cording to some recent theories of the osmotic second virial coefficient in the limit of large excluded volumes, i.e., for high molecular weight polymer molecules in thermodynamically "good" solvents, the ratio A2M%,/(Rl,)'/* should attain an essentially constant value. Qualitatively the constancy of this ratio is an expression of the expectation that the interactions of polymer molecule pairs in such media resemble collisions of spheres whose volumes are proportional to (7?2W)V2. If, then, the volumes of the equivalent hydrodynamic spheres observed viscometrically are also proportional to (i?2w)'/' the ratio AtMw/[rj] should be another constant. _The ratio is plotted against log Mw in the center graph of Fig. 7 for the ten polyvinylacetate fractions in methyl ethyl ketone. Over this molecular weight range the ratio is a constant equal to 4.4 X 1024.A plot of A-iM^I [77] against log M-w for the samesystem in the lower graph of Fig. 7 reveals a remarkably constant value, 1.39, for this ratio over the molecular weight range 246,000 to 3,460,000.Here again data of Howard19 have been used to extend the observations to lower molecular weight polymer fractions.It may therefore be stated empirically that the thermodynamic interaction of a pair of high molecular weight polyvinylacetate molecules in methyl ethyl ketone is similar to the collision of spheres having effective volumes proportional to (A!2W) This observation, coupled with the validity-of the equivalent hydrodynamic sphere treatment of limiting viscosity numbers, yields an empirical relation among the quantities AMw and [17]. It has been found40 that this relation is valid for several polymers in thermodynamically good solvents, and similar magnitudes for the ratio A2MW/ [77 ] are observed.

T e fl on and tetrafluoroethyle ne photopolymers, on py rolysis in a vacuum at 423.5 0 to 513.0 0 C, yield almost J 00 per ce nt of monom er. The r ate of formation of monome r at a n.,· given tem p e rat ure fo llows a first-order react ion and is independe nt of t he method of pre pa ration of poly mer or its initial ave rage molecu lar weight. The activation energy was determined by a press ure method and a wei gh t met hod , and a value of 80.5 k cal was found b.'· both methods . A prelimina ry heating of Teflo n in air a t 400 0 to 470 0 C did not change a ppreciably its rate of degradation into mono me r when it was s ubseque ntl y heated in a yacuum . Polyvinyl fluorid e, 1,I -polyv in y li dene fluorid e, and polytrifluo roethylene were pyr olyzed in t he range 372 0 to 500 0 C. The volatiles consisted in all cases of HF and a wax-lik e mate rial co nsisting of chain fragments of low volatili ty. P olyvinyl fluoride and polyt rifl uoroet hyle ne deg rade to co mplete volatilization, whereas 1,1-poly viny li dene fluoride becomes stabilized at about 70-pe rcent loss of we ig ht. The rate-of-volat ilization curves indicate a fi l'st-o rder reaction for poly vinyl fluo ri de, a zero-order reaction fo r t riflu oroethy le ne, alld an undeterm in ed ord er for 1,1-polyvinyli dene fluoride. The orde r of t hermal s tabili ty for t hese poly me rs, as com pared with polymet hy lene, is as follows: Poly vin yl f1uoride < poly me th,vle ne < polyt riflu oroethylene < ] . J -polyvi nylidene f1uor idc < polytetrafluoroeth ylene.

Samples of cotton , cotton h ydrocelJulose, and viscose rayo n, both by t hemselves an d impreg nat;ed with sod ium carbonate or sodium chloride, were p yl'Olyzed at 250 0 to 397 0 C in a lli g h vacuum. The volatile products were fractionated a nd t he fractio ns analyzed in th e m ass spectrometer a nd by inf rared absorpt ion. Th e volatile fraction s co nsisted mainly of CO, CO2, water, and levoglucosan (tar). The residue consisted main ly of carbon (cha r).Imp reg na t ion of the cellulosic m aterials with salt s caused a decrease in t he y ield of tar and an increase in t he yields of CO, CO" H 20 , a nd char. R ates of thermal degradation of the sam e materials were in vcstigated in the range 245 0 to 305 0 C by a loss-of-w eight m ethod, usin g a ver y sensitive t ungste n spring bala ncc enclosed in a vac uum. Plots of rates of loss of " 'eigh t versus percentage of loss of ' weight, in t h e case of pure cellulosic materials, p ass th rough maxima at a bout 13 to 23 percent loss of " 'eigh t, t he n drop graduall y to t he carb onization end point. In the case of sampl es impreg nated with sodium carbonate or sod ium chlorid e, t he initial ra tes of loss of weight are very hi gh , but drop rapidly to the carbon izatio n end p oi11 t . Th e activation energies o f thermal d egradation of t h e pure cellulosic mater ials are much greate r than t hose of t he sa me material s impregnated with sod ium carbo nate or sodium ch lor ide .

Samples of polyisobutene, polyisoprene, polybutadiene, GR‐S, and polyethylene, weighing about 25 to 50 mg., were pyrolyzed in a vacuum of about 10−6mm. of mercury in a specially designed apparatus at temperatures ranging between 300 to 475°C. The volatile products of pyrolysis were separated into four fractions: (IV) gaseous, volatile at ‐196°; (IIIA) liquid, at ‐75°, (IIIB) liquid, at 25°; and (II) waxlike fraction, volatile at the temperature of pyrolysis. The gaseous fraction was analyzed in the mass spectrometer and was found to consist in all cases of CH4. The liquid fraction, IIIA, was analyzed similarly and was found to give a mass spectrum characteristic for any given polymer. A molecular weight determination of the waxlike fraction by the micro freezing point‐lowering method, showed it to vary from 543 to 739, depending on the polymer from which the fraction was obtained. It is shown that the method of pyrolytic fractionation of high molecular weight polymers, in conjunction with mass spectrometer analysis of the more volatile fractions, can serve as a means of identifying the polymers.