Mr. Davy’s Researches on 
252 
of a considerable quantity of the gas ; and, in consequence, led 
me to form erroneous conclusions concerning the nature of 
this curious operation. 
In all late experiments in which sulphur, or sulphuretted 
hydrogene were concerned, I have used muriatic acid saturated 
with sulphuretted hydrogene over mercury. I have employed 
sulphur distilled from iron pyrites in vacuo, which did not in 
the slightest degree affect litmus paper, and I have combined 
it with potassium in retorts of green-glass, or plate-glass lined 
with sulphur and filled with very pure nitrogene or hydrogene. 
In making potassium act upon sulphuretted hydrogene, I have 
employed the gas only in the quantities of from 1 to 3 cubical 
inches, and have made the combination in narrow curved 
tubes of green glass over dry mercury. With all these pre- 
cautions, and after having made a great number of experiments, 
I am not able to gain perfectly uniform results. Yet there is a 
sufficient correspondence between them to enable me to form 
conclusions, which I may venture to say cannot be far from the 
truth. 
When 1 grain of potassium, which would give by the action 
of water about 1 cubical inch and T 'g of hydrogene is made 
to act upon about half a grain of sulphur, some sulphur 
sublimes during the combination, which always takes place 
with heat and light, and from T \ to t t - of a cubical inch of 
sulphuretted hydrogene is evolved. The compound acted on 
by muriatic acid, saturated with sulphuretted hydrogene, 
affords from T 9 - to yl of a cubical inch of pure sulphuretted 
hydrogene. 
When more sulphur is used so as to be from twice to ten 
times the weight of the potassium, the quantity of suiphu- 
