This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1919 edition. Excerpt: ... V. Volumetric Determination.--(a) Permanganate Methods.--(1) Reduction to F204 by Sulphur Dioxide.--The alkaline vanadate solution, free from nitrate, chloride, arsenate, and chromate, is acidified with sufficient dilute sulphuric acid to give a 5 per cent. solution and a current of sulphur dioxide ...
Read More
This historic book may have numerous typos and missing text. Purchasers can usually download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1919 edition. Excerpt: ... V. Volumetric Determination.--(a) Permanganate Methods.--(1) Reduction to F204 by Sulphur Dioxide.--The alkaline vanadate solution, free from nitrate, chloride, arsenate, and chromate, is acidified with sufficient dilute sulphuric acid to give a 5 per cent. solution and a current of sulphur dioxide passed through the hot solution till it becomes a pure blue: V205+S02 = V204 + S03. The excess of reducing agent is boiled off while a current of carbon dioxide is passing, and the solution titrated at 80 with potassium permanganate (N/10 or N/20: 1 c.c. N/10KMn04=00091 grm. V205). The colour changes from blue through green to pale yellow until finally the characteristic pink tinge of the permanganate appears. Large quantities of sodium salts are objectionable; hence, if present, a preliminary separation of vanadium as lead vanadate should be made ( IV, (d)), but the lead sulphate need not be filtered off. The permanganate is standardised against pure iron or ferrous ammonium sulphate. The iron factor multiplied by 1-6296 gives the value in V205. (2) Reduction to V2Oi by Oxalic Acid.2--To the vanadium solution are added 30 c.c. of strong sulphuric and 0-2 grm. of oxalic acid, and the whole evaporated to fumes while passing carbon dioxide through the flask: V205+H2C204 = V204 + H20+2C02. After cooling, the mass is diluted to 500 c.c., the solution heated to 80 and titrated with permanganate. 1 c.c. N/10KMn04 = 00091 grm. V205. (3) Reduction to V202 by Zinc.3--This process is best carried out in the Jones' reductor (see Introduction). The receiver contains a 1 Roscoe, Ann. Chem. Pharm., Suppl., 1872, 8, 102. 2 Mennicke, op. cit. (p. 118). 3 Gooch and Gilbert, Amer. Journ. Sci., 1903, 16, 389. large excess of ferric alum solution and...
Read Less