INDUSTRIAL A N D ENGINEERING CHEMISTRY
454
acids occurs a t t,he outer region and increases as it approachcs the heartwood. When the heartwood is reached, a material increase in resin acid is noted, but whether the inner or outer heartwood has the larger or smaller percentage of resin acids is dcpendent upon their respective cxtractivc contents. FREEFATTY ACIDS. This constituent iiicreases in per (wit as it passes from the newly formed sapwood to the inner sapwood where it reaches a maximum; then the percentage of fatty acids decreases as it approachcs the pith. VOLATILES. This fraction usually iiicreases in per cent as it approaches the pith of the tree. ESTERS. I n heartwood the percentage of esters decrenses froni t,he outer heartwood to the pith. I n some instances the percentage continues t o increase as it approachcs the out,er sapwood; in others it tends to decrease. UXSAPONIFIABLES. I n general, the perccntage of unsaponifiable is the least a t the outer sapwood and iiicreases, in some < maximum in the outer heartwood and then decreases as it nilproaches the center of the trce. I t is interesting to note that the coniposit.ion of thc outrr niitltll(~ hear,tnood in stand I11 indicates that it is apparently in the trailsition stage from sapwood to heartwood. The relatively lo\\rwin acid content, together withihe slight increase in unsaponifiable material in this outer heartwood region, suggests that this transitional deposition of extractives was t,aking place.
Vol. 38, No. 4
are obtained from the lumbci antl wood waste originating from the butt portion of the trunk and from that portion of the trcl containing massed pitch arcs?. The acetone extractives, R Iictlier from the heartwood or \ u p wood, contain, in addition to rebin acids and terpenes, free fatly acids, fats, and unsaponifiablc msteiial. Thus the extractive. differ from gum oleoresin foiIncd by wounding the tree by bhe presence of these aliphatic and un5aponifiable substances. T h e percentage of each of thesc erilitics is not uniformly distributed throughout the tree but depcntls from which part of the log thc. extractives arc obtained. I n tlic case of heartwood extractive greatly appreciated.
APPLICATION OF RESULTS I11 seeking means for effectively utilizing the potential c.lieriiicw1 products from ponderosa pine, it was found that this wood coiitained a sufficient quantity of extractives to warrant the possible removal and recovery of these materials from the lumber and from forest and mill wood waste. Preliminary investigation\ have shown that it is possible to extract all or a large portion 01 the extractives from lumber; the result is 8 further improveiiicnt in the lumber offered by manufacturers; in addition, a commercial volume of extractive products may become available from this wood. The amount of recoverable extractables is not uniformly distributed throughout the trunk of the tree. The average extractive content in sapwood is usually within tlie limit. 2.0 to 9.8%.of the weight of the dry wood, whilc the heartwood extractables are usually within the limits 3.5 t o 31.5% of tho weight of the dry wood. Tho greater quantities of extractivci
LITEHA7'UL{ 1.: c;t'rl?;l)
(1) Adariis, J. INU.ENO.C m x . , 7, 957 (1913), ( 2 ) A4nderson,Ibid., 36, 662-3 (1944).
( 3 ) Assoc. of Official Agr. Chein., Methods of Analysis, pp. 469-71 (1940). 141 Benson and Jones. .J. ISD. $hi;. CHEM.. , 9., 1096 (191'7i Dore, I t ~ i d . ,11, 556-63 (1919). (6) Hihbert and Phillips, Can. J . licssnrch, 4 , 1-34 (1931) (7) Koch and Kricg, Chem.-ZtN., 15, 1 4 0 - 1 (1938). (8) Kiajriiiovic, Ibid., 55, 894 (1931). (9) Kurth, IXD. ENG.CHEM.,23, 1156 (1931). (10) Schorger, U. S. Forest Service, Bull. 119 (1913). (11) Trendelertburg and Schailc, Papier-Fnhr., 35, 221-30 (1937). (12) Tiertelak and Garbaczowiia, lsn. RSG. CHBM.,ANAL. ED., a , 110-11 (1935). (13) JTise, "Wood Chemistry", pp. X i 3 - 4 , A.C.S. Monograph 87 New York, Reinhold Pub. Gorp., 1944. (14) \TOM and Scholae, Chern,-Zlg., 38, 3G!)-70 (1914).
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issociation Pressure of Ammonium Car k.
P. EG-kN, JR., J. E. POTI'S, JR., AND GEQRGETTE 1). POn'S Tennessee Valley A u t h o r i t y , Wilson D u m , Ala.
T
EMPERATURE-pressure relations for the dissociation of solid ammonium carbamate into gaseous ammonia and carbon dioxide have been measured by several investigators. (1-5). The reported values are divcrgeiit; at a total pressure of 40 atmospheres the divergence is as much as 17 atmospheres. Briggs and Migrdichian (1)-measured the dissociation pressure of ammonium carbamate over temperature range 10" to 49" C. and obtained very consistent data. They also studied the effect of excess ammonia or carbon dioxide and found excellent agreement mith the mass Ian accoiding to the equation:
KII&OZ1\"2
(solid)
=
BTH,(gas)
+ COz (gas)
(1)
The present paper cover5 .t study of the dissociation preism c of solid ammonium carbamate over the temperature range 35' $ 0 83' C. and in the absence of 'til excess of either gaseous reactvnf From the vapor pressure data tlie lree energy of dissociatioii and the heat of dissociation h a w bwn derived. PREPARATION O F SOLID A3tMOh'IUR.I CARBAMATE
Solid ammonium carbam i t e ~ v n sprepared directly in a 50-c sample bulb (Figure 1) which later was connected to the pre?siirci measuring system. Stoichiometric proportioning of the r('ii
