4 BULLETIN OP THE UNIVERSITY OF WISCONSIN. 



it was thought that a systematic study of the effect of solutions 

 on the sense of taste, pursued in the light of the knowledge that 

 has in recent years been gathered concerning the subject of so- 

 lutions, would more clearly define the nature of the substances 

 that produce certain tastes and possibly also indicate the mode 

 of action by means of which these substances cause the sensa- 

 tions of taste. The present investigation is an attempt to study 

 the effect of solutions on the sense of taste in the light of the 

 modern theories of the nature of solutions. 



The Nature of Aqueous Solutions. 



Aqueous solutions may be divided into two classes, those that 

 are practically non-conductors of electricity and those that con- 

 duct electricity readily. The former are generally termed non- 

 electrolytes and the latter electrolytes. The aqueous solutions 

 that practically do not conduct electricity are those of substances 

 that possess neither acid, basic, nor salt-like character, or at least 

 they possess these characteristics only to a slight degree. Into 

 this category belong, for example, solutions of the mono- and 

 polyatomic alcohols, the sugars, the esters, very weak acids and 

 bases, colloidal substances, and other ccmpounds generally 

 spoken of as neutral 1 substances. The solutions that conduct 

 electricity readily are those of compounds of pronounced acid, 

 basic, or salt-like character. This class includes solutions of all 

 the acids, bases, and salts except e )me very weak acids and bases 

 and the salts formed by their combination. 



Measurements of the osmotic pressure, the lowering of the 

 freezing point, and the elevation of the boiling point of solutions 

 of non-electrolytes have shown that generally the dissolved sub- 

 stances contained in these solutions exist in the simple molecular 

 condition that is expressed by their chemical formulas as usually 

 written; in other words, the molecular weight of these substances 

 when in the dissolved condition is that which is generally 

 ascribed to them. When it is possible to find the molecular 

 weight of a non-electrolyte by a vapor density determination as 



1 The term neutral substances as used here does not include salts. 



