Experiment VIII.
Further to examine the Powder remaining after the foregoing Operation.
The Operation.
Seven Drachms and 37 Grains of that Powder in a very clean Glass Retort, cased over with a Coat of Sand and Clay, I put into the naked Fire, which was carefully increased by Degrees, ’till the little Retort, which was entirely covered with the Coals, grew quite red hot. In this Degree of Heat I kept it for four Hours.
The Effect.
In the Receiver was seven Drams of most pure Mercury reviv’d from this Powder. In the Bottom of the Retort were 15 Grains of a dark, subtle, and fixed Powder, in so strong and lasting a Fire. There was a broad Spot, very thin, of a beautiful red, impressed on the Bottom of the Retort, and, as it were, penetrating into the Glass.