PREFACE TO THE FIRST EDITION. 



THIS book differs from all other text-books on Chemistry in several 

 particulars. 



1st. It includes only that which every well-informed person ought to know 

 on the subject, and excludes whatever is of value only to those who are to 

 be chemists, or who intend to apply chemistry to specific branches of busi- 

 ness, as medicine, metallurgy, etc. For the extended and specific knowl- 

 edge required for such purposes other books can be studied afterward, this 

 book being suitable for a preliminary preparation. I will give a single ex- 

 ample of the sort of selection I have practiced in carrying out my plan. I 

 exclude the consideration of the tests of the presence of arsenic in cases 

 of poisoning, because the application of them is so complicated that none 

 but a professed chemist can make the investigation. On the other hand, 

 I notice very particularly the chemical action of the whites of eggs upon 

 corrosive sublimate, because, as poisoning with this substance is quite fre- 

 quent, and promptness in the use of the antidote is all-important, every one 

 ought to know what the antidote is, and he will certainly be the more 

 prompt to apply it if he understand its modus operandi. 



2d. I recognize fully the distinction between a book for reference and a 

 book for study. The pupil should have his book specially adapted for 

 study ; and the teacher should have, in addition to this, books for refer- 

 ence, so that his knowledge may be wider than that included in the text- 

 book, in order that he may meet any inquiries that may arise, or add to the 

 facts and illustrations which the text-book furnishes, as occasion may offer. 

 Most text-books are too extensive, because the distinction referred to is not 

 observed. The attempt sometimes made to draw the line between the mat- 



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