POLE
NO, 1
20 15-
Creosote
105-
1
0 NO. 2
POLE
Distribution
I5
IO 3
,
0
POLE
NO.3
POLE
NO. d
in Treated W o o d
15 10
5 0
STANLEY J. BUCKMAN American Creosoting Company Research Laboratory, Louisville, Ky .
2 1
LCGCND SUMMER WOQ13
I
SPRING
1.5 POLE
251
U20n
n
ll
WOO3
2.5
20
NO 6
POLE
~0.a
POLE
NO
19
POLE
NO
14
30
?!.
25111
LEGEND
SUMMER
0 SPRING 1:o
015
WOO0
WOO0
2:o
l:5
2:s
IO
5 0
POLE
N0.19
POLE
NO
An investigation was made of the creosote distribution throughout the sapwood of freshly creosoted southern yellow pine poles. The comparative amounts of creosote per unit volume in the spring- and summerwood of the majority of the annual rings were found t o be the opposite from that commonly believed, the springwood having the higher concentration of creosote. The observed creosote distribution between the two portions of the annual rings seemed t o be the result of the interaction of two factors-namely, a difference in the amount of space available for creosote absorption and a probable difference in ease of penetration. The results showed there was an appreciable difference in the amount of air space in the two treated portions of the annual rings. This supports the view that the distribution and relative amounts of spring- and summerwood in the sapwood of creosoted poles are factors influencing the bleeding of these poles.
IO
5
0
20 I5
LEGEND
21
SUMMER
WOO3
IO 5
0 DISTANCE
FROM
SURFACE
OF
POLE
(INCHES)
FIQURE 1. CREOSOTE CONCENTRATIONS IN SPRINGAND SUMMERWOOD PORTIONS OF ANNUALRINGS LOCATED AT DIFFERENT DISTANCES FROM SURFACE OF P O L E S Poles I , 2, 3 4 from group I * pole8 6,8, 13, 14 from group f I ; poles 18, 19,'21 from group 111.
474
.53
Distribution of Creosote in the Sapwood of Freshly Creosoted
Southern Yellow Pine Poles with Special Reference to the Bleeding of Treated Poles
@C
0SRII)EII.ABLE attention has been devoted in recent years to the bleeding or liquid exudation of creosote from creosot,ed sout.hern yellow pine poles. As yet, the exact causes and the relative importance of a number of factors which may influence bleetling are not completely understood. On the basis of the available evidence (f, E), however, it seems that the forces which cause bleeding are produced by the influence of heat on the following factors: (a) the expansion of air and creosote in the cells of wood, ( b ) the vapor pressiirc of wat,er in the wood, and to a lesser extent (e) the vapor pressure of creosote in the wood. In accordance with this explanation, it has been found ( 1 ) that bleeding occurs most severely during periods of intense solar radiation and that bleeding is most severe on the surface facing the sun. Likewise it hs,s been observed (t) that poles having darker colored surfaces are heated to higher temperatures and bleed more than poles having lighter colored surfaces when exposed to solar radiation of the same intensity. Some evidence has been obtained which indicates that the r.haraoter of the creosote may influence the amount nf bleeding. The particular characteristic of creosote which has received the most attention with respect to bleeding is the amount of residue distilling above 355' C. (671" F.). Field observations made on posts treated with creosotes of different amounts of residue led to the following conclusions (8:"The greater the amount of residue above 355' C. in the creosote, tho greater is the tendency to bleed The t v o characteristics of creosotes which seem to be functions of the residue snd most likely to affect bleeding are viscosity and color." Thr data obtained in these observations, however, are difficiilt to interpret because of tlie impossibility of discriminating between the fsctors which may influence the amount of exudation of creosote from the pole, and the factors which may influence the amount, of exudate which remains as a more or less permanent deposit on the surface of the pole. For example, the same amount of high- and low-residue creosot.e might exude frnm different poles, but the poles treated with the higher boiling creosote niight be eonsidered as having bled more beeanse a smeller proportion of the exudate evaporated. From a practical standpoint,, the degree of undesirability of the bleeding may bc thc saiiie wfietlier the increased amount of material remaining on the surface of the pole is the result of a greater amount of exudation or tbe eraporation of a smaller portion of t,he exuded material. Nevertheless, at,teiripts to determine the influence of factors such as viscosity and rolor on bleeding cannot disregard the possibility that the differencesob. w v e d may be due to the influence of other factors ~ h i c hmay have varied in somcwliat the same relat,ive proportions.
+
FIQURE 2. RELATIVE AMOOF DIFWRENT SwBTANCEB IN SPRINGANn SUMMERWOOD PORTIONS OF ANNUAL R I N QLOCATED ~ AT DIFFERENT DrsTANCES FROM SURFACE OF Po~efi Poles 1,2,3,4frorn~,oupI.~oIpe6S 13 14fiorngroupll: v o ~ n r is. 19. %ifrom P& irr.
473
Y
3 >
476
1IVDUSTRIAL AND ENGINEERING CHEiVISTRY
The amount of creosote present in treated wood also influences bleeding. Observations made on posts treated with different amounts of creosote by the same treatment process have shown that wood treated with the higher absorptions of creosote has a greater tendency to bleed and bleeds more severely than material treated with the lower absorptions ( 2 ) . Apparently the higher absorptions of creosote result in a greater amount of bleeding because they more nearly fill all of the air space in the wood; consequently less space is available for the expansion of creosote, and there is less opportunity for a release of gaseous pressure which is built up in the interior of the wood when it is subjected to higher temperatures. In addition to the observations that the amount of absorption influences bleeding, it has been found that for posts having the same absorptions, those treated by a full cell process bled more than those treated by an empty cell process (2). The difference in the amount of bleeding was explained on the basis of a difference in the distribution of creosote throughout the sapwood. Posts or poles treated by the full cell process have the same absorption of creosote distributed throughout a smaller proportion of the sapwood than material treated by an empty cell process. The higher concentration of creosote in the outer layers of wood treated by the full cell process more completely fills the air spaces and, as a consequence, creates a situation conducive to bleeding. Although the distribution of creosote has been shown to be one of the factors which influences bleeding, only a small amount of information is available on the manner in which creosote is distributed throughout the sapwood of treated southern yellow pine poles. This is true of the creosote concentration gradient from the outside to the interior of the sapwood (9, 11). In addition, practically no information is available on the relative distribution of creosote in the springand summerwood portions of the annual rings. Teesdale (a), in an early work on the penetration and absorption of small pieces of wood, reported a difference in the ease of penetration of the spring- and summerwood' of longleaf, shortleaf, and loblolly pine sapwood. On the basis of the appearance of the treated wood, Teesdale stated that the summerwood not only was more easily penetrated but actually absorbed more creosote than the springwood. In the case of loblolly pine (not stated whether heartwood or sapwood), actual determination of the creosote concentration showed that the summerwood contained 80 per cent more creosote than the springwood. The general feeling has been that the summerwood of southern yellow pine and a number of different coniferous woods is easier to penetrate than the springwood ( 3 , 4 , 6 , 8 ,1 2 ) . However, as far as is known by the author, the work of Teesdale represents the only determination of the creosote concentrations in the spring- and summerwood of southern yellow pine. The purpose of this investigation was to obtain information on the distribution of creosote throughout the sapwood of a number of freshly treated southern yellow pine poles.
Methods and Materials Twenty-one southern yellow pine poles, treated a t commercial wood-preservation plants along with three different charges of comparable southern yellow pine pole material, were used in the investigation. The different groups of poles had been air-seasoned previous to treatment for approximately the following periods of time: Group I. Poles 1 to 4, inclusive, 5 weeks at Meridian, Miss. (February and March). Groun 11. Poles 5 to 15, inclusive, 1 week at Meridian, Miss. (Marchj. Group 111. Poles 16 to 21, inclusive, 3 months at Brunswick, Ga. (December, January, and February). None of the poles was machine-peeled previous to treatment. Any inner bark which was present on that portion of
VOL. 28, NO. 4
the pole between 9 and 11 feet from the butt was removed by carefully scraping the surface of the pole without cutting into the wood. Samples of the creosote used in the treatment of each of the groups of poles were taken from the retort during treatment. The results of the analyses of these samples are given in Table I.
TABLEI. CHARACTERISTICS OF COAL-TARCREOSOTES Charac teristica 6p. gr. at 3So/15.5OC. (10Oo/6O0F.) Inaoluble benzene Coke residue Water Fractional range: 0
c.
u p to 210 210-235 235-270 270-315 315-355 Hesidue
Group I
--
1.084 0.88 1.67
1.0
Group I1 1.080 P e r cent------0.68 1.17 1.3
Group 111 1.074 0.81 1.94 2.0
F.) (UP to 410,
(410-455) (455-518) (518-599) (599-671)
1.8 12.5 24.9 16.9 19.9 23.5
1.1 10.2 27.3 20.4 21.3 19.4
2.4 11.3 26.2 17.5 22.2 20.1
Table I1 gives the methods employed in the treatment of the different groups of poles, and the gross and net absorptions for the entire charges. Immediately after treatment, portions of the poles between 9 and 11 feet from the butt end were shipped to the laboratory for analysis. As soon as the portions of the poles were received, a disk approximately 0.5 inch in thickness was cut from the center of each portion. Four wedge-shaped pieces then were split from each of the disks in such a way as to obtain samples which represented the layers at different distances from the surface of the pole in the same proportion that they existed in the cross section as a whole. In selecting the wedge-shaped samples, the precaution was taken to avoid areas around knots or any areas which appeared to contain an excess amount of resin. Two of the pieces were used t o obtain samples which represented the layers of sapwood, 0.5 inch in thickness, from the surface of the pole to a depth of 2.5 inches, and the remaining pieces were used to obtain samples of the spring- and summerwood portions of a number of annual rings. A portion of the original piece from each pole which remained after the disks were obtained was used for making observations of penetration, number of rings per inch, and the width of the spring- and summerwood portions of the annual rings. These observations were made on the planed end surface of one of the pieces which immediately adjoined the disk from which the samples for extraction were secured. The amounts of creosote and water present in the samples were determined by extraction with toluene, employing apparatus and methods similar to those described by Waterman, Koch, and McMahon (IO). After extraction, the oven-dry weight of the samples was determined by drying to a constant weight at 105"C. (221' F.). The green volume of the samples was obtained by resoaking the extracted samples and subsequently determining the mercury displacement in a graduated cylinder. On the basis of the methods employed, all of the toluenesoluble materia.ls present in the treated wood were considered as creosote. This introduces an error in the creosote concentrations, owing to the presence of toluene-soluble materials, such as resins, in the untreated wood. Waterman, Koch, and McMahon (10) found that the amount of toluene-soluble materials present in the untreated, air-dried sapwood of southern yellow pine is less than 0.2 pound per cubic foot. As they have pointed out, the results for partially air-seasoned poles may be somewhat higher than those for thoroughly air-seasoned poles. In some determinations made during this investigation, the amount of toluene-soluble materials present in partially air-dried sapwood was found to be less than 0.5 pound per cubic foot and the difference in amounts of such materials present in the spring- and summerwood also was less than 0.5 pound per cubic foot. The results for creosote concentrations, therefore, can be considered as sufficiently accurate to fulfill the purposes of this investigation.
APRIL, 1936
INDUSTRIAL AND ENGINEERING CHEMISTRY
Results Table I11 gives a summary of certain d a t a o b t a i n e d for t w e n t y - o n e southern yellow pine poles which were treated along with three different charges of southern yellow pine pole material. Figure 1 shows the creosote concentrations present in the spring- and summerwood portions of annual rings located a8t different distances from the surf a c e s of e l e v e n poles. The creosote concentrations in these cases were based on the green volumes of the wood samples. Figure 2 shows the relative amounts of wood s u b s t a n c e , water, creosote, and air space present in certain annual rings of the eleven different poles. The volumes of the wood samples used in the calculation of these results were, in all cases, the volumes a t t h e o b s e r v e d moisture contents. When the moisture content of the sample was below 25 per cent (the value assumed as the fiber-saturation point), the volume a t the observed m o i s t u r e content was calculated by assuming that a decrease in moisture content below the fiber-saturation point is accompanied by a change in the volume of the wood equal to the volume of water lost ( 7 ) , and that creosote causes a negligible s w e l l i n g of t h e wood. The v o l u m e s o c c u p i e d by wood substance were calculated using a density for wood substance of 1.52, and the volumes occupied by the different creosotes were calculated on the basis of their specific g r a v i t i e s a t 38" C. (100' F.).
Distribution of Creosote The results shown in Figure 1 do not agree with the common conception which exists in the wood-preserving industry -namely, that the s u m m e r wood of freshly treated southern yellow pine contains a higher concentration of creosote than the springwood. In the majority of the annual rings studied, the situation was found to be the reverse, t h e s p r i n g w o o d containing a greater amount of creosote per unit volume. For t h e o u t e r layers of the poles which obtained average absorptions of a b o u t 8 p o u n d s per cubic foot or more, the results
477
sbow that the creosote concentration, practically without exception, was higher in the springwood than in the summerwood. In the case of those poles which obtained the lower absorptions (18,19, and 21) and in the case of the inner annual rings of the poles obtaining the higher absorptions, there appears to be a definite tendency for the creosote concentration in the summerwood to equal or exceed the concentration present in the springwood. The appearance of the treated spring- and summerwood portions of the annual rings would have suggested, as has been commonly thought, that the creosote concentration was higher in the summerwood portion of essentially all the annual rings. Apparently such a view has arisen because in a visual observation it is impossible to give proper consideration to the difference between the spring- and summerwood which would make the same or a lower concentration of creosote appear higher in the summerwood. It seems reasonable to expect that the same concentration of creosote should make the less dense, larger celled, lighter colored springwood appear as having absorbed less creosote than the denser, smaller celled, darker colored summerwood.
Variation in Air Space In order to explain the results given in Figure 1, it is necessary to assume either that the summerwood was less easily penetrated than the springwood or that factors other than ease of penetration were of sufficient importance to produce a higher creosote concentration in the springwood of the majority of the annual rings. The data in Figure 2 suggest a probable explanation for the higher creosote concentration in the springwood. These data show that in most of the annual rings there is a decidedly different amount of air space present in the spring- and summerwood portions. The average amount of space, occupied by wood substance, water, and creosote in the summerwood was found to be about 80 per cent of the total space whereas in the springwood it was only about 55 per cent of the total. I n other words, the average percentage of air space present in the springwood was about twice that in the summerwood. This is true despite the fact that the majority of the annual rings showed a higher creosote concentration in the springwood. The difference in the average amount of air space can be largely accounted for on the basis of the difference in the densities of the spring- and summerwood portions of the annual rings. The average density of the 159 samples of summerwood based on the oven-dry weight and green volume, was 0.701 with a standard deviation of 0.0560, and the average density for the 159 samples of springwood from the same annual rings was 0.329 with a standard deviation of 0.0366. These differences in density show that the cell wall substance in the summerwood occupies about 45 per cent of the total space, based on the green volume, whereas in the springwood i t occupies only about 20 per cent of the total. In addition to differences in the amount of cell wall substance per unit volume in the spring- and summerwood, the summerwood portion of the outer annual rings of each pole (practically all of which had a higher creosote concentration in the springwood) contained a larger amount of water per unit volume than the springwood. I n these annual rings, which were below the fiber-saturation point, the results showed that the spring- and summerwood portions would have contained essentially the same percentage moisture had it been possible to secure the two portions of the annual rings a t the same distance from the surface of the pole. However, because of the larger amount of wood substance per unit volume in the summerwood as compared with the springwood, the same percentage moisture content represented a larger volume of water, the presence of which resulted in a lower percentage of air space in the summerwood.
TABLE111. Diam. Depth Penetration of of SapGroup Pole Section Sapwood Depth wood
SUMMARY OF DATAFOR CREOSOTED SOUTHERN YELLOW PINEPOLES
-
No. Rings per InohC Summerwood 0-0.5" 0.5-1 1-1.5 1.5-2 2-2.5 0.-0.5 0.5-1 1-1.5 1.6-2 2-2.5
In. In. P e r cent 8.8 3.6 3.1 86 9.1 3.5 3.6 100 8.8 3.7 2.8 76 8.8 3.1 3.1 100 2.9 2.9 I1 10.0 100 3.3 10.4 87 3.8 81 2.1 2.6 10.0 3.8 90 3.4 10.1 3.5 97 3.4 9.9 3.5 100 3.5 10.2 3.4 100 3.4 9.9 3.2 100 3.2 10.0 4.2 71 3.0 10.4 63 2.9 4.6 10.5 3.4 3.4 100 10.2 I11 9.5 3.4 34 100 8.9 2.8 2.8 100 9 2 3.7 2.3 62 9.1 2.8 2.8 100 9.1 3.0 3.0 100 8.8 3.1 3.1 100 Av. 0.60 3.41 3.07 91.1 0 This line of figures showe the distance from
I
VOL. 28, NO. 4
INDUSTRIAL AND ENGINEERING CHEMISTRY
478
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
15 9
....
11 8
7 7
.. .. .. ..
6 7
44 52
37 52
53 44 56 52 54 45 57 59 31 47 47 59 61 56 58 47 54 51.4
47 ~. 54 44 49 48 50 48 61 34 a7 47 49 50 58 41 50 47 48 1
.. .. .. .. . ...
12 21 15 9 6 7 8 7 7 9 17 23 14 7 5 12 1 1 8 9 9 17 15 12 8 5 10 7 7 6 5 21 12 10 7 7 20 17 11 7 5 12 9 7 6 7 10 9 6 6 5 1 1 8 8 7 13 19 11 6 6 4 15 10 7 6 5 9 6 7 6 7 12 9 6 5 4 16 8 5 4 3 13 12 5 5 5 13.6 11.5 8.1 6.6 5.7 the surface of the pole in inches.
Because of the difference in the amount of air present in the spring- and summerwood, it apparently would be necessary, a t least in a number of the annual rings, to fill practically all of the air space in the summerwood before the same concentrations of creosote observed for the springwood could be attained. Undoubtedly, all of the air space is not filled even by the gross absorption of creosote, and the "kickback" (the quantity of creosote rejected from the wood upon the release of pressure) insures the presence of a n appreciable amount of air space in the treated wood. The relative amounts of creosote contributed to the total kickback by the spring- and summerwood portions of the annual ring are not known. Nevertheless, the evidence is adequate to show that the higher creosote concentrations found to the springwood portions of the majority of the annual rings can be accounted for on the basis of the lack of sufficient available space for absorption by the summerwood, despite the fact that the summerwood may be more easily penetrated. The data obtained in these experiments can be used only in a n indirect way as being indicative of the relative ease of penetration of the creosote into the spring- and summerwood because, as already pointed out, nothing is known about the relative amounts of kickback from the two portions of the annual ring. However, the results for all the annual rings of poles 18, 19, and 21 and the inner annual rings of all the poles seem to show a somewhat greater tendency for the creosote concentration in the summerwood to equal or exceed that presented in the springwood. For poles 18, 19, and 21, which obtained the lowest absorption of creosote, the average percentage of air space present in the summerwood portion of the annual ring was about 26 per cent whereas the average percentage of air space present in the other poles was about 17 per cent. Moreover, Figure 2 shows that in the inner annual rings of all the poles the amount of water per unit volume present in the springwood portions of the annual rings nearly equaled or exceeded that present in the summerwood portions. Consequently, the air space available for creosote absorption in the spring- and aimmerwood was more nearly equal in the inner annual rings of all the poles. These observations suggest that, g e n e r a l l y speaking, the summerwood probably is more e a s i l y p e n e t r a t e d than t h e s p r i n g w o o d , but the amount of air space available for
fF9
5 5
.. ..
Per cent--. 37 28 37 38
.. ..
~.
56 54 50 41 56 54 41 53 27 47 53 50 46 49 59 44 42 47.2
17 36
.
-Density (Based on Green Vo1.)0-0.5 0.5-1 1-1.5 1.5-2 2-2.5
, &am veT cc. 0.534 0.497 0.466 0.433 0.401 0.572 0.524 0.501 0.503 0.495
... . . ... . . . . . . . . . . . . . . . ... ... ... ... . . I
43 52 49 41 38 54 25 52 30 46 38 44 50 39 46 41 54 42.5
39 36 38 43 47 54 32
0.560 0.489 0.577 0.593 0.550 0.514 0.590 39 0.565 .. 0.484 35 42 0.462 0.555 32 32 0.518 37 0.497 50 0.546 28 0.498 27 0.485 56 0.520 37.9 0.532
0.524 0.461 0.550 0.598 0.518 0.472 0.505 0.541 0.495 0.475 0.509 0.532 0.511 0.558 0.493 0.485 0.531 0.515
0.515 0.454 0.531 0.555 0.478 0.471 0.532 0.521 0.449 0.468 0.495 0.456 0.475 0.549 0.458 0.492 0.486 0.492
0.544 0.460 0.654 0.546 0.498 0.460 0.508 0.480 0.459 0.465 0.484 0.495 0.453 0.541 0.443 0.462 0.494 0.488
0.490 0.449 0.495 0.521 0.476 0.480 0.485 0.438 0.438 0.477 0.477 0.483 0.432 0.519 0,449 0.452 0.499 0.471
creosote absorption by the summerwood prevents the difference in ease of penetration from resulting in a higher concentration of creosote except under certain relatively restricted conditions. The observation that the volume of water per unit volume of wood substance was higher in the springwood than in the summerwood of the inner annual rings from a number of the poles, is interesting from the standpoint of available space for preservative absorption. Although a portion of the free water present in the summerwood may be forced into the springwood during treatment, some determinations made on untreated southern yellow pine pole material support the view that the bulk of the difference in the volume of water present in the two portions of the annual rings must be due to another cause. An explanation can be found in the fact that in green sapwood the springwood contains about twice as much water in the cell cavities as the summerwood; consequently, unless the rate of loss of water from the springwood is proportionately more rapid, there must be a stage during the drying process in which the summerwood is reduced to a moisture content approaching the fiber-saturation point while the springwood still contains a n appreciable amount of water in the cell cavities. Apparently, the rate of loss of water from the springwood is not proportionately more rapid and the summerwood reaches a stage in which the bulk of the space in the cell cavities is available for creosote absorption sooner than the springwood.
Influence on Bleeding The data given in Figure 2 show that in the summerwood portions of the annual rings there is less opportunity for the expansion of creosote when the wood is subjected to increased temperatures. In addition, the results show that the cells of the summerwood are sufficiently filled with creosote to indicate that the resistance to the release of any gaseous pressure built up in the interior of the wood is localized in the summerwood portions of the annual rings. Granted that such is the case, these results offer evidence of one factor which may have contributed to the belief that machine-peeled poles bleed less than hand-peeled poles. Poles cut during a t least 8 months of the year (first part of July to the latter part of February, 5 ) , have an outer layer composed of summerwood. Hand-peeling does not appreciably alter this condition hecause it consists largely of removing only the portions of the inner bark which remain on the surface of the pole. Consequently, poles cut during the major
INDUSTRIAL AND ENGINEERING CHEMISTRY
APRIL, 1936
479
TABLEI11 (continued) Group
I
Pole 1 2 3
I1
4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21
7 Moisture Content 0-0.5" 0.5-1 1-1.5 1.5-2
15.7 16.5
... ...
33.5 40.0
... ...
Per cent 56.7 48.9
... ...
85.3 56.1
.... ....
2-2.5
Creosote Concn. (Based on Green Vol.) 0-0.5 0.5-1 1-1.5 1.5-2 2-2.5 0-2.6
93.7 62.7
15.2 16.0
.... ....
...
. I .
11.6 10.9
... ...
37.4 53.5 14.7 25.8 64.8 68.5 15.3 32.6 17.4 25.4 90.7 100.7 18.9 67.7 50.1 68.6 16.1 32.3 64.4 15.9 21.6 54.5 62.7 31.7 43.2 13.7 21.4 12.7 35.6 14.7 24.9 75.8 76.0 14.4 67.4 37.1 15.5 78.1 82.1 16.3 66.5 23.9 30.9 20.4 80.3 86.5 11.7 60.8 17.9 37.3 13.7 26.4 70.8 92.0 12.8 54.7 55.2 17.1 28.1 97.8 103.4 13.0 90.0 25.0 102.3 103.8 13.9 38.2 82.0 15.0 35.2 24.9 73.3 78.4 55.2 14.8 11.8 IIK 37.6 47.5 25.6 50.0 54.7 8.6 6.3 30.6 41.0 30.8 62.2 82.0 6.3 3.8 32.7 23.0 47.3 60.2 9.9 5.6 40.4 42.9 29.2 42.9 42.2 7.8 4.0 42.8 42.3 9.1 5.3 31.1 35.1 23.6 36.6 37.5 47.3 26.5 60.1 52.5 9.9 6.0 Av. 24.14 36.28 56.06 67.32 74.37 13.33 11.07 a This line of figures shows the distance from the surface of the pole in inches.
portion of the year and hand-peeled have an outer layer composed of summerwood which will have all but about 10 to 20 per cent of the air space filled with creosote when the poles are treated. It seems logical to expect that such a condition is conducive to bleeding from the surface layer of the pole. Any small amount of exudation from the outer layer of the wood will result in a darker surface of the pole which, it has been observed (g), is a condition coincident with a n increased amount of bleeding. Machine-peeling, on the other hand, removes a layer of wood from the surface of the pole which may be '/le inch or more in thickness, depending upon the degree of unevenness of the surface. Thus, poles which have been machine-peeled, after being cut during the portion of the year in which the outer layer of the xylem was composed of summerwood, have a large portion of the peeled surface composed of springwood. The portion of the surface layer made up of springwood will have roughly 25 to 40 per cent of the air space unoccupied by creosote when the poles are treated with approximately 8 pounds of creosote per cubic foot by an empty cell process. This condition should be less apt to favor bleeding from a large portion of the surface layer and the production of a darker surface which would tend to favor bleeding from the outer layers of the sapwood. The results also suggest that, with regard to the bleeding problem alone, it might be desirable to hand-peel the poles cut during the portion of the year in which the outer layer of the xylem is composed of springwood. In this way it would be possible to preserve a band of springwood as the entire outer layer of the pole. However, selection of the poles which should be hand-peeled would present a number of difficulties. Variation in the factors which influence the portion of the year in which springwood makes up the outer layer of the pole would necessitate the inspection of practically all the poles in this regard. Moreover, a practice of hand-peeling poles cut during certain times of the year solely to obtain beneficial results from the standpoint of bleeding would not be giving due consideration to certain desirable features, unrelated to the bleeding problem, which are possessed by machine-peeled poles. The practice of using different methods of peeling the poles cut at different times of the year also would tend to increase peeling costs. The point might be raised that all of the poles used in the study had a summerwood band as the outermost portion of the sapwood; and if the springwood layer had been in the same position, the observed relationships would have been
Lb. per cu. ft. 8.2 5.0 8.5 6.5
... ...
12.9 12.9 5.7 10.5 8.2 10.6 10.1 9.3 7.5 5.1 11.0 3.0 3.6 4.4 3.1 4.4 3.8 7.52
Creosote Concn. (Based on Concn. in 0-0.5 In. Layer) 0-0.5 0.5-1 1-1.5 1.5-2 2-2.5
I
.. ..
6.1 7.6 4.8 7.8 4.5 7.5 5.7 6.8 2.6 2.3 7.1 2.0 2.6 2.4 3.3 3.4 1.5 4.71
Per cent 54 53
4.2 4.9
9.6 9.6
100 100
76 68
4.6 6.1 2.8 3.4 3.2 4.9 4.4 4.7 1.9 1.4 4.5 0.33 0.39 1.6 2.8 1.3 0.71 3.06
11.5 13.6 9.3 10.3 9.8 11.8 10.9 10.1 9.8 8.6 10.4 4.8 3.7 5.4 4.6 5.2 5.1 8.64
100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100 100
104 109 101 93 9s 105 65 93 76 93 80 73 60 56 51 68 61 80.0
.. ..
... ...
.. .. .. .. .. ..
.. ..
88 74 36 77 56 68 56 68 44 34 74 35 57 44 40 48 38 53.6
33 41
..
..
41 44 30 57 31 48 32 50 15 18 48 23 41 24 42 37 15 35.1
28 31
.. ..
31 35 18 25 22 32 24 34 11 9 30 4 6 16 36 14 7 21.7
greatly altered. Such a conclusion is not supported, however, , by the available evidence. Although the results given in Figure 2 actually show a greater amount of air space present in the second springwood layer than in the first, the difference is not of sufficient magnitude to suggest that there would not have been an appreciable difference in the amount of unoccupied space in the spring- and summerwood when the different portions of the annual rings were present as the outermost layer of the pole. A comparison of the results for the outermost layers of spring- and summerwood with the results obtained for the two portions of all the annual rings in the outer inch of sapwood offers additional evidence in support of this view. Probably more significant than the manner in which the results establish the presence of a factor that may account, a t least in part, for a. difference in bleeding between machineand hand-peeled poles, are the indications of how the character of the entire sapwood layer may influence the bleeding of creosoted southern yellow pine poles. Because of an appreciable difference in the amount of air space present in the treated spring- and summerwood of poles treated in the manner of those investigated, it seems that poles with larger percentages of summerwood in the sapwood would be expected to bleed more than those with smaller percentages of summerwood. In addition, the results show that the relative amounts of spring- and summerwood present a t different distances from the surface of the pole would be expected to influence the amount of bleeding. For example, the results given in Table I11 show a variation in the percentage of summerwood in the outer half-inch of sapwood from 61 per cent for pole 17 to 31 per cent for pole 13. For comparable absorptions and distributions of creosote, there would be decidedly less air space in the outer half-inch of the sapwood of pole 17 than in the same portion of pole 13. This would create a situation which, from the standpoint of bleeding, should be comparable in behavior to differences that have been observed in pole material treated by a full and a n empty cell process.
Summary 1. The distribution of creosote in the sapwood of twentyone freshly treated southern yellow pine poles was studied. Determinations were made of the amounts of wood substance, water, creosote, and air space present in the spring- and summerwood portions of 159 annual rings obtained from eleven different poles.
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INDUSTRIAL AND ENGINEERIKG CHEMISTRY
2. Based on the creosote concentration in the outer halfinch of sapwood as 100 per cent, the average distribution of creosote in nineteen poles was such that the amounts of creosote present in successive layers, a half-inch thick, were 80, 53, 35, and 22 per cent, respectively. 3. Based on the green volume, the average density of the toluene-extracted summerwood from 159 annual rings was 0.701 with a standard deviation of 0.0560, and the average density of the toluene-extracted springwood from the same annual rings was 0.329 with a standard deviation of 0.0366. 4. Evidence was obtained that there is a stage during the drying of southern yellow pine sapwood above the fibersaturation point in which practically all of the space in the cell cavities of the summerwood is available for creosote absorption while an appreciable portion of the space in the cell cavities of the springwood is still occupied by water. 5 . In the majority of the annual rings investigated, the creosote concentration was higher in the springwood than in the summerwood. However, in some of the annual rings, the summerwood was found to contain the higher concentration of creosote. 6. The results showed that the higher concentration of creosote in the springwood of the majority of the annual rings can be attributed to the lack of available space for concentrations of creosote in the summerwood comparable to those found in the springwood. Indications were that the higher creosote concentrations in the summerwood of some of the annual rings can be accounted for on the basis of a difference in ease of penetration, the summerwood being more easily penetrated. However, the difference in ease of penetration
VOL. 28, NO. 4
resulted in the summerwood absorbing a higher concentration of creosote than the springwood only in the case of the lower absorptions of creosote for the annual ring as a whole, or when certain relative conditions of available space were present in the two portions of the annual ring previous to treatment. 7. The observed differences in the amount of air space in the treated spring- and summerwood were discussed (a) as a possible cause of a difference in bleeding between machineand hand-peeled poles, and (b) as a factor which may influence the bleeding of poles with different relative amounts of summerwood either in the outer layers of the sapwood or in the sapwood as a, whole.
Literature Cited (1) Am. Wood Preservers’ Assoc., Rept. Comm. 5-5-1,Proc. Ant. W o o d Preservers’ Assoc., 1932, 101-24. (2) Ihid., 1934, 80-141. (3) Griffin, G. J., J . Forestry, 17, 813-22 (1919). (4) Ibid., J . Forestry, 22, 82-3 (1924). (5) Lodewick, J. E.,J. Agr. Research, 41, 349-63 (1930). (6) MacLean, J. D., U. S. Dept. Agr., Miscellaneous P u b . 224 (1935). (7) Stamm, A. J., IND. ENG.CHEM.,27,401-6 (1935). (8) Teesdale, C. H., U. 8. Dept. Agr.,Bull. 606 (1914). (9) Vaughan, J. A., Proc. Am. Wood Preservers’ Assoc., 1934,188201. (10) Waterman, R. E., Koch, F. C., and McMahon, W., IXD. EN@. CHEM.,Anal. Ed., 6,409-13 (1934). (11) Waterman, R.E.,and Wells, C. O., Ihzd., 6 , 310-13 (1934). (12) Weiss, H.F.,Proc. Am. W o o d Presewers’ Assoc., 1912,158-87. RECEIVEDNovember 15, 1935.
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Absorption Rate of Oxygen by Orange Juice UMEROUS attempts to process citrus juices in an endeavor to avoid the characteristic deteriorations have met with some success, but there is still a lack of understanding regarding the fundamental factors concerned in the deterioration. A clear knowledge of the reactions involved and of the role enacted by the various constituents contributing to this deterioration is necessary before an entirely satisfactory method of processing citrus juice can be furnished. Various theories have been presented to account for the deterioration.‘ Wilson (26) suggested that the dark color formed upon processing and storage of orange juice is due to the melanoid reaction, but in view of the investigation of Nelson, Mottern, and Eddy (18), some other factor may be responsible. The effect of the presence of oxygen during the preparation, processing, and subsequent storage of fruit juices is well known, as is the value of canning fruit and fruit juices under a high vacuum to exclude as much air as possible. In the past the development of the “off-flavor” of orange juice 1 Since the preparation of this paper, an article was published by Joslyn, Marsh, and Morgan [ J . B i d . Chepn., 105, 17-28 (193411 suggesting that the browning of orange juice may be due t o oxidized ascorbio acid and conclude that loss of vitamin c accompanies a decrease in iodine-reduoing and indophenol-reducing value of orange juice.
Effect of Catalysts C. W. EDDY Bureau of Chemistry and Soils, U. S. Department of Agriculture, Los Angeles, Calif.
has been associated in part with oxygen either naturally present in the tissues or incorporated during the processing of juice, since the elimination of air from the product by canning under a high vacuum produces a superior product capable of withstanding higher temperatures and longer storage than juice not so processed. Mottern (14,however, has noted that under certain conditions the off-flavor does develop without appreciable loss of the reducing factor in orange juice. Even under the best processing and canning conditions, it is difficult to keep orange juice for more than a few weeks a t room temperatures without the development of the characteristic off-flavor. While some practical progress has been made during the past few years in processing orange juice (3, 5 , 6, IO, II, 26), little has been accomplished in determining the actual cause
