Formic acid measurement

A sample of the protein, horse heart myoglobin, was dissolved in acidified aqueous acetonitrile (1% formic acid in HjO/CHjCN, 1 1 v/v) at a concentration of 20 pmol/1. This sample was injected into a flow of the same solvent passing at 5 pl/min into the electrospray source to give the mass spectrum of protonated molecular ions [M + nH] shown in (a). The measured ra/z values are given in the table (b), along with the number of protons (charges n) associated with each. The mean relative molecular mass (RMM) is 16,951,09 0.3 Da. Finally, the transformed spectrum, corresponding to the true relative molecular mass, is shown in (c) the observed value is close to that calculated (16,951.4), an error of only 0.002%. 

This explanation is probably applicable to the results recorded by Paesy, who found that with the homologous aliphatic acids the strength of the odour—as measured by the reciprocal of the smallest quantity that could be perceived—of formic acid is comparatively small, a maximum is reached with butyric acid and after diminution to the weak oenanthic acid, another maximum is reached with pelargonic acid, thereafter the odour diminishes very rapidly. 

Ethylenediamine (15 g, 0 5 mol) was added dropwise to 100 ml 9B-100% formic acid in a two-necked 500 ml flask, fitted with an addition tube and reflux condenser with drying tube, cooled in an ice-bath. After complete addition of the base, 53 g of benzaldehyde (0.5 mol) was added in one lot. The ice-bath was removed and the flask was heated to the refluxing temperature. The initial rate of carbon dioxide evolution was too rapid to measure. After twenty minutes, the rate was circa 100 ml per minute and decreased rapidly to B ml per minute in one hour. Heating at reflux was continued for 35 hours. 

The macroscopic dielectric constant of liquid formic acid at 25° has the value 64, not much lower than that of water. Hence, from the simple electrostatic point of view, we should expect. /c for the proton transfer (211) carried out in formic acid solution, to have a value somewhat greater, but not much greater, than when the same proton transfer is carried out in water as solvent. In Table 12 we found that, in aqueous solution, the value of (./ + Jenv) rises from 0.3197 at 20°C to 0.3425 at 40°C. Measurements in formic acid at 25°C yielded for the equilibrium of (211) the value — kT log K = 4.70. Since for formic acid the number of moles in the b.q.s. is M = we find... 

Kinetic studies of the decomposition of metal formates have occasionally been undertaken in conjunction with investigations of the mechanisms of the heterogeneous decomposition of formic acid on the metal concerned. These comparative measurements have been expected to give information concerning the role of surface formate [522] (dissociatively adsorbed formic acid) in reactions of both types. Great care is required,... 

Isothermal a—time curves were sigmoid [1024] for the anhydrous Ca and Ba salts and also for Sr formate, providing that nucleation during dehydration was prevented by refluxing in 100% formic acid. From the observed obedience to the Avrami—Erofe ev equation [eqn. (6), n = 4], the values of E calculated were 199, 228 and 270 kJ mole"1 for the Ca, Sr and Ba salts, respectively. The value for calcium formate is in good agreement with that obtained [292] for the decomposition of this solid dispersed in a pressed KBr disc. Under the latter conditions, concentrations of both reactant (HCOJ) and product (CO3") were determined by infrared measurements and their variation followed first-order kinetics. 

Iodine was determined by an iodometric titration adapted from White and Secor.(3) Instead of the normal Carius combustion, iodide was separated from the samples either by slurrying in 6M NaOH, or by stirring the sample with liquid sodium-potassium (NaK) alloy, followed by dissolving excess NaK in ethanol. Precipitated plutonium hydroxides were filtered. Iodine was determined in the filtrate by bromine oxidation to iodate in an acetate buffer solution, destruction of the excess bromine with formic acid, acidifying with SO, addition of excess KI solution, and titrating the liberated iodine with standard sodium thiosulfate. The precision of the iodine determination is estimated to be about 5% of the measured value, principally due to incomplete extraction of iodine from the sample. 

With this relationship for all samples was calculated from ninh This M is used for evaluating the reaction data. The ultracen rifuge (u.c measurements were carried out in a Spinco model E analytical ultracentrifuge, with 0.4% solutions in 90% formic acid containing 2.3 M KCl. By means of the sedimenta- ion diffusion equilibrium method of Scholte (13) we determine M, M and M. The buoyancy factor (1- vd = -0.086) necessary for tSe calculation of these molecular weights from ultracentrifugation data was measured by means of a PEER DMA/50 digital density meter. 

U.V. absorptions were measured on 0.5% solutions in 90% formic acid at 290 nm. 

This is illustrated by the TPD spectra of formate adsorbed on Cu(lOO). To prove that formate is a reaction intermediate in the synthesis of methanol from CO2 and H2, a Cu(lOO) surface was subjected to methanol synthesis conditions and the TPD spectra recorded (lower traces of Fig. 7.13). For comparison, the upper traces represent the decomposition of formate obtained by dosing formic acid on the surface. As both CO2 and H2 desorb at significantly lower temperatures than those of the peaks in Fig. 7.13, the measurements represent decomposition-limited desorptions. Hence, the fact that both decomposition profiles are identical is strong evidence that formate is present under methanol synthesis conditions. 

TLC analysis of oligomers was performed on Silica gel 60 aluminium sheet (Merk) using buthanol and formic acid (1 1.5) as solvent [26]. The dye reagent was prepared by dissolving 9.5 mg of 1,3 dihydroxynaphtalin (Aldrich) in 5 mL of ethanol/H2S04 mixture (1 0.05, V/V). The migration front (Rf) of each spot was measured and expressed as Rm, were ... 

The GC-MS techniques give much more chemical information than does measurement of only 8-OH-dGua. However, the hydrolysis and derivatization procedures are lengthy and tedious, and may destroy some modified bases, e.g. hydroxymethyluracil (Djuric etal., 1991). It has also been speculated that they might create artefacts, e.g. if the amounts of modified bases increase during the preparation procedures. Data surest that formic acid hydrolysis does not create additional 8-OH-Gua in DNA (Halliwell and Dizdaroglu, 1992) but the question is currently open as to whether the derivatization procedures might do so. 

The amounts of formaldehyde and formic acid have been measured for several Pt single crystals [Batista et al., 2003, 2004 Housmans et al., 2006 Wang and Baltruschat, 2007]. The fraction of methanol molecules oxidized to CO2 is about 20% at 0.60 V and 32% at 0.80 V, with formic acid and formaldehyde being the remaining oxidation products [Wang and Baltruschat, 2007]. 

Figure 8.17 Activities of Pt(l 1 l)-wML Pd electrodes from rotating disk electrode measurements, with corresponding ball models (a) electro-oxidation of formic acid in 0.1 M HCIO4 ...

While very limited data ate presented here, the kinetics of adsorption/decomposition of formic acid molecules [Rice et al., 2002] have been measured by BB-SFG, as shown in Fig. 12.14. A Pt(lll) electrode and a 0.1 M H2SO4 electrolyte containing 0.1 M formic acid were used. The families of spectra at 0.200, 0.025, and 0.225... 

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