Telluric acid analysis

Sodium selenopentathionate 3-hydrate, which was first isolated in 1949,1 is prepared by the reaction used by Norris and Fay2 for the iodometric analysis of selenious acid. Salts of telluropentathionic acid were also first isolated in 1949.3 The reaction utilized in their preparation was also discovered by Norris and Fay.2,4 Tellurous acid cannot be analyzed by a procedure analogous to that which Norris and Fay applied to the determination of selenious acid, because telluropentathionate is not indifferent to iodine but may be titrated directly with it 3... 

The first step in this reaction must be a reduction of telluric acid to tellurous acid. The tellurous acid subsequently forms the ortho ester. The constitution of the product was ascertained by a single crystal X-ray analysis. ... 

Among activated forms of amino acids, mixed anhydrides with inorganic phosphate or phosphate esters require a special discussion because they are universally involved in peptide biosynthesis through the ribosomal and non-ribosomal pathways. These mixed anhydrides have stimulated studies in prebiotic chemistry very early in the history of this field. Amino acyl adenylates 18c have been shown to polymerize in solution [159,160] and in the presence of clays [139]. However, their participation as major activated amino acid species to the prebiotic formation of peptides from amino acids is unlikely for at least two reasons. Firstly, amino acid adenylates that have a significant lifetime in aqueous solution become very unstable as soon as either CO2 or bicarbonate is present at millimolar concentration [137]. Lacey and coworkers [161] were therefore conduced to consider that CO2 was absent in the primitive atmosphere for aminoacyl adenylate to have a sufficient lifetime and then to allow for the emergence of the modern process of amino acid activation and of the translation apparatus. But this proposition is unlikely, as shown by the analysis of geological records in favor of CO2 contents in the atmosphere higher than present levels [128]. It is also in contradiction with most studies of the evolution of the atmosphere of telluric planets [30,32], Secondly, there is no prebiotic pathway available for adenylate formation and ATP proved to be inefficient in this reaction [162]. 

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