Formic acid estimation

The interaal skeletal bonds of the squid Sepia saculenta) contain chitin. Viscometric measurements of the polysaccharide dissolved in formic acid estimate the molecular weight to be 4 x 10 . 

Method, Formaldehyde may be estimated in solution by oxidising it to formic acid by means of a known quantity (in excess) of iodine dissolved in a excess of NaOH solution. The oxidation is, in effect, carried out by the odium hypo-iodite formed by the action of the iodine on the alkali, the formic cid being then neutralised by the alkali present ... 

Attention must be paid to the fact that formic acid, particularly at higher concentrations and temperatures, can, on storage, slowly decompose to Hberate carbon monoxide. This can lead to safety ha2ards from the ensuing buHdup ia pressure or from the toxicity of carboa moaoxide. It has beea estimated that, ia the abseace of leakage, a full 2.5-L bottle of formic acid could develop a pressure of over 700 kPa (7 atm) over a period of oae year at... 

Estimate the rate constants for the acid-base equilibrium of formic acid in water. 

The only practical method which appears to give good results depends on the fact that when a mixture of geraniol and citronellol are heated with strong formic acid (100 per cent.) the geraniol is decomposed and the citronellol is converted into citronellyl formate. The estimation is best carried out as follows... 

Although benzene-sulfonic acid, CnITsSChH, is a strong acid in aqueous solution, it is not completely dissociated in formic acid solution. In a 0.1-molal solution the degree of dissociation was estimated at 60 per cent.2 This is comparable with the dissociation of HIOs in aqueous solution and is compatible with J = 0.14 electron-volt for the formation of (HCOOH2)+. Using this value the level has been included in Fig. 65. 

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. 

These incubations are often carried out at 37 °C for 1-2 h. At different time points, 20-200 /aL of incubation mixture is withdrawn from each incubation and mixed with equal volume of ice-cold acetonitrile by vortexing. For preparation of acyl glucuronide, ice-cold acetonitrile containing 1% of formic acid is used to minimize acyl-migration [3,14]. After centrifugation at 13 000 rpm for 5-15 min, the supernatant (10-30 /aU) is analyzed by high-performance liquid chromatography (HPUC)-UV-MS. The metabolite of interest is identified based on HPLC retention time, UV spectrum and MS/MS data. Conversion yield is estimated based on UV absorption peak areas. A suitable in vitro enzyme system for scale-up is then... 

The density of the mixture is 820 kg/m3 and this may be assumed constant throughout. Estimate the volume of the reactor required to convert 70 per cent of the formic acid to the ester. 

A. T. James and A. J. P. Martin. Gas-Liquid Partition Chromatography The Separation and Micro-Estimation of Volatile Fatty Acids from Formic Acid to Dodecanoic Acid. Biochem. J., 50(1952) 679-690. 

D-xylopyranose units. This structural concept is substantiated by estimation of the formic acid obtained when the xylan is oxidized by periodate ions. On hydrolysis of the fully oxidized xylan there is obtained a small amount of D-xylose which presumably occupied the branch points in the polysaccharide and consequently was protected from periodate oxidation by possessing no adjacent free hydroxyl groups. 

One molecule of periodic acid is used for each pair of adjacent hydroxyl groups. Thus by estimating formaldehyde and formic acid and the amount of periodic acid consumed, it is possible to know the number of free adjacent hydroxyl groups. However, if the sugar is in the... 

Solid-state nmr spectroscopy on a single crystal of KHF2 was interpreted in terms of a centred proton with f = 113.8 pm (Pratt and Smith, 1975). The same conclusion was reached for the other alkali-metal bifluorides (Ludman et al., 1977) and the displacement of the proton from the midpoint was estimated to be less than 60 pm. This technique cannot distinguish between a single minimum and a double minimum with fast transfer. Fluorine-19 nmr spectroscopy has been used to study solutions of HFj" in formic acid, and the data have been interpreted in terms of equilibria involving F , HF, HF2 and H2F2 (Coulombeau, 1977). 

Photolytic. Irradiation of vinyl chloride in the presence of nitrogen dioxide for 160 min produced formic acid, HCl, carbon monoxide, formaldehyde, ozone, and trace amounts of formyl chloride and nitric acid. In the presence of ozone, however, vinyl chloride photooxidized to carbon monoxide, formaldehyde, formic acid, and small amounts of HCl (Gay et al, 1976). Reported photooxidation products in the troposphere include hydrogen chloride and/or formyl chloride (U.S. EPA, 1985). In the presence of moisture, formyl chloride will decompose to carbon monoxide and HCl (Morrison and Boyd, 1971). Vinyl chloride reacts rapidly with OH radicals in the atmosphere. Based on a reaction rate of 6.6 x lO" cmVmolecule-sec, the estimated half-life for this reaction at 299 K is 1.5 d (Perry et al., 1977). Vinyl chloride reacts also with ozone and NO3 in the gas-phase. Sanhueza et al. (1976) reported a rate constant of 6.5 x 10 cmVmolecule-sec for the reaction with OH radicals in air at 295 K. Atkinson et al. (1988) reported a rate constant of 4.45 X 10cmVmolecule-sec for the reaction with NO3 radicals in air at 298 K. 

The detection limit for a 100 yL sample injection volume at 30 ymhos full scale sensitivity is estimated at 0.5 yg/mL. Concentration of samples by freeze-drying affords better detection limits with minimal loss of formic acid. Acetic and carbonic acids are also analyzable under these conditions. 

If these considerations are correct and the observed scattering spectrum of formic acid crystal in the 255-170 cm-1 is really due to the hydrogen bond, one can try to estimate the value of the dissociation energy D of the hydrogen bond in the crystal. We assume that one can make use of the formula for a diatomic molecule ... 

Crunden and Hudson80, by comparison of solvolysis rates in formic acid and aqueous acetone (although the same authors have stated that this may be coincidental), obtained a value of 40% SN1 participation in aqueous acetone (65%) they also estimated the contribution of the SN1 route to the solvolysis of substituted benzoyl halides (Table 6). It must, however, be emphasized that the nature of the intermediate trapped in the work of Gold et al81 could either be the acylium ion RCO+ or the hydrated acylium ion [RC0H20]+. 

This acid can be estimated by reduction of mercuric chloride (a) volu-metrically (Abs., 1875, 1051), (b) gravimetrically (Abs., 1923, 95), or by reduction of potassium permanganate (Abs., 1906, 907). In presence of homologues it can be estimated by the method given in Abs., 1912, 499, the total acidity being determined by titration with alkali and the formic acid by reduction of permanganate. 

Their main results may be summarized as follows. The periodic acid oxidation of polyols afforded a method for quantitative determination of these compounds, and it was demonstrated that the first reaction products are carbonyl compounds, themselves in turn degraded from their reducing end. After complete oxidation, it is possible to make an estimate of the consumption of oxidant, as well as of the formic acid and formaldehyde that are produced. The monosaccharides are attacked preferentially at the neigh-... 

Detection and Estimation of Preservatives.—The antiseptics commonly tested for in meat are formaldehyde, formic acid, boric acid and fluorides. The analytical methods used for the detection of these and other antiseptics are given later (see Sausages). 

The main phase of reaction of pine kraft lignin with formaldehyde proceeds at almost constant pH (Figure 3). The extent of Cannizzaro reaction is insignificant since it can be estimated from the formic acid content. The formation of phenol alcohols (as determined by FeCl3-color reaction) reached its peak after 2 hours, and the stability is rather high even after a day. 

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