Semimicro Qualitative Analysis [antikvár]

PREFACE The numerous advantages of using semimicro amounts of material in qualitative analysis are now generally recognized. Among these are: greatly increased sharpness of separations, since adsorption of ions is much decreased when only small precipitates are involved and filtration is replaced by centrifugation; astonishingly small amounts detectable by an average student; accomplishment of nearly tvnce as much work in a laboratory period; and greatly reduced cost of laboratory instruction. Hitherto the general adoption of small-scale analysis has been retarded by lack of reliable procedures. If the average student is to remain interested and enthusiastic, he must be furnished laboratory directions which are precise and which he finds work in practice. This book is planned to furnish such directions and, at the same time, to teach the maximum amount of inorganic chemistry that can be absorbed in the allotted time. The methods prescribed in the text have been gradually evolved during a period of six years. They have been thoroughly tried out on large classes and found to give exceptionally good results. Two features are, so far as we know, entirely new. These are analysis for anions by elimination, and analysis both of cation Group III without removal of arsenate and phosphate and of cation Group IV without use of the rather unsatisfactory reagent, ammonium carbonate. It has been demonstrated that, after a student has mastered the details, he can make an anion analji^sis with surprising accuracy in a comparatively short time. It is obvious that the time required for a cation analysis can be reduced nearly one half by elimination of the tedious special procedures for precipitation of arsenic from arsenic acid in Group II and removal of phosphate before analyzing for Group III. Experience has shown that accurate manipulation is essential to good results. For this reason a special section is devoted to semimicro technique and all laboratory instructions are given in very full detail. The chemistry of each procedure is discussed fully in notes. Use is made of only a few organic reagents, which have been found valuable in changing possible uncertainty into relative certainty.