Permanent Colours of Opake Bodies. 195 



Fixed air, by its combination with alcalies, di- 

 miniflies their caufticity, and promotes their cry- 

 ftallization. Thefe properties are alfo iuppofed 

 to be communicated by an acid, imparted by 

 fixed air. 



But, this hypothefis does not agree with the 

 efFc(5ts, which are produced by the combination 

 of acids with alcalies. For, neutral falts are 

 formed by the addition of acids to alcalies. And 

 as alcalies do not become neutral faks, by their 

 union with fixed air, but are only changed there- 

 by, from caullic and deliquefcent, to mild alcalies,^ 

 capable of cryftallizing, it is evident that the al- 

 teration, which fixed air caufes in them, does not 

 refultfrom the introdudlion of an acid. 



We mud, therefore, turn our views to the con- 

 fideration of fome other principle, by which thefc 

 effects may be produced. 



It appears from various chymical procefles, that" 

 alcalies are rendered mild, and capable of cryftal- 

 lizing, in proportion as they are united to phlo- 

 gifton. The phlogiflicated alcaline lixivium, whea 

 laturated, is perfectly mild, and, by a flight evar- 

 poration, is reduced tea concrete cryftalline mafs, 

 which docs not deliquefce, or imbibe the leaft 

 moiflure from the air, and no longer retains any 

 alcaline chara6ter or property. 



M. Beaume, by an elegant and ingenious ex- 

 periment, has proved the prefence of phlogifton 

 in mild alcalieS; and has (hewn that their power 



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