146 METALS AND THEIR COMBINATIONS. 



reagents. (Potassium antimoniate precipitates neutral solution of 

 sodium salts, but this test is not reliable.) 



2. The chief reaction for sodium is the flame-test, compounds of 

 sodium imparting to a colorless flame yellow color, which is very 

 intense, brilliant, and luminous. A crystal of potassium dichromate 

 appears colorless, and a paper coated with red mercuric iodide appears 

 white, when illuminated by the yellow sodium flame. (The spectro- 

 scope shows a characteristic yellow line.) 



3. Sodium compounds are white and are not volatile at or below a 

 red heat. 



Lithium, Li = 7. Found in nature in combination with silicic acid in a few 

 rare minerals or as a chloride in some spring waters. Of inorganic salts, 

 lilhium bromide and carbonate are official. Hydroxide, carbonate, and phosphate 

 of lithium are much less soluble than the corresponding compounds of potas- 

 sium and sodium. Sodium phosphate added to a strong solution of a lithium 

 salt produces, on boiling, a white precipitate of lithium phosphate, Li 3 PO 4 . 

 Lithium compounds color the flame a beautiful crimson or carmine-red. 



f\ 1 U 

 * 



21. AMMONIUM. 

 NH 4 i = 18. 



General remarks. The salts of ammonium show so much resem- 

 blance, both in their physical and chemical properties, to those of the 

 alkali-metals, that they may be studied most conveniently at this 

 place. 



The compound radical NH 4 acts in these ammonium salts very 

 much like one atom of an alkali-metal, and, therefore, frequently has 

 been looked upon as a compound metal. The physical metallic prop- 

 erties (lustre, etc.) of ammonium cannot be fully demonstrated, as it 

 is not capable of existing in a separate or free state. There is known, 

 however, an alloy of ammonium and mercury, which may be obtained 



QUESTIONS. 191. What is the composition of common salt; how is it found 

 in nature, and what is it used for? 192. Describe Leblanc's and the Solvay 

 process for manufacturing soaium carbonate on a large scale. 193. How much 

 water is in 100 pounds of the crystallized sodium carbonate? 194. What is 

 Glauber salt, and how is it made? 195. State the composition of disodium 

 hydrogen phosphate, and how is it prepared from calcium phosphate? 196. 

 What difference exists between sodium carbonate and bicarbonate both in 

 regard to physical and chemical properties? 197. Give the composition of 

 sodium hyposulphite; what is it used for? 198. Which sodium salts are 

 soluble, and which are insoluble? 199. How does sodium and how does 

 lithium color the flame? 200. Which lithium salts are official? 



