Digestion, mixed-acid

Nitrophosphate fertilizer is made by digesting phosphate rock with nitric acid. This is the nitrophosphate route leading to NPK fertilizers as in the mixed-acid route, potassium and other salts are added during the process. The resulting solution is cooled to precipitate calcium nitrate, which is removed by filtration methods. The filtrate is neutralized with ammonia, and the solution is evaporated to reduce the water content. The process of prilling may follow. The calcium nitrate filter cake can be further treated to produce a calcium nitrate fertilizer, pure calcium nitrate, or ammonium nitrate and calcium carbonate. 

Nitric Acid and Organic Matter. The use of the mixed acids to digest organic matter may result in explosions. Explosions with vegetable oil,19 milk, calcium oxalate precipitates from plants,21 rat carcasses,22 finely ground plant material,21 and animal tissues21 have been documented. 

The choice of solvent in a microwave-assisted sample treatment is a direct function of the type of treatment used. Thus, digestion and hydrolysis are best done with aqueous solutions of pure or mixed acids, whereas selective extraction of organic compounds from a sample matrix usually requires an organic solvent. 

Solid samples (total) Introduction of a slurry of sample in nitric acid into FIA system using on-line microwave digestion, mix with tin(ll) chloride to form elemental mercury CV-AFS 0.09 ng/g 84-108 (2.9-4% RSD) Morales-Rubio et al. 1995... 

Wash water, tank mixes, Acid digestion in nitric acid or nitric ICP-AES (measured as 0.020mg/L No data Headley et al. 1996 ... 

When Carroll (1958) fed fatty acids as the methyl or ethyl esters, these esters were more efficiently absorbed than the free fatty acids by the rat. However, for fatty acids in the form of triglycerides (TG) the effect was opposite for saturated and monounsaturated fatty acids. A saturated TG was less digestible than the fatty acid itself, while a TG composed of a monounsaturated fatty acid was absorbed better than its free fatty acid (Carroll and Richards, 1958). Triglyceride fatty acids also influence absorption, particularly with the poorly digested fatty acids. For example, the absorption coefficient of erucic acid was increased from 72% when fed as ethyl erucate to 80% when ethyl erucate was mixed with soybean oil (Ziemlanski et al., 1973a). Even the absorption of 22 1 in HEAR oil was improved by mixing... 

Phosphorus analysis is usually carried out after perchloric acid digestion (care ) by the method of Bartlett (1959) (Section 6.2.15). Various new methods have been developed more recently, none of which has any distinct advantage over Bartlett s. However, for small samples a mixed acid method has been recommended and this may be used for routine analysis (cf. Cook and Daughton, 1981). 

Silicic acid (Si02) Decomplexing or depolymerization directly after sampling by adding the water sample to a digestion mix of perchloric and... 

Currently, many routine testing laboratories still determine only total tin concentrations in samples. This analysis typically involves complete digestion of the sample in a mixed acid media or alkali fusion of the material. Alkali fusion with compounds such as... 

Most assays for thallium in blood require hemolysis by detergent, followed by chelation with a dithiocarbamate, and extraction into MIBK [34]. The organic extract is then also assayed by either flameless AAS or DPASV. Typically, 5 mL of heparinized blood is mixed with 1 mL of 2% DDC and Triton X-100, followed by extraction with 2-5 mL of MIBK [16,21,95]. Recent modification of graphite furnace AAS methods allows for detection limits in whole blood or plasma as low as 1.0 and 0.7 p,g/liter, respectively [44], Determination of thallium in tissue requires digestion by acid before treatment. Typically 5 g of wet tissue is digested with 10 mL of a 3 1 1 mixture of nitric/perchloric/sulfuric acids [21]. 

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