Fixative chemistry fixation

Model studies in nitrogen fixation and cobalamin chemistry Nitrogen-fixing plants... 

In 1991 Shi et al. published their seminal observation that high-temperature incubation of formalin-fixed, paraffin-embedded (FFPE) tissue sections in buffers for short periods led to improved immunohistochemical staining.1 However, more than 15 years later, heat-induced antigen retrieval (AR) remains largely an empirical procedure, requiring the optimization of several critical parameters by trial and error.2,3 Further improvements in AR will require an in-depth understanding of the chemistry of formaldehyde fixation and the molecular mechanism(s) underlying the AR method. 

Lavoisier began his scientific career just about the time that pneumatic chemistry became widely recognized as important, so it is not surprising that he saw in this a great opportunity. Lavoisier had attended the chemistry lectures of Rouelle, and there witnessed the phenomena of aerial fixation and liberation, especially in effervescence. Before he was thirty years old, he initiated a systematic investigation of the manner in which gases were fixed into and liberated from solid bodies, the importance of which... 

In addition to the classical Haber process, recent efforts have been directed to finding an alternative economic process for fixing N2 to meet-increasing demands for nitrogeneous fertilizers and others industrial requirements. Thus, numerous results of the recent advances in the Chemistry of Nitrogen Fixation via transition metal complexes have reported (Chatt et al. 1978 A treatise on dinitrogen fixation , Hardy ed. 1979 New trends in the chemistry of nitrogen fixation , Chatt ed.1980). 

Homberg used this axiom in chemistry to classify salts by the ana-lytic/synthetic procedures. Acids combined with fixed alkali salts or lix-ivial salts, earthly or metallic alkalis, and metals to produce mixed salts [sels mixtes], also called middle salts [sels moyens], which were in part fixed, in part volatile.Homberg characterized the production of middle salts as fixation of volatility rather than as neutralization of acidity, diverging somewhat from Lemery s definition of the term. The attention to the physical rather than the chemical characteristics of substances and their reactions set him apart from most chemists. Applying the physical criteria of volatility and fixedness, he placed sal ammoniacs (another commonly accepted salted salt ) in a separate category because they had two volatile components, which rendered them volatile ... 

Phosphate chemistry in soils has been studied more intensively than that of any other element save nitrogen. Phosphate added to soils is first adsorbed quickly and is later fixed into increasingly less soluble states as time increases. Despite this great effort, quantitative predictions of phosphate concentrations in soil solutions are poor and no techniques have been devised to release the large amounts of unavailable phosphate in soils, nor to prevent fixation of fertilizer phosphate by soils. The uncertainties about soil phosphate chemistry and the difficulty of increasing phos-... 

With the reaction per se worked out fairly well, we had occasion to develop this chemistry into what one might call a catalytic process, probably better described at this point as a cycle (9). This process is conceptually and operationally very simple, as demonstrated by Mr. Greeley (Table III) (9). In a normal nitrogen fixation reaction, after liberation of ammonia by the addition of alcohol, it is possible to add more sodium naphthalenide or sodium zero and in eflFect regenerate the nitrogen-fixing... 

The Fixed Nitrogen Research Laboratory, Bureau Of Chemistry and Soils, Dep.uitment of Agriculture, has compiled a very extensive unpublished bibliography on nitrogen fixation which may be consulted In its Library at Washington, D. C,... 

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