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5-Ferric ion is adsorbed t o such a n extent t h a t i t will carry the particles over from a negative charge through t h e isoelectric point t o a condition of positive charge in a manner analogous t o the reversal of charge o n albumin particles. 6-From the experiments with ferric chloride and ferric nitrate i t is apparent t h a t both ions of a n added electrolyte are effective in precipitation of the charged -particles. 7-The decrease in stability of these emulsions upon -the addition of ether is probably due t o the solvent action of t h e ether on t h e asphalt rather t h a n t o any increase in t h e difference in density of the two liquid phases. An ether-carbon disulfide mixture of the same gravity as t h e emulsion will discharge t h e water. 8-The action of certain commercial treating compounds is probably due t o the fact t h a t they are hydrophile colloids. A hydrophile colloid should discharge a n emulsion formed by the use of a hydrophobe colloid, while a hydrophobe colloid should discharge an emulsion formed by t h e use of a hydrophile colloid. ACKNOWLEDGMENT
I n conclusion, t h e author wishes t o thank Mr. E. T. Gregg for aid and helpful suggestions, and Dr. F. M. Seibert and Mr. J. Van der Henst for procuring samples. TESTING THE MILDEW RESISTANCE OF TEXTILES’ By B. S. Levine and F. P. Veitch LBATHER AND
LABORATORY, BURBAU OF WASHINGTON, D. C.
PAPER
CHSMISIRY,
A study of t h e fundamental factors determining the effectiveness and durability of processes of waterproofing and mildewproofing textile fabrics, such as cotton duck and cotton canvas, was undertaken with t h e primary object of finding simple formulas and methods for treating cloth which are applicable for small-scale use on the farm and also suitable for use by commercial treating plants. Prerequisites for successful work on the main problem are, of course, suitable methods for determining water and mildew resistance. The method here described, which is not regarded as final b u t subject t o improvement with experience and greater knowledge of the problems involved, has been used for the past two years and has proved to he useful in judging t h e probable serviceability of mildew-resistant treatments. The methods used for testing the water resistance of fabrics are described in a separate paper.2 Mildewing is due t o the development of various mold growths on and in t h e fabrics. The number of species responsible for t h e deterioration is large, but chief among them are species of A l t e r a a r i a , of Clados p o r i u m , and some Mucors. The simultaneous occurrence of different kinds of molds seems t o play a n important part, and t h e production of pink and yellowish discolorations is probably due, a t least in some cases, t o t h e growth of both a Mucor and a mold pro1 Read at the 57th Meeting of the American Chemical Society, Buffalo, N. Y., April 7 t o 11, 1919.
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ducing a substance having a pink appearance in alkaline or neutral reaction and a yellow one in a n acid reaction. Gueguen’ is of the opinion t h a t t h e spores causing t h e mildewing of fabrics are usually introduced into t h e fibers by the dead parts of the parent cotton plant, where they have been either in a dormant or germinating state, and concludes t h a t mildew is hardly ever due t o contamination of the fabric after weaving. The presence in the air of spores of cellulose-destroying fungi has been demonstrated by McBeth and Scales,2 who have isolated from plates exposed t o air contamination over a dozen cellulose-destroying organisms, among which C l a d o s p o r i u m h e r b a r u m has been identified. Davis, Dreyfus and Holland3 have shown t h a t astonishingly large numbers of mold spores rain into the mill vats containing sizing materials used on t h e component threads, thereby becoming introduced into t h e woven fabric. We have repeatedly mildewed pieces of treated and untreated fabrics by inoculating their surfaces with pure cultures of C l a d o s p o r i u m , A l t e r n a r i a , and other molds, and have found that, under laboratory conditions, converted canvas may be completely destroyed by several species of A s p e r g i l l u s . Sterilized duck inoculated with spores and mycelial fragments of species of A l t e r n a r i a and of C l a d o s p o r i u m and incubated for two weeks, developed mold growth which, at the end of another two weeks, entered deeply into the fabric. Furthermore, heavy fabrics, subjected t o certain finishing processes having a sterilizing effect on the preexisting mold spores and mycelial fragments, readily mildew under favorable field conditions. It is clear, therefore, t h a t even canvas apparently free from original mold impregnation will mildew if exposed t o air contamination and t o conditions encouraging mold growth. M E T H O D S USED T O D E T E R M I N E M I L D E W RESISTANCE
Tests for mildew resistance of fabrics have been in use heretofore. One, occasionally followed, is, briefly, to bury a sample of the cloth under ground at a depth of 1 2 t o I ; in. for a period extending over one month. The ground is kept moist by occasional watering. The condition of the fabric a t the end of t h e test period is considered t o indicate the degree of mildew resistance. This method may give valuable information regarding t h e resistance of fabrics t o bacterial action, but its value for determining mildew resistance is questionable. Waksman4 found that soil samples taken from a depth of 1 2 t o 3 0 in. on plating out developed only Zygorhynchus, and t h a t A s p e r g i l l u s , A l t e r n a r i a , C l a d o s p o r i u m , Pewiculliunz, and other organisms commonly present in the soil had not appeared in the plates in 24 hrs.; while in the upper soil strata there may be I,OOO,OOO fungi per gram of soil. This, really, is a small number of organisms, Compf. rend., 1S9 (1914), 781. U. S. Dept. of Agr., Bureau of Plant Industry, Bullelin 266, pp. 24-25. a “Sizing and Mildew in Cotton Cloth,” 1880, Palmer and Howe, Manchester. 4 Science, N. S., 44 (1916), 320-23. 1
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as compared with the many millions of bacteria period of incubation when testing fabrics for mildew usually present. Canvas buried under ground would, resistance. therefore, be subject t o bacterial rather than t o funA serviceable test for mildew resistance of textiles gus attack. T h a t this is so, is indicated by the fact should include the following factors: t h a t cotton duck coated with a thin layer of paraffin I-Aerobic conditions of growth. remained practically unattacked when buried under z-Proper humidity. 3-Proper temperature. ground for nearly a month, whereas mildew developed 4-Subdued light. in less than a month when inoculated in the labora5-Sufficient period of incubation. tory. 6-Standard conditions with regard to the controlIable facFurthermore, since it is generally recognized t h a t different soils have different microbial flora, t h a t tors involved in the test. 7-Simplicity of procedure. species present under one combination of conditions To meet these conditions the following procedure has may be absent under others even in the same soil, been adopted. Cut six discs about 3l/2 in. in diameter i t is not practicable t o standardize this method of from the sample t o be tested and place in running testing. Another method is t o roll together several samples water a t room temperature for a t least 2 days. I n of the cloth t o be tested with layers of fresh horse the absence of running water place the discs in a manure and of sawdust and keep for about a month beaker of water and change t h e water several times in a moist condition. A t the end of the period the during the day. This soaking and washing is for t h e condition of the cloth is observed, and if no deteriora- purpose of removing from the fabric as much of t h e tion is evident, the samples are again rolled up !and water-sol uble, germicidal and fungicidal substances as possible and also the fermentable material. If left for another month or two. these are left in the fabric, they may suspend or hasten Haubner,l Henneberg and Stohmann12 Knieriemls the development of the mildew spores, making i t apChoukevitch4 and others have shown t h a t cellulose pear t h a t the fabric is highly mildew-resistant or is fermented by bacteria in the intestinal tract of practically all animals, man included. It is reasonable highly susceptible, whereas in practice the substances may be almost completely washed out b y the first t o think, therefore, t h a t cellulose-destroying bacteria rain, and the resistance of the fabric become markedly abound in fresh feces, but t h a t molds are practically different, absent. This statement has been confirmed in this At the end of the period of soaking, place the diBCs laboratory. Finally, this procedure obviously cannot between clean blotting papers or towels and remove be standardized, and, because of its offensive charexcess of water by pressure. Place the discs in six acter, is not suited for laboratory work. The simplest and most useful method heretofore bacteriological Petri plates containing I O t o 1 5 CC. used is that of suspending the test sample in a closed of plain agar jelly free from nutrient matter, being jar containing some water. The jar is kept in a dark, careful t h a t the plates do not become air-tight. The preferably warm, room for 5 to 7 days. A t the end plates with the discs are incubated in a closed chamber of this period, the test is discontinued. This test, a t a temperature of 20’ t o 2 5 ’ c. for 7 t o I O days. though subject t o some criticism, is better than those If they show a heavy and well-developed growth, previously described, since i t can be easily conducted the test is discontinued. I f , however, the growth of under standard conditions. The period of incubation mold is entirely absent or is merely starting, the discs are inoculated with stock cultures of Alternaria, usually employed, however, is entirely too short. Cladosporium, and a pink Mucor, and further incubated We have found t h a t certain fabrics, which have refor from 3 t o 4 weeks. The first period of incubation mained unattacked by molds for over a week, have is designated for convenience as the “pre-inoculation proved t o be susceptible t o mildew and were comperiod.” pletely overgrown in three weeks t o one month of During the second period of incubation weekly incubation. Davis, Dreyfus and Hollands have emexaminations of the plates are made macroscopically ployed a procedure for testing the mildew resistance and with the aid of the binocular microscope whenever of cotton goods similar t o the one just described, with a period of incubation from 40 to 5 0 days. I n experi- necessary. The factors observed and taken into conments on mildewing “pure cloth” the following re- sideration, are: I-Extent of contamination or so-called spontaneous growth. sults, among others, are given: z-Extent of inoculation growth. ‘‘Seventh day.-Damp but nothing visible. Twelfth day. 3-Discoloration. -Visible only under the microscope. Twentieth day.-Slight 4-Strength of the fabric. fructification. Twenty-eighth day.-Badly mildewed, brown 5-Nature of the predominating growth. spots, etc.” A rating on the basis of ten has been worked o u t Their results, together with our observations, have which is, of course, arbitrary, and subject t o future convinced us that 30 days is the shortest allowable modification. Where results cannot be measured 1 Amst-und Anzeigeblott fllr die Landwzrtschaftlichen Vereine der K&nigand expressed mathematically, precision cannot be Nche, Sachson, 1854. expected. The definitions and ratings are based upon a Beitrage eur Begrundung einer rationellen Fvttervng der Wiederkauer, Braunschweig, 1860-4, 2 pts. observable factors which do not lend themselves to 8 Z. b i d . , 2 1 (N. S. 8 ) (1885). 67-139. definite measurement. They are, therefore, subject 4 A n n . Insl. Pasteur, 2s (1911), 247-276. t o errors introduced by the so-called individual equa6 L O C . cit., p . 20.5.
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tion. However, after some experience, t h e worker obtains a concrete understanding of the terms “very heavy,” “heavy,” ‘(considerable,” “fair,” and “negligible.” The rating is based on one month’s incubation. OBSERVATIONS Contamination Inoculation Other NOMENGrowth Growth Characteristics RATINQ CLATURE Very heavyi , , Tendering of cloth 0 Mildew susceptible Tendering not readily .. .. Very heavy’ observable Heavy1 Marked discoloration Not mildew-reHeavy’ ,, Visible discoloration 3 sistant Considerable Fair Slight discoloration 4 Negligibly mildew-resistant Considerable Nealigible N o visible discoloration 5 Slightly mildew_ resistant Negligible No visible discoloration 6 Considerably milFair dew-resistant NeTligible N o visible discoloration 7 Mildew-resistant Negligible Visible only N o discoloration 8 Highly mildewNegligible through resistant binocular microscope None N o discoloration 9 Very highly milNegligible dew-resistant 10 Mildew-proof No None N o discoloration 1 Where t h e contamination growth is heavy t h e condition of the inoculation growth may be overlooked In fact it is frequently overgrown by the spread of contamination molds.
. . . .. . .. . . . . . . .. . . . .. . . .
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Data permitting the comparison of the results of laboratory tests of t h e mildew resistance of textile fabrics by the above.method with field exposures have been obtained, and, though a t present still meager, are indicative of the value of the test. Pieces of treated and untreated cloth were stretched over frames in the form of tents and exposed t o weather conditions in the vicinity of Washington for nearly a year. The samples were then brought into the laboratory and examined for mildew. The table shows the results of the laboratory test and outdoor exposure of some of the samples.
withstand exposure without mildewing is now being determined. The procedure can apparently be relied upon, especially in distinguishing between resistant and nonresistant treatments. SUMMARY
I-The methods heretofore usually employed for testing mildew resistance of fabrics are outlined and their disadvantages pointed out. 11-A laboratory method is described which is simple in execution and the details of which have been standardized. 111-A rating on the scale of I O and a system of nomenclature have been developed on the basis of laboratory observations. The practical significance of these underexposure conditions will be further studied and reported. IV-A comparison has been made of the results of the laboratory test with results of exposure tests. THE IMFLUENCE OF THE METHOD OF MANUFACTURE ON THE USE OF CASEIN IN GLUE MAKING By Samuel Butterman FOREST PRODUCTS LALJRATORY,MADISON,WISCONSIN Received August 20, 1919
The urgent necessity for a water-resistant glue for use in aircraft construction was realized immediately upon our entry into the war, but a t t h a t time, in this country, relatively little was known regarding its preparation. The severe weather conditions t o which airplanes are subjected and the impracticability of LABORATORY TESTcovering all glued joints in a machine with a waterNUM- Contamination Inoculation Ocher EXPOSURE proof coating, led the Air Service of the War DepartBER Growth Growth Characteristics RATING TEST readily observable H e a v i 1y . . . . . . . . N otendering 347911 Very heavy ment and the Bureau of Construction and Repair of of cloth 1 mildewed 347921 Heavy . . . . . . . . Marked discoloration 2 Black mil- the Navy Department t o adopt very exacting requiredew 347801 Heavy . . . . . . . , Marked discoloration 2 Black and ments as t o water resistance for all glue used in the y e l l o w manufacture of certain aircraft parts. The U. S. mildew 34772 Heavy .. . . .... Marked discoloration 2 Black and Forest Products Laboratory, Madison, Wis., was green mildew called upon t o investigate this subject in order t o ob34797 Heavy . . . . . . . . Marked discoloration 2 C o n s i d e r ably miltain definite information as t o the properties of, and dewed 34856 Heavy . . . . . . . . Marked discoloration 2 Black milmethods of obtaining water-resistant glue. dew 33309 Considerable Fair Slight discoloration 4 Some black Two types of water-resistant’ glue have been sucmildew 34828 Considerable Fair Slight discoloration 4 H e a v i 1y cessfully developed, one based on soluble blood almildewed 34832 Considerable Fair Slight discoloration 4 Mildewed bumin and the other on casein. Casein is practically 34834 Considerable Fair Slight discoloration 4 Mildewed insoluble in water, but in the presence of alkaline sub32409 Considerable Negligible N o visible discoloration 5 Some black mildew stances i t forms solutions which are highly viscous and 34826 Considerable Negligible N o visible discoloration 5 S 1 i. g h t 1 y mildewed possessed of marked mucilaginous properties. If 34748 Considerable Negligible N o visible discoloration 5 Mildewed 33331 Fair Negligible No visible discoloration 6 No mildew lime is present, these solutions soon (‘set,” and on 33460 Fair Negligible N o visible discoloration 6 N o mildew No vjsible discoloration 7 KO mildew 32388 Negligible Negligible drying form a hard mass which does not redissolve in 33434 Negligible Negligible N o visible discoloration 7 No mildew 32383 Negligible Visible only No visible discoloration 8 N o mildew water. Such a mixture of casein, lime and other through alkaline substance, t o which certain other ingredients binocular microscope may be added t o confer additional desirable properties, 33017 Negligible . . , . . . , . NN oo visible discoloration 9 No mildew 33001 None None visible discoloration 10 No mildew forms the so-called “waterproof” casein glues which 33003 None None N o visible discoloration 10 No mildew 1 The first three samples were of untreated gray duck-the remainder are commercially available a t the present time. were from treated material. I n the early work a t this laboratory in the developI t will be seen from these preliminary results t h a t ment of casein glue formulas i t was found t h a t shipsamples which by t h e laboratory method give a re- ments of casein from different sources, or often two sistance of six or better withstood exposure for a whole shipments from the same maker, exhibited such marked year under normal weather conditions near Wash1 F. L. Browne, “Water-resistant Glues,” Chem. & Met. En&. ai (1919), ington, D. C. How much longer these fabrics will 136.
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