Sodium hazard

Early estimates of sodicity were based on sodium content. Because of the strong preference of most soil particles for divalent cations over monovalent cations, however, waters with high Na contents may still produce relatively low exchangeable Na levels in soils, if the Ca + Mg concentration is appreciable, 

Cation exchange equations contain the ratio of the monovalent cation concentrations to the square root of the divalent cation concentration, or the square of this ratio. The equation may involve ion activities rather than concentrations, and may include corrections for ion pairs. For most field practice, however, the ratios of total ion concentrations alone are sufficient. 

Workers at the U.S. Salinity Laboratory proposed the sodium adsorption ratio (SAR) to characterize the sodium status of irrigation waters and soil solutions  

The exchangeable sodium status of soils can be predicted quite well from the SAR and a Gapon-type exchange equation  

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Rhoades, J. D., D. B. Krueger, and M. J. Reed. 1968. The effect of soil-mineral weathering on the sodium hazard of irrigation waters. Soil Sci. Soc. Am. Proc. 32 643-647. 

Another property related to the sodium hazard of irrigation waters is the bicarbonate concentration. Bicarbonate toxicides associated with some waters generally arise from deficiencies of iron or other micronutrients caused by the resultant high pH. Precipitation of calcium carbonate from such waters,... 

Early workers used the residual sodium carbonate (RSC) to predict the tendency of calcium carbonate to precipitate from high-bicarbonate waters and thus create a sodium hazard. The RSC was defined as... 

Properties Wh. to It. yel. orthorhombic cryst. sol. in alcohol, benzene, ether, acetone, carbon disulfide, chloroform sol. 99 g/l in water insol. in pyridine, quinoline fumes in air m.w. 228.13 dens. 3.14 vapor pressure 1 mm Hg (49.2 C) m.p. 73 C b.p. 223.5 C ref. index 1.4600 Toxicology ACGIH TLV/TWA 0.5 mg (Sb)/m LD50 (oral, rat) 525 mg/kg mod. toxic by ing. human pulmonary effects by inh. irritant corrosive experimental reproductive effects mutation data reported TSCA listed Precaution DOT Corrosive material reacts violently with aluminum, potassium, sodium Hazardous Decomp. Prods. Heated to decomp., emits very toxic fumes of chlorine and antimony... 

Other sources of hazard arise from the handling of such chemicals as concentrated acids, alkalis, metallic sodium and bromine, and in working with such extremely poisonous substances as sodium and potassium cyanides. The special precautions to be observed will be indicated, where necessary, in the experiments in which the substances are employed, and will also be supplied by the demonstrator. The exercise of obvious precautions and cautious handling will in most cases reduce the danger to almost negligible proportions. Thus, if concentrated sulphuric acid should be accidentally spilled, it should be immediately washed with a liberal quantity of water or of a solution of a mild alkali. 

Since the principal hazard of contamination of acrolein is base-catalyzed polymerization, a "buffer" solution to shortstop such a polymerization is often employed for emergency addition to a reacting tank. A typical composition of this solution is 78% acetic acid, 15% water, and 7% hydroquinone. The acetic acid is the primary active ingredient. Water is added to depress the freezing point and to increase the solubiUty of hydroquinone. Hydroquinone (HQ) prevents free-radical polymerization. Such polymerization is not expected to be a safety hazard, but there is no reason to exclude HQ from the formulation. Sodium acetate may be included as well to stop polymerization by very strong acids. There is, however, a temperature rise when it is added to acrolein due to catalysis of the acetic acid-acrolein addition reaction. 

The first commercial production of fatty alcohol ia the 1930s employed the sodium reduction process usiug a methyl ester feedstock. The process was used ia plants constmcted up to about 1950, but it was expensive, hazardous, and complex. By about 1960 most of the sodium reduction plants had been replaced by those employing the catalytic hydrogenolysis process. Catalytic hydrogenation processes were investigated as early as the 1930s by a number of workers one of these is described ia reference 26. 

The importance of hydrolysis potential, ie, whether moisture or water is present, is illustrated by the following example. In the normal dermal toxicity test, namely dry product on dry animal skin, sodium borohydride was found to be nontoxic under the classification of the Federal Hazardous Substances Act. Furthermore, it was not a skin sensitizer. But on moist skin, severe irritation and bums resulted. 

Methanol does not pose an undue toxicity hazard if handled in weU-ventilated areas, and is rated as a slight health hazard by the National Fire Protection Association (NFPA). The TLV is 200 ppm with a STEL of 250 ppm, and the limit which is immediately dangerous to Hfe and health is 25,000 ppm. Accidental ingestion is immediately treated by inducing vomiting, followed by adrninistration of sodium bicarbonate. Rinsing with water is effective in treating external exposure. 

There are explosion hazards with phthahc anhydride, both as a dust or vapor in air and as a reactant. Table 11 presents explosion hazards resulting from phthahc anhydride dust or vapor (40,41). Preventative safeguards in handling sohd phthahc anhydride have been reported (15). Water, carbon dioxide, dry chemical, or foam may be used to extinguish the burning anhydride. Mixtures of phthahc anhydride with copper oxide, sodium nitrite, or nitric acid plus sulfuric acid above 80°C explode or react violently (39). 

Transportation and Disposal. Only highly alkaline forms of soluble sihcates are regulated by the U.S. Department of Transportation (DOT) as hazardous materials for transportation. When discarded, these ate classified as hazardous waste under the Resource Conservation and Recovery Act (RCRA). Typical members of this class are sodium sihcate solutions having sihca-to-alkah ratios of less than 1.6 and sodium sihcate powders with ratios of less than 1.0. In the recommended treatment and disposal method, the soluble sihcates are neutralized with aqueous acid (6 Af or equivalent), and the resulting sihca gel is disposed of according to local, state, and federal regulations. The neutral hquid, a salt solution, can be flushed iato sewer systems (86). 

The Shoe grouting system is considered nonhazardous and nonpolluting. Sodium silicate is essentially nontoxic. Formamide is toxic and corrosive, but does not present a serious hazard if normal safety precautions are followed. Shoe chemical grout materials are two to five times more expensive than Portland cement, depending on the sodium silicate to formamide concentration ratios. Installed costs are generally more similar to those for cement grouts. 

Sodium Bisulfite, CHRIS Hazardous Chemical Data, Coast Guard, U.S. Dept, of Transportation, Washington, D.C., data sheet revised 1978. Treatment of Chromium Waste Eiquors, General Chemical Corp., Claymont, Del., 1989. 

The most important hazard ia the manufacturiag of xanthates is the use of carbon disulfide (qv) because of its low flash poiat, ignition temperature, and its toxicity. A report on the manufacture of sodium ethyl xanthate at Keimecott Nevada Mines Division discusses the various safety problems and the design of a faciUty (81). A plant layout and a description of the reagent preparations are also given. 

Liquid bromine produces a mild cooling sensation on first contact with the skin. This is followed by a sensation of heat. If bromine is not removed immediately by flooding with water, the skin becomes red and finally brown, resulting in a deep bum that heals slowly. Contact with concentrated vapor can also cause bums and bflsters. Eor very small areas of contact in the laboratory, a 10% solution of sodium thiosulfate in water can neutralize bromine and such a solution should be available when working with bromine. Bromine is especially hazardous to the tissues of the eyes where severely painfiil and destmctive bums may result from contact with either Hquid or concentrated vapor. Ingestion causes severe bums to the gastrointestinal tract (62,63). 

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