. Journal of applied microscopy and laboratory methods. ch may be present. See also remarks under Zinc, Method I. Exercises for Practice. Experiment with salts of cadmium in the manner suggested under Zinc,trying all the exercises mentioned, but having cadmium as the element in excessinstead of zinc. //. Oxalic Acid added to solutions of salts of Cadmium pi-ecipitates CadmiumOxalate. CdSO^ + H2C20^ = C^CO^ 3H2O + H2SO4. Method.—To the test drop add a solution of the reagent by the flowing inmethod. Clear, colorless monoclinic prisms and tabular crystals separate, eithersingly, in Xs, or in clu
. Journal of applied microscopy and laboratory methods. ch may be present. See also remarks under Zinc, Method I. Exercises for Practice. Experiment with salts of cadmium in the manner suggested under Zinc,trying all the exercises mentioned, but having cadmium as the element in excessinstead of zinc. //. Oxalic Acid added to solutions of salts of Cadmium pi-ecipitates CadmiumOxalate. CdSO^ + H2C20^ = C^CO^ 3H2O + H2SO4. Method.—To the test drop add a solution of the reagent by the flowing inmethod. Clear, colorless monoclinic prisms and tabular crystals separate, eithersingly, in Xs, or in clusters. (Fig. 72.)The tabular crystals have the appearanceof rhombs and rectangles. Frequently very concentrated solutionsyield crystals having an octahedral aspect. Retnarks.— The solution to be testedshould be neutral or only slightly acid,and rather concentrated with respect tocadmium. Dilute solutions fail to give good re-sults. The typical crystals of cadmium oxa-late are seen only when working with al-most pure salts of this element. Fig. 1458 Journal of Applied Microscopy In the presence of zinc, only the forms of zinc oxalate are usually obtained. Members of the calcium group and lead are first removed with sulphuric acidand a trace of alcohol. Silver with hydrochloric acid. In the presence of copper, aluminum, iron, manganese, chromium, nickeland cobalt, the reaction with oxalic acid is not reliable and in most casesworthless. Treated with ammonium hydroxide in the manner described under Zinc,cadmium oxalate recrystallizes in the form of rods and tables. This method ofprocedure is often of value in arriving at a decision as to the nature of a pre-cipitate obtained with oxalic acid. Unfortunately, zinc prevents the formationof these rod-like crystals. Exercises for Practice. Test a pure salt of Zn in dilute and in concentrated solution. Repeat theexperiments, substituting Cd for the Zn. Make a preparation of ZnCoO^ • ^H^O ; draw off the supernatant liquid ;add
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