PREFACE TO SECOND EDITION. 



For more than seven years no copies of this book have 

 lieen obtainable, as owing to the author's ill-health it 

 has been impossible to make the I'evision necessary to 

 bi'ing the work up to date. By lapse of time certain 

 portions of the text had become obsolete, and these have 

 b(^L'n deleted and replaced by matter based on the latest 

 inNcstigations. It has been found necessary to re-write 

 many sections and to insert methods which have been 

 devised since the book was tirst published, and this has 

 involved the re-setting of the work throughout, although 

 no alteration has been made in its plan or scope. New 

 illustrations have been introduced and the index greatly 

 improved, and it is hoped that public analysts and 

 other chemists, medical officers, dairy farmers, and those 

 interested in the chemistry of milk, butter, and cheese 

 will tin<l the book of increased ser\ice. 



H. D. R. 



July, 1914. 



