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is required. Fixing of the inside coating is unnecessary because the bulbs are made into lamps shortly after spraying. Miniature lamps, such as those used for Christmas tree lighting, are sprayed with mixtures eontainiug shellac as the binding agent. I n addition to shellac, these coatings contain kaolin and a colored pigment.
Immeralne Coiled Tunfisten Filament In Nitric Acld i n Modern Lamp Factory
materials, such as the oxides of zinc, tin, and titanium, are sometimes d d e d to give certain characteristics. Kaolin appears to he an essential part of the mixtures, since coatings containing it seldom crack or chip off. The coatings are invariably applied to lamps by spraying, since the mixtures are not adapted to dipping. Sodium silicate coatings deteriorate rapidly on standing, because of the action of water and carbon dioxide in the air. This difficulty is overcome by dipping the lamps after spraying and baking in a fixing solution. A number of materials are satisfactory for this purpose, but usually a concentrated solution of ammonium chloride or aluminum sulfate is used. The solutions are used hot in order to accelerate the reaction. If the solutions are acidified, the fixing can be carried out still more rapidly. Recently the American manufacturers have started the manufacture of lamps with coating sprayed on the inside of the bulb (10). The composition of the coating is similar to that used for outside coatings. although less sodium silicate
line Miracles of 1879 and 1929 A t the left the first practicalin-descent lampasioventcd by Thomas A. Edinon. In the main if consisted 01 a glass chamber exhausted of itr air and containing a carbon filnment made from bristol hoard paper. Platinum lead-in wires carried the current t o the carbon burner. Note the erude w w d stand equipped with metal binding poqts. At the right the new IOU-watt innde-frosted Marda lamp which is P result of constant improvements and contributions of chemical &nce dves seventy-six times as much light (or the =me money as its i l l ~ ~ t r i o u s
ancertors of fifty years ago.
Literature Cited (11 Campbell, Phil. Mag., 41, 685 (1921). (2) Campbell and Rrde. Ibid., 40, 555 (1920). (3) Dushman. Gcn. Elec. Re”., P4. 430 (1921). (4) Durhman, I b i d . . 94. 5009 (19211. (5)IGero and Iredell. C h m . Mal. Eng., 55,412 (1928). (0) Gordon and Spring, IND.ENO.Cmla., 16,555 (1924). (7) Jones, Chcm. Mal. En&, 21, 9 (1020). ( 8 ) Langmuir, J . A m , Chrm. Sm., 114. 1310 (1912). ( 9 ) Lanpmuir, I b i d . . 81, I139 (1915). (IO) Lindrtrom, Chcm. Mal. E m . , 86, 410 (1029). (11) Pinkin, INO.END.Ceaw.. 1% 774 (1928).
Chemical Composition of Wood in Relation to Physical Characteristics’ A Preliminary Study H. E. Dadswell? and L. F. Hawley PORHST Px-ODUCTS L ~ e o a ~ r o aM v ,m m m , Wrs.
T
HE chemical nature of wood has been the subject
of much research and samples of different species have been analyzed for cellulose, lignin, pentosans, extractives, and various other constituents. The results of such analyses have formed a basis for comparing the different woods-as, for example, hardwoods with softwoods, or woods of high extractive content with those of low. Ritter and Fleck (67, advancing a step further, have analyzed for camparison the distinctive portions of certain trees-namely, the heartwood and the sapwood, the springwood and the 1 Pregented before the Division of Cellulore Chemistry at the 77th Meeting of the American Chemical Society, Calumbor, Ohio, April 29 to May 3, 1920. * Australian Research Fellow.
summerwood. Little research has been carried out, however, to determine whether wood samples from the %me tree, but having distinct differences in physical properties, are different in chemical composition. The only work of this kind is that of Johnson and Hovey (S), who have r e ported on the chemical composition of a disk cut from a balsam fir and containing (a) slow-growth annual rings, (b) rapid-growth annual rings, and (c) “Rotholz” (“compression” wood). Their analytical data showed that the “compression” wood portion was much lower in cellulose and higher in lignin than the other portions of the disk. The Object Of this work is to show whether there are Other cases in which differences in physical characteristics are reflected in chemical constitution, and in this way bring
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to light data on the question of a definite relationship between them. Experimenta1 Some-tough and brash specimens of Douglas fir were first examined. These specimens were all of approximately the same specific gravity and had been tested for toughness, which averaged 276 cm-kg. per specimen for the tough specimens and 132 cm-kg. for the brash. These contrasting specimens of tough and brash Douglas fir and white oak were selected from material used in an investigation a t the Forest Products Laboratory of the cause of brashness in wood. The method of determining toughness is described by Markwardt (4). A microscopic examination of the brash specimens had revealed no sign of compression wood or of any other abnormality which would account for the differences in toughness. The tough and brash specimens were separately segregated and each batch was ground to sawdust. For analysis, that passing through an 80-mesh sieve and remaining on a 100-mesh was used. The results have been recorded in Table I. All results given in this table are the average of two or more determinations. This preliminary analysis showed only slight differences between the two samples, the lignin content of the brash being higher than that of the tough. When, however, a similar examination was made of tough and brash specimens of wood of the white oak group, much greater divergences in chemical composition were noted. Here again both sets of specimens had approximately the same average specific gravity but one set had an average toughness value of 391 cm-kg. and the others of 830 cm-kg. The tough material showed over 4 per cent more Cross and Bevan cellulose than the brash. This cellulose also had a slightly lower pentosan content and hydrolysis number, indicating an even greater proportion of stable cellulose in the tough material. Again the lignin content of the brash material was higher than that of the tough. The chemical composition of compression wood was also compared with that of normal wood from the same tree.
.
Note-Compression wood consists characteristically of medium t o wide annual rings in which t h e summerwood occupies more than half of t h e width of the ring but is not so dense and hornlike as in normal wood, so t h a t the contrast between springwood and summerwood is not so pronounced. It also differs from normal wood in the microscopic structure of t h e fibers. Compression wood occurs only i n conifers and is associated, as a rule, with eccentric growth. It occurs principally on t h e lower side of leaning trees and of limbs (Manual for t h e Inspection of Aircraft Wood a n d Glue, Navy Department, Bureau of Aeronautics, Washington, D. C.. 1928.)
For a true comparison, samples of both were obtained from positions relatively close in the same tree, as it is well known that the composition of different trees of the same species may vary to some extent. It has long been recognized that compression wood is very much weaker in certain respects than normal wood. I n all cross-bending tests it gives evidences of brash failure, and it also has abnormal properties in shrinkage in comparison to normal wood. I n compression parallel to the grain, however, the maximum crushing strength of compression wood averages higher than that of more normal wood from the same stick. The samples analyzed consisted of heartwood of Sitka spruce and heartwood and sapwood of redwood. I n each case compression and normal wood were taken from approximately the same annual rings, but from different sides of the tree trunk. These. samples were separately sawn and ground to 80-100 mesh sawdust before analysis, the results of which have been recorded in Table I. The results from all three samples demonstrated clearly the fact that in compression wood the cellulose content was much lower
Vol. 21, No. 10
than that of the more normal wood of the same species, while the lignin content was somewhat higher. I n each determination the cellulose from the compression wood showed higher pentosan content than that from the normal wood, again indicating the possibility of even greater differences in the stable cellulose. There were other slight divergences in the chemical composition of each sample of compression wood as compared with the corresponding normal wood, but they are of lesser importance. I n the sapwood of the redwood it was possible to isolate and analyze separately the hard, dense summerwood bands representing 70 per cent of the compression wood. From the analytical results and from the values previously obtained for the sapwood compression wood as a whole, it was possible to calculate the composition of the remaining springwood portion on the basis of 70 per cent summerwood and 30 per cent springwood. These figures are also recorded in Table I. The percentage of extractives is much higher in the springwood, but the pentosan content of the summerwood is considerably greater than that of the springwood. It is also interesting to note that the cellulose content of the summerwood is less than that of the springwood while the lignin content is greater. This is contrary to the observations of Ritter and Fleck (6) in their analyses of the normal spring- and summerwood of a number of species. They found that the lignin is present in larger amount in the springwood and that, in general, the cellulose is appreciably higher in the summerwood of any one sample. The variation in lignin content between normal wood and compression wood is, therefore, probably much greater in the summerwood than in the springwood. Discussion of Results
It has been found that in every case, with the exception of the Douglas fir, the cellulose content of the weaker material (brash wood or compression wood) is much lower than that of the normal, while the lignin content of the weaker material is appreciably higher. These results also agree with those of Johnson and Hovey for “Rotholz” as compared to the normal samples of balsam fir. I n all the analyses the materials weaker in cross-bending tests show lower cellulose and higher lignin content than the average for the same species. It seems rather more than a coincidence that such is the case, and there may be some relation between cellulose and lignin content and mechanical properties. Many different opinions have been expressed concerning the general relation of lignin content to strength properties of wood. It is the common conception of botanists that lignification of cellulosic plant fibers increases their strength, although sometimes certain specific strength properties, such as hardness and elasticity, are ascribed to the lignin, and others, such as plasticity and tensile strength, to the cellulose. This opinion was formed, however, at a time when faulty methods prevailed for determining the relative amounts of lignin and cellulose ( 1 ) and it has, therefore, no satisfactory experimental basis. So common was this opinion that even recently chemists have repeated it (9). On the other hand, Schorger ( 7 ) has definitely stated that “It is known that the amount of lignin present in a wood has no direct relation to its mechanical properties.” The results reported here might make it appear that neither opinion, to the effect that lignin increased strength properties or did not affect strength properties, was correct, but further consideration will show that both may be partly correct. Schorger’s statement is correct as far as comparisons of species are concerned, since there are known variations in lignin content between species without corresponding variations in strength properties, but it is apparently not
INDUSTRIAL AND ENGINEERING CHEMISTRY
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T a b l e I-Chemical C o n s t i t u t i o n of Wood Substance-Analytical Result8 (All values are average of two or more individual determinations. and percentages are based on t h e weisht of oven-drv wood exceDt in last two columns.) SANPLE
I
EXTRACTIVES
ASH aLCoHoL
W ? : &
PENTO-
L~~~~~
NaOH
SANS
CELLULOSE
PENTOSANS HYDROLYSIS IN
CELLU-
NUMBER OF CELLU-
LOSE
LOSE
P e r cent
1
P e r cent
P e r cent
P e r cdnt
P e r cent
Per cent
P e r cent
P e cent
Douglas f i r : O Tough specimens Brash specimens
0.42 0.54
.. ..
3.28 2.91
..
..
13.43 13.84
31.65 33.30
4.44 5.01
8.92 9.09
59.90 60.77
4.90 4.90
...
White oak: Tough specimens Brash specimens
1 0 2 6 0.41
.. ..
8.93 9.75
7 73
..
26.25 29.01
27.40 28.3s
6.01 6.52
20.27 21.78
53.23 48.60
20.53 22.18
22.65 23.88
0.20 0.60
.. ..
5.20 4.20
4 OS 3.91
13 7 13.48
25.64 30.85
.. ..
8.29 8.90
60.60 53.67
5.06 6.32
19.37 18.50
Sitka spruce: A-ormal wood Compression wood Redwood sapwood: Normal wood Compression wood
1
Pt.r ceni
..
Per cent
P e r cent
...
..
3.75
7.16
..
18.20
36.15
..
11.57
46 57
10.22
...
Redwood heartwood: Normal wood Compression wood
..
.. ..
11.49 11.55
..
25.50 24,50
32.17 37.74
..
10.39 9.27
44 34 37.99
9.49 10.50
...
Redwood sapwood: Summerwood isolated from compression wood Springwood (calcd )
..
3.15 4.48
4 05 14.36
..
15.42 24.67
36.85 34.45
..
12.36 9.74
45.47 49.17
11.35 7.60
...
..
..
.. ..
I
..
..
..
...
Results based on benzene-alcohol extracted material.
correct for the comparison of normal and abnormal wood from the same species. The other conception cannot be properly discussed without considering the fact that lignin exists in wood in two different conditions and in two different types of structure (1). I n the middle lamella the lignin occurs in practically free condition without any known admixture of other material, while in the fibrous structural elements it is mixed with relatively large proportions of cellulose and other carbohydrates. Structurally, these two locations of the lignin are different in that the middle lamella is a continuous structure serving as a cement between the discontinuous fibrous structural units. Variations in the amount of lignin in wood may, therefore, have entirely different effects on the strength, depending on where the variation occurs. Increased lignin content in those parts of the structure where it is mixed with cellulose may increase certain strength properties of the wood, while increased lignin content due to increased size of the middle lamella may decrease certain strength properties. It may also be idle t o speculate further on relationships between chemical composition and physical properties when the variations in physical properties may be due more to structural than to chemical variations. In the case of the tough and brash specimens of oak and Douglas fir, there were no known structural differences to account for the variation in strength properties; in the case of the compression wood samples there were known differences in structure but we are not certain that they are the cause of the variations in strength properties. In both cases, however, there may be structural differences that fully account for the strength differences. In other words, the structural
variable has not been surely eliminated in these comparisons between physical properties and chemical composition. Summary
1-The
results obtained in this research have shown
(a) that a certain type of brash oak has slightly higher
lignin content and slightly lower cellulose content than tough wood of the same species, and ( b ) that in the species studied compression wood has considerably higher lignin content and lower cellulose content than the normal wood of the same species taken from relatively close positions in the same tree. 2-It has also been shown that the dense summerwood bands isolated from redwood compression wood have higher lignin content than the springwood bands from the same annual growth rings. These differences are contrary to those generally found in the analyses of the springwood and summerwood of normal wood of any species. 3-It has been pointed out that no general conclusions can be drawn on the effect of lignin on strength without knowing the portion of the wood structure in which the variations in lignin content occur. Literature Cited (1) Hawley and Wise, “Chemistry of Wood,” pp. 233 and 296, Chemical Catalog Co., 1926. (2) Ibid.,p. 43. (3) Johnson and Hovey, J . Soc. Chem. Ind., 37, 135T (1918). (4) Markwardt, Wood Working Ind , 2, 31 (1926). (5) Ritter, IND.ESG. CHEX., 17, 1194 (1925). (6) Ritter a n d Fleck, Ibid.,16, 1056 (1923); 18, 608 (1926). (7) Schorger, “Chemistry of Cellulose and Wood,” p. S, McGraw-Hill Book Co., 1926.
French Chemical Industry Expands The remarkable expansion of the French chemical industry during recent years is revealed in a study of French chemical production and trade by Acting Commercial Attache Daniel J. Reagan, Paris, which has been issued by the Department of Commerce. Notwithstanding this growth, the study shows that the French output is only one-fifth that of the United States and less than half that of Germany. The desire to attain self-sufficiency in this branch of industry, according to the survey, has been largely responsible for the recent developments in French production of chemicals, and expansion has been chiefly in connection with coal-tar products and the fertilizers fixed nitrogen and potash. As in the case of other
European chemical-producing countries, expansion is envisaged primarily in terms of export. At present over 25 per cent of the French production is marketed outside that country, principally on the Continent and in French possessions and protectorates. A decided raw material and marketing interdependence has sprung up among European chemical producers, which, together with a common aim as to export expansion, has brought about the preliminary mergers and cartels and the subsequent international accords of recent years. France and Germany have been prominent in such movements, but their success has been nullified to a large degree through inability to interest the United Kingdom.
