Disco tar distillates in the lower boiling range show favorable lacquer-solvent characteristics such as aniline point and dilution ratio (cotton tolerance). Alkali washing tends to improve the dilution ratio. However, these distillates evaporate rather slowly. Disco tar, its soft pitches, and all its distillates become more fluid upon being washed with caustic soda solution in excess. When the soft pitch is washed with an excess of caustic soda at a temperature high enough for complete liquidity of the pitch, about 25 per cent (or more) of the pitch dissolves to form a brown solution. The carbon-disulfide-insoluble matter is thus concentrated in the pitch but to a considerably less
Vol. 33, No. 7
extent than is calculated from the decrease in the volume of pitch. Disco tar distillates boiling below 300" C. and containing about 50 per cent tar acids show an "unsulfonated residue" of about 8 per cent. A typical high-residue Disco-type creosote oil shows about the same sulfonation residue. This indicates that Disco tar is quite different from certain low-temperature tars described in the literature as having distillates equivalent to a mixture of tar acids arid petroleum oil. If a rather closeboiling fraction of Disco tar dist,illate is treated with strong sulfuric acid, as in the U. S. Department of Agriculture method for determination of unsulfonated residue, the unsulfoliated residue will have higher boiling points than the original oil. This is in spite of the fact that still lower boiling distillates show about the same amount of unsulfonated residue. While this has not been thoroughly investigated, i t seems to indicate the possibility that, in the case of some Disco tar distillates, the effect of the sulfuric acid is to convert some of the constituents of the oil into polymers which resist further attack of sulfuric acid and are insolublc in it. Treatment, with 66" B6. sulfuric acid, of Disco t'ar distillates boiling below 300" C. results in complex changes apparently soinewhat analogous to similar treatment of coke-oven light oil; home polymerization takes place, and the acid solution bccornes cffective as a pickling inhibitor. This dark acid solution, however, does not tend to deposit carbonaceous matter to such a n extent as the acid sludge from coke-oven benzene plants. Disco t a r distillates boiling below 300" C. can be washed with dilute sulfuric acid in steel equipment without attacking the steel. This is probably due to inhibiting effect of the tar bases. When heated with free sulfur, high-boiling Disco tar distillates react vigorously, hydrogen sulfide is evolved, and the viscosity of the oil increases. If t'he temperature is a little too high or the action continued too long, the oil is changed t80 coke by this treatment. One sample of Disco-type creosote oil with specific gravity of 1.06 (38"/15.5" C.) and 39 per cent residue above 355' C. (A. TV. P.A. method) was examined by the method of Fielrlner et al. (2) and showed the following composition: Tar acids Tar bases Olefins Aromatics Paraffins and naphtheneq
No moisture-free distillates of Disco tar will deposit crystals when chilled. Oils boiling below 300" C. arc clear and fluid below 0" P. (- 17.8" C.). The high-boiling oils become waxy and viscous when cool, but apparently do not deposit anthi acene crystals. American Tar Business in General Commercial tar products are usually made under simple well-standardized laboratory control. Even with a new type of tar the plant operators do not ordinarily have to use any such conglomeration of more or less technical information as given in the preceding part of this paper. The quantity of coke-oven tar sold for refining in the United States in normal times is of the order of 300 million gallons per year. This does not include water gas tar or some tar processing done by producers. Construction of Disco carbonization plant capacity for about 600 tons of coal per day would be required in order to add one per cent t o this amount of coal tar. The principal commercial products of coal tar are road tars, wood preservatives, pitches, and specialties.
July, 1941
INDUSTRIAL AND ENGINEERING CHEMISTRY
Road tars are produced to the extent of perhaps 150 million gallons per year. Some distillate is produced in connection with certain grades only. Tars largely compete with and take higher price than asphalts amounting to more than 600 million gallons per year for similar use. They are superior to asphalts in respect to coating moist aggregate, penetrating characteristics of prime coats, and antiskid characteristics of surface coats. Wood preservatives consist of creosote oil, coal tar, and mixtures of the two. About 164 million gallons were used in 1939, including comparatively small amount of creosote oil mixed with petroleum oil. Pitches and some specialty products are made in connection with creosote oils. The principal uses of these preservatives are in railroad ties (over 34 million in 1939) and in poles (over 4.5 million in 1939), various other uses being important. There is a trend toward increasing use of straight tar and of mixtures of petroleum oil and creosote oil. Pitches are utilized for waterproofing, roofing (principally for flat built-up gravel roofs), carbon electrode manufacture (of great importance for aluminum and ferroalloys), and fuel. They are produced largely as by-products of creosote oil. The gallonage of specialties is a small but growing proportion of the total. They include some raw materials which are essential to, but minor cost factors in, the manufacture of coal tar dyes and pharmaceuticals, and also include raw materials for certain important plastics and coatings, as well as disinfectant oils, bituminous paints, some orchard insecticides, and various other products.
Disco Tar Products Disco tar products have been sold and successfully used in road tars, wood preservatives, roofing pitch, disinfectant oil, and orchard insecticide oil, all with no evidence of technical inferiority to the older types of tar materials, and in certain cases with some technical advantages in the Disco tar products. The Pittsburgh Coal Carbonization Company's tar plant includes the following: 1. Two horizontal tank stills, each about 10 feet in diameter and 33 feet long, equipped with steam coils (250 pounds per square inch), direct steam distributor, tubular condenser, and facilities for operation under a vacuum of about 27 inches mercury. 2. One small pipe heater, fired with pulverized pitch and equi ped with small vacuum flash tanks, pitch cooler, pitch bay, congnser, etc., so that liquid soft pitch leaving the heater at about 380' C. is subjected t o vacuum steam distillation in the small flash tanks and converted into fuel pitch with a softening point of about 200' C. cube in air. 3. Necessary storage and blending tanks, pumps, air compressor, piping, loading track, etc. 4. A small laboratorv for miscellaneous research as well as plant control. 5. A coking unit (under construction) which will flash soft pitch into coke and oil vapors, and thus make more and higher boiling distillates. This includes a two-stage condenser, and is designed t o avoid coke-handling labor and deterioration of heating surface.
ROADTAR. The viscosity or consistency is controlled by distilling off water and oil, or by adding oil or other flux. As with high-temperature tar, removal of the last 1 or 2 per cent of water results in a great increase of viscosity. For most of the usual road tar specifications, the Disco tar cannot be prepared for shipment merely by adjusting to the required viscosity, because of the too high softening point of the residue after standard test distillation to 300" C. vapor temperature. This softening point probably corresponds more or less to the tendency of the tar in the road surface to become hard and brittle after the low-boiling constituents have had an opportunity to evaporate out during a year or two. If the specification has a reasonably low minimum specific gravity (such
863
as the rather recent American Association of State Highway Officials' specifications), the softening point of distillation residue of Disco tar is usually lowered by addition of very high-boiling distillates from another portion of the tar. This means the substitution of high-boiling oil for some of the lower boiling constituents of the tar and increases the production of the disinfectant grades of our tar distillates. Disco tar with the softening point of distillation residue adjusted in this way has given excellent results in service, holding the chips in surface treatments for prolonged periods in both heavy and light traffic. Also, such distillation residue shows higher needle penetration a t 5" and a t 25" C. than a distillation residue of the same softening point made from straight high-temperature tar. I n other words, Disco road tars plasticized with high-boiling Disco tar oils may be expected to make road coatings of lower temperature susceptibility in service than the corresponding straight-run hightemperature tar. (High temperature susceptibility of tars makes it difficult to avoid excessive brittleness in winter without excessive softness in summer.) Of course, if the specification is of the identification type t o the extent of requiring high minimum specific gravity, the Disco tar is blended with a high-temperature tar which has low softening point of distillation residue. Such blends have also given satisfactory service throughout long periods. In addition t o service tests, Disco tars have given satisfactory comparative results in Kriege machine tests of coated aggregates under both wet and dry conditions, and also in accelerated weathering tests of coated sand. ROOFING PITCH made from Disco tar has given good results in exposure tests and is in successful use in a number of large pitch-and-gravel roofs built up in the usual way. The oldest of these roofs of which we have positive record was installed about four years ago. This material meets Underwriters' specification but deviates slightly from Federal specification, principally in respect to ash. As usually made, this pitch fumes more than high-temperature roofing pitch when heated to application temperature. This is due t o the fact that Disco tar in straight-run distillation reaches the roofing pitch softening point with less oil removal than high-temperature tars similarly distilled. The straight-run Disco-type roofing pitch thus contains an unusually large amount of lowboiling oils and therefore has an unusually high vapor pressure when melted for application. This practical objection can be overcome by addition to the still charge of very high-boiling distillates of Disco tar and thus permit the lower boiling oils to be distilled off without exceeding the softening point limits for roofing pitch. Such plasticized roofing pitch has unusually low temperature susceptibility and thus avoids excessive brittleness in cold weather. Disco-type roofing pitch, cut back with suitable thinner, makes an excellent tar paint. MOLDINGPITCHES, comparing favorably with high-temperature tar products, have been made experimentally from Disco tar but have not been sold, owing to the fact that makers of storage battery boxes now prefer asphalt or hard rubber compositions to coal tar pitch products. DISINFECTANT OIL is one of the most important products of Disco tar. Roughly speaking, it is the highest boiling 95 per cent of the total distillate of Disco tar boiling below about 300" C. vapor offtake temperature, and is chemically treated and redistilled for elimination of certain impurities, principally dihydric phenolic compounds which, if present, would impart pink or red color to emulsions of the oil and would cause excessive deterioration of the oil in storage. The lowest boiling 5 per cent or so of the total distillate below 300' C. is diverted to other uses (such as road tar flux or tar acid manufacture for plastics) in order to improve odor and phenol coefficient of the disinfectant oil and decrease its content of berizophenol (C6H60H) so as to avoid necessity for labeling
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INDUSTRIAL A N D ENGINEERING CHEMISTRY
Vol. 33, No. 7
the finished product under the Caustic Poisons Act. The is an additional indication of the great difference between the Disco-type disinfectant oil is sold to customers who add suithigh-boiling tar acids found in Disco tar and the common lowable emulsifiers and, usually, some coal tar neutral oil, and boiling tar acids such as benzophenol and the cresols. thus make an emulsifiable oil which readily disperses in a large volume of water to form a white or very light gray emulsion Future Uses suitable for use as a general disinfectant and also as an animal Possible future uses of Disco tar products include various dip and general parasiticide. The addition of neutral oil, in inadequately investigated items which are also potential outaddition to lowering the cost, sometimes increases the opacity lets for high-temperature coal tar products, such as deteror whiteness of the emulsion and makes the odor more in acgents from sulfated or sulfonated constituents, thermoplastic cordance with trade custom. The emulsifier should be seresins from polymerized constituents, and various chemical lected with care. Excellent results can be obtained with derivatives. On the other hand, very definite and favorable some cheap ones, but certain formulas which work well with laboratory indications have been obtained from the following high-temperature tar oils are unsuitable for use with DiscoDisco tar items: type material. Previous mention has been made of the naDISCO-TYPECREOSOTE OIL FOR CEINCHBua BARRIERS. ture of the unsulfonated residue and of the relation between Large quantities of high-temperature creosote oils have been boiling point and phenol coefficient. Most of our product as used for this purpose in the corn belt. The effectiveness of shipped contains nearly 50 per cent tar acids and will make a Disco-type oil has been established experimentally. disinfectant with a coefficient of about 6 or 7 conforming to DISCO-TYPE CREOSOTE OIL IN INSECTICIDAL DUSTB.ExCommercial Standard CS70-41 of the National Bureau of tensive tests have shown that dusts containing a small amount Standards. of this oil are not injurious to foliage but are effective repelCREOSOTE OIL from Disco tar is principally shipped for use lents of Japanese beetle, Mexican bean beetle, and various in treating railroad ties. Some red oak ties treated with other pests. Laboratory tests have shown such dusts to be Preosote oil from another low-temperature carbonization toxic to the first and second instars of the Mexican bean beetle. process have been in satisfactory use by one of the railroads “BROWNSOLUTION”AS WOODPRESERVATIVE AND SOIL and under the systematic observation of the U. S. Forest ProdPOISON FOR TERMITE CONTROL.This is a brown aqueous ucts Laboratory since 1921, long before the Disco process was solution obtained by contacting a caustic soda solution with put into commercial use (1). Our own oil has given good reliquid roofing pitch made from Disco tar, and then purifying sults in exposure tests and also in a rather elaborate series of or stabilizing the solution so that it can be heated or diluted accelerated tests of treated, seasoned, and leached blocks for without precipitating tarry matter. Although this is an aqueresistance to fungi, using recently published methods (6, 6). ous solution, wood which has been impregnated with it, seaI n some of these tests subnormal retentions of creosote oil soned, and then leached thoroughly will resist fungi under were obtained by treating the blocks by the full cell method severe test conditions. Although the solution is strongly but using preservatives diluted with various amounts of benalkaline, the treated wood near the surface does not show alzene. Seasoning of the treated blocks then removed the benkalinity to phenolphthalein. Apparently the wood or wood zene. Thus an indication of the necessary dosage or creoacids react with the brown solution, precipitating an insoluble sote oil retention was obtained. Comparison of Disco-type preservative soon after the solution penetrates. Wood creosote oil with a good grade of creosote oil from high-temtreated by this method has an attractive sepia or brown a p perature coke-oven tar was satisfactory. I n some of the pearance, cannot bleed, and may therefore be particularly earlier comparative laboratory tests of fungicidal properties suitable for poles in cities. Brown solution has given good of creosote oils by the Petri dish method, the Disco-type and results against termites, both as a wood treatment and as a high-temperature creosote oils gave similar results, except soil treatment. I n the latter case it is probably less harmful that the Disco-type material boiling above 355” C. inhibited to vegetation (foundation plantings, etc.) than other products growth of Fomes annosus, although the corresponding highwhich are used for poisoning the soil around termite-infested temperature material did not. This is probably due to the houses. The brown solution developments utilize the very presence of very high-boiling tar acids in the Disco-type high-boiling tar acids which are peculiar to low-temperature material. The resistance of the high-boiling Disco-type tar coal tars. acids to leaching has already been mentioned. The highPHENOLIC RESINSFROM DISCO-TYPETAR ACIDS. Formboiling portion of the preservative is the most permanent. erly, this development was not considered urgent, as our tar Disco-type creosote oil of a special grade is also sold for the acids were satisfactorily marketed in disinfectants, but recent manufacture of material for spraying dormant apple trees to laboratory results are promising. The plastics field is growkill insect eggs. It is used as an ingredient of a physically ing rapidly. I n spite of the introduction of resins from a stable creamlike emulsion which is readily diluted with a number of new sources, the strength and other desirable charlarge amount of water before use. These preparations usuacteristics of the phenolic resins are such as to keep their ally contain petroleum oil. The combination of Disco-type volume of production in the front rank of this rapidly expandcoal tar oil with petroleum oil gives good control of both ing industry. Disco tar in future should be an increasingly European red mite and the aphid group. A similar combinaimportant source of raw material for these resins on a sound tion of high-temperature coal tar oil and petroleum oil gives economic basis. similar good control of aphids, but inferior control of red mite. Petroleum oil, without any coal tar oil, gives good control of Literature Cited red mite but has little effect on aphids. Petroleum oil with (1) . . Am. Wood-Preservers’ Assoo.. Comm. 9-1 on Tie Service Recthe addition of certain high-priced synthetic organic chemicals ords, Report, Feb., 1941. gives results which are comparable with the Disco-type oil (2) Fieldner, A. C.. Davis, J. D., Thiessen, R.,Kester, E. B., and mixed with petroleum oil, but this mixture is likely t o kill the Selvig, W.A,, U. S. Bur. Mines, Bull, 344 (1931). trees if applied late. The Disco-type mixture can even be (3) Fisher, C. H., Ibid., 412 (1938). (4) Lesher, C.E..Am. Inst. Mining Met. Engrs., Tech. Pub. 1176used as a delayed-dormant spray if excessive concentration F116 (1940). is avoided. The Disco-type tree spray oil is said t o be easier ( 5 ) Leutrita,‘John’, Phytopathol., 29, 901-3 (1939). on the skin of the face and hands than most of the high-tem(6) Waterman, R. E., Leutrita, John, and Hill, C. M., IND. EN& perature tar oils which have been used for this -purpose. This CHEM.,Anal Ed., 10,306-14 (1938). End of Symposium
