MICROCHEMICAL REACTIONS OF THE COMMON ACIDS 421 



Group III. — Non-volatile with sulphuric acid. 



Arsenate. 



Arsenite. 



Chromate, bichromate. 



Manganate. 



Permanganate. 



Phosphate. 



Sulphate. 



The separation by the above method may be carried out as 

 described under Distillation, page 293. 



ACETATES. 



a. With Silver Nitrate in concentrated, approximately neutral 

 solution, pearly scale-like crystals of silver acetate are obtained. 

 Later these develop into long thin prisms with more or less 

 irregular sides and ends. Those in which six edges are developed 

 give terminal angles a trifle over 90 degrees, and extinction 

 almost parallel with their length (extinction angle 8 degrees). 

 To confirm the test take a new portion of the unknown and distill 

 a portion acidified with phosphoric acid. Then test the dis- 

 tillate, after partial neutralization with sodium hydroxide. In 

 the absence of phosphoric acid, sulphuric acid may be employed. 



b. With Mercurous Nitrate added to concentrated solutions. 

 Colorless plates and prisms ; the thin six-sided prisms have their 

 terminal angles equal to 100 degrees and exhibit parallel extinc- 

 tion. Sulphates give rods and sheaves of needles. 



c. With Sodium Chloride and Uranyl Nitrate in approximately 

 neutral solutions. Sodium uranyl acetate is obtained. See 

 Sodium, Method A, page 320. Add the uranyl nitrate to the 

 drop of unknown, and draw this solution across the dry film of 

 sodium chloride. 



ARSENATES. 



a. With Silver Nitrate. See Silver, page 383 ; Arsenic, page 397 . 



b. With Zinc Acetate and Ammonium Chloride in Ammoniacal 

 Solution. See Magnesium, page 352. 



c. With Ammonium Molybdate. See Phosphates. 



