November, 1927
I Y D USTRId L -4ND E,VGINEERING CHEXISTR Y
123 1
Experiments in Wood Preservation‘ IV-Preservative Properties of Chlorinated Coal-Tar Derivatives By Leo Patrick Curtin and Marston Taylor Bogert ZXGIXEERING
LABOR \TORIES,
XvSSTERN U b I O N
TELEGR4PH
CO.,NEW
YORK,
N. Y.
U
BERd of treated m-ood, particularly of railroad ties, petroleum increases the solubility of beta-naphthol sufficiently frequently require that the preservative shall be an to overcome this fault. Pine oil, however, is rather expenoil. They believe that the moisture-excluding and sive to use in wood preservation. Reference has already been fiber-binding properties of an oil are of assistance where the made t o combinations in various proportions of coal-tar wood is subjected to severe mechanical shock. For this creosote and petroleum. reason creosote, either alone or mixed with water-gas tar, .4n efficient wood preservative of the oil type, which is to coal-tar, or petroleum, is favored for the treatment of rail- be much cheaper and more abundant than creosote, must consist largely of petroleum with the addition of one or more road ties. Heavy petroleum appears to be superior t o creosote as a substances to furnish toxicity. It was thought desirable waterproofing oil and is more permanent. It, is more effec- to develop a preservative of this type with petroleum as a tive, also, in protecting ties against “broomiiig,” separation base. No attempt was made to provide toxicity by the of the wood fibers. It is obtainable in practically unlimited addition of oil-soluble compounds containing inorganic radicals. Some of these matequantities, n-hereas the suprials-for example, organic ply of creosote, a by-prodarsenicals-are too expenuct of the coke industry, It is shown that chlorination of the hydrocarbon sive and others might in the is so limited that more than portion of coal-tar creosote reduces its toxicity toward c o u r s e of t i m e undergo half of the present Ameriwood-rotting fungi. On the other hand, the monoc h e m i c a l c h a n g e which c a n c o n s u m p t i o n is imand di-chloro derivatives of certain coal- tar phenolic would render them valueported from Europe. This bodies are less volatile, less soluble in water, more reless. F u r t h e r m o r e , the situation is reflected in the sistant to oxidation, and much more toxic toward mechanism of the toxic reacprices of the two oils. Creowood-rotting organisms than the unchlorinated parent tion may be such that an oilsote, in storage tanks a t substances. Chlorination of the cresols and xylenols soluble substance containing wood-treating p l a n t s , is gave the largest increases in toxicity, dichloroxylenol a toxic inorganic atom may worth 18 to 19 cents per being the most toxic of all the substances tested. notjhare the same toxicity in gallon, while petroleum fracThe chlorination of tar acids boiling above 270’ C. oil solution that the atom t i o n s s u i t a b l e for woodresulted in a slight decrease in toxicity. In this case would have in water solutreatment are TI-orth 3 to 6 the increase in toxicity due to chlorination was aption. Ionization may also cents per gallon. Unforparently more than offset by a decrease in solubility be a factor. For these reatunately, these advantages in water. sons it seemed preferable to are more than offset by the use. as a toxic agent. a mafact that petroleum is nonterial which was &elf an oil. Doisonous toward wood-rotting fungi while creosote possesses abundant toxicity. For Since there are no oils which fulfilled the requirements of this reason the present use of petroleum in wood preservation high toxicity, abundant supply, and low cost, it was evident that the material would have to be synthesized. The most is limited to acting as a diluent for creosote. A great many processes have been devised for the purpose promising field appeared to be the chlorination of aromatic of making petroleum suitable for use as a wood preservative. (coal-tar) oils. Although petroleum fractions could be chlorinThese generally require the addition to the petroleum of a ated, it was believed that the resulting compounds would substance which is highly toxic toward fungi. A few of the not be of high toxicity and, because of the comparatively ready hydrolysis of the alkyl haloids, they would be lacking proposed methods will be cited. Snellingz proposed the use of copper naphthenate dissolved in permanence when exposed to the weather. The idea of chlorinating coal-tar creosote and anthracene in petroleum or other inexpensive oil. Ellis3 niade petroleum toxic by the addition of copper oleate or resinate; oil-soluble oil for wood-preserving purposes was by no means new. In compounds of arsenic, lead, mercury, and zinc; and organic 1823, Oxfort was granted a French patent on the chlorination compounds o f high toxicity toward fungi, such as dinitro- of tar oil by means of a stream of gaseous chlorine. Many chlorobenzene, dinitro-o-cresol, etc. A wood preservative years later, Avenariuss patented a wood preservative whicll consisting of 5 per cent cresylic acid in crude petroleum has he called Carbolineum. This material was prepared by passing gaseous chlorine into anthracene oil. Avenarius did not been made in the western states. A number of attempts have been made to use beta-naphthol give the percentage of combined chlorine in his product, but as the toxic agent. This substance is highly toxic and prob- gave the densities before and after chlorination as 1.1217 ably quite permanent, since its boiling temperature, under and 1.1303. Tar oils do not appreciably increase in volume atmospheric pressure, is 286” C. It is of rather low solu- on chlorination; the increase in mass is almost entirely combility in petroleum and, when dissolved in hot petroleum, pensated for by an increase in density. For example, an has a tendency t o crystallize out when the oil strikes the American creosote was chlorinated until the final product cooler surface of the retort or the wood to be treated. Wood4 contained 20 per cent combined chlorine. The initial and has shown that the addition of 10 per cent of pine oil to the final densities were 1.03 and 1.22. From this it is evident that Avenarius’ Carbolineum contained about 1 per cent of 1 Received September 12, 1927. combined chlorine. Hodurek6 analyzed ilvenarius’ product 2 U. S. Patent 1,482,416 (1924) U S Patents 1,045,110. 871,392, 991,434, l,Oli,63li, 1,028,201. ‘ P r o c A m Wood-Preservers .Issocn 22, 100 (1926)
a
D . R. P. 46,021 (1888). Oestevr Chem - Z & , 16 (1904)
INDUSTRIAL AND ENGINEERING CHEMISTRY
1232
and found but 0.16 per cent chlorine in it. Avenarius claimed greater permanence and an improved odor for his preservative; he makes no reference to increased toxicity. Noerdlinger' patented an insecticidal and fungicidal composition containing chlorinated naphthols, anthranols, and phenanthrols. Boehringer and Soehne8patented oils, waxes, resins, and fats containing 30 per cent combined chlorine as an impregnating material for wood, fabrics, etc. Malencovicg patented as a wood preservative hydroxy derivatives of diphenyl in which chloro or nitro groups might be substituted for nuclear hydrogen. Norrislo used "chlorinated sharp oilJJ(dead oil of creosote) as a wood preservative. The foregoing are cited to show what attempts have been made to use organic chloro compounds in wood preservation. There is in addition a vast array of patents describing the use of chloro compounds as waxes, fire retardants, antiseptics, waterproofers, etc. Although none of the chloro compounds have found use in commercial wood preservation, there appeared to be possibilities in this field and it was decided to make a laboratory investigation of the problem.
The oil a t the bottom of the list is but little more toxic than crude petroleum residuum, which permits growth a t 40 per cent. Bateman and Henningsen'* have shown quite conclusively that, while the toxicity toward fungi of aromatic hydrocarbons and phenols increases with increasing molecular weight, a limiting factor is the solubility of the substance in water and that certain of these compounds of high molecular weight, in theory highly toxic, have actually very low toxicity because of their insolubility in water. It has been shown in the second paper of this series that certain salts of weak acids, such as zinc arsenite, although practically insoluble in water, are readily soluble in acids evolved by wood-rotting fungi. Hydrocarbons and phenols, however, could not be brought into solution by fungi, since they would not be appreciably more soluble in dilute acid than in pure water. Bateman and HenningsenI2 report the following killing points for coal-tar acids: SUBSTANCE
Preliminary Experiments
I n November, 1924, a few gallons of commercial coal-tar creosote of density 1.03 a t 25' C. were chlorinated by passing into it dry, gaseous chlorine in the absence of light. The reaction took place with great ease, considerable heat being liberated. Chlorination was continued until the original weight had been increased by 25 per cent, indicating that the creosote contained 20 per cent combined chlorine. There was but slight increase in volume, the final density being 1.22 a t 25' C. The reaction was assumed to be RH
+ Clz +RC1 + HCI
The chlorine cylinder was weighed before and after chlorination, and it was then found that a small part of the chlorine had been consumed in addition reactions without evolution of hydrogen chloride. If only substitution reactions had taken place, the yield would have been 103 per cent of the theoretical. Petri dish cultures were made with standard agar-malt sirup gels and the killing point toward the wood-destroying fungus Fomes annosus of the chlorinated creosote was found to be 0.25 per cent. This compared with a killing point of 0.50 per cent for the unchlorinated creosote. The percentages were on a weight basis; if a volume basis were used, the ratio would be somewhat more favorable to the chlorinated material. This increase in toxicity was not great enough to justify the expense of chlorination. It was next decided to separate the creosote into fractions and chlorinate each fraction separately. It was thought probable that the chlorine consumed by some of the higher boiling components might have been wasted, since such materials are quite inert in the unchlorinated condition. This was shown by Humphrey and Fleming" in toxicity tests on various kinds of creosote used in wood preservation. Some of their data are given in Table I. T e s t s on Chlorinated Creosote Fractions KILLING PRESERVATIVE DISTILLATION DATA FUNGUS POINT Per cenl Creosote oil 9 5 . 9 % below 287' C. Fomes annosus 0 225 Creosote oil 74.170 below 320" C. Fomes annosus 0 . 5 5 Anthracene oil (S. P . F . carbolineum) 30.0% below 320' C. Fomes annosus 3 . 5 Anthracene oil (Avenarius Carbolineum) 6 . 1 % below 275' C. Fomes annosus 5 25 Anthracene oil 1O.OY' below 320' C. Fomes annosus 3 3 . 0 T a b l e I-Toxicity
U. S. Patent 1,205,924 (1916). French Patent 433,415 (1911). 9 Austrian Patent 64,818 (1913). 10 British Patent 171,418 (1921). 11 U. S. Depl. Agr.. Bull. 227. 7
8
Vol. 19. No. 11
Phenol Cresol Xylenol Beta-naphthol
FUNGUS Fomes Fomes Fomes Fomes
annosus annosus annosus annosus
COMPLETE INHIBITION Per cent 0 10 0 06 0 04 0.02
These values were used as a basis for comparison with some of the corresponding chloro derivatives. Toxicity Tests
The toxicity tests listed below were made in the Western Union Engineering Laboratories, the culture medium being standard agar-malt sirup gel and the test fungus Fornes annosus. The figures are percentages by weight unless otherwise specified and the "killing point" percentage is italicized. PRESERVATIVE. Chloronaphthalene, 22 per cent combined chlorine. monochloro derivatives. 0 15 Growth 0.29
Mainly
PRESERVATIVE: Chloronaphthalene, 33 per cent combined chlorine. dichloro derivatives. Growth 0.19 0.11
Mainly
Investigation of the chloronaphthalenes was discontinued because it was clearly evident, from the healthy vigorous growths in the cultures, that these substances were inferior to naphthalene in toxicity and valueless as wood preservatives. Bateman and Henning~en'~ state that Fomes annosus is totally inhibited by naphthalene a t 0.0033 per cent concentration. They used saturated water solutions of naphthalene in their tests. Because of the perfect distribution of the toxic agent in this type of culture, the killing point is very much lower than when the preservative is dispersed as very fine droplets in an agar gel. PRESERVATIVE.Dead oil of creosote, b p. 240-270" C. with acid and alkali. Puo' growth 0.195 0 230 Growth 0.140
Neutral, washed 0.294
PRESERVATIVE: Chlorinated dead oil of creosote, 22 per cent combined chlorine. Mainly monochloro derivatives. Growth 0.200 0.167 Vigorous growth. Series discontinued. PRESERVATIVE: Chlorinated dead oil of creosote, 33 per cent combined chlorine. Mainly dichloro derivatives. No growth 0.66 Growth 0.58 0.44 0.35 0.31 0.24
The chloro derivatives were prepared from the sample of neutral dead oil used in the toxicity test. The dichloro derivative was one-fourth as toxic as the unchlorinated material. 12 '8
Proc. A m . Wood-Preservers' Assocn., 21, 22 (1925). I b i d . , 19, 142 (1923).
November, 1927
I-VD USTRIAL A-VD ENGINEERING CHE.MISTRY
From the tests on chloro derivatives of naphthalene and dead oil, it was apparent that chlorination of aromatic hydrocarbons of molecular weight equal to or greater than that of naphthalene results in a decrease in toxicity. While the chloro derivatives are less volatile, and therefore more permanent, there is no need to chlorinate hydrocarbons to secure permanence since the hydrocarbons of anthracene oil are themselves highly permanent. The investigation was next turned to a study of the effects of chlorination on the properties of the "tar acids," or phenolic components of creosote. In the toxicily tests on the tar acids it was thought preferable t o use distillation fractions of conimercial material rather than highly purified simple substances. The basic components were not studied because, with the exception of pyridine, they are not available commercially and pyridine is much too expensive to use in wood preservation. Furthermore, the substitution of chlorine in the pyridine nucleus would n u k e the molecule less basic, probably resulting in a marked decrease in toxicity. PRESERVATIVE. Low-boiling, commercial-grade cresylic acid containing 33 Der cent combined chlorine. Mixture of mono- and dichloro cresols. h-o growth 0.0060 0.013 0.019 0.043 0.067 Growth 0.0057 0,0030
PRESERVATIVE:Cresylic acid as above containing 40 pir cent combined chlorine. Mainly dichloro derivatives. No growth 0.0010 0.0060 0,0075 0.00h4 0.0150 Growth 0.0037 0,0032 0,0030 0.001 0
The mixture of dichloro cresols is ten to fifteen times as toxic as the unchlorinated material. PRESERVATIVE:Crude xylenol (mixture of isomers), b. 13. 207-230' No growth 0.034 Growth 0.021 0,008
C.
PRESERVATIVE:Crude xylenol as above containing 22 per cent combined chlorine. Mostly monochloro derivatives. 0.0094 0.0140 No growth 0.0078 0.0058 0.0034 0.0028 0,0068 Growth PRESERVATIVE:Crude xylenol as above containing 35 per cent combined chlorine. Mostly dichloro derivatives. No growth 0.0038 0.0040 0.0052 0.0099 0.0130 Growth 0.0033 0.0029 0,0024
Dichloroxylenol is eight to ten times as toxic as unchlorinated xylenol and one hundred to one hundred and fifty times as toxic as commercial creosote. Its toxicity is definitely greater than that of mercuric chloride, arsenious oxide, or dinitrophenol. It is also more toxic than the phenols above and below it in molecular weight, either chlorinated or unchlorinated. PRESERVATIVE:Coal-tar acids, b. p. 230-270' 0,029 iYo growth 0.018 Growth
C.
0.049 0.008
PRESERVATIVE:Coal-tar acids, b. p. 230-270° C., containing 22 per cent combined chlorine. 0.010 0.013 No growth 0.0066 0.0052 0.0020 Growth
The monochloro derivative is about three times as toxic as the unchlorinated material. PRESERVATIVE: Coal-tar acids, h. p. 270-300' C. A-o growth 0.010 0.011 Growth 0.006
0.025
PRESERVATIVE:Coal-tar acids, b. p. 270-300O C., containing 22 per cent combined chlorine. No growth 0.012; 0.016 0.019 Growth 0.0100 0,0075
In this case the monochloro derirative is but 80 per cent as toxic as the unchlorinated material. These results were checked by three independent determinations. This fraction is the lowest in which the increase in toxicity due to replacement of nuclear hydrogen by chlorine is more than offset by the lower solubility of the chloro derivative. Doubtless the decrease in vapor pressure is also a factor, since it
1233
has been found in this laboratory that fungi may be killed by the vapors of certain oils even when held out of physical contact with the liquid phase of the oil. . PRESERVATIVE:Coal-tar acids, b. p. 233-303O C., mainly phenols above xylenol in molecular weight. No growth 0 . 0zz 0.061 Growth 0.012 PRESERVATIVE:Coal-tar acids, b. p. 230-300O C., containing 35 per cent combined chlorine. A-0 growth 0.015 Growth 0.0092 0.0060
This dichloro derivative showed but a 50 per cent increase in toxicity as compared with the unchlorinated material. Several samples of commercial grades of high-boiling tar acids mere obtained and test'ed for toxicity. The xylenol fraction was the largest in each case, ranging from 60 t o 80 per cent, with 5 per cent of meta- and para-cresol. The remainders consisted of tar acids boiling from 230" t o 300" C. After chlorination t o 35 per cent combined chlorine content, the toxicities were six to nine times as great. PRESERVATIVE:5 parts by volume crude xylenol containing 35 per cent combined chlorine dissolved in 95 parts by volume heavy California petroleum. No growth 0.26 0.33 ' 0 21 0.17 0.125 Growth PRESERVATIVESame as immediately above except t h a t petroleum was first washed with 10 per cent sulfuric acid, then thoroughly with water. 0 20 h a growth 0 14 0 10 0 05 Growth
A much better distribution of the preservative was obtained in the second case. Washing with acid decreased the surface tension of the oil against water and a very fine dispersion of the preservative in the jelly was obtained. Cultures mere very light in color and no droplets visible to naked eye. Corresponding cultures of unwashed oil mere brownish and droplets of oil easily visible as very small specks. The apparent diminution in toxicity of preservatives dissolved in petroleum undoubtedly results from enclosure within the droplets of petroleum. Discussion of Results
The chloro derivatives of naphthalene were semi-solids at room temperature. The dead oil, after chlorination, remained liquid. The xylenol increased but little in viscosity on chlorination and showed no sign of solidification a t - 10" C. The chlorinated tar acid, b. p. 270-300" C., was a very viscous liquid a t room temperature. All the chlorinated tar acids have powerful, clinging odors suggestive of iodoform but more intense. No exact information is available as to the part played by leaching in the loss of organic preservative from wood. It is probably less important than losses due to vaporization. In general, the effect of chlorination would be to reduce losses due to solution in water of the preservative by making it less soluble. For example, phenol is more than three times as soluble in mater as any of its three monochloro derivatives and about one hundred times as soluble as its symmetrical trichloro derivative. A similar but less marked difference obtains with the corresponding creosol and xylenol compounds. Perhaps the principal reason why the phenols have failed as long-term preservatives is that they tend to oxidize to non-toxic forms when exposed to the air. In accordance with the well-known rule that the introduction of electropositive groups into the benzene nucleus niakes it more resistant to oxidation, the dichloroxylenols should be much more resistant to change than the parent substances. No tendency to oxidize has been noted in more than two years' observation. Dichloroxylenol has stood for more than a year in an open beaker with no formation of gummy material or other indication of oxidation or polymerization.
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I-VDUSTRIAL A N D EAVGILVEERISGCHEMISTRY
The loss of volatile preservative from wood will be, of course, a function of its vapor pressure. Because of the difficulties in measuring vapor pressures of mixtures of oils a t the outdoor temperature, it is more convenient to form opinions as to the vaporization losses of oils by comparisons of boiling points a t 760 mm. pressure. It is known that oils below naphthalene in boiling point are of little permanence. Naphthalene, b. p. 218" C., is fairly permanent in wood below ground and under water, but when exposed to the winds it largely disappears by vaporization in five or six years. On the other hand, creosote oils boiling above 270" C. are quite permanent under any ordinary conditions. A certain commercial tar acid was found to distil under 760 mm. pressure as follows: initial point, 200" c.; 10 per cent below 207" C.; 80 per cent below 230" C.; and 95 per cent below 285" C. After chlorination to 35 per cent combined chlorine, a distillation under 15 mm. pressure was made and from the data thus obtained a distillation curve a t atmospheric pressure was constructed. The error in this curve vas probably not greater than 4 degrees a t any point. This curve showed that the chlorination had raised the boiling point an average of 30"C. A fractionation under 760 mm. pressure was not possible, since the chlorinated tar acids commence to decompose a t 220" C.
Vol. 19. No. 11
Mixtures of Chloro Tar Acid with Petroleum
The Western Union Company has treated southern yellow pine, on an experimental scale, with petroleum containing from 1 to 10 per cent chloro tar acid. No difficulty was encountered in the treatment, and it was noticeable that the penetrations were better than when petroleum alone was used. The petroleum was asphaltic base, 18' to 22" BB grade, in most cases, although both lighter and heavier oils were used. Field tests are now in progress on the wood so treated. With most of the petroleum oils used, the chloro tar acid dissolved readily. This was especially the case with distillate oils or when the petroleum had been washed with dilute acid or when the chloro tar acid had been incompletely freed from hydrogen chloride. I n certain other cases, particularly with residuum oils, a film of gummy material was deposited. Some of this was collected and treated with a dilute solution of sodium hydroxide. A yellowish oil of powerful odor separated and rose to the top. This was easily identified by its appearance and odor as pyridine or homologs of pyridine. When the water layer was acidified, chloro tar acid was recovered. Evidently, the gummy material consisted in part of the pyridine salt of the chloro tar acid.
Protection of Marine Piling against Borer Attack' Chemical Aspects By W. D. Ramage and J . S. Burd r N I V R R S I T Y OF CALIFORNIA,
T
H E chemical treatment of wooden piling to preserve it against the attack of marine borers has been practiced for many years, but only within the last few years has its full economic bearing been generally recognized. Recently extensive investigations2 of the borer problem have been carried out in the hope of improving methods of protection. The San Francisco Bay Marine Piling Committee was formed in 1920 for the purpose of studying the engineering, chemical, and biological aspects of borer attack on marine piling. The material here reported represents the results of the chemical investigations. Note-This committee was a coiiperative organization, supported by voluntary contributions from the industries interested in water front structures on San Francisco Bay. The complete report of the committee will be published shortly in book form. The chemical investigative work of the committee was concluded in March, 1924, before the completion or publication of the work of any other large agency studying the same or similar problems.
BERKRLBY, CALIF.
nected with the preservation of wood from marine borers. Within the field indicated, only those preservatives or preservative methods were considered which involve penetration of the preservative into the wood. This naturally resulted in centering much of the work upon coal-tar creosote. The principal preservatives studied were coal-tar creosote and possible inorganic inhibitants. Furthermore, since experience has shown that properly creosoted piling is very resistant to borer attack, no treatments were studied which might be expected to cost much more than a good creosote treatment. Outside the field indicated, some work was done in studying the effects of chlorine on marine borers. Creosote Study
OBSERVATION OF TESTPIECES TREATEDWITH VARIOUS CREOSOTE FRACTIONS-The test timbers used in these experiments were 2 by 4 by 48 inches. Half of them were Free use has been made of the publications listed in the Douglas fir and the rest were redwood, as indicated in Table I. bibliography on marine borers compiled by A. L. Barrows As far as possible they were sapwood and free from large (National Research Council Report, 1924). On account knots or defects. Both species are more or less refractory to of the large number of overlapping publications in this field. impregnation. All the test pieces were treated to refusal, no attempt has been made to give specific credit. It is be- by the standard vacuum-pressure method used for impreglieved that those familiar with the field will readily recognize nating marine piling with creosote. In commercial treating how many of our data are new and how many merely confirm practice varying impregnations often result from substanthe previous findings of others. Particular reference should tially uniform treating conditions, owing to differences in the be made to the various studies of E. Bateman, of the U. S. penetrability of different wood species or specimens used, Forest Products Laboratory, and of L. F. Shackell, with the or to varying viscosities of different oils or fractions. This U. S. Bureau of Fisheries, especially on the subject of toxicity.3 is largely a function of the time factor, however, as well as Our work was confined almost entirely to problems con- of temperature and pressure, and the difficulty was practically overcome in our experimental work, as it can be whenever 1 Received February 23, 1927. :"Marine Structures-Their Deterioration and Preservation," Naminimum treating time is not a requisite. On account of tional Research Council Report, 1924; "The Deterioration of Structures in the small size of the test pieces there was practically no core Sea Water," Reports 1 to 6 of the Committee of the Institute of Chemical of untreated wood. The amount of creosote remaining in Engineers (British). all the test pieces was about 15 pounds per cubic foot, except 3 Proc. A n . Wood-Preservers' Assocn.. 11, 232 (1915).
