IhTD USTRIAL A N D EXGINEERING CHEMISTRY
June, 1923
is furnished by an Illinois glass plant, the sheet metal being exposed to sulfurous producer-gas fumes and soda-ash dust. Fig. 6 illustrates a balloon flue after eleven years' service for a Missouri lead corporation. To meet the severe corrosive conditions (gases heavily laden with sulfur and corrosive compounds), the structural engineers tested several ferrous metals of various analyses and chose commercially pure iron as the most resistant. The long service life justifies the engineers' decision. Representing the soap industry, attention is called to Fig. 7, commercially pure iron tanks installed a t a Missouri soap manufacturer's plant. After more than fifteen years of service they are in excellent condition, having been used for storage of fatty acids, oils, and other raw materials required for soap-making. Steel exposed to the same conditions pitted badly.
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Laboratory Table-Top Materials By C. R. Hoover WESLEYANUNIVERSITY,MIDDLBTOWN, COKN
H E REQCIRERIEKTS for a satisfactory morkingtable surface are rather exacting-more exacting than those of most pieces of laboratory apparatus or industrial equipment-because of the wide variety of substances with which it is brought into contact. Some of the points that should be taken into consideration in choosing a material for this purpose are as follows:
T
1---Resistance to the action of corrosive materials 2-Resistance t o t h e action of Rater 3-Resistance t o t h e action of nonaqueous solvents 4-Combustibility 5-Thermal conductivity 6-Resistance t o mechanical and heat shock and abrasion 7-Surface condition and appearance 8-Breakage of glass apparatus 9-Cost of maintenance 10--Cost of installation
PRELI~VINARY TESTS Based upon these ten points a series of tests was devised to furnish information which could be used in giving a number of materials a relative, if not independently reproducible, rating. The results of six of these tests applied to selected moods are shown in Table I. TABLEI
WOOD TXEATMENT 1 Test No.. . . . . . . . . 68 71 Beech %?ne black 70 77 Birch x%&e black 71 75 :%%e black 70 Oak {:%?ne black 73
.. .
{ { {
2 59 70 61 72 55
64 46 59
3 4 6 1 82 38 35 81 35 75 87 42 38 92 38 79 88 41 40 84 35 79 82 38 29 79 33 63
0 146 110 150 115 155 120 163 128
427 442 448 473 450 457 428 425
}
1 1
1
As a result of these preliminary tests it was evident that, while birch appeared to slightly better advantage than any other wood, the treatment of the wood may cause more variation in the properties of the finished material than the kind of wood. Several different finishes were next tried in an effort, to increase the resistance of wood to corrosion, heat, and decay without materially increasing its cost.
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TREATMENT WITH AKILINEBLACK Aniline-black wooh stain applied according to the usual directions1 was chosen as a standard of comparison. It was a t once evident that this stain offers little resistance to the action of strong acids, its chief benefit being to mask the disfiguration. The oxidized film of linseed oil is the component which contributes most largely to the resistance of a wellaged finish. Paraffin applied by hot impregnation, as a substitute for raw linseed oil, was tried with improvement in some properties, particularly if the wood is to be used within a few days after finishing. Zinc salts have well-knoim preservative and fire-resistant effects upon wood; hence, the effect of replacing the copper sulfate in the aniline-black* treatment by zinc salts was studied. It was found that as much as 90 per cent of zinc sulfate could be used without altering the depth of color produced. The fire-resistant quality of wood treated with this solution was increased, and in no way could the zinc sulfate stain be found to be inferior to that produced with copper sulfate. Other modifications of the standard black stain did not improve its properties-e. g., sodium silicate solution or soap solution in place of water as a wash after each treatment produced no noticeable change. The addition of graphite or carbon black to the oil or paraffin coat tended to cause. pitting and increased roughness of the surface etched by strong acids. The practice of heating the wood after water solutions have dried and before the oil is applied, was found to lower such acid- and water-resistant qualities as are possessed by the stain. However, any means by which the penetration of the various solutions can be increased tends to produce improvement in the wearing qualities of the stain. Judicious application of direct heat immediately after solutions have been applied improves the results, provided too great excess of potassium chlorate has not been used. Embodying these results, the following modification of the usual procedure is recommended for the production of a stain of superior fire-resisting and preserving qualities : To warm, clean, dry wood apply, working in well with a stiff brush kept hot, a hot solution of 100 g. of potassium chlorate, 100 g. of zinc sulfate (heptahydrate), and 20 g. of copper sulfate (pentahydrate) in 1000 cc. of water. When t h e first coat is dry apply a coat of a warm solution of 110 cc. of aniline and 175 cc. of concentrated hydrochloric acid with water to make 1000 cc. Allow the wood to dry 15 to 24 hrs. and repeat the application of the two solutions as described above. While the wood is still wet with t h e second coat of aniline hydrochloride solution, warm the wood very carefully with a gas flame, but d o not heat any portion of the surface which appears dry. Allowthe wood to dry and the stain to develop for 48 hrs , then wash thoroughly with boiling water and dry for 15 to 24 hrs. Apply a coat of melted paraffin and impregnate by carefully heating the surface of the wood with a gas flame. After the wood has cooled, warm gently with a flame and wipe off excess paraffin An electric or gas iron is a n excellent substitute for a gas flame in the impregnation of wood. With ordinary usage, the paraffin treatment should be repeated about twice each year.
LIGHT-COLORED WOODFINISHES Other finishes found to increase the resistance of wood a r e interesting to those who prefer a light-colored working surface. A paraffin-impregnated wood shows considerable resistance to corrosion and if the action of concentrated sulfuric BUY. Standavds, C Z Y C69, . 53. "A method or producing a permanent black, which is a very satisfactory finish for wooden tops of laboratory tables, is as follows. Solution A, 125 g. of copper sulfate, 125 g of potassium chlorate, and water to make 1000 cc. Solution €3, 60 g of aniline, 90 cc. of hydrochloric acid (sp. gr. 1.2), and water to make 500 cc. First paint with Wash with Solution A and when dry with Solution B for several hours. hot water and repeat the whole operation until the wood is dark green, Finish by rubbing with raw linseed oil until a black surface is secured, By going over the work a t intervals of 1 t o 2 wks. with a cloth moistene4 with raw linseed oil i t may be kept in perfect condition."
INDUSTRIAL AND ENGINEERING CHEMISTRY
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Nonaqueous Corrosion Water Solvents MATERIAL Test No.. 1 2 3 Alberene. 99 99 95 99 99 Alberene plus paraffin and graphite.. 96 90 Asbestos wood (transite) 91 78 85 95 Asbestos wood plus paraffin and graphite 83 92 Ebony asbestos wood.. 88 94 97 Bakelite, brown. 89 95 99 Chemical stoneware. 100 100 Concrete. 67 77 85 99 98 Enameled iron.. 100 77 Linoleum. 78 50 94 Marble ............................... 77 89 86 96 88 Rubber flooring (Stedman) 91 Slate 93 97 99 99 98 Tile unglazed.. Woid bjrch, standard aniline black 77 72 92 ,Wood birch, modified black 79 76 90 a Estimated.
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.............. ................................. ....................... ...... .............
Combustibilitv 4 100 98 95 98 80 20 100 98 100 20 90 40 95 100 38
45
acid can be avoided and frequent resurfacing can ,e provided, it forms a satisfactory finish. Wood or other material impregnated with sodium silicate, treated with hydrochloric acid, dried, and scrubbed with hot water, acquires a resistant coating of silicic acid. White laboratory enamels or resistant varnishes over a priming coat containing considerable finely divided silica (Silex) produce a good surface for titrating benches and laboratory tables not subject to heat. Before employing paints and varnishes in a laboratory, samples should be tested in ways designed to duplicate working conditions. Some preparations placed on the market for special purposes, such as label protectants and rubberizing solutions, produce surfaces which are very resistant to most reagents, but which are destroyed by heat. Cellulose acetate-impregnated wood appears to offer interesting possibilities. COMPARISON OF TABLE-TOP MATERIALS
For final comparison twelve materials were chosen from a total of about seventy different materials or finishes tested. Many of the reiected materials are excellent for special purposes, generally not table-top use. Others are a t the present time too costly or entirely inaccessible. Table I1 summarizes the results of tests of these twelve materials which were considered to be best suited to table-top use. The method of combining the results of the tests may be varied to suit different needs. Two summaries are given, the first on the basis of seven groups of experiments, rated equally. This summary should be of more general value than the second rating, which involves costs, applicable at best only to the vicinity of New York City. DISCUSSION OF REsuLTs-Alberene ranks slightly higher than any other material tested. It is chiefly deficient in thermal conductivity and apparatus breakage. That the per cent breakage was not higher is due chiefly to the strength of modern laboratory glass. Alberene discolors considerably in organic laboratories, and asphaltum diluted with petroleum ether has been recommended to mask stains produced in this type of laboratory. Benzene appears to serve equally well as a diluent. Carbon black in turpentine or pinene also serves well for the purpose. It was found that a mixture of paraffin and finely divided graphite, diluted with several parts of ordinary paraffin thoroughly heated on Alberene and well rubbed after cooling, gives a coating of greater chemical resistance and equal masking power. This treatment also tends to lessen the pitting which is marked with some samples of Alberene. Unglazed tile and asbestos wood rank next in the experimental summary. The standing of the former is somewhat lowered by the breakage of some samples during the heat tests. The chief objection to tile is the difficulty of securing proper installation. Asbestos wood shows a remarkably high score in both summaries, partly because, being stronger
Thermal &paConduc- Surface ratus tivity Effects Breakage 5 6 8 91 89 82 82a 90 890 92 97 89 9% 975 90 960 90 85 94 75 97 86 60 82 80 35 80 64 73 86 68 100 100 71 80 87 98 81 100 70 45 87 76 74 88 96 79 98 965 78 985
Vol. 15, No. 6 Experimental Rating Basis 700 655 653 632 640 635 567 627 522 620 493 588 589 578 634 552 562
c o s t of Maintenance 9 90 90 75 78 80 50 90 50 85 55 75 75 70 70 65 65
Cost of* Installation 200 10 100 .95 120 115 30 0 0 165 0 177 65 120 115 65 115 115
Final Rating Basis 1000 845 838 827 833 745 617 717 737 705 725 728 784 763 769 732 742
L a n Alberene and other materials, it can be used in thinner sheets, thus lowering its first cost. fmpregnated with paraffin and graphite as described in the preceding paragraph, its chemical resistance is slightly increased and its discoloration masked. Ebony wood is an excellent material if physical strength and insulating resistance are desired. Blisters and extruded matter make it objectionable if subjected to elevated temperatures, and the rather high first cost lowers its rating. If chemical stoneware could be prepared with a plane surface a t reasonable cost, it would be an excellent material for many purposes. Enameled cast iron is another material which would probably have a future as a table-top material if it could be produced a t a reasonable cost. Concrete and linoleum rate rather low, but considering cost and low replacement expense they offer interesting possibilities combined. Rubber flooring, which is now obtainable in large sheets, is another material which could be combined with wood, concrete, or asbestos wood to form a top upon which it would be a pleasure to work. CONCLUSION I n conclusion, it is the opinion of the author that on account of lower first cost, for special purposes or if carefully used, wood, rubber, and similar materials are acceptable; but for ordinary purposes refractory monolithic materids of low maintenance cost are the most satisfactory. More attention can well be paid to decreasing the fire risk in chemical laboratories. This end will be secured by using materials which are rated highly in this investigation. The conclusions reached seem to be supported by the practice in recent laboratory construction. I n twenty-five relatively new 'laboratories in the eastern and central parts of this country about 75 per cent of the desk tops are Alberene, 10 per cent tile, 10 per cent wood, and 5 per cent other materials.
Analysis of Economic Poisons The California Department of Agriculture has recently published a report of the work of the Division of Chemistry in the analysis of economic poisons for the period July 1, 1920, t o June 30, 1922. The examination of materials herein reported is in the nature of a survey of the condition of the market and is t o be used as the basis of future inspection work under the California Economic Poison Act of 1921. The work was done under the authority of two legislative acts. The first, known as the Insecticide and Fungicidq Law of 1911, was in force from July, 1911, t o August, 1921. Thls was repealed and superseded by the California Economic Poison Act of 1921, which became operative August 2, 1921, and regulates the manufacture and sale of insecticides, fungicides, herbicides, and rodenticides, collectively known as economic poisons.
