AQUA method

Method- 3. From platinum metal or platinum residues. Dissolve the platinum metal or platinum residues in aqua regia, evaporate just to dryness several times with concentrated hydrochloric acid, dissolve the final residue in a httle water and precipitate as ammonium chloro-platinate with excess of saturated ammonium chloride solution. Filter and dry the precipitate at 100°. Then proceed according to Method 1. 

The PGM concentrate is attacked with aqua regia to dissolve gold, platinum, and palladium. The more insoluble metals, iridium, rhodium, mthenium, and osmium remain as a residue. Gold is recovered from the aqua regia solution either by reduction to the metallic form with ferrous salts or by solvent-extraction methods. The solution is then treated with ammonium chloride to produce a precipitate of ammonium hexachloroplatinate(IV),... 

The l ,J -DBFOX/Ph-transition metal aqua complex catalysts should be suitable for the further applications to conjugate addition reactions of carbon nucleophiles [90-92]. What we challenged is the double activation method as a new methodology of catalyzed asymmetric reactions. Therein donor and acceptor molecules are both activated by achiral Lewis amines and chiral Lewis acids, respectively the chiral Lewis acid catalysts used in this reaction are J ,J -DBFOX/Ph-transition metal aqua complexes. 

We employed malononitrile and l-crotonoyl-3,5-dimethylpyrazole as donor and acceptor molecules, respectively. We have found that this reaction at room temperature in chloroform can be effectively catalyzed by the J ,J -DBFOX/Ph-nick-el(II) and -zinc(II) complexes in the absence of Lewis bases leading to l-(4,4-dicya-no-3-methylbutanoyl)-3,5-dimethylpyrazole in a good chemical yield and enantio-selectivity (Scheme 7.47). However, copper(II), iron(II), and titanium complexes were not effective at all, either the catalytic activity or the enantioselectivity being not sufficient. With the J ,J -DBFOX/Ph-nickel(II) aqua complex in hand as the most reactive catalyst, we then investigated the double activation method by using this catalyst. 

If only platinum metal is available this is dissolved in aqua regia and evaporated to dryness several times with hydrochloric acid, until free from nitrates (Note 9) and the product purified according lo the method of Wichers. 

Determination of palladium with dimethylglyoxime Discussion. This is one of the best methods for the determination of the element. Gold must be absent, for it precipitates as the metal even from cold solutions. The platinum metals do not, in general, interfere but moderate amounts of platinum may cause a little contamination of the precipitate, and with large amounts a second precipitation is desirable. The precipitate is decomposed by digestion on the water bath with a little aqua regia, and diluted with an equal volume of... 

Apparent indicator constant 264, 267 Apparent stability constant 59 Aqua regia 111 Arc alternating current, 764 direct current, 763, 771 sensitivities of elements, (T), 766 Aromatic hydrocarbons analysis of binary mixtures, 715 Arsenates, D. of (ti) 357 Arsenic, D. of as silver arsenate, (ti) 357 as trisulphide, (g) 448 by iodine, (am) 634, (ti) 397 by molybdenum blue method, (s) 681 by potassium bromate, (ti) 406 by potassium iodate, (ti) 401 in presence of antimony, (s) 724 Arsenic(III) oxide as primary standard, 261... 

A migration test was developed to simulate human exposure patterns. 5 g of rubber material was cut into 1-2 mm stripes and then immersed in 20 ml of standard test solution of artificial saliva (4.2 g NaHC03, 0.2 g K2CO3, 0.5 g NaCl, 0.03 g NaNO, ad 1000 ml with aqua dest.j. After 24 h incubation at 40 C volatile nitrosamines were determined in an aliquot and determined after destination with a standard technique (GC-TEA-method). 

Ahlgren, RM. Economic Production of Boiler Water through Membrane Methods, pamphlet published by Aqua-Chem Inc., Waukesha, 1970. 

Selective cleavage of peptides and proteins is an important procedure in biochemistry and molecular biology. The half-life for the uncatalyzed hydrolysis of amide bonds is 350 500 years at room temperature and pH 4 8. Clearly, efficient methods of cleavage are needed. Despite their great catalytic power and selectivity to sequence, proteinases have some disadvantages. Peptides 420,423,424,426 an(j proteins428 429 can be hydrolytically cleaved near histidine and methionine residues with several palladium(II) aqua complexes, often with catalytic turnover. 

Two commercial partial extraction techniques improve anomaly contrast in B horizon soil samples compared to aqua regia-ICPMS for Cu and Au. However, whereas the MMIsm and Bio LeachSM Cu profiles are similar, the MMIsm Au signal is much larger than that for Bio LeachSM. Analysis of samples at different depths down the B soil horizon profile indicates that the geochemical response from these methods is depth dependant. 

Methods and Results At 15 sites along a 1000 m transect across the Talbot deposit, soil profiles were sampled in 10 cm depth intervals, up to 50 cm. The <250 pm (silt + clay) and <2pm (clay) fractions of the soil samples were analysed using an aqua regia digestion and ICP-MS measurement of 53 elements. 

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