MICROCHEMICAL REACTIONS OF THE COMMON ACIDS 429 



page 354 ; Copper, page 386. Add a trace of copper and increase 

 the delicacy of the reaction. 



TARTRATES. 



Note. - - Before testing for tartrates always neutralize any free 

 mineral acid present. 



a. By means of Calcium Acetate. 



The solution may be neutral or acidified with acetic acid. 



Large, colorless, well-formed, highly refractive crystals are 

 obtained. 



The solution to be tested must be concentrated, otherwise the 

 calcium tartrate will not separate save on long standing. Ex- 

 posure to alcohol vapors (Method VI, page 305) will hasten the 

 formation of a crystal deposit. 



Magnesium salts greatly retard the separation of crystals of 

 calcium tartrate. 



b. With Potassium Salts, tartrates yield characteristic color- 

 less, highly refractive, orthorhombic, short, stout prisms of the 

 primary salt KHC4H4O6. 



c. With Silver Nitrate. 



A granular precipitate only is obtained unless in very dilute 

 solution, then there will be obtained tiny squares and rectangles 

 and short, stout prisms giving a six-sided outline. 



Most other acids interfere with the detection of tartrates by 

 means of the silver salt. 



