30 Cufa Nitre. [feook Vt 



or atmofpheric mephitis. His experiment, wherein 

 the nitrous acid was formed by the combination of 

 this gas with vital air, by means of the decline fpark, 

 has been already mentioned. 



CUBIC NITRE, or nitrat of foda, confifts of the 

 nitrous acid and the fixed mineral alkali. It refembles 

 common nitre in all its ftriking qualities j almoft its 

 only difference is the form of its cryftals, which is 

 a paralellopiped. The cryftals adhere fo ftrongly, 

 that they are fcarcely ever found diftinct and regular. 

 For the deflagration of cubic nitre, charcoal is moft 

 proper ; when performed with fulphur, Glauber's falc 

 is produced. 



Cubic nitre has not yet been found in nature, but 

 is always produced by art. The Ihorted method is 

 adding nitrous acid to foffil alkali. Its tafte is cooling, 

 and rather more bitter than that of common nitre. 

 Fire decompofes it j but it decrepitates, and does not 

 fo eafily melt as common nitre j like that fait, however, 

 it gives out vital air during its decompofition. It is 

 (lightly deliquefcent when expofed to air. It is more 

 foluble in cold water than the common nitre, two parts 

 of water, at the temperature of fixty degrees, diflblving 

 one of the fait. It is fcarcely more foluble in boiling 

 water, and therefore cannot be had in regular cryilals,- 

 except by flow evaporation. 



Siliceous earth combines with the bafis of this fait, 

 and difengages the nitrous acid j clay likewife feparates 

 the acid, and affords a refidue in the form of frit *, 

 which is porous and opake when a ftrong heat has 

 been applifd. Ponderous earth decompofes this fait, 

 and difengages the mineral alkali. Magnefia and 

 lime do not fenfibly change it. The vegetable fixed 



*' The mixed materials for making glafs. 



alkali 



