3i8 
Sir H. Davy's new experiments on some 
operation, and satisfied myself that it was the same as that 
formed by other methods, it became evident that there were 
no sources of error in the experiments on the combustion of 
phosphorus in oxygen gas, arising from the formation or 
separation of water ; and the only circumstance which could 
be urged against the accuracy of processes on this combustion, 
was the small quantity of materials* on which they had been 
made. 
The vividness and rapidity of the combustion of phosphorus, 
renders it impossible to burn considerable quantities of phos- 
phorus in the common way in glass vessels. Phosphuret of lime 
burns much more slowly and less intensely. I endeavoured to 
ascertain the quantity of oxygen absorbed by a given weight 
of phosphorus converted into phosphuret of lime ; but the 
experiment did not succeed. Though the phosphuret of lime 
was in fine powder and distributed over a large surface, yet 
the phosphate of lime which formed and fused on the exterior, 
defended the interior of the phosphuret from the action of the 
oxygen, and prevented its combustion. 
After various unsuccessful trials to convert considerable 
quantities of phosphorus into phosphoric acid by combinations 
containing oxygen, I at last thought of a very simple mode 
of burning phosphorus, which answered perfectly. 
Phosphorus requires a considerable heat for its volatili- 
zation. By inclosing it in a small tube, so constructed that 
the phosphorus can burn in vapour only from the aperture of 
• A source of error might be suspected in carbon combined with phosphorus ; but I 
have been convinced by experiments made on the action of chlorine on the phosphorus 
I employed, that it contained no appreciable quantity of carbon. I suspect that what 
is often taken for carburet of phosphorus, is in reality a red oxide. 
