236 Experiments on the Oxygenated 
EXPERIMENT VII. WITH SULPHURET OF 
ARSENIC, (Orpiment.) 
A grain or two of the salt rubbed with an equal 
weight of this substance produced little more than a 
flash; but a grain of the salt with half a grain of the 
sulphuret gave a strong report, though very little 
friction was used. Reducing the quantity of sul- 
phuret to a quarter of a grain, the explosions were 
weak and successive. A larger quantity of this 
mixture, than is mentioned above, makes a report 
which is very unpleasant, with considerable flame, 
I was greatly surprised the first time I made the ex- 
periment with two or three grains of the salt and a 
portion of the sulphuret, by their exploding in a 
most violent manner, though a very slight friction 
had been used. The sulphuric or nitrous acids 
gave a very strong flame the moment they were 
dropped upon this mixture. 
EXPERIMENT VIII. WITH COTTON-WOOL. 
A small quantity of very dry cotton-wool was 
rubbed with a little of the salt; no detonation took 
place. The wool was afterwards dropped into the 
sulphuric acid and took fire immediately ; but the 
nitrous acid would not inflame it, 
EXPERIMENT 1X, WITH LOAF-SUGAR, 
One grain of this substance rubbed with two of 
