The heats of combustion of polytetrafluoroethylene (teflon) and graphite in elemental fluorine

Abstract

Bomb calorim e tri c meas ure ments a re reported for the co mbu stio n in flu orine of polytetrafluoro· e t.hyle ne (T eflon) and graphite·polyte traflu oroethyle ne mixtures. Mass s pectrometri c ex amination of the produ ct gases show ed C F" to be the only maj or produc t with C" F6(g) prese nt in only very s mall a mount s . Th e co mpl e te ness of co mbu sti on of th e graphit e wa s de termin ed by c he mi cal analysis of co mbu stion res idu es and found to ra nge from 97 to be tte r than 99 perce nt. Fro m th e co mbu stion data, th e hea ts of form ati on ~H;l>I8 [ CF4(g)] and ~H;,,,~[ C"F4 (solid polym e r)] we re de te rmined to be -222.87 ± 0.38 kcal mol -I and -197.82 ± 0.39 kcal (gfw C2F.) -I , respectively. Th e un certainties are estimates of the ove raU experimental e rrors .A previously re port.ed value for the heat of formati on of AlF3(c) is adju sted to be co ns iste nt. with t.h e presen t work. An e valu ation of oth er data on CF 4 is prese nted. Th e heat of formation of CF.(g) is co mbined with other wo rk to de rive the heats of formation of HF soluti ons a t three s pecific con· ce ntrati ons.Key Words : Alum inum fluorid e, c arbon te trafluorid e . flu orine, fluorin e bomb calorim e try, graph ite , heat of co mbusti on, heat of form a tion, hydroge n flu oride aqueous, T efl on.

Ideal Gas Thermodynamic Properties of Eight Chloro- and Fluoromethanes

“…They obtained 6.HF(CF-\, g, 298)=-223.05± 0.18 kcal mol-t which is in excellent agreement with that reported by Domalski and Armstrong (1967). If one combines the enthalpy change of reaction 9-6 obtained by Domalski and Armstrong (1967) (the high fluorine pressure makes this the preferred datum) with that of reaction 9-2 measured by Scott, Good, and Waddington (1956), one has AHrO(298)=-I?<}.] + O_S krHl mol-I for rf~a~tion 9-8. from which one may calculate 6.HF(CF -I, g, 298) = -223.17±0.5 kcal mol-I.…”

“…Greenberg and Hubbard (1968) also determined the enthalpy of formation of CF -\ (reaction 9-7) in a bomb calorimeter using 25 atm of fluorine. They obtained 6.HF(CF-\, g, 298)=-223.05± 0.18 kcal mol-t which is in excellent agreement with that reported by Domalski and Armstrong (1967). If one combines the enthalpy change of reaction 9-6 obtained by Domalski and Armstrong (1967) (the high fluorine pressure makes this the preferred datum) with that of reaction 9-2 measured by Scott, Good, and Waddington (1956), one has AHrO(298)=-I?<}.]…”

“…Thus, aHr (CCI4 , g, 298) -aHr (C, s, 298) =-25.6 ±0.4 kcal mol-I. Domalski and Armstrong (1967) summarized the available data on the observed enthalpy of formation of solid carbon (soot) and' concluded that aHlo (C, s, 298) 3 ± 1 kcal mol-1 was reasonable in the absence of other data. This leads to aHr (CCI4 , g, 298) = -22.6 ± 1 kcal mol-I.…”

“…Using the auxiliary data from Wagman et al (1968) and 6.HfO(HF• 20H 2 0, aq, 298)=-77.004 kcal mol-I (Settle, Greenberg, and Hubbard, 1971;Johnson, Smith, and Hubbard, 1971) From the enthalpy change . for reaction 9-1 determined by Scott, Good, and Waddington (1955), one can calculate 6.Hr(C 2F-4, poly, 298)=-199.0± 0.9 kcal mol-to Incorporating this value with 6.HrO(298) for reaction 9-6 yields 6.HF(CF .. , g, 298)=-222.9± 0.9 kcal mol-t. Domalski and Armstrong (1967) studied the same reaction (9-6) but with 15 atm fluorine which, they report; suqJn:~88ed Lhe fUrIllaLiull uf higher pedluolOalkanes. They obtained 6.HrO(298)=-247.92±0.07 kcal mol-I [compare to 6.HrO(298)=-246.84 kcal mol-1 of Wood, Lagow, and Margrave (1967)].…”

Mass spectrometric study of the photoionization of some fluorocarbons and trifluoromethyl halides

“…However , recent measurements have given improved values for some fundamental data-from which most bond energies are derived-such as the heat of formation of HF in aqueous solution by Johnson e t a1. [30] and the heat of formation of CF4 by Domalski and Armstrong [31]. Ge neral and critical reviews have bee n made by Be nson [27], Ke rr [28], and Lacher and Skinner [29].…”