n THE ACIDS 23 



SUMMARY AND SUPPLEMENT. 

 A and B. DISCOVERY AND PROPERTIES OF THE ACIDS. 



Vegetable Acids include : 



Acetic acid, C 2 H 4 O 2 , from Vinegar (known to Geber) ; 

 Tartaric acid, C 4 H 6 O 6 , from Tartar (Scheele, 1770) ; 

 Benzoic acid, C r H 6 O 2 , from Benzoin (Scheele, 1775) ; 

 Uric acid, C 5 H 4 N 4 O 3 , from Bladder-stones (Scheele, 1776) ; 

 Lactic acid, C 3 H 6 O 3 , from Sour Milk (Scheele, 1780) ; 

 Oxalic acid, C 2 H 2 O 4 , from Oils (Scheele, 1783) ; 

 Citric acid, C 6 H 8 O 7 , from Lemons (Scheele, 1784) ; 

 Malic acid, C 4 H 6 O 6 , from Apples (Scheele, 1786). 



Mineral Acids include : 



Oil of Vitriol, Vitriolic acid, or Sulphuric acid, H 2 SO 4 , pre- 

 pared by distilling Alum (Geber) or Green Vitriol (Glauber). 



Aqua Fortis, Acid Spirit of Nitre, or Nitric Acid, HNO 3 , pre- 

 pared by distilling Nitre and Alum (Geber) or Nitre and Oil 

 of Vitriol (Glauber), 2KNO 3 + H,,SO 4 ->K 2 SO 4 + 2HNO 3 . 



Spirit of Salt, Muriatic acid, or Hydrochloric acid, HC1, pre- 

 pared by heating Salt and Oil of Vitriol, and collected in 

 water (Glauber), 2NaCl + H 2 SO 4 -> Na 2 SO 4 + 2HC1. 



Aqua Regia, a mixture of Aqua Fortis and Spirit of Salt 

 prepared by adding Sal-ammoniac to Aqua Fortis (Geber), 

 NH 4 Cl + HNO 3 -> NH 4 N0 3 +HC1, or by distilling a mixture 

 of Nitre and Salt with Oil of Vitriol (Glauber). 



The acids as a class possess the following properties, though 

 some of them may be lacking in the case of individual acids : 



(a) General Properties : Sour taste ; acids turn syrup of violets 

 red and redden blue litmus ; the mineral acids are corro- 

 sive when concentrated but harmless when dilute ; 



(b] Acids dissolve Alkalis and Chalk, liberating gas, e.g., 

 "Vinegar upon Nitre (i.e., soda)" and upon Chalk, 



Na 2 CO 3 + 2C 2 H 4 O 2 ->2NaC 2 H 3 O 2 + H 2 O + CO 2 

 CaCO 3 + 2C 2 H 4 O 2 ->Ca(C 2 H 3 2 ) 2 + H 2 + CO 2 ; 

 Oil of Vitriol with Soda gives " Glauber's salt," with Chalk gives 

 " Gypsum" or "Selenite" (almost insoluble in water) 

 Na 2 CO 3 + H 2 SO 4 -> Na 2 SO 4 + H 2 O + CO 2 

 CaCO 3 + H 2 SO 4 ->CaSO 4 + H 



