MICROCHEMICAL REACTIONS OF THE COMMON ACIDS 427 



with a crystal of morphine sulphate as described under iodates, 

 page 425. 



OXALATES. 



a. With Strontium Acetate. See Calcium, page 337; Stron- 

 tium, page 343. 



b. With Silver Nitrate or Lead Nitrate. See Calcium, page 337. 



PHOSPHATES. 



a. To the drop to be tested, add a drop of Nitric Acid. Then 

 apply a drop of Ammonium Molybdate by Method 7, page 299. 

 Warm gently. Phosphates yield a yellow precipitate at first 

 appearing amorphous under the microscope unless a magnifica- 

 tion of over 200 is employed. Later light yellow almost trans- 

 parent, octahedra-like crystals are formed; especially in the pres- 

 ence of sodium salts. A similiar reaction will be obtained if 

 silicomolybdates or arseno-molybdates are formed. 



This reaction is of value if arsenic and soluble silicates are 

 absent and as indicating whether much or little phosphate is 

 present. If a heavy precipitate is obtained, apply test b. 



b. To the Ammoniacal Solution add Ammonium Chloride and 

 Magnesium Acetate, proceeding as described under Magnesium, 

 page 351. Arsenates must be absent. 



Note. Phosphates frequently interfere with the detection 

 of certain bases and must be removed before reliable reactions 

 can be obtained; their removal may be accomplished by means 

 of tin in acid solution. Acidify with nitric acid, add a few tiny 

 bits of pure tin-foil and as soon as the reaction has ceased, heat 

 to boiling. Cool and extract the material with dilute nitric acid. 



SILICATES. 



a. Treat the material upon a celluloid object slide with ammo- 

 nium fluoride, sodium chloride and sulphuric acid. Sodium silico- 

 fluoride is formed. See Sodium, page 324. Boron, zirconium 

 and titanium must be absent. 



SULPHATES. 



a. To the drop add a trace of Nitric Acid, then a drop 

 oj Calcium Acetate by Method 7, page 299. Characteristic 



