24 AMtiwnlacal Vitriol. [Book VI. 



jire. Vitriolated tartar does not appear to be a foffil 

 falti it is found in the juices of vegetables, and remains 

 in their afhes after they are burnt. What is ufed iu 

 dying and medicine, is obtained by art, moft commonly 

 by adding vitriolic acid to nitre, in order to diflodge 

 the nitrous acid. 



One hundred parts of vitriolated tartar contain, ac- 

 cording to Bergman, about 52 parts of fixed vegetable 

 alkali, 40 of vitriolic acid, and 8 of water of cryftalli- 

 zatiori. 



The vitriolic acid combined with the volatile alkali 

 is called AMMONIACAL VITRIOL, or fulphat of am- 

 monia. Ammoniacal falts, it is proper to remark, are 

 fo called from ammcMy an Arabic word for iand ; or, 

 as Pliny conjectures, from the temple of Jupiter 

 Ammon, near which ammonia ufed to be found in 

 great quantities, on account of the camels dung and 

 urine brought thither. With refpect to the general 

 properties of ammoniacal falts, as their alkali is very 

 volatile, they are unable to bear any great degree of 

 heat without being converted into vapour, though 

 much m6re than might be expected from their in- 

 gredients. They emit pungent fumes if a fixed alkali 

 or lime is added to them, as thefe fubftances, having 

 a ftronger '.affinity with the acids, expel the volatile 

 alkali. 



When ammoniacal vitriol is very pure, it has the 

 form of needles, which, on careful examination, are 

 found to be flattened prifms of fix fides, two of which 

 are very broad, terminated by fix-fided prifrns irre- 

 gularly formed ; but the whole figure of the cryftallj- 

 zation is fubject to considerable varieties. This fait 

 is fometimes in the form of quadrangular prifms, an-^j 

 is 'fom crimes obtained in very thin plates. 



Its tafle is bitter and urinqus j it is light, and very 

 friable. It is fcarcely changed by expofure to air ; 



it 



