New amalgams and methods of colouring have been discovered, and fresh forms have been diligently studied.
Many amalgams are formed by the direct contact of a metal with mercury, sometimes with absorption, sometimes with evolution, of heat.
Some amalgams are liquids, especially when containing a large proportion of mercury; others assume a crystalline form.
In some cases definite compounds have been isolated from amalgams which may be regarded as mixtures of one or more of such compounds with mercury in excess.
By the addition of sodium amalgam to a concentrated solution of ammonium chloride, the so-called ammonium amalgam is obtained as a spongy mass which floats on the surface of the liquid; it decomposes readily at ordinary temperatures into ammonia and hydrogen; it does not reduce silver and gold salts, a behaviour which distinguishes it from the amalgams of the alkali metals, and for this reason it is regarded by some chemists as being merely mercury inflated by gaseous ammonia and hydrogen.