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Potassium

oxalate and ounces

POTASSIUM OXALATE.(Formula, ; molecular weight, 164; synonym, neutral oxalate of by neutralizing oxalic acid with caustic potash or potassium car bonate. Obtained in white crystalline masses or in powder. As it is always used in the liquid state, the following simple method for preparing it in that form will be found useful: Dissolve 26 ounces of potassium carbonate in 6o ounces of water, and very slowly add about i8 or 19 ounces of oxalic acid till, after boiling, the solution is neutral to test paper. Filter and add water until the whole measures 128 ounces, when a 25 per cent. solution is then obtained.

Potassium oxalate is soluble in about three parts its weight of water. It sometimes con tains sodium oxalate, which may be detected by moistening a ltttle of the salt with strong sul phuric acid, evaporating in an open dish to complete dryness, then gently igniting until fumes cease to be evolved, and again moistening the cold residue with hydrochloric acid. By dipping

a platinum wire in the mixture and holding it in a flame of a Bunsen burner the colorless flame will turn yellow if sodium be present.

In purchasing this oxalate from drug stores be sure that potassium binoxalate or salt of sorrel is not substituted for it. This can be distinguished from potassium oxalate by its inferior solubility (i in 4o). In the event of a mistake having been made, salt of sorrel can be converted into the photographically useful oxalate by neutralizing it with potassium carbo nate, thus + + Potassium oxalate is much used in photography as a solvent of ferrous oxalate for use as a developer for silver bromide and silirer chloride plates and papers, and also as a developer in the platinotype process.