A manual of microchemical analysis / by H. Behrens ; with an introductory chapter by John W. Judd.

Date:
1894
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Licence: Public Domain Mark

Credit: A manual of microchemical analysis / by H. Behrens ; with an introductory chapter by John W. Judd. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

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    § 155. Compounds of the Cerite Metals, associated with Compounds of Iron, Aluminium, and Bivalent Metals. a. Precipitation with oxalic acid (§ 15, c) answers well for solutions containing the cerite metals, together with aluminium, iron, or chromium. With bivalent metals it is apt to lead into errors, binary oxalates being formed, some- times to such an extent that both metals are masked (cerite metals with magnesium or cadmium). Such fal- lacious oxalates can be analysed by calcination and evapora- tion of the oxides with formic acid. The residue is treated with cold water, which will leave formates of the cerite metals undissolved (solubility from 1 : 300 to 1 : 500). b. With beryllium, magnesium, manganese, cadmium, and copper, precipitation of the cerite metals with sodium sulphate (§ 15, a) will give satisfactory results. With zinc, calcium, barium, strontium and lead it is otherwise. If zinc is present in any considerable proportion, sodium sulphate will not precipitate the well-known lenticular crystals (§ 15, a), but small needles, which might be taken for crystals of gypsum. Ammonia is of no use for extract- ing the zinc; for an effectual separation caustic soda must be employed (§ 131). Barium and lead may be separated from the cerite metals by precipitation with potassium bichromate (§ 19, c; § 22, c). c. Calcium and strontium will be found more trouble- some. Their sulphates form, with the sulphates of the cerite metals, granular compounds that cannot be dis- tinguished under the microscope from barium sulphate. They must be converted into carbonates by fusion with sodium carbonate and careful washing of the fused mass, or into oxides by heating with a solution of ammonium