214 ESSAY XIX. 



an ammoniacal salt, in shape like the points of small pins. 

 This salt, on distillation, yields its alkali in a caustic state ; 

 the acid remaining behind in the retort in the form of a dry 

 powder of a yellow colour. This ammouiacal salt decom- 

 pounds nitrated lime, in consequence of which regenerated 

 tungsten is produced. (/) With magnesia the acid of 

 tungsten forms a neutral salt of difficult solubility in water. 

 (g) It produces no change on solutions of alum or lime, but 

 it decompounds acetated ponderous earth, and the precipitate 

 is altogether insoluble in water, (h) The following metallic 

 solutions are precipitated of a white colour by the acid of 

 tungsten, viz. vitriolated iron, zinc, and copper, nitrated 

 silver, quicksilver, and lead, as also muriated lead ; but tin, 

 combined with the same acid, is precipitated blue ; and 

 corrosive sublimate and the solution of gold undergo no 

 change. 



SECTION VI. 



When the acid of tungsten is calcined in a crucible, it 

 loses the property of being soluble in water. That the acid 

 is much disposed to attract phlogiston, appears from the 

 blue colour it acquires with fluxes (Sec. v. (#), (&)). This 

 circumstance induced me to mix the dry acid with a little 

 linseed oil, and to expose the mass to a strong fire in a luted 

 crucible. When it was grown cold, I found the acid black, 

 but in other respects quite unchanged. I also mixed one 

 part of the dry acid with two parts of sulphur, and distilled 

 off the latter ; I then mixed with the residuum two parts 

 more of sulphur, and again distilled it off. The acid had 

 acquired a grey colour, but was in other respects unaltered. 

 Solution of liver of sulphur was precipitated of a green colour 

 by acid of tungsten, but the phlogisticated alkali white ; the 



