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Updated: May 23, 2025
Ferrous salts may be promptly and completely oxidized to ferric salts, even in cold solution, by the addition of potassium bichromate, provided sufficient acid is present to hold in solution the ferric and chromic compounds which are formed. The acid may be either hydrochloric or sulphuric, but the former is usually preferred, since it is by far the best solvent for iron and its compounds.
Again, the base known as mauve, or mauveine, has a composition shown by the formula C H N . It is produced from the sulphate of aniline by mixing it with a cold saturated solution of bichromate of potash, and allowing the mixture to stand for ten or twelve hours.
As soon as the blue appears to be less intense, add the bichromate solution in small portions, finally a single drop at a time, until the point is reached at which no blue color appears after the lapse of thirty seconds from the time of mixing solution and indicator. At the close of the titration a large drop of the iron solution should be taken for the test.
Wet 6 lbs. of goods thoroughly; and to the same quantity of water add 9 oz. of sugar of lead; and to the same quantity of water in another vessel, add 6 oz. of bichromate of potash; dip the goods first into the solution of sugar of lead, and next into that of the potash, and then again into the first; wring out, dry, and afterwards rinse in cold water. FOR STAINING GLASS No. 1 FLUX
The processes of volumetric analysis are easily classified, according to their character, into: I. NEUTRALIZATION METHODS; such, for example, as those of acidimetry and alkalimetry. II. OXIDATION PROCESSES; as exemplified in the determination of ferrous iron by its oxidation with potassium bichromate.
The solution of the wire in hot acid and the short boiling insure the removal of compounds of hydrogen and carbon which are formed from the small amount of carbon in the iron. It is also evident that any excess of the agent used to reduce the iron must be removed; otherwise it will react with the bichromate added later.
Of this finger-print a photograph is taken, or rather, a photographic negative, which for this purpose requires to be taken on a reversed plate, and the negative is put into a special printing frame, with a plate of gelatine which has been treated with potassium bichromate, and the frame is exposed to light.
Weigh out two portions of about 0.5 gram each into small porcelain crucibles. Proceed with the solution of the ore, treat the residue, if necessary, and reduce the iron by the addition of stannous chloride, followed by mercuric chloride, as described for the bichromate process on page 56.
It is, in general, true that oxidizable substances are determined by !direct! titration, while oxidizing substances are determined by !indirect! titration. The important oxidizing agents employed in volumetric solutions are potassium bichromate, potassium permangenate, potassium ferricyanide, iodine, ferric chloride, and sodium hypochlorite.
The sensitive mixture is composed of: The whites of four fresh eggs beaten to a froth......................... 100 parts Pure bichromate of ammonia......... 2.50 " Water.............................. 50 " After this mixture has been carefully filtered through a paper filter, a few drops of ammonia are added. It will keep good for some time if well corked and preserved from exposure to the light.
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