IV PEEFACE. 



pounds, has been adhered to for the reason that the author believes it to 

 be the best adapted for purposes of instructing beginners in chemistry. 

 All our classifications of either natural objects or phenomena are 

 imperfect, because nature does not draw those distinct lines of demar- 

 cation which we adopt as necessary for our studies. The most 

 simple and natural classification is, therefore, always to be preferred, 

 even if, as in the above case, the student might derive from it the 

 impression that matter was thus separated into distinct groups. 



In considering the various elements and their compounds, much 

 stress has been laid upon their occurrence in nature, for an under- 

 standing of chemical phenomena as they take place in the animated 

 and inanimated world, depends largely on a knowledge of these facts. 



Of elements those only are considered having either intrinsically or 

 in combination a practical interest, or which take an active part in 

 the various chemical changes in nature. 



For the special benefit of pharmaceutical and medical students all 

 chemicals mentioned in the United States Pharmacopoeia are included, 

 and when of sufficient interest are fully considered. 



The fifth part is devoted to qualitative analysis and will serve the 

 student as a guide in his laboratory work. 



The sixth treats of organic chemistry. It was with much hesitation 

 that the author has so briefly considered this portion of his subject, 

 but he felt that a more extended consideration of this highly developed 

 branch of chemical science in a volume of so condensed a character 

 would unduly curtail attention to matters equally important. 



The seventh and last part, giving some of the more important facts 

 of physiological chemistry, has been added for the benefit of the 

 medical student, but it is hoped that it may also serve as a guide to 

 others who extend their studies to this very interesting part of the 

 science. 



The decimal system has been strictly adhered to in all weights and 

 measures ; degrees of temperature are expressed in the same system, 

 except where otherwise stated. 



Having frequently noticed how difficult it is for beginners to 

 become familiar with the variously shaded colors of chemicals and 



