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CALCULATIONS

Ву

Raymond

R. HARMAN ASHLEY, Ph.D.
Professor of Chemistry, Tufts College

FOURTH EDITION

NEW YORK
D. VAN NOSTRAND COMPANY, INC.

1929

COPYRIGHT, 1915, 1918, 1923,

BY
D. VAN NOSTRAND COMPANY

1929, By D. VAN NOSTRAND COMPANY, INC.

All rights reserved, including that of translation
into the Scandinavian and other foreign languages

First Published, June 1915
Second Edition, November 1918
Third Edition, August 1923
Fourth Edition, May 1929

PRINTED IN THE UNITED STATES OF AMERICA

BY THE PLIMPTON PRESS, NORWOOD, MASS.

7-15-24 19862

PREFACE TO FIRST EDITION

H7 2 29 HCM.

In putting forth this small work, the author has intended to write a textbook on Chemical Calculations following more closely than other books at present on the market, the needs of the student who will later find occupation in chemical laboratory work. For this reason, constant reference will be made to Chemists' Handbooks, the best of which, in the author's opinion, is “VAN NOSTRAND'S CHEMICAL ANNUAL FOR 1913,” edited by Prof. J. C. Olsen. Constant reference will be made to this work by means of footnotes, with the intention of leading the student to the most convenient source of tabulated data, and to explain the method of utilizing the same. The purchase of the “ANNUAL” will not be necessary, much as it may be desirable, in following the explanations or solving the problems.

The problems are numerous and of varying degrees of difficulty; the instructor is the best judge of the type of problem to assign a class or individual. Those of the more difficult sort may be given the more advanced student, thus holding the class together. Many of the problems conform to the type usually found in works of this nature and in the selection of these, most of the books on this subject have been consulted. Some of the types are new to works of this kind; their inclusion is made in the hope of making the book more practical.

The method of solving the problems is treated in the text, and in the earlier chapters typical problems are solved at the end of the reading matter just before the problems are stated. The answer or answers have been attached to each problem rather than given in a list in the appendix, with the belief that it is more convenient for student and instructor. It may be urged that the inclusion of the answer with the problem may be a temptation offered the student to work for this answer. However, a student who will do this, will always take the trouble of looking up the answer, even if it is at the end of the book.

Some of the topics are discussed from two or more methods of approach in the belief that one of the methods may appeal to a student and be more easily comprehended by him than the others. If some of the topics are treated in too elementary or extended a fashion to suit some, it must be remembered that this subject is not simple to all students. The author does not anticipate adverse criticism on the score of the work being too elementary when taken as a whole. The treatment of ratios may be so full as to be tedious. This is for the reason that it is wished to lead the student away from proportions as generally expressed, i.e., x: y = a : b, but to have him at once set down his mathematical expression in a form for immediate solution. The algebraic method has been extensively employed and the treatment of indirect analysis and the calculation of indirect factors have been given considerable space, an amount of space not measured by the importance of indirect analysis, but rather by the importance of the methods of chemical and algebraic reasoning. Many problems have been solved in steps, after which it is shown how the same problem may be solved by one expression. The problems are more numerous than will be solved by one class, if small; two or more problems of the same nature are included so that in a large class there will be enough to go around. Furthermore, a large number of problems will give the instructor more choice, and there is less likelihood of their being solved by one class and handed on to the next in the nature of heirlooms.

In the calculation of the problems, the use of logarithms is strongly recommended; as also is the slide rule. The latter is to be especially recommended, as the time allotted the subject may be devoted to theory, relegating the mechanical solution of the problems to a subordinate place. With the use of this device the subject may be thoroughly treated in half the usual time.

The problems have been checked and rechecked, but not withstanding this, errors will undoubtedly creep in. The author will appreciate having his attention called to such. As five-and, in a few instances, six-place logarithms have been used, answers are often stated to a number of significant figures not justified by the number of significant figures in the data given. It was thought best to carry out the answer, as this involved no extra work and is valuable in inculcating accuracy.

The author wishes to express his appreciation to Mr. Harry R. Lee, Superintendent, of the Virginia Electrolytic Company for checking problems, reading the manuscript and giving much criticism and advice; to Mr. G. C. Merrill, formerly of the College of Montana, for the checking of a large number of problems. Professors Ralph H. McKee and Charles W. Easley of the University of Maine have been generous with help and advice, as have many others of the author's colleagues. An expression of thanks is due Mr. Charles F. Guhlmann of the General Chemical Company for reading the chapter on mixed acids and offering very helpful advice for this section.

R. H. A. UNIVERSITY OF MAINE, ORONO, MAINE,

Jan. 30, 1915

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PREFACE TO FOURTH EDITION, REVISED

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This' revision has entailed a complete recalculation of all the material to make it conform to the Atomic and Molecular Weights as given in the Sixth Issue of Van Nostrand's Chemical Annual although the logic underlying the subject of Chemical Calculations remains the same irrespective of slight changes in atomic weights. It is the hope and belief of the author that errors have been reduced to a minimum. Users of this book will be bestowing a favor on the Author if they will bring errors to his attention. Frequent references to Van Nostrand's Chemical Annual are retained but are made to the Table number rather than the Page number in the hope that subsequent new Issues of the Annual will change the Table number little if at all.

Considerable new matter has been added in this revision together with many new problems. The author wishes to thank all who have brought errors to his attention and especially Professor Irving T. Coates for many suggestions and new problems.

R. H. A. BOSTON,

June, 1929

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