Document LJV487nyz6ko9yMjV16dEEQkQ

INTER-OFFICE CORRESPONDENCE Et h y l Ga s o l in e Co r p o r a t io n Re s e a r c h La b o r a t o r ie s 723 Ea s t Mil w a u k e e Av e n u i: De t r o it , Mic h ig a n June 8, 1938. Dr. Robert A. Kehoe College of Medicine University of Cincinnati Cincinnati, Ohio Dear Bob: I am sending you herewith a copy of our Report LTD 38-25 on the mechanism of decomposition of triethyllead bromide by steam distillation. As I told you during your last visit, vie are pursuing those studies, and I will send you reports from time to tine on the other alkyl lead salts. 0022263 LID #38-25 O.R.Kurt F.J.Dykstra 263-XP-1S, pp 41-51 May 23, 1938. STEAM DISTILLATION 0? LEAD TRIE1BYL BBQMIDE PURPOSE Tills study ic part of the problem of determining tiro volatility of lead ethyl salts and their decomposition products* The run reported here was h e.do by Mr. Dykstra in order to verify the results of previous runs (230-XP-19 and 230-XP-22 reported in LID #37-28 and 230-XP-23 reported in LID #38*1) and in order to acquire technique for subsequent runs on other lead alkyl salts. COHCLUSIOMS - The decomposition of PbEt^Br proceeds as follows. these results confirming those of previous runs* 2 PbBtgBr <* PbBtA + FfcBtoBrg 2 PbSt2Br2 * PbEtgBr + PbBrg + EtBr PbEtgBTg a PbBrg + 2 St ' orcent decomposed at 100 C Time of Run 2S0XP22 63?$ 37 89 210 230XP23 84$ 16 81 160 This Run 83 17 72 160 SIMiARY Very good yields of pure EtBr and PbSfcA were obtained* The composition of the hydrocarbon products was not established because gas analysis results were unsatisfactory* The yield of gas, though measured more accurately than previously, is still much lower than theoretical. The relative extent of the two decomposition reactions of FbStgBrg was calculated from the data for PbEtgBr, Fbt4, PoBrg and EtBr, which are in good agreement with each other. All f the lead was accounted for except 2.5 percent, which loss can bo ascribed to handling. LETAILS The apparatus and procedure were similar to those of runs 23Q-XP-22 and 230-XP-23. Several modifications were made which improved the products and reduced the work required. A 500 co, 3-neek round-bottom flask was used as a boiler. Ono side neok was fitted with a etopoooked inlet for nitrogen. The other side neck was connected to the reflux condenser and PbEt. trap. The PbEt^ trap was fitted with a water return tube which worked satisfactorily, ho beads were used in the distilling column or in the condenser* The condenser was oooled with cold tap water at approximately 15C. A small tube connected the upper end of the condenser to a trap kept in a dry-foe acetone bath and then led to the gas burette. Ilia apparatus is sketched in the attached blueprint. X* 0022264 N22447.01 Tho PbEtgBr ms freshly raorystalllsod fioa dry mixed hexane. 300cos distilled water was placed in the boiling flask, the air in the apparatus was replaced by nitrogen, the water was boiled until equilibrium was reached, then a filter paper thimble filled with FbStgBr was placed in the flask through the central neck* Consequently the increase in the gas volume in the apparatus, which is measured by the gas which passes into the burette, is all due to gas generated and not partly due to thermal ex pansion of the nitrogen ns in previous runs * The gas was drawn into evacuated 100 cc. pipettes after being msasured in the burette. The run v,as stepped after 160 minutes* The system was flushed with, nitrogen to collect the gas in the system* The initial material cad the pro ducts were analysed to obtain the results presented in the attached table. Analysis of the initial material gave two values far % ?b and one value for % Br equal within experimental error to those of pure PbBt^Br* The other % Br seems unreliable in view of the method of purification so the most probable composition to aoeept is that of pure PbStgSr. The PfcSt4 layer of the distillate had a specific gravity so close to that of pure FbEfc^ that it was not considered necessary to give it any further treatment, it was assumed to contain 1% EtBr. Analysis for Fb showed it to be quite pure, but the fi pb was used to calculate the mobs of PbEb^. The material which condensed in the dry ioe trap was quite pure EtBr according to the specific gravity and refractive index measurements* There was/considerably larger amount than was obtained in previous runs, even after including the EtBr found condensed in the FbEt4 layer in previous runs. The water solution left in the boiler deposited beautiful crystals on cooling, presumably of PbBtQ, It was reheated to put the pbBrg and undsecapoaed FbEtgBr into solution, the flask was washed and an aliquot portion of the solution analyzed. A residue remained in the flask which was molten in hot water and solid at room temperature. All except a small portion of it and the residue on the filter paper were put into solution vith ether. The residue was dissolved in nitrio acid and analyzed for lead. The gas was collected in three 100 oc. pipettes. The atialyaes were mostly unsatisfactory. The results on the first pipette did not check each other. The results on the second pipette gave an lyQ ratio of 2.38. The contents of the third pipette were not analysed. The molecular weight calculated from the weights of the gas in the pipettes,which is mostly nitrogen, indicate that the hydrocarbon gas may be C2K4 end CgH#* 63.3 oos. of evolved gas at 25C and 760 can. would be .00259 mola. If the gaa were C2H4 and CgHg this would account for .00259 mol Et. Borne Et might havo polymerised to fora higher hydrocarbons but then some of those [should be found in the dry ioe trap with the BbBr* The missing it calculated from the other products, 0.00345 mol equals 0,100 gm,, is small enough so that it might easily bo lost in the EtBr, the PbEt^, or absorbed in the rubber connections. 2 K 0022265 The missing Pb is assumed to be FbSfc^, which has either been volatilised or held up in the condenser* or decomposed to Pb in. the pbEt4 trap. It is also partly due to experimental errors in analysis. The relative extent of the two FbEtgB-ra decomposition reactions are calculated from the data for PbEtgBr, PbBrg and pbBfc* in the attached table. It will be noted that the sum of equations (4) and (5) necessarily equals (3) because all the Pb has been accounted tor by assigning the miss ing ?b to equation(4), consequently there are really only two equations for solving for the two unknowns, a and b. The only check on the results lies in the fact that experimentally the Pb balance is quite good, Even so the 2,S^ of missing Pb is a large enough amount to cause a high uncer tainty in the values of a and b except for the fact that we can ascribe the missing Pb quite definitely to PbEt^, A high uncertainty could occur in the analytical results, so it Is recommended that the technique be improved to recover all of the Pb, d'JEM DXSTIUATIOB OP PbBtgBr - 263-XP-1S Initial PbBfcv3^Br 14.^56 gsa, Theoretical; ANALYSIS oS","34>Ob ' "20 50,44 21,43 56,37 21,36 COMPOSITION- Gm.Mo 0,03996 PbEtjBr Distillate - P'oEt^ layer 3,40 os '4 26 Sp.Cr. 1,646, 1,843 (of, 1,8528) 83.40/, Pb 63.55 Theoretical; 64,06 0.01712 Fbt4 ,00051 BtBr Dry ice trap 0.35 oc %>.Gr.^ 23.5, 1,445, 1,467 (of. 1.450) 0,00526 DtBr B.I. 1.4233 (of. 1.4239) Still residue -water sola. ** n ether extract B " residua 0.01846 mol Pb, 0.028817 mol Br .00312 mol Pb, .00311 mol Br .00023 Pb 0.01036 PbBr2 .00810 PbEtgBr .00311 PbEtgBr .00023 (PbBT2 ? Volatile gas Missing Pb 53*3 cos. #1 ml.wt. 27,85 16,6% combustible #2 " 27.96 12.7 " #3 ' 27.95 not analyzed .00269 Bfc H/C 2.33 .00104 PbEt4 3a FbEtgBr 2b PbEtgBr PbEtgBr PbEt4 PbBrg StBr 2 Pbt4 + PbBr2 + E-tBr 3a 0.02271 (1) PbEt4 + PbBrg + 2 Et 2b 0.00604 (2) 3a * 2b *.03996 - (.00810 + .00811) * .02876 (8) 2a + b * ,01712 + .00104 * .01816 (4) * a + b * ,01036 + .00023 .01059 (5) a * 0.00787 b 0.00302 * a * .00757, Recoveredt .00061 + .00528 * .00629. Missing * 2b * .00604, Recovered .00259^ Missing .00346 (7) ,00228 (6) mom 0022266