Page:Proceedings of the Royal Society of London Vol 1.djvu/300

Rh every ﬂuid in which they are attempted to be kept, and more or less on the solid ingredients of the vessels in which they are examined.

The ﬂuid substance containing the least oxygen, and consequently best adapted for preserving them, is naphtha recently distilled. In this they may be kept many days without any considerable change; and when taken out of it, their physical properties may be conveniently examined in the atmosphere while their surface is yet moist, and pro- tected by a thin ﬁlm of naphtha.

The base of potash, at the temperature of 60°, appears as a ﬂuid globule, having the full metallic lustre, opacity, and so much the ge— neral appearance of a globule of mercury, that a difference cannot be detected by the eye. Its ﬂuidity, however, even at this temperature, is not perfect, and at 50° it becomes a soft solid; at 40° it is mal- leable, and has the lustre of polished silver: at about the freezing point of water it is brittle, and. when broken, its fragments exhibit a crystalline texture.

When its temperature is, on the contrary, raised to 100°, its ﬂuidity is perfect; and when it is heated to adegree approaching to redness, it boils, and after distillation is found in its condensed form unaltered. Like metals, it is a perfect conductor of electricity; but when the globule exposed is too small for the quantity of electricity to be transmitted, it is completely dissipated with explosion, accompanied with a vivid White light,.

It is also, like most known metals, an excellent conductor of heat, when brought into contact With mercury, &c. When the base of potash is brought into contact with mercury, it instantly amalga- mates. If the globule of mercury be much the larger, the compound appears to be more ﬂuid than mercury; but when the mercury ex- ceeds in size only in the proportion of 2 to l, the compound, though ﬂuid at ﬁrst from the heat of union, consolidates as it cools, and ap- pears as a soft metal, similar to silver.

The ﬂuid compound unites with all metals that have been exposed to it, acting readily even upon iron and platina.

The base of potash will also combine with other metals without the assistance of mercury, if applied to them in its ﬂuid state; and it is remarkable, that in most inshmces the point of fusion of the compound is much higher than could be expected from that of the ingredients.

With sulphur and with phosphorus it also combines, and the com- pounds agree in appearance with the metallic sulphurets and phos- phorets.

But though it resembles the metals in all these properties, it dif- fers from all most remarkably in speciﬁc gravity, since it rises' to the surface even in doubly—distilled naphtha, of which the speciﬁc gravity is only T1.,Z,,th of water.

As the quantity which can be obtained is necessarily small, it is difficult to determine any points in which quantities are concerned, with minute precision; and accordingly the average obtained from several experiments, conducted with great care, and with a very