Combustion train

C03-0150. A sample of a component of petroleum was subjected to combustion analysis. An empty vial of mass 2.7534 g was filled with the sample, after which vial plus sample had a mass of 2.8954 g. The sample was burned in a combustion train whose CO2 trap had a mass of 54.4375 g and whose H2 O trap had a mass of 47.8845 g. At the end of the analysis, the CO2 trap had a new mass of 54.9140 g and the H2O trap had a new mass of 47.9961 g. Determine the empirical formula of this component of petroleum. 

An important criticism of the use of combustion trains is that combustion is not site specific, that is all atoms in the analyte end up in the gas transferred to the IRMS. For studies of carbon isotope effects this is invariably C02. The question is especially important for carbon isotope analysis because analyte molecules of interest usually contain several different kinds of carbon atoms and therefore combustion methods average or dilute the IE s of interest. Should site specific isotope ratios be required another method of sample preparation (usually much more tedious) is necessary. Combustion methods, however, are frequently used to study nitrogen and sulfur IE s because many organic molecules are singly substituted with these atoms. Obviously, oxygen isotope effects cannot be determined using combustion trains because external oxygen is employed. Rather some type of pyrolytic sample preparation is required. 

Some of the aldehyde-amine condensation products have been recommended as ingredients of nondetonating, deflagrating, expl compns (similar in properties to black powder) for use in the delay combustion-train devices of fuzes. Other ingredients of such compns are non-explosive, such as alkali metal nitrates and charred carbonaceous compounds(Ref 1)... 

Organic carbon analyses were made in duplicate by a combustion train method in the Microanalytical Laboratory, School of Chemistry, University of Minnesota, and Kjeldahl nitrogen analyses were done in triplicate in the Minnesota State Board of Health Laboratory. Averages of the readings are used here (Table III and VI) and are rounded off to the second decimal. Carbonate was removed from the samples by treatment with 0.5N hydrochloric acid prior to the carbon analyses. 

Figure 1-1 Schematic representation of a combustion train for determination of carbon and hydrogen in combustible substances...

The combustion train is first attached to the combustion tube by reliable rubber connections and the boat then placed in position. The CuO spiral behind the boat is heated and the substance slowly distilled into the previously heated CuO filling. A short time after the commencement of the combustion 11,0 will make its appearance in the snout end of the tube. It should be driven into the CaCL, tube by holding a pair of hot tongs around the tube. This should be done regularly. After 10 minutes, 0 is switched on and passed for 15 minutes, or until the contents of the combustion tube are completely oxidised. Air is passed again for about 15 minutes to displace the 0. The absorption tubes are detached and treated as already described. 

It is essential that both air and oxygen be pure. If not, purification can be assured by passage through a purification train consisting of (1) 30% aqueous solution of potassium hydroxide, (2) concentrated sulfuric acid, and (3) two U-tubes charged with soda lime (or other dry absorbent for carbon dioxide) and calcium chloride. It may be advisable to use two purification trains (one for each gas) leading to a common tube for delivery to the combustion train. 

The combustion train and recording method was developed by R. D. Goodwin (Goodwin, 19), and allows measurements to be made on individual catalyst particles, and quantities of catalyst material of 100 mg. and less. The total amount of CO2 produced at any one time is recorded vs. time on a pen recorder. The total recorder deflection reached supplies the value of initial carbon concentration Cc. The air (or oxygen) flow rate is maintained sufficiently high to provide the known constant oxygen partial pressure Co in the gas stream. The ratio n is found to be close to unity in the case of coke laid down on the porous catalysts by exposure to hydrocarbon vapors at cracking temperatures. The diffusivity is best... 

A hydrocarbon is a compound that contains only carbon and hydrogen. Its empirical formula can be determined by using the combustion train shown in Figure 2.3. In this device, a known mass of the hydrocarbon is burned completely in oxygen. 

Burning a compound of calcium, carbon, and nitrogen in oxygen in a combustion train generates calcium oxide (CaO), carbon dioxide (CO2), nitrogen dioxide (NO2), and no other substances. A small sample gives 2.389 g CaO, 1.876 g CO2, and 3.921 g NO2. Determine the empirical formula of the compound. 

In an experiment using the combustion train, a gaseous fuel used in welding (containing only C and H) is reacted with 02. The mass of the absorbers in Chamber increases by 0.9 grams and the mass of the absorbers in chamber 2 increases by 4.4... 

What would happen if the order of the chambers in the combustion train were reversed ... 

Why is it necessary to react the 02 in excess when using a combustion train ... 

Figure 2-10 A combustion train used for carbon-hydrogen analysis. The absorbent for water is magnesium perchlorate, Mg(C104)2. Carbon dioxide is absorbed by finely divided sodium hydroxide supported on glass wool. Only a few milligrams of sample is needed for analysis.

Hydrocarbons are organic compounds composed entirely of hydrogen and carbon. A 0.1647-gram sample of a pure hydrocarbon was burned in a C-H combustion train to produce 0.4931 gram of CO2 and 0.2691 gram of H2O. Determine the masses of C and H in the sample and the percentages of these elements in this hydrocarbon. 

Naphthalene is a hydrocarbon that is used for mothballs. A 0.3204-gram sample of naphthalene was burned in a C-H combustion train to produce 1.100 grams of carbon dioxide and 0.1802 grams of water. What masses and percentages of C and H are present in naphthalene ... 

Figure 2-5 A combustion train used for carbon-hydrogen analysis. The increase in weight of the H2O absorber can be converted into the amount of hydrogen present, while the increase in weight of the...

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