Mercury preparations criticisms

In the sixteenth century, Paracelsus added some mineral compounds to the Materia Medica and powerful medicines were obtained from the ores of metals like mercury and antimony by alchemical processes. Antimony has a very long history in medicine, but it came into greater prominence at a critical time in the sixteenth century when syphilis, then a new killer disease, was rapidly spreading across Europe.5 Paracelsus mercurial preparations were also effective, although their poisonous... 

Pollman CD, Porcella DB, Engstrom DR. (In preparation). Assessment of trends in mercury-related data sets and critical assessment of cause and effect for trends in mercury concentrations in Florida biota phase II. 

The calibration step is critical. In general, the basic principle is always to use two independent calibration solutions. One of these can be made from pure chemicals, for example, Hg° dissolved in concentrated HN03 and diluted to the appropriate volume. For mercury, commercially available standard solutions can be used, but regular checks against a reference standard must be made. Certified reference materials (CRFs) should be used if available, but reference standards can also be prepared from pure mercury compounds. In the absence of aqueous-phase reference standards, solid materials may be used. 

Four different thiourea complexes of mercury(II) are easily prepared from aqueous solutions of mercury(II) chloride and thiourea. The proportions of reagents are not as critical as the temperature, elevation of which results in precipitation of black mercury (II) sulfide. Electrical conductivities and freezing points provide evidence for the constitution of the complexes. 

Arnold s demonstration" that oxocarbenium ion intermediates can be formed through homobenzylic ether radical cation fragmentation reactions shows that mild oxidizing conditions can be used to prepare important reactive intermediates. Scheme 3.2 illustrates a critical observation in the development of an explanatory model that allows for the application of radical cation fragmentation reactions in complex molecule synthesis. In Arnold s seminal work, cleavage of the benzylic carbon-carbon bond in substrate 1 is promoted by 1,4-dicyanobenzene (DCB) with photoirradiation by a medium-pressure mercury vapor lamp. With methanol as the solvent, the resulting products were diphenylmethane (2) and formaldehyde dimethyl acetal (3). 

The chemical preparation step in which the protein is isolated, purified, and crystallized is critical in that the protein preparation must be chemically homogeneous otherwise, the resulting disorder will muddle the electron-density map. The preparation of isomorphous derivatives by soaking native protein crystals in various mercury, platinum, lead, uranium, etc., solutions also is critical since several crystals of each derivative are required for x-ray data collection (because of irradiation damage) and all the crystals should have the same heavy-atom distribution and concentration. The protein structure documentation should provide evidence that the preparative protein chemistry is sound. 

The book edited by Ives and Janz [1 ] and more recently that by Bard, Parsons, and Jordan [2] contain both theoretical and practical aspects related to reference electrodes. Preparation, application and limitations of various types of reference electrodes such as the hydrogen electrode, the calomel and other mercury-mercurous salt electrodes, the silver-silver halide electrodes, and sulfide and sulfate electrodes are covered and general reference to these excellent critical reviews is recommended. 

In response to a criticism of his findings, Boyle performed an experiment to show that air could be compressed to a pressure greater than that of the atmosphere. First, he prepared a glass J-tube with the short end sealed off and the long end left open. Then, he poured mercury into the tube, making sure that the levels in the two ends were the same. He then let air travel freely between the ends to ensure that each column was at atmospheric pressure. 

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