MICROCHEMICAL REACTIONS OF THE COMMON ACIDS 429 



page 354 ; Gopper, 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 oj 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 KHC^Oe. 



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. 



