1 6 Mr. Davy’s Lecture on the Decomposition and Composition 
fluid together, burn, and produce phosphate of potash. When 
the experiment is made under naphtha, their combination takes 
place without the liberation of any elastic matter, and they 
form a compound which has a considerably higher point of 
fusion than its two constituents, and which remains a soft solid 
in boiling naphtha. In its appearance it perfectly agrees with 
a metallic phosphuret, it is of the colour of lead, and when 
spread out, has a lustre similar to polished lead. When 
exposed to air at common temperatures, it slowly combines 
with oxygene, and becomes phosphate of potash. When 
heated upon a plate of platina, fumes exhale from it, and it 
does not burn till it attains the temperature of the rapid com- 
bustion of the basis of potash. 
When the basis of potash is brought in contact with sul- 
phur in fusion, in tubes filled with the vapour of naphtha, they 
combine rapidly with the evolution of heat and light, and a 
grey substance, in appearance like artificial sulphuret of iron, 
is formed, which if kept in fusion, rapidly dissolves the glass, 
and becomes bright brown. When this experiment is made 
in a glass tube hermetically sealed, no gas is liberated if 
the tube is opened under mercury ; but when it is made in a 
tube connected with a mercurial apparatus, a small quantity of 
sulphuretted hydrogene is evolved, so that the phenomena 
are similar to those produced by the union of sulphur with the 
metals in which sulphuretted hydrogene is likewise disengaged, 
except that the ignition is stronger.* When the union is effected 
* The existence of hydrogene in sulphur, is rendered very probable by the ingenious 
researches of M. Berthollot Jun. Annales de Chimie, Fevrier 1807 page 143. The fact is 
almost demonstrated by an experiment which I saw made byW. Clayfield, Esq. at Bristol, 
in 1799* Copper filings and powdered sulphur, in weight in the proportion of three 
