79 
which becomes a violet coloured Gas by Heat, 
but when I heated it in a small retort, containing pure am- 
moniacal gas, no such change occurred, and it combined with 
the ammonia and formed a compound which volatilized with- 
out leaving any oxide. 
The compound of the substance with tin was soluble in 
water, and had the characters of an acid. It combined with 
the alkalies without depositing oxide. 
The crimson compound of the substance with mercury 
united in the same manner without decomposition to potassa? 
and by the action of sulphuric acid, sulphate of potassa was 
formed, and. the compound of the substance with mercury 
disengaged. 
When the substance is made to act upon phosphorus, the two 
bodies combine with great rapidity at common temperatures, 
producing heat without light; small quantities of a strongly 
acid gas generally arise from the mixture, and by the appli- 
cation of heat, it is produced in greater quantities. When the 
substance is in excess, an easily fusible and volatile compound 
of a red colour is obtained ; when the phosphorus is in excess, 
the greater part of the product is more fixed. 
I examined the gaseous acid formed by the action of phos- 
phorus with attention. It gives dense white fumes by com- 
bining with the aqueous vapour in the air. It has a smell very 
similar to that of the solid compound of chlorine and phos- 
phorus, which itself is very analogous to that of muriatic acid. 
It is rapidly absorbed by water. When made to act upon 
ammonia, it forms with it a dense white salt, which, when 
acted upon by sulphuric acid, affords the peculiar substance, 
and at the same time a smell of hydrogen is perceived. When 
mercury is heated in the acid gas, the same compound as that 
