Organic matter acidity

KEYWORDS Cadmium forms, organic matter, acid soils... 

Gamier, C., Mounier, S., and Benaim, J. Y. (2004). Influence of dissolved organic carbon content on modelling natural organic matter acid-base properties. Water Res. 38, 3685-3692. 

Membrane distillation - photocatalysis To solve the problem of membrane fouling observed in the pressure-driven membrane photoreactor, Mozia et al. [90] studied a new type of PMR in which photocatalysis was combined with a direct contact membrane distillation (DCMD). MD can be used for the preparation of ultrapure water or for the separation and concentration of organic matter, acids and salt solutions. In the M D the feed volatile components are separated by means of a porous hydrophobic membrane thanks to a vapor-pressure difference that acts as driving force and then they are condensed in cold distillate (distilled water), whereas the nonvolatile compounds were retained on the feed side. 

During combustion of organic matter, acids are formed from non-metallic oxides, mainly H2SO4, HNO, and HCl. They are collected in bomb washings with methyl red saturated deionized water and titrated with 0.0725 M Na2C03 to the methyl red endpoint as recommended in the Parr manual. Investigations showed that 4 J ( 1 cal) per ml NazCOj have to be subtracted from the observed heats of combustion Schroeder determined a mean acid correction of -0.33 % with sample masses of 0.10 g and of -0.14 % at 0.30 g in the semimicro bomb and of -0.57 % (5 mg) and - 0.31 % (20 mg) in the Phillipson type bomb. Acid corrections are less pronounced for plant than for animal matter and more important with the more accurate semimicro bomb as they form 20 to 30 % of the technique variations in this instrument [62]. 

The silver salts of most carboxylic acids are only sparingly soluble in cold water, and hence are readily prepared. Moreover they very rarely contain water of crystallisation, and therefore when dried can be analysed without further treatment. The analysis itself is simple, rapid and accurate, because gentle ignition of a weighed quantity of the silver salt in a crucible drives off the organic matter, leaving a residue of pure metallic silver. 

Organic matter Hot concentrated sulfuric acid plus a few drops of sodium or potassium nitrate solution. 

Nitric acid, fuming Organic matter, nonmetals, most metals, ammonia, chlorosulfonic acid, chromium trioxide, cyanides, dichromates, hydrazines, hydrides, HCN, HI, hydrogen sulflde, sulfur dioxide, sulfur halides, sulfuric acid, flammable liquids and gases... 

Peroxoacetic acid Acetic anhydride, oleflns, organic matter... 

Phosphorus trichloride Acetic acid, aluminum, chromyl dichloride, dimethylsulfoxide, hydroxylamine, lead dioxide, nitric acid, nitrous acid, organic matter, potassium, sodium water... 

Sodium peroxide Glacial acetic acid, acetic anhydride, aniline, benzene, benzaldehyde, carbon di-sulflde, diethyl ether, ethanol or methanol, ethylene glycol, ethyl acetate, furfural, glycerol, metals, methyl acetate, organic matter... 

In addition to the main acidulation reaction, other reactions also occur. Free calcium carbonate in the rock reacts with the acid to produce additional by-product calcium compounds and CO2 gas which causes foaming. Other mineral impurities, eg, Fe, Al, Mg, U, and organic matter, dissolve, the result being that the wet-process acid is highly impure. 

For many years fluorine has been deterrnined by the Willard-Winters method in which finely ground ore, after removal of organic matter, is distilled with 72% perchloric acid in glass apparatus. The distillate, a dilute solution of fluorosiUcic acid, is made alkaline to release fluoride ion, adjusted with monochloroacetic acid at pH 3.4, and titrated with thorium nitrate, using sodium a1i2arine sulfonate as indicator. 

Acid amide herbicides are nonionic and moderately retained by soils. The sorption of several acid amide herbicides has been investigated (369). Acetochlor [34256-82-1] is sorbed more than either alachlor or metolachlor, which are similarly sorbed by a variety of soils. Sorption of all the herbicides is well correlated to soil organic matter content. In a field lysimeter study, metolachlor has been found to be more mobile and persistent than alachlor (370) diphenamid [957-51-7] and napropamide [15299-99-2] have been found to be more readily leached (356). 

Sulfonylurea herbicides ate weak acids and, in general, ate not strongly sorbed to soils. Sorption of chlotsulfuton and metsulfuron—methyl is inversely related to soil pH (407) and is positively correlated to soil organic matter (408). 

In the absence of organic matter, silver nitrate is not photosensitive. It is easily reduced to silver metal by glucose, tartaric acid, formaldehyde, hydrazine, and sodium borohydride. 

In addition to the acid—base components shown in Figure 9, various organic acids are often found. Many of these acids are by-products of the atmospheric oxidation of organic matter released into the atmosphere. Of special interest are formic, acetic, oxaUc, and benzoic acids, which have been found in rainwater in concentrations occasionally exceeding a few micromoles per Hter. 

SuperchlorinationShock Treatment. Superchlorination or shock treatment of pool water is necessary since accumulation of organic matter, nitrogen compounds, and algae consumes free available chlorine and impedes disinfection. Reaction of chlorine with constituents of urine or perspiration (primarily NH" 4, amino acids, creatinine, uric acid, etc) produces chloramines (N—Cl compounds) which are poor disinfectants because they do not hydrolyze significantly to HOCl (19). For example, monochloramine (NH2CI) is only 1/280 as effective as HOCl against E. coli (20). 

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