68 Mr. Davy's Lecture on some new analytical Researches 
off. The light of the Voltaic spark in the phosphorus was 
at first a brilliant yellow, but as the colour of the phosphorus 
changed, it appeared orange. 
I heated three grains of potassium in sixteen cubical inches of 
phosphuretted hydrogene; as soon as it was fused, the retort 
became filled with white fumes, and a reddish substance pre- 
cipitated upon the sides and upper part of it. The heat was ap- 
plied for some minutes. No inflammation took place.* When 
the retort was cool, the absorption was found to be less than 
a cubical inch. The potassium externally was of a deep brown 
colour, internally it was of a dull lead colour. The residual gas 
had lost its property of spontaneous inflammation, but seemed 
still to contain a small quantity of phosphorus in solution. 
The phosphuret acted upon over mercury by solution of 
muriatic acid evolved only one cubical inch and three quarters 
of phosphuretted hydrogene. 
From this experiment, there is great reason to suppose that 
phosphuretted hydrogene contains a minute proportion of 
oxygene, and consequently that phosphorus likewise may 
contain it ; but the action of potassium on phosphorus itself 
furnishes perhaps more direct evidences of the circumstance. 
One grain of potassium and one grain of phosphorus were 
fused together in a proper apparatus. They combined with 
the production of the most vivid light and intense ignition. 
During the process one tenth of a cubical inch of phosphuretted 
hydrogene was evolved. The phosphuret formed, exposed 
* It is stated, in the account before referred to of M. M. Gay Lussac’s and 
Thenard’s experiments, that potassium inflames in phosphuretted hydrogene. My 
experiments upon this gas have been often repeated. I have never perceived any lu- 
minous appearance ; but I have always operated in day-light. 
