ACID A. 1 2 7 



Source. Obtained from the juice of the Lemon ((.'it ran 

 Zimoniim), or of the Lime (Citrus Limetta], by neutralising it 

 with Chalk, decomposing the Citrate of Lime thus formed by 

 Diluted Sulphuric Acid, purifying, and crystallising. 



Characters. Colourless crystals, in the form of right 

 rhombic prisms. Very soluble in water. 17 gr. in ^ fl.oz. of 

 water make a solution resembling lemon juice in strength and 

 acidity, and exactly neutralise 2-5 gr. of Potassae Bicarbonas, 

 20 gr. of Sodae Bicarbonas, or 15 gr. of Ammoniae Carbonas. 



Impurities. Copper, sulphuric acid, mineral matters. 

 Tartaric acid, detected by precipitate with acetate of potash. 



Dose. 10 to 30 gr. 



Citric Acid is used in preparing! Ferri et Ammoniaa 

 Citras, Ferri et Quinise Citras, and Vinum Quiniae. 



Acidum Tartaricum. Tartaric Acid. H 2 (C 4 H 4 6 ). 



Source. Obtained from Acid Tartrate of Potash by neutral- 

 ising its solution with (1) Chalk and (2) Chloride of Calcium, 

 (3) decomposing the Tartrate of Lime thus formed by Sulphuric 

 Acid, and purifying. (1) 2KHC 4 H 4 O fi + CaCO 3 = CaC 4 H 4 O 6 + 

 K 2 C 4 H 4 6 + H.p + C0 2 . (2) K.,C 4 H 4 6 + CaCL 2 = CaC 4 H 4 O 6 

 + 2KC1. (3) 2CaC 4 H 4 6 + 2H,SO 4 = 2H,C 4 H 4 6 + 2CaSO 4 . 



Characters. Colourless oblique rhombic prisms, with a 

 strongly acid taste, readily soluble in water. 20 gr. exactly 

 neutralise 27 gr. of Potassae Bicarbonas, 22 gr. of Sodae Bicar- 

 bonas, or loiy gr. of Ammoniae Carbonas. 



Impurities. Lead, oxalic acid, lime, mineral matter, acid 

 tartrate of potash. 



Dose. 10 to 30 gr. 



Tartaric Acid is used in preparing Soda9 Citrotartras 

 Effervescens. 



Carbonic Acid. Although not officinal as such, 

 carbonic acid gas is extensively used in medicine, being obtained 

 from Bicarbonates and Carbonates, commonly of Soda, Potash, 

 or Ammonia, by decomposition with Citric or Tartaric Acid. 

 The process is known as effervescence. The reaction may be 

 thus represented : 

 3(NaHC0 3 ) + (C 6 H 5 0,)H 3 = Na^CWW + SCO, + 3(H 3 O). 



- Sd* Citras +<*+ Water. 



ACTIONS AND USES. 



1. IMMEDIATE LOCAL ACTION'S AXD T 



. Acids are irritants, and some of them very 

 powerful corrosives. The strong acids are used as caustics ; 



