Sept
,
1920
T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
T h e operator retired behind a barricade and inverted t h e cradle by pulling a wire, causing t h e shell t o slide down t h e pipe, where i t detonated on t h e anvil. After t h e gases resulting from t h e detonation had been cleared out, workmen swept up t h e fragments in t h e pit. The results of t h e fragmentation tests with various explosives are shown in Tables I11 a n d IV. Explosive A, containing TNT alone, gave a greater number of fragments t h a n Explosives B or C. Likewise Explosive B gave more fragments t h a n Explosive C. This is no doubt due t o t h e greater brisance of Explosive B as compared with Explosive C. I n Table IV, T N T is shown t o be superior t o t h e other two explosives, due t o greater brisance. While Explosives F a n d G are stronger t h a n T N T , t h e latter has a higher velocity of detonation, a n d this characteristic seems t o overbalance the inferiority in strength, within certain limits. The fragmentation results indicate t h a t any of these explosives would be satisfactory as shell fillers. S U &I MA R Y
I-The strength of several explosives, used or proposed for military use, is given, as compared with T N T , t h e comparison being based on t h e results of the ballistic mortar test. 2-The velocity of detonation of several military explosives has been determined under known conditions of density and confinement. 3-Several military explosives have been detonated i n steel shells, and the resulting fragments have been compared as t o number and size with those obtained when using T N T as a standard bursting charge.
873
tremuloides) after extraction with ether, alcohol, a n d water. Schwalbe and Beckerl have analyzed typical species of German woods and obtained results which on t h e whole correspond satisfactorily with those of Schorger for similar American woods. K6nig a n d Becker2 have examined several European woods particularly for their non-cellulose content. Determination of lignin by four different methods gave surprisingly concordant results. T h e pentosan-free cellulose values obtained by difference are much lower t h a n those obtained by Schwalbe a n d Becker using the chlorination method. A proximate analysis of five California woods has been made by D ~ r e . ~ These contributions, as well as earlier ones, are characterized by the diversity in form of material employed for investigation and also b y suggested modifications in methods, apparatus, or procedure, particularly for t h e determination of cellulose. Schorger4 .has pointed out t h a t one of t h e most important points in determining cellulose consists in obtaining the sample in proper physical condition, and Schwalbe6 has indicated the necessity of further standardizing methods and apparatus for t h e analysis of all fibrous raw materials. It is the purpose of this paper t o give some data, obtained in connection with the analysis of woods, which have a bearing on these two problems. EXPERIMENTAL^ THE
EFFECT
OF
SIZE
OF
PARTICLE
ON
YIELD
OF
CELLULOSE-wood is exceedingly difficult t o disintegrate uniformly, and material in a uniform s t a t e of division and composed of particles of rather limited dimensions appears t o be of prime importance for t h e determination of cellulose if comparable results a r e SOME OBSERVATIONS ON THE DETERMINATION t o be obtained. OF CELLULOSE IN WOODS1 I n the application of their chlorination method By S. A. Mahood t o wood Cross a n d Bevan7 state t h a t i t should be reFORESTPRODUCTSLABORATORY, U. s. DEPARTMENT OF AGRICULTURE, duced “ t o a state of t h e finest possible division,” MADISON, WISCONSIN Some time ago t h e Forest Products Laboratory and suggest the use of a fine plane for this purpose. Dean and Towers found ground wood passing a a4-mesh took up the systematic study of t h e chemistry of sieve unsatisfactory, b u t obtained more suitable American woods. The results of a preliminary study material by using a woodworker’s rasp and removing of the subject were published in 1917 b y Schorger.2 t h e fine particles from t h e sample by sifting through The complex nature of wood from a chemical point of view, together with the scattered a n d incomplete cheese cloth or a very fine sieve. Sieber a n d Waterg inforrnation on methods, necessitated confining t h e used finely rasped wood graded to pass through a No. 7 5 sieve but not through a No. 110. method of attack t o t h e determination of a number of Schorger used shavings not over 0.00; in. thick from constants under arbitrary b u t rather well-,defined conditions which would show ( I ) possible variations which all particles passing a 40-mesh sieve had been in the composition of t h e different woods, and ( 2 ) removed. Johnsen and Hovey employed raspings the presence and percentage of constituents of possible passing an 80-mesh sieve but not a Ioo-mesh sieve. commercial value, in addition t o those already known; Dore’s samples consisted of “fine sawdust,” while and which would give d a t a upon which conclusions Schwalbe and Becker and Konig and Becker analyzed might, be drawn regarding t h e chemical constituents material in t h e form of wood flour (holzmehl). T h e variations t h a t may be obtained by using maof wood as a whole. Since t h e publication of Schorger’s results several contributions t o t h e subject of wood chemistry have been made. Johnsen and Hovey3 have investigated balsam fir (Abies balsamea) and aspen (Populus 1 Read at the Symposium on Cellulose Chemistry at the 59th Meeting of the American Chemical Society, St. Louis, Mo., April 12 to 16, 1920. 2 THIS JOURNAL, 9 (1917), 556, 561. Fa9er, 21 (1917-18). No. 23, 36.
Z . angew. Chem., 32 (19191, 229. I b i d . , 32 (1919), 155. a THIS JOURNAL, 11 (1919), 556. 4 Lac. c i t . , p. 566. 5 2.angew. Chem., S i (1918), 193; J . Sac Chem. I n d . , 37 (1918). 685a. 6 Acknowledgment is made to Mr. D. E. Cable for assistance in securing 1
2
the experimental data given. 7 “Cellulose,“ 1903, 266, 244. 8 J . A m . Chem. Sac., 29 (1907), 1121, 1125. 9 P a p i e r f a b r i k . , 11 (1913), 1179; J . SOC. Chem I n d , 32 (1913), 974
T H E JOURNAL OF I N D U S T R I A L A N D ENGINEERING CHEMISTRY
874
terial secured by some of the above methods are shown in Table I. The samples of western larch ( L a r i x occidelztalis) had been extracted for 4 hrs. with a minimum boiling-point mixture of ethyl alcohol and benzene. All values in this and subsequent tables are calculated on an oven-dry ( 1 0 j O C.) basis. SAMPLE No. 1 1
1 2 2
TABLEI
Cellulose CONDITION OF SAMPLE Per cent Shavings obtained with a cabinetmaker's scraper. Retained on a 40-mesh sieve .................... 54.20 Shavings obtained with a plane. Retained on a 40-mesh sieve.. ................................ 55.10 Sawdust passing a 40-mesh sieve., . . . . . . . . . . . . . . . . . 50.30 Shavings obtained with a cabinetmaker's scraper. Retained on a 40-mesh sieve., , , 58.87 Sawdust passing a 40-mesh sieve.. 54.90
.. ..
These values were obtained under uniform conditions and are, therefore, comparable, but the cellulose residues were not entirely free from unchanged particles of wood. The variations are due: ( I ) To too wide a range in the size of particles in the material used, which causes an attack on the cellulose of thg smaller particles before the non-cellulose material can be completely removed from the larger particles. (2) To a possible fractionation of the material due to sifting out certain portions. (3) To incomplete extraction of the resinous materials which if not completely removed form a protective coating to some portions of the sample. To determine t h e effect of the size of particle on t h e yield of cellulose t h e series of determinations given in Table I1 were made. The material for analysis was obtained by converting the wood first into sawdust and then grinding the sawdust t o the various sizes in a disk mill having a shredding effect. Care mas taken to avoid fractionation of t h e material. The ground sawdust was sifted b y using t h e standard testing sieves of the American Society of Civil Engineers. The samples were all extracted for 4 hrs. or more with a minimum boiling-point mixture of benzene and ethyl alcohol prior t o chlorination. TABLEI1
Size of Material No. SPECIES Mesh 1 Western larch (Larix occidenlalis). . . . . . . . . . . . 40- 60 60- 80 80-100 100-120 2 Western larch (Lariz occidentalis) . . . . . . . . . . . . 40- 60 60- 80 80-100 100-120 3 Eucalyptus (Eucaly9tus globulus) . . . . . . . . . . . . . 40- 60 60- 80 80-100 100-120
SAMPLE
Cellulose Per cent 49.16 50.54 52.49 51.03 55.05 55.64 56.78 51.56 56.18 56.92 59.69 59.09
The cellulose obtained in each case was treated with chlorine and sodium sulfite t o the point where no color was obtained and the residue was entirely free from unchanged wood particles. The results show a maximum yield of cellulose with material which passes an 80-mesh but is retained on a Ioo-mesh sieve. This size of material has the further advantage t h a t in contrast t o the larger mesh material it is uniformly reduced, and unlike the finer material, gives a product which is easily handled, does not tend t o pack, and is readily filtered in the course of the analysis. Since raspings or shavings have been considered the best forms for wood for an analysis, comparison was made between raspings and material obtained
Vol.
12,
No. 9
b y grinding sawdust. T h e materials when sifted gave t h e percentages of different sized material recorded in Table 111. The wood used was Eucalyptus gl o bulus. TABLSI11 -RaspingsGrams Per cent Total.. ..................... 94.5 100 Retained on 80-mesh sieve.. . . . 4 6 . 0 48.7 15.3 80-100 mesh . . . . . . . . . . . . . . . . . 1 4 . 5 36 .O Passing 100 mesh.. . . . . . . . . . . . 3 4 . 0
-Ground Sawdust-. Grams Per cent 167.0 100 14.3 8.5 44.1 26.4 108.7 65.1
The ground sawdust gives a larger percentage of material in t h e desired fraction and is probably more representative, since a larger portion of the wood has been disintegrated t o a fineness beyond t h a t desired. Cellulose determinations on the two samples after extraction with alcohol-benzene gave the following results : TABLEIV ----Per cent Cellulose from---Raspings Ground Sawdust 58.31 59.43 59.59 58.23 58.30 59.23 58.64
Ground sawdust appears t o be as satisfactory as raspings as a form of material for analysis from t h e standpoint of yield, and is equally as satisfactory from t h e standpoint of manipulation. T H E CELL U L 0S E D E T E R M I N A T I 0 N-T he chlorination method of Cross and Bevan continues to be t h e only method applicable t o t h e determinatiqn of cellulose in woods. It has been subjected from time t o time t o modifications for t h e purpose of facilitating manipulation and also for the purpose of obtaining a better yield of cellulose or a supposedly purer product. Renker' found t h a t a preliminary digestion with one per cent caustic soda was unnecessary and reduced the yield of cellulose. Schorger confirmed this conclusion. Sieber and Walter modified the procedure b y allowing the material t o remain in the crucible throughout t h e treatment with chlorine and sodium sulfite. Johnsen and Hovey used this procedure, and recently Dore2 has employed i t in preference t o a modification devised by him. Johnsen and Hovey also modify the method b y subjecting t h e wood samples t o a preliminary hydrolysis with acetic acid in glycerol a t 13 j o t o 140' C. For the purpose of comparing t h e two methods of procedure, i. e . , chlorination in a beaker in a closed vessel and chlorination in a Gooch crucible, the analyses recorded i n Table V were made. TABLEV
CELLULOSE Cross and Bevan's Method as Modified by Renker---Sieber and Walter's Schorzer's SA.MPLE SPECIES Apparatus Apparatus 1 50.97 52.73 . . . . Western . . . . . . . .larch . . . . ...................... ... . 50.82 52.24 1 Western larch.. 56.84 2 Westernlarch , 53.51 56.72 2 Westernlarch 53.23
................... .......... .......... .....................
~~
The loss in weight due t o the action of chlorine on the fibrous pad used in t h e Goocli crucible was found t o be appreciable, giving cellulose values 0 . 2 9 per cent too high on the average. A corresponding correction was made in the values given. 1
"Bestimmungsmethoden der Cellulose," 1910, p. 44.
2
THISJOURNAL, 12 (1920), 264.
Sept.,
1920
T H E J O U R N A L OF I N D U S T R I A L A N D E N G I N E E R I N G C H E M I S T R Y
Five one-half hour chlorinations were required for complete reduction following Cross and Bevan’s procedure, while periods of 2 0 , 15, ~ j I,O , and I O min. were required with t h e modified procedure. The higher yield obtained using t h e original procedure, notwithstanding t h e longer exposure t o chlorine, is probably accounted for b y a lower concentration of chlorine and a lower chlorination temperature. Cross and Bevan’ have pointed out t h a t t h e yield of cellulose can be augmented by allowing t h e chlorination t o proceed a t as low a temperature as possible. Renker2 made his chlorinations a t zero. Johnsen and Hovey obtained yields of cellulose by their modification of t h e chlorination method which were from 2 t o 4 per cent lower t h a n those obtained b y t h e original method. We obtained similar reductions in yield as indicated in Table VI, t h e wood analyzed being western larch. One of t h e purposes of t h e modification is t o reduce t h e furfural-yielding constituents i n t h e cellulose, and t h e d a t a show a small reduction has been secured. TABLEVI Johnsen and Hovey’s Cross and Bevan‘s Method Modification as Modified by Renker Constituent Siebdr & Walter’s Sieber & Walter’s Schorger’s SAM- Determined Apparatus Apparatus Apparatus Per cent Per cent Per cent PLE Ind, Mean Ind. Mean Ind. &Iean 1 Cellulose., . . . . . . . 4 6 . 1 8 50.97 52.73 46.23 46.21 50.82 50.90 52.24 52.49 2 Cellulose . . . . . . . . . 50.43 53.51 56.84 1
Pentosan in cellu- 5 0 . 4 8 5 0 . 4 6 lose.. .......... 67,Ol ,76 6,89
1
Pentosan-free cel1dose. . . . . . . . . . . . . .
...
53.23 7 . 76 23
43.03
... ...
53.37 7.68
46.99
56.72 6 7 ,. 7 95 4
... ...
56.78 7.35
48.64
The figures show t h a t t h e proposed modification lowers not only t h e percentage of pentosan or furfuralyielding constituents b u t also t h e pentosan-free cellulose. The ratio of loss of pentosan-free cellulose t o loss of pentosan is approximately I : 2. This does not confirm t h e statement of those proposing t h e modification t o t h e effect t h a t t h e acetic acid-glycerol mixture is “able t o hydrolyze t h e lower carbohydrates and a large portion of t h e furfural-yielding constituents without attacking t h e cellulose.” Dore3 in a recent article shows t h a t t h e more resistant portion of t h e cellulose, t h e a-cellulose, is attacked by t h e acetic acid-glycerol mixture. This modification of t h e chlorination method appears, therefore, t o be of doubtful value, especially since approximately t h e same result could be attained by a further chlorination of t h e sample t h a n usual. S U31 MA RY
A uniform size of particle is essential if comparable results are t o be obtained in t h e determination of cellulose in woods. Material which passes an 8 0 mesh standard (American Society of Civil Engineers) sieve b u t is retained on a Ioo-mesh sieve has been found t o be most satisfactory from t h e standpoint of both yield and manipulation. Material obtained by a single mechanical process of disintegration may give a sample on sifting which is not representative. To . Chem. Soc., 41 (1882). 105. cit. a THISJOTJRNAL, i a (igzo), 264. 1J
2 LOC.
875
avoid this a combination of two processes, sawing and grinding, has been used. The procedure recommended b y Sieber and Walter for chlorination gives a lower yield of cellulose t h a n t h e original Cross and Bevan method, probably because of t h e higher temperature a t which chlorination takes place. The modification of t h e Cross and Bevan method proposed b y Johnsen and Hovey appears t o be of doubtful value since t h e cellulose as well as t h e hemicelluloses and furfural-yielding constituents are a t tacked. THE DETERMINATION OF TRUE FREE SULFUR AND THE TRUE COEFFICIENT OF VULCANIZATION IN VULCANIZED RUBBER’ By W. J. Kelly RESEARCH LABORATORIES, THE GOODYEAR TIRE AND RUBBERCo., AKRON,OHIO
Sulfur in vulcanized rubber has generally been considered as present in two forms, t h e so-called free and t h e combined sulfur. It has been realized for some ti:me, however, t h a t sulfur which was called free and hence, implicitly at least, considered available for further vulcanization, did not exist entirely in t h e elementary form. It is evident t h a t during vulcanization t h e sulfur will react with other materials present, such as resins, proteins, organic and inorganic accelerators, and fillers. This naturally removes a certain amount of sulfur from active participation in t h e reaction between rubber and sulfur. All of t h e inorganic compounds will be insoluble in acetone; hence, unless a correction is made for t h e sulfur present as sulfide or sulfate, t h e results on t h e coefficient of vulcanization will be high. The reaction products of sulfur with t h e resins, proteins, and organic accelerators may be wholly or partly soluble, or entirely insoluble in acetone, and any of t h e old methods which did not take into account their formation gave erroneous results for free and combined sulfur. Furthermore, any compounds formed by t h e reaction between sulfur, resins, proteins, etc., will, on heating, give up their sulfur in t h e form of H2S o r some other compound, and never as elemental sulfur. Hence, although t h e compouads may decompose, no sulfur, once combined, becomes available for further vulcanization unless there is an oxidizing agent present, an extremely rare condition in t h e vulcanization of rubber. The liberation of sulfur from polysulfide is not considered in this paper. The behavior of accelerators, fillers, etc., is being investigated along t h e lines laid down, and t h e work is confined for t h e present t o stocks which are made up of rubber and sulfur only. It is t h e object of this paper t o present two methods, one for t h e true free sulfur determination and t h e other for a more accurate figure for t h e coefficient of vulcanization t h a n could be obtained b y t h e older methods. It is evident from t h e foregoing remarks t h a t t h e sulfur present in vulcanized rubber may be divided into four parts: 1 Paper read before Rubber Division at the 59th Meeting of the American Chemical Society, St. Louis, Mo., April 12 t o 16, 1920.
