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

Date:
1894
Catalogue details

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.

    58/288 (page 22)
    5. Hydrochloric Acid.—The acid commonly used for qualitative analysis, of sp. gr. r.12. The acids 3, 4, 5 must from time to time be tested for calcium, potassium, and ammonium. Some drops are evaporated on platinum ; if any considerable residue is left, the acid must be thrown away. A volatile residue points to ammonium. In this case something is amiss with the stoppers. 6. Hydrofluoric Acid.—Pure acid, leaving no residue of fluor-salts when evaporated on platinum. It is kept in bottles of ebonite; small quantities in stoppered tubes of the same material.1 As the keeping of this reagent is often troublesome, preference will generally be given to the following one :— 7. Ammonium Fluoride.—It is tested for silicon with sodium chloride (§ 39, a). Purification is effected by heating with a little ammonium hydrate and by subliming the dry mass in a platinum crucible. The first and the last quarter of the sublimate is thrown away. It is crushed to coarse powder and kept in a tube of ebonite. Its solution in hydrochloric or in sulphuric acid is employed in the same way as hydrofluoric acid. Its action is, however, less violent. It is necessary to heat strongly after evaporation of the solvent, to make sure of the expulsion of all ammoniacal compounds ; otherwise erroneous conclusions may be drawn as to the presence of potassium, rubidium, or caesium. 8. Acetic Acid.—Glacial acid, diluted with one-tenth part of water. Used for neutralising and for acidulating, also for retarding some reactions. 8b. Formic Acid is sometimes used for precipitating the cerite metals. 1 Such tubes for the reagents 6 and 7 are furnished by Dr. R. Muencke, Berlin, I.uisenstrasse 58.