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INDUSTRIAL AlYD ELV(X:INEERING CHEMISTRY
pared in accordance with the patent specifications, and that it represented the most desirable product for commercial use. Another experiment, not previously reported by us, is of decided interest in this connection: Cloth was treated in the same manner as described in our article, with a solution consisting of 2 per cent quinidine and 4 per cent oleic acid in a petroleum distillate (Varnolene, manufactured by the Standard Oil Company of New York). The treated fabric was air-dried overnight and when exposed to moth larvae (as usual, in Petri dishes) there was not the slightest indication of damage; in fact, when tested immediately after application, we considered the treated material as entirely moth-resistant. Another portion of the same treated fabric was aired on a line in the laboratory for about one month and then exposed to larvae attack in the same way. I n this case the larvae actually placed in the dish would not eat the fabric, but spun cocoons and started transformation into the pupae. After the usual length of time, the pupae hatched, a number of flying moths appeared, and in a few weeks young larvae were observed. The young larvae had no food but the treated fabric: several of the larvae of this second generation continued to grow during a period of several months, and the fabric gradually became more and more damaged Now it is quite badly damaged and some larvae are still alive. We believe there is no question but that the treatment of woolen fabric as described by Jackson and Tassel1 does provide a certain degree of resistance to moth damage. However, in our experience this resistance is not permanent, and disappears after treated material has been exposed to the air for a period of months. The question as to who was the first to note the mothproofing quality of oleic acid is of no practical importance, fatty acids in general being of such a nature as to render them entirely impractical as mothproofing agents. However, it is apparent t h a t Doctor Jackson’s recollection of this situation is not entirely correct. During the conference in New York (held on September 28, 1927) referred to by Doctor Jackson, he was quite surprised a t our suggestion that perhaps oleic acid was a more important mothproofing agent in his compound than the alkaloid itself, and expressed considerable skepticism as to the possibility of oleic or any other fatty acid imparting any mothproofing qualities whatsoever. During this conference we showed Doctor Jackson the actual dishes containing samples of cloth experimentally treated with alkaloids and oleic acid, these being the actual dishes which were later reported in our article which AND ENGINEERING CHEMISTRY. appeared in INDUSTRIAL Doctor Jackson’s comments upon the method of testing the resistance of treated fibers to the action of moth larvae are interesting, but in our opinion do not give a true understanding of the situation. To a certain extent Doctor Jackson is undoubtedly correct. We believe that there is no question that wool fiber treated with cinchona alkaloids may show more resistance t o damage by moth larvae than will fiber that has not had a n efficient treatment with silicofluorides, provided an ample supply of untreated wool is immediately available. I n other words, cinchona alkaloids in petroleum distillates are objectionable as food t o moth larvae. If there is a choice, the moth larvae will undoubtedly eat untreated fibers in preference to those containing the above substances. On the other hand, silicofluoride is not repellent; it is effective only as it is taken into the digestive tract of the larvae. It is quite obvious that when two food supplies are available side by side, neither of which is repellent, the larvae may (provided that one material is somewhat undertreated) maintain a degree of normal health by eating the untreated fiber and a t the same time do considerable damage t o the poorly treated. On the other hand, it is probably quite true that fibers treated with alkaloids, oleic acid, and petroleum distillates would show less resistance t o moth larvae when tested in the absence of other food than when an unlimited
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supply of more suitable food were available. However, one could hardly expect a treated garment to be intentionally hung beside an untreated one in order that the moth larvae might always have a choice of material on which to feed.
M. G . MINAEFR J. H. WRIGHT THELARVEXCORPORATION 250 PARK AVE. NEW YORK, N. Y. February 20, 1930
Drying of Exterior Paints under Various Weather Conditions and over Different Woods Editor of Industrial and Engineering Chemistry: The article under this title by Schmutz and Palmer, IND. ENG. CHEM.,22, 84 (1930), should not go unchallenged, because the authors pass adverse judgment upon two woods widely and properly used for such purposes as exterior construction on houses. Their experimental data are susceptible of very different interpretation, more in line with common experience with paint on these woods. The authors report observations of the time required for a single coat of paint t o dry when applied to glass or t o wood under certain weather conditions produced artificially in the laboratory, some of which are considered adverse. Four different paints, described only as A, B, D, and E, were used in the experiments on wood. Five species of wood were used and named. The following observations are recorded:
(1) All four paints dried promptly on all woods under good drying conditions. (2) All paints were retarded by low temperature (32’ F.) both on glass and on wood, “but the average time differences were not so great (on wood) as on glass.” (3) Paints B and E in the presence of high humidity, either a t 100’ or a t 32” F., dried very much more slowly on cypress than on other woods or on glass. (4) Paint B in the presence of high humidity dried much more slowly a t 100” F. on redwood than on other woods (except cypress) or on glass, but at 32” F. this paint dried about as rapidly on redwood as it did on the other woods and more rapidly than on glass. On the basis of these findings the authors conclude that “excessive moisture and low temperature, particularly the latter, contribute to poor painting conditions, and this retarding effect can readily be intensified by poor lumber.” Although not expressly so stated, the reader is evidently expected to understand that cypress and redwood are “poor lumber,” a n inference that is totally unjustified. It would be far more logical t o conclude that paints B and E are poor paints, because they are not so well adapted as paints A and D to some of the extreme conditions that might conceivably be encountered in practice. However, it would be just as unfair to pass judgment upon the paints on the basis of the evidence presented as it is to condemn the woods, for it is not yet clear that the findings reported are of practical significance and the paints, if their composition were revealed, doubtless possess substantial merit. The following quotation from page 80 of my “Fourth Progress Report for the Study of the Painting Characteristics of Wood,” a copy of which was sent t o the Research Laboratory of the New Jersey Zinc Company on April 10, 1929, contributes additional experimental evidence and offers suggestions that should not be overlooked: Paint applied to dry redwood hardens as rapidly as it does on other woods, but if the redwood is wet, with a moisture content of 30 per cent or more, the paint remains tacky for many days pro-
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vided that the wood be kept wet. When a wet board, with a tacky paint coating, dries, the paint hardens promptly. Moreover, white paint applied to wet redwood becomes discolored with the red or brown substances from the wood. Paint applied t o white pine containing 30 per cent moisture hardens properly, but if the white pine be first painted with a solution in water of the extractive material from redwood, the paint coating acts exactly as it does on wet redwood. Apparently in the presence of free water there is a partition of certain extractive materials in redwood between the aqueous solution and the paint coating, and in the coating these substances act as antioxidants or “negative catalysts” in the oxidation of the linseed oil. It has already been pointed out that paint coatings on redwood, under normal conditions of exposure, seem to maintain their integrity longer than would be expected from the texture and density of the wood; perhaps the presence of small amounts of some extractives from redwood in the coating exerts a favorable influence upon i t without being present in sufficient quantity to discolor or retard the initial hardening of the paint.
It may be added that some green redwood was painted a t this laboratory about three years ago in a room a t 80” F. and 90 per cent relative humidity, the top coats being applied without regard for the tacky condition of the priming coat. The boards were then exposed to the weather on our test fence. Thus far these adverse conditions of application seem t o have had no serious consequences, because the coatings are still in excellent condition. Redwood and cypress are among the species generally preferred for use on exteriors of buildings where they will be painted and exposed to the weather. Both woods possess properties that make them eminently suited to such use and the common experience in painting them has been satisfactory. I n the tests conducted by this laboratory they have been classed among the woods on which coatings, under normal conditions of exposure, last longest. Under abnormal exposure conditions, permitting water to gain access to the wood behind the painted surface, blistering troubles occur. Such troubles are no more likely to occur on cypress and redwood, however, than on other woods. It is especially desirable that derogatory statements about any of the woods commonly used for houses be avoided a t this time, because a serious effort is now being made to bring the technical men of the paint and the lumber industries together in a concerted effort to improve practice in the painting of wood. Some progress can be made by encouraging milling practices that furnish lumber in those forms that hold paint best, but it is clear t h a t significant improvement must be achieved through research having for its object the modification of paint or of painting methods in such a way that coatings will cling firmly and permanently to all kinds of wood.
F. .,I BROWNE FORESTPRODUCTS LABORATORY MADISON,WIS. January 14, 1930
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Editor of Industrial and Engineering Chemistry: “Drying of Paints” as it appeared in the January issue may be interesting, but is of no practical value, with every respect due to the authors. The kind of paint used is not explained, and the result of such tests would be entirely different with various mixes. Recently the Bureau of Standards investigated many paints and found them to contain varying amounts of water (illegally and not on the formula printed on the cans), but all were sold as pure paint. Were the tests made with such material? If so, they are useless. What drier was used? Cobalt, manganese, lead, etc., are all different in their action. Was turpentine or turpentine substitute used? Each would give different results. Drying on glass or metal is no criterion as to results on wood, and wood of different kinds would vary according to the kind of
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wood used, its dryness, and whether or not a filler coat was used. Sunlight is very different from light in an oven and “low temperature” is indefinite. The use of China wood oil instead of linseed oil would materially change results. It is also important to know whether the wood was “fresh” kiln-dried or sun-dried. The results on mahogany, yellow pine, maple, etc., would not be alike, and there would be a difference if the paint contained white lead instead of zinc. What is meant by humidity? New Orleans and Florida frequently have 80 to 85 per cent humidity, while in the North such high humidity long continued is not so well known. What dry Colorado and wet Florida would produce would be different from New York,’New England, or Canada. The difference in film thickness is almost impossible to determine accurately except possibly on glass, but that is of no value for house-paint conditions. The absorption value of the wood, its thickness of grain, whether “filled” or not, would alter the tests. Paint applied by spraying also gives different results from brush painting. S.S. EVELAXD 360 MADISON AYE. I~EW YORK,N. Y. February 9, 1930 .
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Editor of Industrial and Engineering Chemistry: We wish to thank you for forwarding the comments upon our paper on paint drying. Such comments and their replies serve a valuable purpose in that they tend to clear up vague points or incorrect impressions. Since the work as covered in the paper concerns itself with drying as such, we would emphasize that no attempt should be made, a t this time to interpret the drying rate as a criterion of durability. The effect of delayed drying upon durability is another phase, which is now being investigated. The results given in the paper indicate that under the most desirable drying conditions paints B and E-both reputable commercial products-have the slowest drying rates of the paints tested. Although low temperature retards the drying of all the paints regardless of whether the application is on glass or wood, this retardation is most evident in the cases of paints B and E. On cypress and redwood it is so marked that the influence of another factor directly associated with these woods must be considered in addition to the effects of the atmospheric conditions. Doctor Browne suggests in his letter, with a quotation from his “Fourth Progress Report,” that “antioxidants or negative catalysts” in the wood may play a part in the drying delay. To support this contention we have observed in more recent work that washing the surfaces of these woods with a solvent, as ether, before applying paints B and E greatly decreases the degree of retardation under adverse conditions. To summarize, it may be said that the slower drying paints are quite sensitive to adverse atmospheric conditions and that this sensitivity may be greatly emphasized over certain woods. The use of the words “poor lumber” in the last paragraph of the paper is unfortunate in that it may convey an incorrect impression. More properly, the materials could be designated as “dry retarding,” which in the light of the above discussion does not necessarily admit any inference that poor durability must result. The dangers to which an exterior paint may be subjected during a prolonged drying period are such that every factor which may have a retarding influence should receive consideration. The primary object of the paper is t o evaluate individually a few of the numerous factors, that have not been generally recognized, which may affect drying. F. C. SCHMUTZ F. C. PALMER THEh’Ew JERSFIY ZINC COXPANY PALMERTON, PA. February 19, 1930
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Is Steam Decomposed b y Copper? Editor of Industrial and Engineering Chemistry: On page 1167 of the December issue, in the valuable article on the “Effect of Atmospheres on the Heat Treatment of Metals,” by Coriolis and Cowan, is the statement that “the earliest lessons in chemistry have taught him [the chemist] that steam passed over heated copper is broken down with formation of copper oxide.” I have always understood that steam is not decomposed by copper. Jago, in his textbook of inorganic chemistry, states: “At a red heat copper combines readily with oxygen but is unable to decompose water a t any temperature.” Roscoe, in his textbook, states that “steam is not decomposed by metallic copper a t red heat.” In view of these statements it would be interesting to know which is correct. T. H. BYRON WIGANCOAL& IRONCo., LTD. WIGAN,ENGLAND December 24, 1929
............ Editor of Industrial and Engineering Chemistry: There seems to be some difference of opinion with regard to this matter as indicated by the usual college texts. For instance, Alexander Smith’s “College Chemistry’’ says on page 411 :
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“It [copper] does not decompose water a t any temperature.” Remsen’s “College Chemistry,’’ page 546, says: “it [copper] decomposes water only a t a bright red heat.” I n Mellor’s “Comprehensive Treatise on Theoretical and Inorganic Chemistry,” Vol. 111, page 73, in the article entitled “Copper,” I find the following notes : In 1800 J. I,. Proust reported that water is decomposed by copper. H. V. Regnault found that the water is slowly decomposed a t a white heat forming cupric oxide. S. Kern noted the formation of oxides of copper when steam is superheated in copper tubes; and G. K. Elliott found that under these conditions the copper becomes crystalline and brittle. I,. Wohler and 0. Bale studied the equilibrium of steam in contact with copper a t 450” C. and observed no other than cuprous and cupric oxides are formed. According to M. C. Schuyten, copper reduced by hydrogen does not decompose water even if potassium permanganate were present, nor could W. Van Rijn or M. M. P. Muir detect any action of distilled water in copper.
It would seem from these additional references that there is some difference of opinion with regard to this matter and we wish to thank you for calling our attention to it. I n preparing our paper, we had not consulted any of the authorities, but had in mind only recollections of earlier studies. R. J. COWAN S U R P A C ~CoMBUsTIoN COMPANY TOLEDO,OHIO March 6, 1930
BOOK REVIEWS Colloid Symposium Annual (E’ormerly Colloid Symposium 19. The Chemistry of Bacteria and the Development of a Practical Technique for the Chemical Analysis of Cells. Treat B. Johnson. Monograph). Volume VII. Edited by H. B. WEISER. 20. Human Blood Serum as a Colloidal System. S. Dew. Ludlum, 296 pages. John Wiley and Sons, Inc., New York, viii A. E. Taft, and R . L. Nugent. 1930. Price, $4.50. 21. The Lieserang Phenomenon in Gall Stones. J. E. Sweet. -~ 22. Studies on the Porous Disc Method of Measuring Osmotic Pressure. This volume contains the papers presented a t the Seventh J. C. W. Frazer. Symposium On at the Johns 23. Adsorption and the Permeability of Membranes. Harry B . Weiser. Hopkins University in June, 1929. Titles and authors of the This volume is an excellent indication of the growing interest twenty-three papers are as follows: in colloid chemistry and of the manifold applications of the 1. The Scattering of Light in Sols and Gels. F. G. Donnan and K . science. I t is gratifying to see many new names among those Krishnamurti. contributing to the success of this important annual symposium. 2. The Structure of Gelatin Sols and Gels. S. E. Sheppard and J. G. It is also gratifying to see colloid chemistry rapidly emerging McNally. from the inexactness of a qualitative science to one which is 3. The Measurement of Hydration of Gelatin and Similar Materials and founded on exact quantitative measurements. the Relation of Hydration to Swelling. Harvey -4.Neville and As has been pointed out by others, qualitative experiments, Edwin R. Theis. while often interesting, a t the same time are likely to produce 4. The Influence of Adsorption on the Growth of Crystal Surfaces. more confusion than clarity, and this surely was the case in Karl F. Herzfeld. the early days of colloid chemistry. The present volume con6. Crystal Structure and Adsorption from Solution. Wesley G. France. tains many quantitative data with adequate descriptions of 6 . Significance of the Electrocapillary Curve. A. Frumkin. experimental technic, and these, with the conclusions drawn, 7. Determination of the Number of Free Electric Charges on Air Bubbles constitute a record of accomplishment which will be of permanent and Oil Droplets Dispersed in Water Containing a Small Amount value.-J. H. MATHEWS
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8. 9.
10. 11. 12. 13.
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15. 16.
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of Cetyl Sulfonic Acid. James W, McBain and Robert C. Williams. The Electrostatics of Flotation. H. B. Bull. Some Evidence on the Nature of Extra-Molecular Forces. Donald H . Andrews. The Adsorption d Vapors. Walter A. Patrick. The Specific Surface Area of Activated Carbon and Silica. F. E. Bartell and Ying Fu. Compound Formation with a Volatile Base or Acid. Wilder D. Bancroft, C. E. Barnett, and B. C. Belden. Nature of Interaction between Hydrous Oxides and Mordant Dyes. Otto Reinmuth and Neil E. Gordon. The Apparent Specific Gravity and Moisture Content of Clay. Frank K. Cameron and Richard A. Lineberry. Progress in the Study of Clay Minerals. Edgar T . Wherry, Clarence S . Ross, and Paul F. Kerr. The Colloidal Nature of Some Finely Divided Natural Phosphates. K. D. Jacob, W. L. Hill, and R. S. Holmes. The Nature of Flow. Eugene C . Bingham and Baxter Lowe. The Adsorption of Fats from Volatile Solvents. Harry N. Holmes and Clifford J. B. Thor.
AND Milk and Milk Products. BY C. H. ECKLES,W. B. COMBS, H. MACY. 365 pages. McGraw-Hill Book Co., I n c , Xew York, 1930. Price, $3.50.
Present-day dairy practices involve chemistry and bacteriology to so great an extent that prescribing a one-year course of study for students not familiar with both of these sciences seems a hopeless task. The assumption that the students have some knowledge of chemistry has, however, greatly aided the authors in the presentation of t h e chemical, physical, and nutritive properties of milk-Chapters I1 to V, inclusive. Chapter VI, on microorganisms, is written to familiarize the student with certain morphological and growth characteristics of the type of organisms encountered in dairy practices. The material presented in these chapters is well chosen, though too abbreviated in many instances. The subjects treated can be supplemented by the instructor, but for the student who desires to go beyond a mere statement of fact the
