P R E F A C E
T h e contributions included in this volume continue the aims set forth in Volume I t o describe those physical methods t h a t have either proved of considerable value in analytical work or are destined t o play an impor- t a n t role in t h e future. Electrical, magnetic, and miscellaneous tech- niques are discussed. I n addition, a chapter on the statistical analysis of experimental d a t a is included.
I n carrying out an analysis the analyst usually performs two major tasks:
1) preliminary operations t h a t bring the system under investigation into physical states suitable for analysis,
2) measurement of physical constants t h a t can be compared with known systems for identity or can be interpreted in terms of structure and organization.
Among the preliminary operations are included such changes in struc- ture and phase as m a y be necessary for the subsequent physical measure- m e n t (ionization in the mass spectrometer, vaporization and heating in emission spectroscopy, etc.) and the m a n y techniques of separation (distillation, distribution between immiscible solvents, separation of ions in a magnetic field, etc.). T h e determination of physical constants leads to identification as t o t y p e and n a t u r e of t h e structure under investiga- tion (qualitative analysis). If a definite relation between physical con- s t a n t a n d concentration can be established, q u a n t i t a t i v e results are obtainable. M e a s u r e m e n t of nonspecific colligative properties of t h e system (mass, volume, ionization current, etc.) also lead t o q u a n t i t a t i v e results, provided a separation from all interfering admixtures has been accomplished. Such separations are not required if a characteristic property can be measured (intensity of spectral lines in emission or adsorption, discharge current in polarography) where difficulties due to overlapping by interfering substances are absent or can be t a k e n into account.
T h e discussions of analytical procedures in these volumes deal primarily with nonchemical m e t h o d s a n d techniques useful in establishing the qualitative n a t u r e of unknowns. I n addition, a n u m b e r of methods are discussed t h a t measure nonspecific properties only b u t are of great value in obtaining q u a n t i t a t i v e information on relatively simple systems
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(conductometric titration, radioactive tracer methods). Preliminary operations are not described unless t h e y are essential steps in t h e over-all procedure.
I t is indeed a great pleasure and privilege t o express m y t h a n k s here t o all t h e contributors for their splendid help a n d advice, a n d t o t h e publishers, who cooperated in every w a y possible.
W A L T E R G . B E R L
