382 CARBONATES. 



Water impregnated with carbonic acid merely, is erroneously 

 called soda water; it is a pleasant brisk acidulous drink, and to a de- 

 gree useful, but it will not remove acidity ; it will act feebly in cor- 

 recting the alimentary canal, and it will have only partial activity as 

 a diuretic and lithontriptic. 



(c.) If the water contains only a little carbonate of soda, it will 

 still fall far short of the qualities of genuine soda water. 



(df.) It is not sufficient to add the solution of the salt at the time, 

 and to draw the water impregnated with carbonic acid upon it ; this 

 will indeed be more useful than the water named at (b) &c. but it 

 will be, comparatively vapid, because the alkali attracts away the 

 free carbonic acid, which gives briskness to the water, and the satur- 

 ation which ought to have been fully made in the machine, is very 

 imperfectly made in the drinking glass. 



(e.) The genuine soda vmter, with the full charge of alkali and 

 gas, is an excellent antacid, diuretic, lithontriptic and anti-dyspeptic 

 remedy ; but much that is called soda water, possesses these proper- 

 ties only in a very small degree. 



(/.) Soda water may be used too freely. Large quantities of 

 water may weaken the digestion, and produce injury also by the cold ; 

 and where the diuretic effect is needed, it is better to repeat the 

 drinking at convenient intervals. 



(g.) Cordials and syrups mixed with the soda water, greatly im- 

 pair or destroy its salutary effects, and may lead to other bad results. 



BI-CARBONATE OF SODA. 



1. PREPARATION. 



(a.) The saturated solution just described, or a similar solution 

 impregnated to saturation in any other way, will, when gently evapo- 

 rated without heat, afford confused crystals of bi-carbonate. 



(b.) Or 100 parts of the solution of common carbonate, mixed 

 with 14 of carbonate of ammonia, distilled, evaporated and crystalliz- 

 ed, as in the case of carbonate of potassa, will produce the salt. 



(c.) Exposure of the carbonate, in a brewer's or distiller's vat, to 

 the action of carbonic acid gas, will spontaneously effect the com- 

 bination. 



2. PROPERTIES. 



a.) Taste mild ; at 60 soluble in 9 or 10 parts of water. 

 b.) Gentle heat expels part of the gas and it escapes in a vacuum. 

 c.) Effects the test colors, as the sub-carbonate. 

 d.) 100 grains, at low ignition, lose 37.4, and 62.6 remain of 

 dry anhydrous carbonate. 



(e.) Constitution carb. acid, 57.9 or 2 pro. 44 

 soda, 42.1 or 1 " 32 



100. 76 its equivalent. 



