186 OUTLINE OF CHEMICAL STUDY 



that is left. Is it zinc ? Is it hydrochloric acid ? Is it a new sub- 

 stance ? Name the three elements that you had in the test tube 

 at first. Which one of these escaped ? What ones have united ? 

 The substance is a salt zinc chloride. 



Repeat the experiment, using HNO 3 and Hg ; again, using 

 H 2 SO 4 and Cu. What elements combine in each case ? 



Salts are named usually from the metals and the 

 acids that compose them. For example, salts of H 2 SO 4 

 (sulphuric acid) are called sulphates: Cu and H 2 SO 4 

 form CuSO 4 , copper sulphate ; Fe and H 2 SO 4 form 

 FeSO 4 , iron sulphate; Zn and H 2 SO 4 form ZnSO 4 , 

 zinc sulphate ; etc. Salts of HNO 3 (nitric acid) are 

 called nitrates: NaNO 3 , sodium nitrate; KNO 3 , potas- 

 sium nitrate ; AgNO 3 , silver nitrate ; etc. Salts of HC1 

 are called chlorides : NaCl, sodium chloride ; KC1, potas- 

 sium chloride ; CaCl 2 , calcium chloride ; HgCl 2 , mercuric 

 chloride ; etc. Not only metals but positive radicals may 

 unite with acids to form salts. The positive radical NH 4 

 (ammonium) forms two common salts, NH 4 C1, ammo- 

 nium chloride (sal ammoniac), and NH 4 NO 3 , ammonium 

 nitrate. 



Since there are many different acids and metals, the 

 number of different metallic salts is great. Some of 

 these occur in the earth ; NaCl (common salt) is very 

 abundant, also KNO 3 (saltpeter) and NaNO 3 . Many 

 salts can be prepared by man, and in some cases they 

 are prepared by him in great quantities. 



The uses of salts are also numerous. Some are useful 

 as foods, notably chlorides and phosphates ; very many 

 are used in medicine, chlorides, bromides, phosphates, 

 sulphates, nitrates, carbonates, etc. ; others are used as 



