72
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 25, No. 1
TABLEX. EFFECTOF TEMPERATURE ON GEL FORMATION IN 7. Temperature of about 120' F. (48.9" C.) causes better 2 PER CENT SOLUTION OF SODIUM METASILICATE gel formation than other temperatures. SUBSTANCEB ADDED r TEMPERATORE, e F. 8. A certain minimum amount of metasilicate is necessary TO SOLN. 32 60 70 100 120 140 180 for gel formation. Best gels are formed in solutions contain:22il%;%er,( - - - + ++ + t ing 1to 3 per cent of metasilicate. I n solutions having higher 30% 8our milk percentages of metasilicate, the tendency is for the gel to The solutions were placed a t temperatures of 32", 50°, become a gelatinous precipitate. 70", loo", 120°, 140', and 160' F. (O", lo', 21.1", 37.8", 9. The amount of sour milk and of milk solids necessary 48.9', 60", and 71.1' C.) and allowed to stay there 24 hours. for gel formation is large. It requires a t least 50 per cent The solutions kept at 32", 50', and 70" F. did not form gels; of skim milk before a firm gel is formed. A washing solution the solutions a t loo", 140', and 160" F. formed weak gels; containing that amount of milk solids, since its reaction is and the solutions a t 120" F. formed strong gels. in the gel-forming zone, will have poor cleansing properties. Gel formation in washing solutions may well be considered as CONCLUSIOM a sign of faulty operations. 1. Sodium metasilicate solutions do not form gel when 10. Apparently gel formation in sodium metasilicate no other substance is added. washing solutions in the milk bottle washing machines may 2. The addition of lactic acid causes gel formation in those take place when the solutions contain less than 3 per cent of solutions which are near neutral point in reaction. The gels the metasilicate and when about 4 per cent or more of the become weaker as the acidity or the alkalinity of the solution milk solids accumulate. is increased. Gel formation ceases when a certain point in Hence, gel formation can be avoided by using solutions that reaction is reached. contain not less than 3 per cent of the metasilicate and by dis3. The addition of other alkaline washing powders, except carding the washing solutions before about 4 per cent of milk that of sodium bicarbonate, does not increase the tendency for solids other than fat accumulate in them. gel formation. LITERATURE CITED 4. The addition of sodium bicarbonate causes gel formation. 5. The addition of sour milk and milk solids causes gel (1) Vail, J. G., Paper presented at meeting of Am. In3c Chein. formation. The milk solids, as well as the acid, lowers the Eng., New Orleans, La., Dee. 8-10, 1930. (2) Vail, J. G., "Soluble Silicates in Industry," A. C. S.Nonograph p H value of the solutions. Series No. 46. Chemical Catalog, 1928. 6. Agitation tends to break up the gel and thus prevent gel formation to some extent. RECEIVED December 11, 1931.
Tests of Chemical Treatments for Control of Sap Stain and Mold in Southern Lumber R. M. LINDGREN,T. C. SCHEFFER,AND A. D. CHAPMAN Bureau of Plant Industry, United States Department of Agriculture, New Orleans, La.
D
URING the seasoning process a t the mill the freshly sawed sapwood of a number of commercially important species of southern woods is subject to permanent discoloration by certain fungi, principally Ceratostomella species and some of the Fungi zmperfecti. Such discolorations have been commonly called blue stains or sap stains because of the color of the portion of the wood attacked. The stain occurs in spots, streaks, or patches of various intensities of color and is due to the dark fungal hyphae which may ramify throughout the sapvood. In addition to stains the fructifications of a number of mold fungi cause discolorations of various hues which are largely superficial in nature and therefore removed in surfacing the wood. The widespread occurrence of these discoloring fungi has been the source of serious annual losses to pine and hardwood lumber manufacturers, especially in the southern region where the climatic conditions are particularly favorable for their development. Such losses are due principally to reductions in grade, value, and marketability of the stained material. Although the stain and mold fungi do not impair the strength of wood seriously, it is evident that their occurrence injures lumber for usks where a natural finish is desired. Recently buyers have come t o discriminate against stained material even in the common grades of lumber,
For some thirty years spasmodic efforts have been made to find an economical means of controlling these fungi in lumber, but not until recently has intensive work been directed a t the problem. Because of its economic importance, this problem was selected in 1928 by the Division of Forest Pathology for concentrated effort. As a result of an estensive survey of existing conditions and mill practices in the southern region, it was evident that of the two general methods in use for preventing stain-namely, the use of chemical dipping treatments or of rapid seasoning practices such as kiln drying, end racking, and steaming-the former would lend itself more readily to improvement. The soda dipping treatment, which was being used by some southern mills to control sap stain, had never proved fully satisfactory on pine and had failed completely on hardwoods. I t was felt that tests of a sufficient number of chemicals would reveal some of greater efficiency and of wider application than past treatments and therefore of immediate practical value to both pine and hardwood manufacturers. The present paper summarizes the results of a number or' such tests conducted over the 3-year period 1929 to 1931.
TESTS Since it was obviously impossible to make tests on a commercial scale of all the chemicals warranting trial, prelimiSMALL-SCALE
January. 1933
INDUSTRIAL AND ENGINEERING CHEMISTRY
73
TABLEI. RELATIVE EFFECTIVENESS OF CHEMICALS USEDIN PRELIMINARY EXPERIMENTS ON CONTROL OF SAPSTAINAND MOLDIN PINE AND SAP GUM^
--
CHEMICALS T E B T E D b
CONCN.c
Tests
V" Ammonium borate NH4F NH4F NH4F sodium o-phenylphenoxide NH4F sodium o-phenylphenoxide NH4F sodium o-phenylphenoxide AszOs (10% soln.1
++ +
6.0 6.0
2 - . 4. 0.9 0.56, 0.40, 0.16
. .. 7.2
7 7
Borax Borax Borax Borax
+ KaOH Borax + NHlOH + NaOH Borax + sodium o-phenylphenoxide Bordeaux Boric acid Boric acid + ZnSOl CdSO4 Colloidal creosote CurCOa CUZCOS borax Copper phenylsulfonate
+
CUSOl cusoc CuSOc KHnOH Cresylic arid (crude 97-99%) NaOH Dipdust Diversol Ethyl chloroacetate Ethylmercury chloride, 3 parts: inerts, 97 parts (No. 652) Ethylmercury chloride, 3 parts; inerts, 97 parts (No. 652) Ethylmercury chloride, 4.3 parts; inerts, 95.7 parts (No. 745)
+
+
Ethylmercury chloride 4.3 parts' inerts, 95.7 parts Lignasan) Ethylmercury ehlorjde: 4.3 partsf inerts, 95.7 parts {No. 745-B) Ethylmercury chloride 3 parts. W andotte soda, 97 parts (K-1) Ethylmercury chloride'(K-1) adgtional soda Ethylmercury cyanjde, 2 parts; jnerts, 98 parts (No. 697) Ethylmercury fluoride, 2 parts; p e r t a , 98 parts (No. 696) Ethylmercury oxalate, 3 parts; inerts, 97 parts (No. 674) Ethylmercury phosphate, 3 parts; inerts, 97 parts (No. 673) Ethylmercury phosphate (No. 961) Ethylmercury phosphate, 3 parts: inerts, 97 parts (No. 673)
4
3 3 2 1 3 3 1 1
24 40 65 63 5 I!?
2
25
; 2
19 34 36 61 18
1
--SAP Tests
3 3 3
4
5 1 3
5 . 4 , 0.6, 0 . 3 4.2,0.3 1.2 3.6 1.8, 1 . 8 0.3 0.9 1.2 0.3, 5.4 0.45
2 3 2 3 3 3 1 3
43 37 48 33 57
3
79
3.6 1.2 3.0, 0.6 1.9, 0 . 8 0.48 2.4 0.21 0.24 0.48 0.48
1 1 2 3 1 2
12 48 13
15 61
17 14 5
4 6
73 31 51 47 53 5 2 2
5
4
4
6
..
2 2
2 3
1 1
, .
6 4
46 7 9 56 76 53 1 61
16
..
13 25 22 50 87 63 69 1 0.5 0.7
22
59 58
..
2 0.6
1 4 3 2 1 1 3 4 1 1
0.1 20 3 5 22 4.8 0.2 1 31 0.1
3 1
10 0.1 4 31
83 54
i
Av. of sapwood stained
%
8
6 13 37
GUM-
37 39 12 68 46 40 5 10 13 27
i
5.4 7.2 5.4, 0.3
0.48 0.24 0.57 0.3, 5 . 3 0.48 0.48 0.48 0.48 0.24 0.48 (Continued on page 74)
Av. of sapwood molded
%
I-
7.2 7.1 1.2 1.6 1.08 1.5 0 5 0 5 1:s: 0 : 4 0.5, 0.4 2.4
PIN=
Av. of sapwood stained
5
0 7 5
5 1
..
3 4
..
46 0.3 0.7 0.6 10
..
a T p R t R in 1929 were conducted a t Great Southern Lumber ComDanv. Bonalusa. La.: Eastman-Gardiner Lumber Comoanv. Laurel. Miss.: and J. J. Newman-Lumber Company- H a t t i e s b u r g ~ M i s s - Testscn 1930 were' coLductgd-at EGtmaGGardiner Lumber Company, L i u r d , ' Miss. * Louisiana Cenfral Lumber Company, Clarks, La.: and W. 'i Smith '. Lumber Company, Chapman Ala. Tests in 1931 were conducted a t Goodyear Lumber Company, Picayupe, Miss.; Jasper County Lumber Company, Jas er, Tex. : Gloster Lumbe; Company, Gloster, Miss.; Eastman-Gardiner Lumber Company, Laurel, Miss.: Tremont Lumber Company, Rochelle, La.; Brant Timber and Manufacturing Company, Selma, La.; and E . L. Bruce Lumber Company, Laurel, Miss. b Bordeaux, powdered form, Orchard brand. Colloidal creosote, supplied by Baird &nd McGuire, Inc., Holbrook, Mass. Dipdust, a patented disinfectant consisting of 6 % hydroxymercurichlorophenol sulfide, 2 7 .hydroxymercurinitrophenol sulfate. Diversol a patented sterilizing agent composed of 2.5% sodium hypochlorite, 92.5% alkayine sodium hosphate. Ethylmircury compounds, phenylmercury ace!ate, sodium silicofluoride (50%), furnished by the E . I. d u de Nemours & Company, Wilmington, Del. Fungimors, a patented German stain preventive understood t o be mercurial. Ialine, a reversible colloidal sulfur. Mercurophen, a mercury compound (sodium oxymercuri-o-nitr,ophenoxide), furnished by H. K . Mulford Company. Metaphen, a n organic mercury compound (4-diacetoxymercuri-2-nitrocresol). Minerec a flotation reagent consisting of 10% xanthic anhydride and 90% ethyloxycarbonyl sulfide, furnished by the Minerec Corporation. Nekyan' a patented Swedish stain preventive. Pine oil'emulsion, a steam-distilled emulsified, ine oil, furnished by the Johnston-Mapkie Company: Protexwood, a product, qf the destructive distifiation of wood, furnished by the Termite01 Corporation of Louisiana. Semesan a patented disinfectant (hydroxymercurichlorophenol). Shirlan dompounds, proprietary British antimildew compounds used in conditioning cotton yarn. Soda (Wyandotte), a mixture of carbonate and bicarbonate, furnished by the J. B. Ford Agency. I n the large-scale tests a sodium bicarbonate, manufactured by the Mathieson Alkali Works, was used also. tetrachlorophenol, and sodium tetrachlorophenoxide, furnished by the Dow Chemical Sodium o-phenyl henoxide, sodium 2-ohloro-o-phenylphenoxide, Company, Miiand.,M!ch. Solbar, a compound principally of barium sulfide, furnished by E. I . d u Pont de Nemours & Company, Wilmington, Del. Sterilac a n alkaline chloroamine mixture used for disinfectant urposes. Tri-Trebt, a patented wood preservative, furnished by Bruce zhemical Company. e Concentration of all solutions selected on the basis of a n approximate cost of solution of 20 cents per thousand board feet of lumber. I n the cane of mixtures, the concentration per cent is figured on the basis of the weight of the total sample (including inerts) unless the individual concentrations are given in the order of the components named.
gent
nary tests n-ere made on a small scale under actual mill conditions. Such small-scale tests, which are less costly and time consuming than commercial trials, have permitted the testing of a large number of untried chemicals and the elimination of all but the most effective ones. They have proved of value also in determining the influence of concentration and temperature changes on the efficiency of the most promising treatments. The technic employed, permitting
as it does the close control of environmental factors, assures uniform conditions of exposure and therefore an accurate comparison of a large number of chemicals a t one time. Such a condition is not attainable in commercial testing. The reliability of the method for the intended purposes is indicated by the consistency of the results and the corroborative evidence from subsequent commercial trials of the most promising treatments.
I S D U S T R I .4 I, A N D E N G I S E E R I N G C H E bl I S T R Y
74
VOl. 25, No. 1
OF CHEMICALS USEDIN PRELIMINARY EXPERIMENTS ON COSTROL OF SAP STAINAND TABLEI. RELATIVEEFFECTITENESS MOLD IN PINE AND SAP GUM^ (Continued)
--
CHEMICALS TEsTEDb
CONCN.C
5-c 0.48 0.48 I .2 1.2 0.3 0.24 0.6 0.6 0.16 0.05
Ethylmercury sulfate, 5 parts; inerts, 95 parts (h’c. 647) Ethylmercury tetraborate, 2 parts: inerts, 98 parts (No. 730) FeSOl Formaldehyde Fungimors Ialine Lime sulfur MgSiFa HgClz HgIi
++
0.15,0.19 0.028, 0.028, 2 . 4 0.11 0.3 0.3 0.24 0.32 2.7 1.45
HgIz KI HgIz KI soda Mercuric salicylate Mercurophen Metaphen Minerec Minerec Nekyan p-Dichlorobenzene
+
Phenylmercury acetate, 3 parts: inerts, 97 parts (P. hl. A Phenylmercury nitrate (“X” compound) Phenylmercury nitrate (“X” compound) Phenyl salicylate Pine oil emulsion KpS Protexwood Salicylic acid Semesan Shirlan N. A. Shirlan (50% paste) %&ap,; w der andotte alkali) Soda Soda Soda (in uae in vat) Soda Soda borax Soda Soda NaHSOa
0.57
)
0.08 0.13
0.6 2.4 3.0 3.0 1.8 0.48 0.5 0.9 0.2 7.2
7.2
5.3 11.0 5.4 7.2 3.6, 3 . 8 3.8, 2.9
++ Soda + N a F Sodium benzoate
NaHS08 Sodium 2-chloro-o-phenylphenoxide Sodium dinitrophenoxide Sodium dinitrophenoxide Sodium dinitrophenoxide Sodium dinitro-o-phenylphenoxide NaF borax NaF
+ N a F + NaHS03 NaOCl
3.5,1.9 1.2 7.2 0.4 1.2 0.9 0.15 0.48 4.1 2.08, 3.35 1.9,3.5 3.1 4.2 5.4 6.4 5.4 0.21 0.9 0.48 0.3
NaOCl NatSiOs NaiSiOs Sodium monoborate Sodium naphthionate Sodium o-phenylphenoxide Sodium o-phenylphenoxide Sodium o-phenylphenoxide
0.9 0.9
Solbar Sterilac Tetrachlorophenoxide Tri-Treat ZnFz Zinc phenylsulfonate Untreated Untreated Unrreated Untreated
+ NaOH
Tests 3 1 1 3
; Q
3 3 1
3 2 3 1
2 1 1 3 3
3
1 1
1 ?
3 1
; 1 1
1 3 4 3
1 3
1
%
0.2
10 27 12 36 21 3 0 9 20 0
5 6
43 17 30 35 45 11 33 0.7
62
70 35 36 57 3 31 30
i
0.1 11 32 18 52 28 27 38
32 38 4 3 4 6 63 g.8
,
7
2 2
3
1
1 1
4
3 1
14 75 67 58 1.5
60 80
9 4 1.5
3.2 0.9 1.9 0.9 0.48 0.48 0.48, 0 . 4 8 0.24, 0.24 0.4 0.15 1.3, 0.16 3.3 3.2 0.9
2 2 3 1 1 3
68 21 47 52 80 75
3
52 52 65 64
In selecting the chemicals for trial and in evaluating them later for stain control, such qualities as cost, ease of solution and application, effect on equipment and color of lumber, and injuriousness to workmen were considered, as well as toxicity to stain and mold organisms. Included in the group selected was a large number of organic and inorganic salts of the heavy and alkali metals, and chlorinated and nonchlorinated phenol compounds. Some of the materials had shown promise in closely related lines of investigation ;
.. .... ..
1
4
6 3
1
1
8
8 2
2
52 67 41 44 42 17
0 0 1
0.7 2 0:8 0
3 77 72
21
1
2 2 3
0.4 1 18 62 63 20 38 45 29
1 1
1
I
70 3 1 1 3
6 12 0 0 13 1 0 30 10 0
4 21 71 0.1
5
stained
46 54
7 51 23
1 3 3 2
sapwood Av. of
Tests
1
3 3
0.4
~ GUM~
i
12 5
2”2
S
3 3 4
20
1
v
3 Trace Trace 36 7 1 0 9 10
2
3 3 3 2 1 1 1 3 2 1
checks checks checks checks
Av. of sapxood molded
%
10 63 33 32 7 42 82 30 3 1.3 9.4
6.0
sodium o-phenylphenoxide o-phenylphenoxide ++ sodium
PIXE
0 0 1 0.5
27 29
1
2 1
1
3
1
3
2
.. 3
1 2 2
2 1 9
1
..
62 60 7 39 31 85
20 18
..
..
2
i
4 2
1
1
9 50 11
1 2
3
0.2
1 2 1 2 2 1
9 7
2 2 4
1 1
35 74 47
..
2 69 14 27 14
1 60 35 67 44 67 63 9 0.3
0.8
7
35 35 5
36 58
1.3
4
67
20 9 0.5
1 4 6 3
71 48 60
0
I
..
4
0 0 0
.. .
3
0.6 0
..
58
2
0 0
..
i
Trace 2 0.1 0.4
8
..
a3 31 34
4
0
..
1 4 3
0.5 0 0
57 59 43 42 53
..
77
‘0
3
68
others were proprietary compounds recommended as stain preventives in the United States and in foreign countries; the remainder was untried chemicals which had shown promise in laboratory toxicity tests on the sap stain fungi (1). Data on the extent to which each of these treatments met the requirements enumerated above were gathered during the course of the tests which continued through the summers of 1929, 1930, and 1931. The usual procedure in treating was to immerse freshly
January. 1933
I S D U S T 12 I
A\
L -4 S D E N G I S E E R I N G C H E AI I S T R Y
sawed pieces of sapwood, 1 X 2 X 24 inches (2.5 x 5 x 61 em.) in size, for 15 seconds in solutions kept a t a temperature of 160" F. (71.1" C.), In some of the tests, especially in the later ones, the solutions were also applied at air temperatures to determine the extent to which the application of heat increased the effectiveness of the treatment. The initial concentrations of most of the chemical solutions were based on an approximate cost for materials of 20 cents per thousand board feet of lumber treated, the highest cost considered practicable by most southern operators. The dipped pieces, together with untreated control material for comparison purposes, were semibulk-piled in a moist location which presented uniformly severe moisture conditions for the different treatments. At the end of a testing period of 30 to 40 days, the piles, each of which contained forty t o sixty pieces, were examined and the effectiveness of each of the various treatments determined on the basis of the percentage of sapwood stained and molded.
R E ~ U L TOFS TREATMEST The results of the preliminary small-scale tests are presented in Table I. Mold occurrence in gum is not included because of its unimportance in all treatments. Where a treatment was used in two or more trials, an average figure of effectiyeness in stain and mold control a t the various mills is given. The term "stain," as used here, is meant to include those fungous discolorations, usually bluish black in color, which are not readily removed in surfacing the lumber. The results of the hot and cold treatments were averaged and are presented as one figure becaube little or no difference in effectiveness -was noted, with the exception of those solutions containing sodium carbonate or bicarbonate, in which case the hot treatments were definitely superior to those applied a t air temperatures. The degree of control obtained by any given treatment varied somewhat a t different mills as would be expected of tests made in the field under widely varying conditions of humidity and temperature. The results of the tests, however, are fairly consistent, in that the different treatments ranked in about the same order of efficiency in different experiments. Of the one hundred or more treatments tested, several \yere quite effective in controlling stain and mold in both pine and hardwoods; others prevented stain but not mold, or vice versa, or were limited in effectiveness to one kind of ivood. Borax, for instance, proved effective on hardwoods but relatively ineffective on pine, whereas the reverse condition held true for sodium o-phenylphenoxide, Ammonium fluoride controlled stain effectively but permitted too much mold growth to be of practical value unless combined with a compound effective in preventing mold development. Of the entire list, only the following compounds were believed to combine enough of the required qualities of a practical treatment to warrant commercial trial: borax, ethylmercury chloride, ethylmercury phosphate, sodium o-phenylphenoxide, sodium tetrachlorophenoxide, and sodium 2-chloro-o-phenylphenoxide. These, with the exception of the last-named compound, have already been tested on a commercial scale-borax on hardwoods only, and the remainder on both pine and hardwoods. The results of these commercial tests, which have been published briefly elsewhere, corroborate closely those reported in the present
75
paper ( 2 ) . Soda, the principal treatment in current use, !\-as included as a standard of comparison in all large-scale trials on pine, and proved definitely inferior to the other treatments tested. Although most of the treatments used in the preliminary tests were eliminated on the basis of ineffectiveness against stain and mold fungi, several which looked promising from the standpoint of control possessed certain qualities which made them undesirable. For example, mercuric chloride, Fungimors, mercuric iodide plus potassium iodide, and certain of the organic mercury compounds were eliminated because of corrosiveness t o metal or possible injuriousness to workmen handling them. Others, such as sodium dinitrophenoxide, copper sulfate alone or in mixture, ferrous sulfate, and Protexwood were objectionable because of their discoloring effect on wood. Under ayerage drying conditions the critical period for stain occurrence in lumber is during the first 30 days of seasoning. If staining does not occur within that period, the surface moisture content of the lumber has in most cases been reduced sufficiently to prevent further infection by staining organisms. For this reason the tests were run for periods not longer than 40 days and no attempt was made t o determine the permanence of the treatments over longer periods of time. It has become evident, however, that a certain degree of permanence is an important quality and one upon which more emphasis must be placed in further tests. Lumber stacks in the South are frequently exposed t o heavy rains, which prolong the period of susceptibility to discoloration either by retarding drying of the green lumber or by increasing the moisture content of the dried stock sufficiently to permit stain development. Under such conditions the toxic elements of some of the present treatments may be removed by leaching or volatilization to the extent that their efficiency will be greatly reduced. The only instance in which permanence might not be desirable is in the treatment of stock to be used for food containers, where chemicals with an offensive odor or high toxicity to humans would be undesirable.
SUMMARY Of the one hundred or more chemicals and combinations of chemicals tested for the control of stain and mold on pine and hardwood lumber, borax, ethylmercury chloride, ethylmercury phosphate, sodium tetrachlorophenoxide, and sodium o-phenylphenoxide show greatest promise of commercial practicability. Although a t least one of the above treatments has already been adopted in commercial practice, further rTork is essential before their maximum efficiency under various conditions of application can be assured. The search for new materials as well as experimentation directed a t the improvement of the best of the present treatments will be continued. LITER.4TURE C I T E D
(1) Hatfield, I , PIOC. A m . Wood-Preserber,' Assoc., 27, 304-14 (1931); 28, 330-3-20 (1932). (2) Lindgren, R. M , Scheffer, T C., and Chapman, A. D., Southern Lumherman, 145, 43-46 (May 15, 1932). RECEIVEDAugust 4, 1932 The tests Mere conducted by the Bureau of Plant Industry in cooperation \+ith the Southern Forest Experiment Station and the American Pitch Pine Export Company, New Orleans, L a , and its member mills.
