Group 4 Insoluble Phosphates

At this stage, all of the cations have precipitated except those belonging to the alkali metal family (group 1A in the periodic table) and the alkaline earth metal family (group 2 A in the periodic table). The alkaline earth metal cations can be precipitated by adding (NH4)2HP04 to the solution, causing Mg, Ca, and Ba to precipitate as metal phosphates, which are separated from the liquid. 

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Group 4. Insoluble phosphates At this point the solution contains only metal ions from groups lA and 2A of the periodic table. Adding (NH4)2HP04 to a basic solution precipitates the group 2A elements Mg, Ca, Sr ", and Ba " because these metals form insoluble phosphates. 

The thermochemical radius of phosphate ion is 238 pm. Thus smaller cations like Na and K would give soluble phosphates, whereas larger cations of heavier Group 2 elements (i.e., Ba ) would likely produce insoluble phosphates. 

Group 5. The alkali metal ions and The ions that remain after removing the insoluble phosphates are tested for individually. A flame test can be used to determine the presence of KT, for example, because the flame turns a characteristic violet color if is present. 

P04 Most phosphates are insoluble. Group lA phosphates, (NH4)3P04... 

The solubility of the barium salts depends on the number of acid groups and therefore on the pH of the solution. At neutral pH where the primary and secondary acid groups of phosphate are dissociated, inorganic phosphate and the sugar diphosphates form water-insoluble barium salts. At a pH of about 4 the secondary acid groups are not appreciably dissociated so that the salts become water-soluble. 

Zinc phosphate, Zn2(P0 2> forms the basis of a group of dental cements. Chromium and zinc phosphates are utilized in some metal-treating appHcations to provide corrosion protection and improved paint adhesion. Cobalt(II) phosphate octahydrate [10294-50-5] Co2(P0 2 8H20, is a lavender-colored substance used as a pigment in certain paints and ceramics. Copper phosphates exhibit bioactivity and are used as insecticides and fungicides. Zinc, lead, and silver phosphates are utilized in the production of specialty glasses. The phosphate salts of heavy metals such as Pb, Cr, and Cu, are extremely water insoluble. 

Multilayers of Diphosphates. One way to find surface reactions that may lead to the formation of SAMs is to look for reactions that result in an insoluble salt. This is the case for phosphate monolayers, based on their highly insoluble salts with tetravalent transition metal ions. In these salts, the phosphates form layer stmctures, one OH group sticking to either side. Thus, replacing the OH with an alkyl chain to form the alkyl phosphonic acid was expected to result in a bilayer stmcture with alkyl chains extending from both sides of the metal phosphate sheet (335). When zirconium (TV) is used the distance between next neighbor alkyl chains is - 0.53 nm, which forces either chain disorder or chain tilt so that VDW attractive interactions can be reestablished. 

Lithium orthophosphates are unimportant and differ from the other alkali metal phosphates in being insoluble. At least 10 crystalline hydrated or anhydrous sodium orthophosphates are known and these can be grouped into three series ... 

SOLUTION The mixed solution will contain Na+, P043 , Pb24, and NO, ions. All nitrates and all compounds of Group 1 metals are soluble, but phosphates of other elements are generally insoluble. Hence, we can predict that Pb2+ and P043- ions will form an insoluble compound and that lead(II) phosphate, Pb,(P04)2, will precipitate ... 

This is illustrated in Scheme VI. The protected glyceryl derivatives are insoluble in aqueous media and appear to be hydrolytically stable. The deprotected species (structure 27) is water-soluble and hydrolyzes in aqueous media at neutral pH at 37°C to give glycerol, phosphate, and ammonia. The free hydroxyl units of the deprotected polymer provide sites for the covalent attachment of drug molecules. Water insolubility can be imparted by the use of appropriate hydro-phobic cosubstituent groups to generate solid, erodible materials. 

Dissolve the peptide containing an N-terminal serine or threonine group at a concentration of at least 2mg/ml in 0.04 M sodium phosphate, pH 7.0. Higher concentrations of peptides or proteins may be used without modification to the rest of the protocol, because the amount of periodate used in the reaction is in sufficient molar excess, even when low-molecular-weight peptides are being oxidized. Peptides that are initially insoluble... 

Naturally occurring monoterpene alcohols were heated in water without prior deriva-tization with typical biological water-solubilizing groups such as phosphates or glyco-sidic units. Biomimetic reactions that normally would be acid-catalyzed, proceeded on the underivatized compounds in the absence of added acidulant. Cooling of the mixtures rendered the products insoluble, readily isolable and the aqueous phase did not require neutralization before workup. 

Hall et at. 300) described an indirect method for the determination of urinary a-amino nitrogen. Copper is solubilized from insoluble copper phosphate by complexing with a-amino groups at slightly alkaline pH. The remaining copper phosphate is removed by filtration and the filtrate is diluted 1 10 or 1 20 with 0. IN hydrochloric acid to measure the dissolved copper by atomic absorption. Standards are prepared using alanine. 

Most carbonates (CO2 ) and phosphates (POf-) are insoluble except those of Group IA metals and the ammonium ion. 

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