230 PHILOSOPHICAL TRANSACTIONS. [aNNO 17Q2. 



phosphorus on the water and sides of the vessel, and exploded on applying to it 

 a ligiited wax taper. This powder therefore I apprehend consists of phosphorus 

 and lime united by heat; it readily decomposes cold water, and then the inflam- 

 mable air disengaged unites with, or rather suspends, a portion of phosphorus, 

 and forms phosphoric air. The phosphorus thus suspended by standing, is de- 

 posited, and inflammable air alone remains; the other constituent of water, 

 respirable air, unites to another portion of phosphorus, and composes phos- 

 phoric acid, which combines with lime, and forms phosphoric selenite. This 

 compound of lime and phosphorus, which some of my chemical friends have 

 called fulminating hepar of phosphorus, may be used to obtain phosphoric air 

 with much more ease than by the usual method*. This experiment seems de- 

 cisive, that the charcoal afforded in the former ones was derived from carbonic 

 acid. 



My next experiment was with caustic alkali and phosphorus. The caustic ve- 

 getable alkali I employed was blackish, partly from a very small quantity of calx 

 of iron, and partly, I think, from other causes which I do not understand; and 

 I was not able to prepare myself, or obtain from others, fixed caustic alkali in a 

 solid form which was colourless. It also always contained a small quantity of 

 carbonic acid. I introduced into a glass tube 50 grs. of phosphorus, and 150 

 of pulverized caustic vegetable alkali, previously found to contain 3 oz. measures 

 of carbonic acid, in each 100 grs. This charge was exposed to heat, as in the 

 former experiments. On breaking the tube when cold, the alkaline matter was 

 blacker than before: a little of it thrown into hot water emitted bubbles of phos- 

 phoric air, but not in cold water: in rubbing off this alkali from the sides of 

 the tube some pieces of it took fire. I dissolved as much as I could of this 

 black alkaline matter, by pouring boiling water on it on a filter: a greenish lixi- 

 vium passed through first, then a less coloured alkaline liquor; and last of all 

 limpid water. A residue left on the filter being dried, weighed 10 grs.; it was a 

 blackish brown, impalpable powder, at least 5 times specifically heavier than the 

 charcoal obtained in the preceding experiments. 



(a) Six grains of this residue on a thin plate of iron, heated over a candle, 

 burnt with a green and blue flame, emitting a somewhat arsenical odour, and it 

 did not remain ignited after the flame ceased. A coal-like matter was left, which 

 weighed 3 grs. 



(b) These 3 grs. (a) being placed on an iron plate, red hot, again emitted a 

 little green and blue flame, with the like, but a weaker smell than before; the 

 substance remaining continued ignited but a (ew seconds of time, though the 

 iron was red hot much longer. The residuum, which was black, weighed 

 2J- grs. 



• Dr. Ingenhousz has devised some surprising and beautiful experiments with tliis substance. — Orig. 



