ssolved in aqua regia and the
solution is dried on the sand bath, without, however, producing
decomposition. Though the instructions are not definite, I presume
that the formation of PtCl4 is contemplated.

The dried salt is added little by little to rectified oil of lavender,
placed on a glass paint-grinding plate, and the salt and oil are
ground together with a muller. Care is required to prevent any
appreciable rise of temperature which would decompose the compound
aimed at, and it is for this reason that the salt is to be added
gradually. Of course the absorption of water from the air must be
prevented from taking place as far as possible. Finally, the compound
is diluted by adding oil of lavender up to a total weight of 1400
grams (of oil).

The liquid is poured into a porcelain dish and left absolutely at rest
for eight days. It is then decanted and filtered, left six days at
rest, and again decanted (if necessary). The liquid should have a
specific gravity of 5 deg. on the acid hydrometer. (If by this the Baume
scale is intended, the corresponding specific gravity would be 1.037.)
A second liquid is prepared by grinding up 25 grams of litharge with
25 grams of borate of lead and 8 to 10 grams of oil of lavender. The
grinding must be thoroughly carried out.

This liquid is to be added to the one first described, and the whole
well mixed. The resulting fluid constitutes the platinising liquid,
and is applied as follows:-

A sheet of clean glass is held vertically, and the liquid is painted
over it, carrying the brush from the lower to the upper edge. The
layer of oil dries slowly, and when it is dry the painting is again
proceeded with, moving the brush this time from right to left; and
similarly the process is repeated twice, the brush being carried from
top to bottom and left to right. This is with the object of securing
great uniformity in the coating. Nothing is said as to the manner in
which the glass is to be dried.

The dried glass is finally heated to a temperature of dull redness in
a muffle furnace. The resinous layer burns away without running or
bubbling, and leaves a dull metallic surface. As the temperature
rises this suddenly brightens, and we obtain the desired surface
(which probably consists of an alloy of lead and platinum). It is
bright only on the surface away from the glass.

I have not had an opportunity of trying this process since I
discovered the detailed account giv