eterioration of W EDCARD FARBER Timber Engineering Co., Washington 6 , D . C .
HEX a railroad crosstie ia removed from track aftcr many years of service, the area under t'he tie plate irequently shows a degree of deterioration beyond t h a t which can be readily attributed to mechanical damage. The tie plate 1 and 2 Ehow this dest,ruction. ?rIicroscopic inareas in Figures spection of sections from these areas reveals crushing of cells, shifting, and buckling of rags (Figures 3 and 4). It vias suspected that this physical deterioration of wood in contact TTith the iron of the tie plate over long periods involved chemical decomposition. I n the spike holes arid under the tie plates, wood of a crosdie is in close, but not aholutely tight, contact with iron. At these locations air and water have access to the interfaces and can maint,ain catalyzed oxidation and hydrolysis reactions. Such chemical reactions are modified by the presence of creosote and coal tar oil Tyith IThich the tie has bccri i n pregna ted.
mexits in which some parts of the total effect on crossties were art'ifically produced. Chemical and mechanical properties were studied. CHEMICAL ANALYSIS OF USED CROSSTIES
llailroads in various parts of the country selected typically deteriorated ties from those being removed from track and shipped them to t,he Timber Engineering co, laboratory for examination. Investigations were undertaken to establish possible causes of deterioration and also to determine the t y p e of changes or deterioration that had occurred in the ties during their seivice life. This report is concerned with thc cheniic':il changes disclosed by researches on old ties, Several procedures were used in the analyses for the main c'onstituents of the wood samples. Figure 5 shows the location of sections from the t.ie and their designation. T'ne iiow slicct of Figure 6 is a standard analytical procedure. The mood wmples were broken into sinal1 pieces and ground in n, laboratory Wiley mill. I n order t o determine Xvhether changes in the wood subatmice in used crossties had t'aken place, the imprcgnank had t o lie removed first. Extractions v i t h alcohol, benzene, and toluenc: removed only those parts of the impregnants which reniairicd soluble. Samples from old crossties always retzl,incri a dai,Ii color after extraction. Extraction x i t h hot water dissolved small amounts of reducing substances and mincrala.
Figure 1. Area tinder Tie Plate Showing Splits That Start from Spike Holes and Cutting of Tie Plate into 'vc oorl
It has previously been established t h a t cellulose fibers are weakened n-here they have been soiled by iron or copper conipounds. The Army learned in 1919 of the deteriorating effects of iron o n cotton fabrics. Where pup tents were equipped with iron grommets a t the corners, the fabric deteriorated and tore away after limited t,ime of exposure. Cleaners and dyers know and caution customers that in cotton fabrics containing rust stains, the fibers may be weakened around the stain. It has been reported t h a t iron salts cat,alyze the degrading effect of ultraviolet light on cotton cellulose (f-3, 7 ) . An older observation connects the superficial graying of wood, after lengthy exposure to air, with iron compounds said to be present in dust (6, 8). Detailed studies of changes in wood through the presence of iron and its oxides are lacldng. Such studies are very debirablc in view of the many combinations of wood with iron in practical use. It can be expected t h a t railroad crossties offer a particularly great opportunity for the ackion of iron on wood to take place. Tn other combinations, where the interface between the two materials is lese exposed to the at'mosphere, the results may be lese pronounced or of a basically different nature. The present investigation comprised chemical analyses of samples from used ties, and accelerated tests in model experi-
Figure 2.
Crossties Removed from Track Because o f Deterioration after Long Service
Since most of the samples contained amounts of niinerd substances, wood after extraction witli organic solvents and hot water was heated in hydrochloric acid of 2% concentration for 2 hours. This converted a larger part of the heniicelluloses into soluble sugars and dissolved the nonsilica part of the ash. The wood residue after this acid treatment was dried and suhjectcd to the standard complete hydrolysis b y means of sulfuric acid of 72% concentration. The Rertrarid method was used for ilic sugar analyses.
1968
September 1954
I N D U S T R I A L AND E N G I N E E R I N G CHEMISTRY
Figure 3. Cross Section of Tie Plate Area of Red Oak Tie, Showing Severe Lateral Shifting or King Shear in Springwood ireas
In considering the proportions of materials dissolved by such extractions, i t is necessary to remember that the creosote treatment is not a chemically controlled operation and does not result in uniform penetration. Thus, the values found for organic extractives varied considerably. Samples from several locations on the surface of two red oak ties contained between 15 and 24% extractables, whereas a third tie had only 5 to 9%. Of the sections from a red gum tie, those which were taken from the tie plate areas were much lower in extractives (7 to 14%) than sections from the middle of the length of the tie (23.6%). The very low values found for beech, ponderosa pine, and Texas pine may have been caused by tie plate abrasion of the top layers and poor preservative penetration. Since the treating history of these old tiea is not accurately known, these analytical findings cannot be reliably correlated with other factors. One of the samples came froin a decayed western pine tie. The small amount of alcohol and benzene extractable materials in this tie indicated one cause of the decay. The water-extractable portion was considembly higher than in the nondecayed wood. Dilute acid dissolved more sugar from this wood than from the other ties, but the iron content was comparatively low. Comp1et.e hydrolysis of the residual wood from the extraction and prehydrolysis steps gave the lowest lignin value where iron was highest, and a much higher lignin content in the decayed wood. The red oak sample had unusually low hemicellulose in prehydrolysis and less lignin than normal. Analysis of wood from the critical areas of ties showed considerable changes in the proportions of the usual constituents. In detail, the deviations in composition of the old wood varied in several samples taken from red oak, beech, ponderosa pine, and Texas pine. The portion of wood which was dissolved by boiling with dilute (2%)hydrochloric acid was generally greater for old crossties than was normal for the same epecies of wood. The amount of reducing sugar obtained in these solutions W R Y lower than normal, so that the difference between substances dissolved and sugar found in solution was particularly great. Considerable propol*tionsof iron were found in many of these solutions. The best preparation of the solutions for iron determination consisted of heating for a few minutes after an addition of hydrogen prroxide. This reaction converted the ferrous into ferric
1969
iron which could be completely precipitated with ammonia in a n easily filterable form. Treating the solution with nitric acid, however, made i t impossible to precipitate the iron as the hydroxide. Solutions which had been heated mith 2% nitric acid turned a deep red when they were made alkaline, but they remained clear. Precipitated ferric hydroxide added to such alkaline solutions was dissolved. After prehydrolyyis, cellulose and lignin were determined in the residual wood. I n samples which had contained much iron, cellulose values were usually l o m r than normal. F’ariations were found which could not be directly correlated with other analytical determinations. Table I summarizes analyt,ical results obtained on ties that were in track in New bfexico for 15 to 23 ycars. Tahle I1 presents results of the analytical work on ties sectioned according to Figure 6, with the corresponding figures for a sample of sound red oak as control. ,4sh and material extracted by alcohol and toluene are given in percentage of the original air-dry weight of the wood (usually -ivith 9% moisture). The ratio of total carbohydrates (from dilute as well as from concentrated hydrolysis) to lignin is given. The carbohydrate to lignin ratio is depressed by losses of hemicellulose, cellulose, or both. However, the lignin counted in this ratio is only that remaining as the insoluble residue of complete hydrolysis by sulfuric acid of 72% concentration; the acid-soluble kinds of lignin alao show variations not expressly accounted for in these tables.
Figure 4. Cross Section of Tie Plate Area of Beech Tie, Showing Buckled Rays and Crushed Springwood Cells (TOP) ALKALIRE EXTRACTIOKS
Some of the iron in these samples is originally present as rust particles, but another part of the iron is in the form of complex compounds Dilute solutions of sodium hydroxide extract some of this iron, together with gums and acidic substances. A fractional extraction of wood from old red oak tied with alkali a t room temperature brought little iron into solution in the first itage, when the amount of alkali introduced was neutralized by the wood acids. Larger amounts of iron were dissolved in the later stages which retained most of their alkalinity. Several samples were heated with 10 times their weight of dilute (0 5 % ) sodium hydroxide solution. After 2 hours of gentle heating a t atmospheric pressure, the solution was cooled and titrated with the acid, using phenolphthalein as the indicatoi
INDUSTRIAL AND ENGINEERING CHEMISTRY
1970
wood originally used. Of the original mineral content, 60.77, was thus removed in the settled 11.7% of the sample. A 100-gram sample of unextracted wood from section 10 of oak tie S o . 5 was separated by flotation in carbon tetrachloride according t o the follon-ing :
TABLE I. A 4 ~ . O~F ~WOOD ~ - sFROM ~ ~ DIRECTLY BESEATH TIE PLATES (Ties removed in N a r c h 1952 from track in New Mexico) Western Western Western Pine Pine Pine (Decayed) Red Oak Year placed in track 1929 193G 1929 1937 Extracted, grams./100 grains original (dried) Benzene 7.00 Alcohol-benzene 2.35 Alcohol ... Hot, water 2.50
sample, by 4 00 0.40 1.75 1.33
...
...
2.00
5,33
Prehydrolysis, granis/100 grams extracted, dry wood Sugar 20.6 20 6 Residue 67.6 64.G Dissolved iron :as FezOs) 7.5 8 0
3.50 1.00 3 70 3 :o
24.0 65.0 2.4
The enrichment in ash content of the heavy fraction was not as high as tie No. 4. '4 repeated flotation of the light fraction gave only a slight additional separation. An ash content of 1.78 was, therefore, so intimately combined with the wood that it could not be separated with the stationary flotation method. Combined parts of section 9 and 10 from tie No. 6 were separated b y repeated flotation with the following results. The settled fraction was 17.7% and contained 59.4% ash; the subpended fraction lyas 82.1% with 5.2270 ash. In this manner, 71% of the total ash was concentrated in about 18% of the total wood.
57 2 17.2 4 45
The decrease in free alkali measures the amount of acidic materials liberated during this treatment. From a comparison with fresh wood it appears t h a t the amount of acidic material produced during this alkaline heating is not greater in the samples from old railroad ties than from fresh wood. An extraction of 50 grams of wood from section 2, red oak tie No. 2, was carried out with fresh 0.5% alkali solut'ion in 2-hour periods until practically no change in the alkali concentration occurred (Table 111). The combined alkali extracts were then evaporated to dryness and ashed. The iron in the ash amounted to 1.79% of the wood.
I SECTION
control Red Oak Tie N o . 1 (Red ___ O a k ) 2 7 9 1 0.43 5.6 1 . 7 3 24.4
5,O 9.0 1 6 . 7 20.0
2
,
~
' B
7
TIE PLATE AREA
'
I ~
9 O l l l Z
13
1 1 1
Sectioning
Railroad .4nalysis
Ties for
Chemical
ACCELERATED ACTION OF IROZ O W WOOD
The action of iron on wood i ~ a 5accelerated, in comparison v-ith its action on crossties, by using thin veneer under conditions of relatively high temperature and moisture. Red oak veneer inch thick was cut into 300 strips, 5Isinch wide and 10 inches long. These dimensions were selected so t h a t the strips could be used
.%SALYSIS O F
7
5.
I
Table IT' contains results from the consecutive use of the two flotation methods. Hydrolysis dissolves more substance than is accounted for by the sugar found in solution. For prehydrolysis, this is a common experience which Campbell and McDonald have recently attributed to an acid-soluble, modified lignin (4). For afterhydrolysis. to account for the difference between dissolved material and the amount of >ugarfound in Eolution, further study is required.
CSEDCROSSTIES
Red Oak Tie No. 3 2
I
TIE IP-ATE I AREA 2 3 4 5
Ii
Figure
I n order t o purify the wood samples for analysis, the finely ground mat,erial was separated by suspension in carbon tetrachloride and acetone in several steps. The selection of these two liquids was based more on their xett,ing action and differences in specific gravity than on their action as solvents. The heavy material t h a t settled in carbon t'etrachloride contained large proportions of mineraI matter; the light mat,erial from this operation had a relat,ively low ash content. Suspension in acet,one separated this light material into a more nearly pure sediment,and a small proportion of dissolved and suspended dark products resulting from the creosote impregnation. Section 9 from tie No. 4 contained 9% moisture and 4.22% ash. After solvent extraction of 100 grams of air-dry x-ood, the oven-dried residue weighed 83.33 grams. Flotation of this residue in carbon tetrachloride separat'ed a heavy portion weighing 9.77 grams. The heavy fraction had an ash content of 26.2%, which is equal to 2.56% calculated on the basia of the amount of
Ash % O r g k c solubles, %
Nc
I
SEPARATIOIV BY FLOTATIOK
T.ABLE 11.
Suspended Settled Fraction Fraction Keight, .Ish, Keight, Ash, grams W grams % 80.0 1.94 8.82 14.1 78.56 1.78 1.44 10 (approx.)
First flotation Second flotation
19.4 74 6 6.5
Hydrolyais of residue, grams/100 grams extracted, dry wood 45.4 47 0 36.8 Sugar Lignin 20.4 17.4 30.0 Sugar/lignin, wt. ratio 3.23 3.88 2.03
Vol. 46,No. 9
9
1
Red Gum Tie ________ Section number 2 2 7 9 1 2
Basis, 100 Grams Air-Dry Wood 4.46 0 . 8 6 5 . 6 5 2 . 9 8 6 . 2 4 4 20 18:9 8.90 8.13 8.95 7 . 2 2 1 4 . 0 23.6
-_ 2
Ponderosa Pine
Beech 7
9
9
1
T~was
__ Pine 0
9
9 . 2 8 2 . 9 2 3 . 2 0 2 . 2 2 7 . 1 7 1 2 . 5 1 3 . 0 18 1 8 . 4 3 9 4 3 9.20 3.71 1 8 3 5 0 1 1 . 9 5 9 2 0
Basis, 100 Grams Extracted Wood Disso2ed b y dilute acid, 70
Total 24.6 Sugar 12.8 Iron (as FezOa) 0 Dissolved b y concentrated acid, % Cellulose 46.7 Lignin 30.1 Total carbohydrates/ lignin, wt. ratio 2.0
1 8 . 4 2 1 . 4 2 8 . 8 24.6 2 3 . 8 2 5 . 6 34.: 2 2 . 6 2 0 . 3 2 6 . 7 3 2 . 2 2 7 . 9 2 8 . 4 29.2 2 5 . 1 2 3 . 4 2 3 . 8 2 5 . 8 9 . 2 1 2 . 3 9 . 5 1 1 , 6 - . . _ 15.6 17.a 1 4 . 0 10.5 14.6 13.8 15.7 13.6 13.7 15.6 9 . 7 7 . 7 12.1 1.14 0 4.14 1.05 . . . 0.77 6.25 . . . 1.89 1.34 4.30 . . , . . . . . 2 . 6 2 . . , . . . 4 81
.
43 6 27.3
46.7 39.5 40.8 43.1 3 5 . 4 2 6 . 8 2 5 . 5 23.2
1.83
1 . 6 6 1.83 2 . 0 5
...
5 3 . 6 2 9 . 3 3 5 . 6 3 4 . 1 4 0 . 2 4 3 . 4 4 7 . 6 4 4 . 0 4 8 . 5 4 2 . 2 4 2 . 9 81.1 44.0 23.7 3 2 . 5 24.2 4 0 . 4 1 4 . 7 2 1 . 8 2 4 . 6 2 2 . 6 1 8 . 5 29.1 3 7 . 0 3 6 . 2 2 9 . 5 2.92
1.44 2.05
1.10 3.73
2.62
2.57 2.53 3.36
1.95
1.42 1.62 1.90
INDUSTRIAL AND ENGINEERING CHEMISTRY
September 1954
TABLE 111. ALKALIKE EXTRACTION OF REDOAKCROSSTIE (50 Grams from tie No. 2 , section 2) 0.5%
Addition NO.
Added
500 300 180 200 150 150 190 200 200 200 200
68.0 40.8 24.5 20.8 15.6 15.6 23.7 23.8 23.8 22.0 22.0
5 6
7
8 9
10 11 Total
fastened around a drum mounted on the axis of a pendulum. The energy consumed in breaking the specimen was indicated by the reduced angle of swing of the pendulum.
Sodium Hydroxide, Millimoles After reaction Neutralized
Sodium Hydroxide, M1.
1 2 3 4
1971
29.0 14.7 4.5 10.8 7.6 7.0 15.6 12.8 18.6 16.6 19.0
39.0 26.1 20.0 10.0 8.0 8.6 8.1 11.0 5.0 5.4 3.0 144.2
-
as specimens for toughness tests. One third of the specimens were kept a t the ambient air conditions of the laboratory to serve as controls. T h e rest were divided into two groups which were placed in the same conditioning chamber and subjected to a water vapor saturated atmosphere a t 140" F. for 10 weeks. For 4 hours each weekday, the wood was immersed in water. Iron filings (40 mesh) were added to one group a t the start of the treating period. At the end, the free iron particles were removed by washing and gentle brushing. Thirty of each of the two kinds of treated strips were brought to about 11% moisture content in a conditioning chamber held a t 70" F. Controls of untreated wood were conditioned in the same chamber. Toughness tests were made on a Forest Products Laboratory toughness testing machine with the weight removed from the pendulum. T h e specimen was tested as a beam supported by two vertical pins. The load was applied by means of a cable
GROUND WOOD SAMPLE
I
i
1
Burnt for mineral residue = ash
TABLE IV. FLOTATION ANALYSIS OF REDOAK CROSSTIES Crosstie No. 11 23 Carbon Tetrachloride Settled material, % Ash % Feads, % of ash Suspended material, % ' Ash, % FezOs, % of ash Extracted by alcohol-toluene,
8.38 47.09 41.0 91.6 3.07 68.9 7.5
%
Bcetone Suspended material (from CClr suspension) Prehydrolysis Dissolved, % Sugar, ,% Hydrolysis Dissolved, % Spgar, % Lignin, %
3.50 47.5 23.4 96.5 2.56 57.7
5.7
100
100
14.2 6.3
8.0 4.77
58.5 48.35 27.3
65.4 54.5 26.6
The average values for the toughness, shown by statistical analysis to be highly significant, were as follows: 32.7 inchpounds for the controls, 24.6 inch-pounds for the water-treated wood, and 15.05 inch-pounds for the iron-treated wood. Individual values varied widely, as summarized in Table V. T h e difference between the short, brittle break of the iron-treated samples and the splintering of the other samples was unmistakable. The reduction of strength through the influence of the iron was correlated with chemical changes which substantially increase the amount of easily hydrolyzed part of the wood. H o t water extracted more material and dilute hydrochloric acid dissolved more sugar from the iron-treated samples than from any of the others. T h e direct hydrolysis by 72% sulfuric acid showed little difference between the water-extracted wood samples.
I
1
Extracted by benzene, alcohol, and mixtures of benzene with alcohol
1
TABLE V. EFFECT OF IRON ON TOUGHSESS OF REDOAK
I
7'
Extracted by hot water
I
M700d'residue
Solution water solubles
X j / ~ X 10 inches) Toughness, Inch-Pounds Water Water-iron Control treated treated 15.5 12.7 7.6 46.1 39.4 27.5 32.7 24.fi 15.05 91 65 46.68 23.21
(30 Specimens,
Wood residue
Solution of extractables, distilled
Lowest value Highest value Average value Group variance (82) Mean difference = Standard error
l/g
-7.8/2.33
= 3.35-9.2/1.35
___- 1 7 . 0 / 2 . 0 5
=
=
5.94-
8.3--
1
Prehydrolyzed by heating with dilute (2%) hydrochloric acid
1 Solution of sugars,
I
Prehydrolyzed wood
iron, solubilized lignin
I
1
Hydrolyzed by concentrated (72%) sulfuric acid
7 -
4
Solution of hydrolyzed cellulose
PREVENTION OF DETERIORATION
.1
Lignin residue
I 1
Burnt for ash determination Figure 6.
Analytical Procedures
Sodium hydroxide solutions of 17.5%, a t room temperature, dissolved almost twice the normal amount of material from the iron-treated wood. With a more dilute sodium hydroxide solution, a t about 100' C., the amounts of wood substance dissolved from normal, water treated, and water-iron treated wood were approximately in the proportion of 3.3:4:5.2. These relationships are shown in Table VI.
Sttempts to prevent or reduce the wood deterioration caused by iron were based on the assumption that acidity is a primary factor. Chips of '/*-inch red oak veneer were exposed to air and moisture with intermittent heating on a water bath, in the presence of iron in the form of nails. I n one series, 1% of the wood weight of the following substances was added separately-
1972
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
TABLE
\'I.
CHEAllC.lI,
;\S.ILYSIS
Vol. 46, No. 9
01.'1tb21) O A K U S E D FOR
T o c ~ r i s ~Ts cs s x ~
Con:rol
Consecutive extraction by .4lcohol 3 30 .4lcohol-bi.nzene 0 20 Water 1 18 .4lternative hydrolysis of c-stractcd u ood hs 7 2 % Sulfuric acid, cold Suear 77 7 Lignin 19.9 3 % Hydrochloric acid, boiling 31 5 Sugar Iron 0 OR ti2 !i Residue 1 7 . 3 % Sodinin hydroxide. cold Ilissolved 17 3 470 Sodium hydroxide, hot 33.0 Dissolved
hnalgsis, Water treated
Yc
~
Water-iron treated
4,65 8.23 60
3.42 0 46 2.13
77 7
7'3.7
32.4 0 03 62.6
34 5
0.88
21.4
30.3
40.0
52 0
I ,
21.7
19.3
(j0.6
Basis. Bcnzcne-Extiacted Wood Sdihpl? extracted by matci, grams li.80 18.35 18.51 Cxtracted, grams 0.91 1.25 0.96 m 5.11 5 23 6.78 /O p H oi evtract 3.80 6.60 3.90 Iion in extract (as I'e) piitins 0 . 0 5 0 002 0,062 e/-
Residue, grams
%
Sugar, grain8
%
%
Residue, grams
(6).
TABLE VII. EFFECTOF i\linr,rrvcs o s Iaos ABSORBED U Y \Vooi> (Intermittent exposure to v a t r r vapor) Additive, Exposure %(& Time, Weeks None Calcium carbonate Zinc stearate
Pliosyhainide 1Xphenylan;iiio
' Based
1 2 1 2 1 2 1 2 1 2
6 83
3 8.7 0,075 0.30
0.011 17.17
0.33 17.02 91.79
17.30 91.52
3.90 21.91 0.15 0.84 11.50 64.6
4 03 21.98 0.10
3.95 21.31 0.40 2.16 12.15 65.5
4 23 22.12 0.20 1.05 12.80
6 jl 36.57
o.ti3 36 13 4 00 % I 80
5.52 29.77 4.41 23.79 0 12 0 .ii5 4.29 23.14
3 , ti 1 29 :34 5.00 2R 1.7 0 72 1.28 22.38
1.29 2 21
1.31 2.30
0.28 i6.27 91.40
93.56
I'rehydrolysis Iron (as F e ) , grams
aalciurn carboilate, zinc swaratc,j plioeplismide (Victor C'heiiiical Co., T'ictamide), and diphenylamine. -4fter 1 week of esposurc, only calcium carbonate had reduced tha amount of iron taken u p by the wood. When 5y0 of the same substances were used, the iron content of the mood after 2 Tveelcs exposure again TTM low only when calcium carbonate had been present. Diphenj-l:tniinc, when present in a n amount of I%, did n o t reduce t,he iron acquired by t h e wood; 570 diphenylamine v a s more effective than the other substances, except calcium carbonate (Table 1-11), Iron mas determined colorinietricnll~~with o-pheiianthroline, ibed by L:iywel! arid Cunnirigham according t,o the method d
I 9 1% 1 31
70
"
"
Sugar, gi81iis 0 /O
Insoluble, grains V" Ash in insoluble, grarris
- ._
lignin. grains
4.06 2 2 , $0
4.06 D 80
1"
...
...
B
76
Celliilose/lignin, wt. ratio Carbohydrates/lignin, wt. ratio
1.60 2.36
0.55 it.95 .JJ.I
... .... 4.00
21.80 1.66 2 . ti8
65,9
3.77
not sufic+mt,ly explored; they should not be attributed solc~lyto tho pII change produced by the addition of calcium carhoii;i io. Subsequent hydrolysis by 72% sulfuric acid gave considc~rwh1-y lcss sugar from the titanium dioxide treated samples t1i:tn f1,orn the otiicr9.
Iron in Wood, %" 1.21 2 20 0.20 0 41 0 66 1 03 0,Iiii 1.37 I37 0.55
on oren-dry weight of Food.
111 another series, the test period m s ex;tended t o 20 nceks. Chips of red oak veneer were mixed Lyitli iron, moistened occasionally, and heated for a few hours each day on a water bath. Creosote in an amount of 20'34 of the dry wood weight was added t o each test specimen. Calcium carbonate was mixed into one group of samples (test 2 ) ; a neight equivalent to 5% of the wood was added in five portions during the first 5 days. Titanium dioxide was used in the other t,csts; in test 3, 1% of tit,aniuni dioxide was used a t the start, and in test 4, 5 7 , was distributed over the first 5 days of twntnient. At the end of the tert period! the nails n-er'e removed. The wood was extracted with benzrnc, and analyzed (Table 17111), The hot water extract from t,hc coiitiol (test 1j, wood which had been treated u-ithout additional sub n c c ~ ,had a pH of 3.80, approximately the same as t h a t from the samples with titanium dioxide (tests 3 and 4). Calcium carbonat,cx treatment (test 2 ) gave an extract with pH 6.60. The iron content,in these extract? iws about the same in tests 1, 3, and 4, a,nd negligible in test 2. Prehydrolypis with 394 hydrochloric acid dissolved more sugar from the wood of test 4 than from t,he others, although the iron content of the wood of test 3 was highest. Calcium cwbonate suppressed the amount of iron acquired by the wood. At prescnt, the causes for this great difference in iron (.ontent, are
\Vooii IOSCS niechanical st.r:.rigtli and chemical stnhility iiffcr it has b c ~ nexposed t o moisturc and air in contact with ii,on. This deterioration of wood (:anbe measured by mechanical tcqtr and rhemical analysis. Comples c-haiiges in the chemical coinposition of ~ o o rd( ~ring u uncler the influence of iron irivolvc a reductio11 of carboliydrato r ~ ~ n t r a11d n t lignin solub'lity. Thc Irsults of the noi,k rcportcd in this paper indicate that lurt,her dst,a on chemical deter ion of wood may be fount1 b y measuring degree of polyinc tion of the carbohydrtitep ;irid soluhilitiea of the lignin roiiipoiients. Preliminary indirattions are that means of prcventiiig chcmiical deterioration of ivood i n conlaet n-ith iron can hc devcloprd either by improving trchniqiiea r i t h calcium carbonate or by other chemicals. LI'IEE t'l'CRE C17'EJJ
Haec:hler. K. t I . , arid Richards, C . l u d r e s . Trans. A ~ e r ,. S m . d f e c k Engrs., 73, 1055 (1.951). 13rowning, B. L., and Ruhlitz, I,. (I.,IND.ERG.CIIIM.,45, I . i l 6 (1953). Cooling Tower Institute, Palo .kIto, Calif., Summary 1
