NOVEMBER. 1935
INDUSTRIAL AiVD ENGINEERING CHEMISTRY
an industrial standpoint. The fact that these industries are growing so rapidly makes it imperative that engineers and architects be familiar with this field. So many data have been published on the subject of thermal insulations that it can be called a definite branch of engineering.
wool. This clearly illustrates the effect of convection in the larger air cells found in glass wool. It is difficult to cover even partially the field of thermal insulations in a paper of this length. All that can be done is to stimulate interest in thermal insulations as a necessary adjunct to the building industry, both from a domestic and 0
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Preservatives and Antitermite Protection of Timber NUMBER of wood preservatives, such as
C. DEMERE E. L. Bruce Company, Memphis, Tenn.
Some new wood preservatives and a new method of applying these preservatives to the wood have resulted from recent research and development work. These new preservatives are designed to meet the requirements of those phases of building which are not satisfactorily served by other preservatives and methods of application. This brief summary has not attempted a detailed treatment of the numerous considerations involved in the development of improved wood preservatives but has endeavored to show what one group of investigators is doing to solve the problems involved.
QA
creosote and zinc chloride, are excellent for outside use for treatment of crossties, bridge timbers, poles, etc., since they are cheap and effective. The field for new preservatives has its basis in the limitations of these old types. Creosote’s limitations are its persistent and sometimes objectional odor, the fact that its fumes under certain conditions may be injurious to human health, its discoloration of the wood, and the difficulty of painting wood after treatment with creosote. Zinc chloride and other preservatives of the same general type use water as a carrying agent. The application of water causes wood to expand and become distorted and, when it is dried to the moisture content satisfactory for use, the grain tends to raise, the wood tends to check and warp, and some woods become discolored. The need for new preservatives for use in the building industry is most clearly recognized in the field of home construction and for certain uses in other building construction, packing houses, dairy buildings, farm buildings, textile plants where the humidity is high, and refrigerator, box car, and automobile construction, etc. A program of research, which has resulted in the development of a series of new preservatives, was begun by the laboratories of the E. L. Bruce Company in 1927. After careful study it was decided that a preservative t o meet the
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VOL. 27, KO. 11
Three New Preservatives
Three types of preservatives were formulated to meet the requirements of the different fields of service which are encountered in the building industry. These three types are designated Bruce Preservatives L4,5-B, and 5-C. The toxicant used is @-naphthol,and each one of these formulas contains it in the same percentage by \!-eight. Bruce Preservative 5-A consists of P-naphthol in solution in a combination of two grades of black fuel oil. This particular preservative imparts a dark brown color to the wood, and painting is not recommended. I t s use is for outside construction where painting is not usually indicated. Preservative 5-B uses as a carrier a colorless petroleum distillate which evaporates from the wood very soon after impregnation. This type of preservative is admirably suited to building and home construction because it leaves no odor after the vehicle has el-aporated and does not discolor or degrade the wood in any way. The preserved material may be glued and painted. The specifications for this preservative are : Percentage of toxicant by aeight Percentage of eolvent by weight Sp. gr. of finished product Flash point (Tadiabue closed cup),
5 90-95
O
F.
0 789-0.804 11s-122
Preservative 5-B is listed by the Fire Vnderwriter's LaLoratories under application 31-C-790 No. 2306, and their summary is as follows :
TIMBER M'ORK DESTROYED BY TERMITES uncared-for needs of the industry should h a w the following characteristics : 1. The preservative should possess a high toxicity t o rot arid wood-destroying insects. 2. It should resist leaching. 3. The toxicant should be nonvolatile, or practically - 0 . 4. It should not discolor the wood. 5. The toxicant should be nontoxic to human beings. 6. It should be noncorrosive to met,als. 7 . It should not raise the grain of the \\-ood, or check, wqij or change its shape or size. 8. Its application should not impair the strength of the
wood. 9. There should be no chemical reaction within the vood
tending to reduce the toxic values. 10. The preserved wood should be capable of being glued JTith commercial glues. 11. The preserved wood should be easily a n d economically painted. 12. The preserved wood should be no more inflammable th:in the untreated wood. 13. The preservative should be of such character that it could be applied to the wood with sufficient penetration at :i loa-er cost than prevailing methods. 14. The preserved lumber should be available to the market at an economic level so t,hat the cost of preservation would not put wood out of position with respect to its competition with socalled substitutes. After experimentation and tests extending over a period of approximately seven years, a number of preservatives have been developed which approach closely the requirements listed. Particularly gratifying have been the U. 8. Government tests in the Panama Canal Zone1 which indicate effective protection both against decay and termite attack. 1 American Wood Preeervers .issoc., advance copy, Rept. t o .inn. Meeting, 1935; Wood Preservation Sect., Forest Research Inst., Dehra D u n , U. P., India, Inspection Repta.; Div. of Forest Products, Council for Sci. and Ind. Research, East Melbourne, .-\ustralia, Progress Repts.
The product is a relatively stable chemical and is not considered liable to undergo decomposition resulting in increase of hazard. Consideration of the chemical properties show it is of stable nature and relatively inactive chemically. Tests show no tendency t o heat or ignite spontaneously under conditions designed t o start and accelerate the process. Bruce Preservative 5-C has the same general characteristics as 5-B but contains a cert'ain amount of asphalt which is ueed as a coloring agent and as a moisture-resistant sealer. During the past four years this material has been used extensively by certain builders of motor car bodies. Because of the asphalt contained, this type of preservative is not recommended for treating wood which is to be painted. Method for Applying Preservative t o Wood
The Bruce process is in operation, a t present, in five preserring plants located a t Memphis, Tenn., Bruce, Miss., Dallas, Texas, Milwaukee, Ris., and Jacksonville, Fla. Other special plants are used by various indust.ries for treating wood used in the manufacture of their products. Lumber to be preserved is heated to 190" F. under humidity conditions so controlled that no moisture is absorbed or lost by the luniber. The three advantages of this heating are: (1) The lumber is completely sterilized; (2) the air in the cells of the wood is materially expanded; and (3) the surface pores are opened. Lumber usually cont'ains between 50 and 60 per cent of air, and when it is heated to 190" F., between 90 and 95 gallons of air are forced from 1000 board feet of lumber by expansion of the air itself. During the next step in the process-immersion of the hot lumber in the \\-ood preservative-the air contracts and preservative is drawn into the pores of the mood. If the lumber v-ere allowed to remain immersed until it returned to atmospheric temperature, 90 to 95 gallons of preservative would be absorbed per 1000 feet of lumber. Since this is greatly in excess of the amount of preservative required for most purposes, the lumber generally is left in the preservative only long enough for approximately 35 gallons per 1000 feet to be absorbed, which requires cooling of the lumber to approximately 120°F. in the tank. After removal from the
NOVEMBER, 1933
ISDUSTRIAL AND ESGINEERING CHEMISTRY
commonly used and needs the protection to a rnuch greater extent. The impregnation process used and the superior penetrating power of the preservative itself permit ample protection to be obtained by the Bruce process without the necessity of using the high pressures required to accomplish sufficient penetration in many of the older processes. Another interesting feature of this process is that the preserved lumber is ready for use immediately after treatment. Lumber delivered to the treating plant in the morning can be delivered to the contractor the same day. This feature allows the architect to specify any kind of construction without danger of long and costly delay.
tank, penetration still continues for a time because of further contraction of the air in the interior of the lumber. Apparent rapid drying of stock thus processed is due rather to this progressive penetration than to rapid volatilization of solvent from the surface. With 35 gallons per 1000 feet absorption of Bruce Preservative, there is approximately twenty times as much toxic principle in the lumber as is required to inhibit fungus and termite attack. The penetration secured is beyond any probable depth of checking. The lumber has been sterilized completely during the heating process. I n commercial treatment 20 to 30 gallons of preservative per 1000 feet is common practice. The sapwood usually absorbs the preservative more readily than the heartnrood, which is fortunate since sapwood is most 0
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Fire Prevention and Protection in Chemical Industries BERNARD F. FLOOD R o p l Li>erpool Groups, Columbus, Ohio
Courtesy, A merican-LaFrance and Foarnzte I n d u s t r i e s , Inc.
FOI~TY-GALLON FOAMITE ENGINEBEING~ J S E I I O N 4N INFL43lMABLE LIQUIDFIRE ORIPARATITELT little published information can be found on the subject of fire and explosion hazards of the chemical industries. Reports of inveFtigations of government bureaus. fire insurance companies, the Cnderwriters’ Laboratories, and inspection and fire insurance rating bureaus are available upon request. These, however, do not corer the entire subject, nor is their availability well known in the industry. Although the chemical industry is still young and primarily interested in developing new processes and products, the importance of prevention of fire and explosion cannot be overemphasized. The chemical industry deals with hazardous materials. Nearly all organic compounds are combustible. Many of them are highly inflammable or explosive, and Some
are auhject to spontaneous ignition, e.specially when storetl under certain conditions or in contact with certain other materials. Inorganic compounds are generally considered noncombustible but there are exceptions, such as oxidizing agents or explobives, x-hich are quite hazardous. Xot only are the handling and storing of these compounds hazardous, but there are also hazards encountered in processing them 77-hich are distinct from the hazards of either the raw materials or the finished products. I t is not intended to set forth all the hazards of chemical processes in this article but rather to describe some of the methods of controlling arid preventing weeping fires in chemical plants by proper construction and protection of the buildings which house the industry. When a new chemical plant is to be designed or an old plant remodeled, the following general points are important: 1. Construction should be as nearly fireproof as feasible. 2 . The hazardous processes should be isolated within separate
fire areas.
3. All specially hazardous processes should be properly
safeguarded. 4. -411 hazardous conditions not’inherent to the process should be eliminated or safeguarded. 5 . Ample fire-fighting equipment should be provided.
Construction The word “fireproof” is a misnomer. Records show many instances of so-called fireproof buildings that have been seriously damaged or destroyed by fire. However, a building is
