Acidity constants of benzidine in aqueous solutions

Thermodynamic acidity constants have been measured over the temperature range 5-50� for aqueous solutions of sodium 4?-dimethylaminoazobenzene- 4-sulphonate (methyl orange) and sodium 4?-dimethylaminoazobenzene-2- sulphonate (ortho-methyl orange). From these data values of the standard enthalpy, entropy, and heat capacity changes have been calculated for these compounds. These results are discussed in conjunction with previous spectrophotometric and other data with reference to the nature of the equilibrium systems involved in these protonation reactions. It is concluded that existing evidence does not allow an unequivocal assignment of the sites of protonation of these and related molecules.

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Studies of the rate of inversion of sucrose in aqueous solutions of some strongly dissociated acids. Part II. Acidity constants for acetylenedicarboxylic and propiolic acids

Journal of the Chemical Society Perkin Transactions 2 ◽

10.1039/p29730000102 ◽

1973 ◽

pp. 102 ◽

Cited By ~ 1

Author(s):

A. D. Pethybridge

Keyword(s):

Aqueous Solutions ◽

Acidity Constants

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A SPECTROPHOTOMETRIC REEXAMINATION OF THE SPECTRA AND STABILITIES OF THE IRON (III) – TIRON COMPLEXES

Canadian Journal of Chemistry ◽

10.1139/v64-284 ◽

1964 ◽

Vol 42 (8) ◽

pp. 1917-1927 ◽

Cited By ~ 22

Author(s):

W. A. E. McBryde

Keyword(s):

Aqueous Solutions ◽

Stability Constants ◽

Equilibrium Constants ◽

Sodium Perchlorate ◽

Potassium Nitrate ◽

Low Ph ◽

Exact Nature ◽

Simple Complex ◽

Acidity Constants ◽

The Stability

Variations in the spectra of the aqueous solutions of the iron (III) – sodium catechol disulphonate (Tiron) complexes may be interpreted in relation to pH of the solutions to show which complexes are present at any chosen pH. With this knowledge it is possible in this system to evaluate equilibrium constants for the formation of each complex in turn. Combining these with separately determined acidity constants for Tiron, the stability constants of the complexes may be calculated. These have been determined for background solutions of potassium nitrate or sodium perchlorate each at three different concentrations, and for three different ratios of reagent to metal. Averages of a number of determinations made under these conditions are given in Table III of the paper. The constant K1 in perchlorate media shows an unmistakable dependence suggestive of the existence of a protonated species at low pH as well as the simple complex ML. However, there is some ambiguity in the interpretation of the results so that the exact nature of the protonated complex cannot be decided.

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Ultrathin frozen sections of yeast without aldehyde prefixation

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100081152 ◽

1978 ◽

Vol 36 (2) ◽

pp. 58-59

Author(s):

K. J. Böhm ◽

a. E. Unger

Keyword(s):

Aqueous Solutions ◽

Biological Material ◽

Yeast Cells ◽

Frozen Sections ◽

Good Preservation ◽

Ultrathin Frozen Sections

During the last years it was shown that also by means of cryo-ultra-microtomy a good preservation of substructural details of biological material was possible. However the specimen generally was prefixed in these cases with aldehydes.Preparing ultrathin frozen sections of chemically non-prefixed material commonly was linked up to considerable technical and manual expense and the results were not always satisfying. Furthermore, it seems to be impossible to carry out cytochemical investigations by means of treating sections of unfixed biological material with aqueous solutions.We therefore tried to overcome these difficulties by preparing yeast cells (S. cerevisiae) in the following manner:

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Imaging polymers, proteins and dna in aqueous solutions with the atomic force microscope

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100152136 ◽

1989 ◽

Vol 47 ◽

pp. 32-33

Author(s):

S.A.C. Gould ◽

B. Drake ◽

C.B. Prater ◽

A.L. Weisenhorn ◽

S.M. Lindsay ◽

...

Keyword(s):

Amino Acids ◽

Dna Sequencing ◽

Aqueous Solutions ◽

Atomic Force Microscope ◽

Piezoelectric Crystal ◽

Atomic Force ◽

Structure Of Molecules ◽

Optical Lever

The atomic force microscope (AFM) is an instrument that can be used to image many samples of interest in biology and medicine. Images of polymerized amino acids, polyalanine and polyphenylalanine demonstrate the potential of the AFM for revealing the structure of molecules. Images of the protein fibrinogen which agree with TEM images demonstrate that the AFM can provide topographical data on larger molecules. Finally, images of DNA suggest the AFM may soon provide an easier and faster technique for DNA sequencing.The AFM consists of a microfabricated SiO2 triangular shaped cantilever with a diamond tip affixed at the elbow to act as a probe. The sample is mounted on a electronically driven piezoelectric crystal. It is then placed in contact with the tip and scanned. The topography of the surface causes minute deflections in the 100 μm long cantilever which are detected using an optical lever.

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