392 On the Movements Camphor upon Water, ^c. 
M. Serullas ascribes the impetuosity with which potash moves 
upon water to the rapid emission of the hydrogen which is pro- 
duced. In order to prove this, he put portions of the alloy of 
potassium and bismuth under a receiver of dry atmospheric 
air, and reversed upon dry mercury, the alloy remained sta- 
tionary, and was quietly dissolved in the mercury. Other pieces 
were placed in the same manner under another receiver, and 
were left for a sufficient time to establish their immoveability. 
As soon as two drops of water were thrown into the air across 
the mercury, the fragments began to move with their accustom- 
ed velocity. The same effect was obtained by substituting in 
place of atmospheric air dry azote, or oxygen equally dried. 
Similar results were obtained by substituting potassium in place 
of the alloy. M. Serullas now placed a capsule containing 
mercury, upon which he had put some fragments of the alloy, 
and having introduced it under the receiver of an air-pump, 
the fragments instantly expired as soon as the air was with- 
drawn, and were reanimated by its introduction. 
On the Motion of the Alloys of Potassium and Lead, Potassium 
and Tin, and Potassium and Iron, upon Mercury. 
The two first of these alloys are decomposed with difficulty 
when in contact with water. No doubt, however, the serrated 
contexture of these metals^protects the potassium from the aque- 
ous fluid. When they are thrown on mercury, however, they 
are soon set in agitation, their motion gradually increases, and 
they acquire a still greater velocity, if water is poured upon it. 
W^hen the alloys have disappeared from the surface of the 
bath, and have left only a black and unctuous water, M. Se- 
rullas observed, that they occasioned starts which raised the 
pellicle with a species of explosion, and he supposed this to 
be part of the amalgamated potassium which decomposed the 
water in the mass of mercury. 
M. Serullas likewise remarked, that the alloy of potassium 
and iron turns like the other alloys upon a bath of mercury 
covered with water ; and he informs us, that all that he has said 
of the alloys of potassium is equally applicable to those of so- 
dium. 
