Introduction 



been lapses, and differences of opinion will probably arise. For 

 some of the substances carrying a large literature a review 

 article often is cited. In general an attempt has been made to 

 cite the isolation, final structure determination and synthesis 

 papers insofar as they exist. In the references cited care has 

 been taken to include the complete list of authors as given on 

 the paper. A bibliography of books, general references and re- 

 views is included at the end. 



Occasional comments may be found at the bottom of an entry, 

 reflecting the manner in which this material evolved from a 

 card file with a few notes. These comments were allowed to 

 stand without expansion for what they are worth. For the most 

 part the work is uncritical, structures and properties having 

 been transcribed just as given in the literature. Structures and 

 empirical formulas designated as tentative or approximate by 

 the authors have been so designated here. 



The indexes were not available prior to printing, and it is 

 hoped that they will point out hitherto unrecognized relation- 

 ships. 



