AMMONIUM. 125 



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 process for manufacturing sodium carbonate 

 on a large scale. 



193. How much water is in 100 pounds of the crystallized sodium 

 carbonate ? 



194. What is Glauber's 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 bicar- 

 bonate, both in regard to physical and chemical properties ? 



197. Give the composition of sodium hyposulphite, and what is it 

 used for ? 



198. Which sodium salts are soluble, and which are insoluble? 



199. How does sodium and how lithium color the flame? 



200. Which lithium salts are officinal ? 



21. AMMONIUM. 

 NH 4 i = 18. 



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

 semblance, both in their physical and chemical properties, to 

 those of the alkali-metals, that they may be most conveniently 

 studied at this place. 



The compound radical NH 4 acts in these ammonium salts 

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

 frequently been looked upon as a compound metal. The phy- 

 sical metallic properties (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 by dissolving potassium 

 in mercury and adding to the potassium-amalgam thus formed, 

 a strong solution of ammonium chloride, when potassium 

 chloride and ammonium-amalgam are formed. The latter is a 

 soft, spongy, metallic-looking substance, which readily decom- 

 poses into mercury, ammonia, and hydrogen : 



HgK + NH 4 C1 = KC1 -f NH.Hg; 

 NH 4 Hg = NH 8 + H + Hg. 



