PREFACE. 



THE object of this work is to present the science of Chemistry in 

 the most intelligible form, to those who are learning its elements ; 

 and for the convenience of the classes in Yale College, the topics 

 are arranged in the order in which they are now discussed, in the 

 lectures given in that Institution. As the Medical Class constitutes a 

 part of the audience, the most important pharmaceutical prepara- 

 tions, and leading uses of such substances as belong both to the Ma- 

 teria Medica, and to Chemistry, are briefly mentioned ; and in gen- 

 eral, throughout the work, practical facts are interwoven with scien- 

 tific principles. The attempt has been made, to unite copiousness 

 with condensation ; perspicuity with brevity ; and a lucid order, and 

 due connexion of subordinate parts, with a general unity of design. 



By numerals* and letters, the topics have been digested under 

 appropriate heads ; and by the use of large and small capitals, and 

 italics, the writer's impression, as to the relative importance of the 

 leading facts and propositions, has been indicated. 



It is supposed that these mechanical helps, not novel indeed, but 

 in this work, more extensively employed than usual, may facilitate 

 the progress of the student, by enabling him to take, at pleasure, a 

 more general, a more particular, or a detailed review ; and the same 

 facility is, of course, presented to the instructor. 



Exact accounts of processes and manipulations have been given ; 

 and Dr. Hare, having kindly permitted the introduction of the cuts,f 

 from his Compendium, his own language, sometimes abridged, has 

 been generally employed in the descriptions of his figures. The val- 

 uable illustrations, thus derived from his liberality, render it unne- 

 cessary to apologize for the frequent use of his name. 



* Adopted, to some extent, by Dr. F. Bache, in his System of Chemistry for Med- 

 ical Students, and more fully by Dr. Henry. 

 t The more complex figures have been omitted. 



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