Chap. 7.] Sal Ammoniac. 45 



Pure clay has very little action on marine fait. 

 Ponderous earch decompofes it, but lime and magnefia 

 produce no effect. Common fait is ufed to vitrify the 

 furface of fome kinds of pottery. This is done by 

 throwing a certain quantity of it into the furnace, where 

 it is volatilized, and applies itfelf to the furface of the 

 pottery. This is the kind of glazing ufed in the 

 making of white Engliih pottery. Common fait is 

 alfo ufed in making glafs, to render the glafs whiter 

 and clearer. It is alfo employed as a flux to facilitate 

 the precipitation of metals from the fcorise, and to 

 prevent their calcination from the contact of the at- 

 mofphere. 



jd. Common SAL AMMONIAC is the muriat of 

 ammoniac of the French chemifts, and confifts of the 

 muriatic acid united to the volatile alkali. This fait 

 is converted into vapour before it melts, but may be 

 brought into fufion by being combined with other 

 fubflances, or even uncombined, if properly confined. 

 When thrown into the fire, it increafes the flame, and 

 tinges it with a blue colour, efpecially the flame of 

 charcoal. When the air is very moift, this fait deli- 

 quefces. It is very remarkable for producing a great 

 degree of cold when mixed with water. 



in order to obtain one ton of fait, and yet gain as much clear profit 

 as thofe do, who, in counties lefs favourably fituated for fuel, boil 

 down the ilrongeft brine. 



' The advantage refulting fom ftrengthening weak brine or 

 fea wat^r, by means of rock (ale, is very obvious. Suppofe that 

 the fea water at Liverpool, where large quantities of rock fait 

 are refined, would yield one ton of fait from forty-eight tons 

 of water, then muft a quantity of fuel fufHcient to evapora'e forty- 

 feven tons of water be ufed in Border to obtain one ton of fait. 

 JJut if as much rock fait be put into the forty-eight tons of f;-a 

 water, as can be diffolved in it, then will the fea water refemH* 

 9 brine fully faturated, each fixreen tons of which will give four 

 tons of fait, and the whole quantity yielded by the evaporation of 

 forty f.,-v en tons of water, will be twelve tons of fait.' 



Wutfin't Cbem. EJ vol. II. p. 41. 

 If 



