24 History of physical Science from [July, 



over, and there remains behind a very acid liquid, which on 

 cooling deposits crystals of oxalic acid. When caustic ammonia 

 is mixed with this oily matter, or with a solution of this oil in 

 alcohol, a white precipitate immediately falls. This precipitate 

 appears to be a compound of the oily matter with ammonia. It 

 is destitute both of taste and smell, and is neither soluble in 

 cold nor hot water. When heated, it is volatilized in a white 

 smoke without undergoing decomposition. Neither nitric nor 

 cold muriatic acid dissolves it ; but boiling muriatic acid readily 

 dissolves it. Concentrated sulphuric acid readily dissolves it 

 when assisted by heat. The solution is transparent and colour- 

 less, and no precipitate appears when the acid is saturated by an 

 alkali. When boiled with potash or soda, it is not decomposed, 

 nor is any ammonia disengaged. When it is mixed with liquid 

 potash, and distilled in a retort, the liquid that comes over con- 

 tains ammonia and alcohol ; and when the portion remaining in 

 the retort is saturated with muriatic acid, and mixed with muriate 

 of lime, a copious precipitate of oxalate of lime falls. — (Schweig- 

 ger's Journal, xix.308.) 



VIII. ALKALIES AND EARTHS. 



1. Alkaline Sulplturets. — Vauquelin has suggested that what 

 is called sulphuret of potash is probably sulphuret of potassium ; 

 for he found that when sulphur and potash are combined toge- 

 ther in close vessels by means of a red heat that the sulphuret 

 formed contains a quantity of sulphuric acid which contains 

 exactly the portion of oxygen that existed previously in the 

 potash. Gay-Lussac has put this intricate subject in a very 

 clear light. He finds that when equal weights of sulphur 

 and potash are mixed together, and made to unite by ex- 

 posure to a low heat, a sulphuret is formed which contains 

 no sulphuric acid whatever. For when it is dissolved in water, 

 only sulphurous and hyposulphurous acids can be detected in it ; 

 but when sulphur and potash are exposed to a red heat, abundance 

 of sulphuric acid is formed. It would appear then at a low heat, 

 that sulphur and potash combine together, and form sulphuret of 

 potash ; but that at a red heat the potash is decomposed, and 

 the mixture is converted into sulphuret of potassium and sul- 

 phuret of potash. — (Ann. de Chim. et de Phys. vi. 321.) 



2. Preparation of Alumina. — Gay-Lussac has suggested an 

 easy method of obtaining pure alumina. In France it is 

 very easy to meet with alum formed by means of ammonia 

 instead of potash. When this variety of alum is exposed to a 

 strong heat, it loses its acid, its ammonia, and its water, and 

 nothing remains but the alumina in a state of purity. Unfor- 

 tunately this method of procuring alumina cannot be had recourse 

 to in Great Britain, as all our alum is made by means of potash; 

 and, certainly, ammonia alone is never employed in its formation ; 

 for ammonia could not be procured, even by means of urine, at so 



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