. Journal of applied microscopy and laboratory methods. -tion of this double oxalate of bariumand iron, save that its separation isoften somewhat retarded. In suchmixtures the oxalates of calcium andstrontium first appear in their usualform, then after a time the hair-liketufts of the double oxalate the quantity of barium is quitesmall, little rosettes of radiatingneedles are obtained, separating nearthe edges of the drop. Aluminum gives rise to the for-mation of a similar product, but the crystal masses are colorless, while those ofthe iron salt are light brown. Chlorplatinic acid i
. Journal of applied microscopy and laboratory methods. -tion of this double oxalate of bariumand iron, save that its separation isoften somewhat retarded. In suchmixtures the oxalates of calcium andstrontium first appear in their usualform, then after a time the hair-liketufts of the double oxalate the quantity of barium is quitesmall, little rosettes of radiatingneedles are obtained, separating nearthe edges of the drop. Aluminum gives rise to the for-mation of a similar product, but the crystal masses are colorless, while those ofthe iron salt are light brown. Chlorplatinic acid interferes with the formation of barium oxalate in a mannersimilar to iron and aluminum. Hence it is inadvisable to test a preparationwith oxalic acid for borium, which has already been tested for potassium. For a list of the elements with which oxalic acid may give a crystalline pre-cipitate, see the list of reagents*. Exercises for Practice. Try the reaction of oxalic acid on salts of Ca, Sr, Ba, in neutal solution, first*Jour. App. Micros. Ill, Fig. 56. and Laboratory Methods. 1297 cold then hot. Draw off the mother Uquor and test the precipitate with Ho SO 4. Try the three elements in test drops acidulated with nitric acid. To the dropfrom which barium oxalate does not separate add sodium acetate. Try oxalic acid on a salt of magnesium, then add an excess of acetic acid tothe test drop and examine again. Test salts of Zn, Cd, and Pb. Make a mixture of Ca, Sr, Ba. Add H2C2O4. Repeat the experiment inHNO, solution; after a few moments, draw off the clear solution, concentrateslightly and add sodium acetate. Try the effect of the presence of ferric chloride on the precipitation of theoxalates of Ca, Sr, Ba; first each element separately, then in mixtures of Ca andBa ; Sr and Ba ; Ca, Sr, Ba. If barium borate is at hand, try testing it for Ba. E. M. Chamot. Cornell University. Simple Washing Device. A copper tube twenty-four inches long and two inches in diameter, placedho
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