(d.) Platinum Foil.—­For the heating or fusing of a substance, whereby its reduction would be avoided, we use platinum foil as a support.  This foil should be of the thickness of good writing paper, and from two and a half to three inches long, by about half an inch broad, and as even and smooth as possible.  If it should become injured by long use, cut the injured end off, and if it should prove too short to be held with the fingers, a pair of forceps may be used to grasp it, or it may be placed on a piece of charcoal.

(e.) Platinum Spoon.—­When we require to fuse substances with the acid sulphate of potash, or to oxidize them by detonation with nitrate of potash, whereby we wish to preserve the oxide produced, we generally use a little spoon of platinum, about from nine to fifteen millimetres[1] in diameter, and shaped as represented in Fig. 7.  The handle of this spoon is likewise of platinum, and should fit into a piece of cork, or be held with the forceps.

    [1] The French millimetre is about the twenty-fifth part of an
    English inch.

[Illustration:  Fig. 7.]

(f.) Platinum Forceps or Tongs.—­We frequently are necessitated to examine small splinters of metals or minerals directly in the blowpipe flame.  These pieces of metallic substances are held with the forceps or tongs represented as in Fig. 8, where ac is formed of steel, and aa are platinum bars inserted between the steel plates.  At bb are knobs which by pressure so separate the platinum bars aa, that any small substance can be inserted between them.

[Illustration:  Fig. 8.]

(g.) Iron Spoons.—­For a preliminary examination iron spoons are desirable.  They may be made of sheet iron, about one-third of an inch in diameter, and are very useful in many examinations where the use of platinum would not be desirable.

(h.) Glass Tubes.—­For the separation and recognition of volatile substances before the blowpipe flame, we use glass tubes.  These should be about one-eighth of an inch in diameter, and cut into pieces about five or six inches in length.  These tubes should have both ends open.

Tubes are of great value in the examination of volatile substances which require oxidizing or roasting, and heating with free access of air.  Also to ascertain whether a substance under examination will sublimate volatile matter of a certain appearance.  Such substances are selenium, sulphur, arsenic, antimony, and tellurium.  These substances condense on a cool part of the tube, and they present characteristic appearances, or they may be recognized by their peculiar smell.  These tubes must be made of the best kind of glass, white and difficult of fusion, and entirely free from lead.  The substance to be examined must be put in the tube near one end, and exposed to the flame of the blowpipe.  The end containing the