^6 PHILOSOPHICAL TRANSACTIONS. [aNNO 1786. 



a yellowish brown ; th?t of sublimate corrosive, yellow mixed with black; but 

 by agitation it becomes white. The nitrous solution of bismuth becomes, by 

 mixture with this water, reddish brown, and even assumes a metallic appear- 

 ance; that of cobalt becomes dark; that of zinc, of a dirty white, that of 

 arsenic, in the same acid, yellow mixed with red and white, orpiment and realgar 

 being formed. 



If oil of vitriol, whose specific gravity is 1 .863, be dropped into hepatised 

 water, it renders it slightly turbid; but if the volatile vitriolic acid be dropped 

 into it, a bluish white and much denser cloud is formed in the water. Strong 

 nitrous acid, whether phlogisticated or not, causes a copious white precipitation; 

 but dilute nitrous acid produces no change. Green nitrous acid, whose specific 

 gravity was 1.328 immediately precipitated sulphur from it. Strong marine 

 acid produced a light cloud; but neither distilled vinegar nor acid of sugar had 

 any effect. 



Of the Properties of Alkaline Liquors, impregnated with Hepatic Air. — 

 Colourless fixed alkaline liquors receive a brownish tinge from this air. The 

 residuum they leave is of the same nature as the part they absorb. A caustic 

 fixed alkaline liquor, saturated with this air, precipitates barytes from the acetous 

 acid, of a yellowish white colour. It also decomposes other earthy solutions, 

 and the colour of the precipitates varies according to their purity, and perhaps 

 this test might be so far improved as to supply the place of the Prussian alkali. 

 It precipitates the solution of vitriol of iron, and also marine salt of iron, 

 black; but this latter generally whitens by agitation. The solutions of silver 

 and lead are also precipitated black with some mixture of white; that of gold is 

 also blackened; but that of platina becomes brown. Solutions of copper let fall 

 a reddish black or brown precipitate. Sublimate corrosive by this test discovers 

 a precipitate partly white and black, and partly orange and greenish. 



In the nitrous solution of arsenic it forms a yellow and orange; and in that of 

 regulus of antimony, in aqua regia, an orange precipitate mixed with black. 

 Nitrous solution of zinc, thus treated, shows a dirty white; that of bismuth a 

 brown mixed with white; and that of cobalt a brown and black precipitate. 

 As Prussian alkali always contains some iron, it gives a purple precipitate with 

 this test, which precipitate is easily dissolved. It turns tincture of radishes, 

 which is my test for alkalis, green. 



Water saturated with the condensed residuum of alkaline hepatic air, that is, 

 with the purest volatile liver of sulphur, does not precipitate marine selenite, 

 though it forms a slight brown and white cloud in that of marine baro-selenite. 

 It produces a black precipitate in the solution of vitriol of iron, and a black and 

 white in that of marine salt of iron; but by agitation this last becomes wholly 

 white. It precipitates both vitriol of copper, and the nitrous salt of copper, red. 



