Precipitation of barium chromate in the presence of strontium and lead by complexation followed by volatilization of ammonia

Cation-release is used to precipitate barium chromate from homogeneous solution in the presence of lead and strontium. MEDTA or DCTA is added to complex the metal ions at pH 10.3 (adjusted with ammonia). On heating, the ammonia slowly volatilizes and the consequent increases in acidity releases the metal ion bound in the least stable chelate (barium). Precipitation is about 99.3-99.7% complete at pH 6.7-6.8, with less than 0.1% co-precipitation of lead or strontium. Lower pH values can be attained by volatilizing acetic or hydrochloric acid into the solution in a closed system.     

Precipitation of barium chromate from homogeneous solution using complexation and replacement A separation of barium from relatively large amounts of strontium and lead

A new procedure is presented that efficiently separates barium from relatively large amounts of strontium and lead. The barium is precipitated as the chromate from a solution in which the multivalent cations are complexed with EDTA. The barium ions are homogeneously released in solution when magnesium ions are slowly introduced into the solution. The magnesium ions gradually replace the barium ions from their EDTA complexes, bringing about a precipitation of barium chromate from homogeneous solution.

This slow formation of barium chromate crystals holds co-precipitation to a minimum and produces crystals that are easily filtered and washed. More than 99.7% of the barium can be precipitated as the chromate, with less than 0.6% of the strontium, when the two ions are in equal molar concentration.     

Realizability and inscribability for simplicial polytopes via nonlinear optimization

We consider the problem of screening where a seller puts up for sale an indivisible good, and a buyer with a valuation unknown to the seller wishes to acquire the good. We assume that the buyer valuations are represented as discrete types drawn from some distribution, which is also unknown to the seller. The seller is averse to possible mis-specification of types distribution, and considers the unknown type density as member of an ambiguity set and seeks an optimal pricing mechanism in a worst case sense. We specify four choices for the ambiguity set and derive the optimal mechanism in each case.