Fuchsin sulfurous acid

The test for ethylene glycol was performed by oxidation of the sample with periodic acid and detection of the resulting formaldehyde with fuchsin-sulfurous acid reagent (9). 

For the reaction between a simple aldehyde and Schiff s reagent it has been postulated77 that a complex is formed between two molecules of the aldehyde and the fuchsin-sulfurous acid reagent and there is evidence to support this idea.78,79... 

Procedure Transfer 10.0 mL each of the Standard Preparation and the Test Preparation to separate 25-mL volumetric flasks. Add 5.0 mL of Potassium Permanganate and Phosphoric Acid Solution to each, and mix. After 15 min, add 2.0 mL of Oxalic Acid and Sulfuric Acid Solution to each, stir with a glass rod until the solutions are colorless, add 5.0 mL of fuchsin-sulfurous acid TS (see Solutions and Indicators), dilute with water to volume, and mix. After 2 h, using a suitable spectrophotometer, concomitantly determine the absorbances of both solutions in 1-cm cells at the wavelength of maximum absorbance at about 575 nm, using water as the blank. The absorbance of the solution from the Test Preparation is not greater than that from the Standard Preparation. PH Determine as directed under pH Determination, Appendix IIB. 

Fuchsin-Sulfurous Acid TS Dissolve 200 mg of basic fuchsin in 120 mL of hot water, and allow the solution to cool. Add a solution of 2 g of anhydrous sodium sulfite in... 

Fuchsin — sulfurous acid (Schiff s reagent for aldehydes). 

The M. show the following common reactions 1) copper, silver, and bismuth salts are reduced in solution. - 2) M. react with bases to form alcoholates, with concentrated alkali resinification occurs to furnish yellow and dark-colored products. - 3) No reaction occurs with hydrogen sulfite or fuchsin/sulfurous acid because the aldehyde group is masked. - 4) Reduction leads to multifunctional alcohols, e.g., hexitols. - 5) Oxidation gives rise to mono- and dicarboxylic acids (sugar acids). - 6) The alcohol groups can be esteri-fied. - 7) Addition of hydrogen cyanide occurs. - 8) Osazones are formed with phenylhydrazine. 

Fuchsin — sulfurous acid (SchifTs reagentfor aldehydes). Dissolve 0.5 g of fuchsin and 9 g of sodium bisulfite in 500 mL of water, and add 10 mL of HCl. Keep in well-stoppered bottles and protect fiom light. 

The above substitutes for the iodometric determination with one or two exceptions have not been tested for specificity for free SO2. Mathers (1949) on the basis of the fact that free sulfur dioxide is removed early in the distillation of wine proposed that 10 ml. of the distillate from the alcohol determination be mixed with 0.5 ml. of 5% neutral lead acetate and the turbidity of the suspension formed be used to correct volatile acidity for sulfur dioxide. La Rosa (1950) assumed that the color formed on mixing the fuchsin-sulfuric acid-formaldehyde reagent with white wine was a measure of free SO2 but did not give any data to confirm this. The fuchsin procedure and the lead sulfite procedures are very sensitive, the former more so, and can be applied only to very small aliquots or to dilute solutions. 

Pentoses. The names and formulas of the aldopentdses may be found in Section 1. Ribose and ribose phosphates are components of the nucleic acids and the nucleotide coenzymes. In these derivatives the furanose form has been proved to be present, whereas free ribose exists in the pyranose form (formulas in Section 2). Deoxy-ribose (formula in Chapt. VII) is responsible for the name of the deoxyribonucleic acids. The free sugars are in equilibrium with the aldehyde form, which in this case can be demonstrated with fuchsin sulfurous acid. The lack of a hydroxyl group on C-2 is the basis of this reaction (used in Feulgen s nuclear staining technique). 

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