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DPPH-I (m.p. 106 °C) is orthorhombic, DPPH-II (m.p. 137 °C) is amorphous and DPPH-III (m.p. 128–129 °C) is triclinic. [2] DPPH is a well-known radical and a trap ("scavenger") for other radicals. Therefore, rate reduction of a chemical reaction upon addition of DPPH is used as an indicator of the radical nature of that reaction.
Potassium ferricyanide reacts with ferrous iron in acidic solution to produce the insoluble blue pigment, commonly referred to as Turnbull's blue or Prussian blue. To detect ferric (Fe 3+ ) iron, potassium ferrocyanide is used instead in the Perls' Prussian blue staining method. [ 13 ]
Dragendorff's reagent is prepared by mixing a concentrated solution of potassium iodide with a solution of bismuth subnitrate in a diluted acid (acetic acid or tartaric acid, hydrochloric acid or sulfuric acid is rarely being used) as a low pH is mandatory for this reagent. [2] The formation is as follows:
An example given states that a 12C solution is equivalent to a "pinch of salt in both the North and South Atlantic Oceans", [24] [25] which is approximately correct. [26] One-third of a drop of some original substance diluted into all the water on earth would produce a preparation with a concentration of about 13C. [27] [28] [29]
By the time phase III clinical trials are reached, the formulation of the drug should have been developed to be close to the preparation that will ultimately be used in the market. A knowledge of stability is essential by this stage, and conditions must have been developed to ensure that the drug is stable in the preparation.
McIlvaine buffer is a buffer solution composed of citric acid and disodium hydrogen phosphate, also known as citrate-phosphate buffer.It was introduced in 1921 by the United States agronomist Theodore Clinton McIlvaine (1875–1959) from West Virginia University, and it can be prepared in pH 2.2 to 8 by mixing two stock solutions.
A serial dilution is the step-wise dilution of a substance in solution, either by using a constant dilution factor, or by using a variable factor between dilutions. If the dilution factor at each step is constant, this results in a geometric progression of the concentration in a logarithmic fashion.
By measuring any two of these solutions, the unknown concentration is calculated. [1] As polarographic standard addition involves using only one solution with the standard added – the two-level design, polarographers always refer to the method as singular, standard addition. [4]