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 /, 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 sili co- 

 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 

 of Calcium Acetate by Method /, page 299. Characteristic 



