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PREFACE TO THE TENTH EDITION. 



IN this new edition the Manual preserves the plan and characteristics 

 that have won for it the degree of approval shown in the exhaustion of 

 the nine previous issues, each in several large printings. Numerous 

 additions have been made, most of which are of fundamental importance, 

 and again bring the Manual abreast of modern thought in chemistry to 

 its date of issue. They embrace articles on the following subjects: 

 Exothermic and endothermic reactions ; reversible reactions and chemical 

 equilibrium ; mass action ; extension of the articles on acids and bases ; 

 thermochemistry;* a new chapter on solution, in which, among other 

 matters, the solution of gases and Henry's law, freezing-points, boiling- 

 points and osmotic pressure, Raoult's law and the laws of osmotic pres- 

 sure are discussed, and the existence of ions foreshadowed ; a new chapter 

 on the theory of electrolytic dissociation, in which are considered the 

 origin of the theory, ionic equilibrium, ionization of acids, bases, and 

 salts, reactions on the ionic basis, activity of acids and bases, hydrolysis 

 of salts, neutralization, electrolysis and Faraday's laws, etc. ; electrolytic 

 solution tension of metals ; principle of the storage-battery ; and ionic 

 explanation of the action of indicators. Ionic relations are discussed in 

 practically every chapter on acids and the metals, and a number of 

 compounds have been added to the sections on inorganic and organic 

 chemistry. Many of these are of medical interest, for example, sodium 

 cacodylate, atoxyl and salvarsan, phenolphthalein, fluorescein, phenol- 

 sulphonephthalein. 



The section on physiological chemistry has been rewritten and brought 

 in line with present-day knowledge and theories. A table of inter- 

 national atomic weights on the 'oxygen = 16 basis has been added to 

 the U. S. P. table of weights on the hydrogen = 1 basis. 



It is hoped that with these alterations and additions the Manual will 

 fully accomplish its object, viz., to furnish to the student in concise form a 

 clear presentation of the science, an intelligent discussion of those substances 

 which are of interest to him, and a trustworthy guide to his work in the 

 laboratory. 



As heretofore, the subject has been divided into seven parts, each one 

 of which contains so much of the matter under consideration as is believed 

 to be necessary for a fair understanding of the subject. At the same time 

 care has been taken to place in the foreground all facts and data which 

 are of direct interest to, the physician, pharmacist, and dentist. 



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865 



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