pipe flame is considerably increased. The apparatus is sufficiently small to be used whilst travelling, and it may even be put into the pocket.

The author has devised a very convenient self-acting blowpipe apparatus, shown in Fig. 5, which may be very readily constructed. It consists of two capacious bottles connected by a caoutchouc tube. One of them, filled with water, is placed on as high a shelf as can be conveniently reached, about a yard and a half being a suitable height, whilst the other is provided with a cork, bearing a tube communicating with the blowpipe. As the water passes from the upper to the lower bottle, the air in the latter is compressed and passes out to the blowpipe in a regular stream. Flasks of four liters capacity will supply a blowpipe jet of 0.4 mm. diameter with a constant stream for ten minutes. After this it is only necessary to change the flasks in order to continue the current. If bottles provided with holes near the bottom cannot be obtained, ordinary ones can be used by passing a tube to the bottom of each bottle, and then joining these as before. In this case it is necessary to exhaust the connecting tube, on changing the bottles, so as to cause the water to flow. The current of air can be regulated by placing a screw clip on either of the caoutchouc tubes.

FIG. 6.

2. The most convenient blowpipe flame is obtained by taking a Bunsen lamp and placing within its tube a second tube, cut off obliquely at the upper end, and flattened so as to have an inside width of from 1 to 2 mm. (Fig. 6). The tube is about 100 mm. long, and, when in use, closes the air-holes of the burner.

Unfortunately this flame cannot be employed when testing a substance for sulphur, as coal-gas frequently contains sufficient sulphur to vitiate the results.

Next in importance stands Berzelius' blowpipe lamp as improved by Plattner (Fig. 7). This consists of an oil

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b

FIG. 7.

vessel, a, on a stand, c, and provided with two openings which can be closed by screw-caps, the one opening being used for charging with oil, and the other, d, being fitted with a burner bearing a flat wick. Olive oil or refined rape oil is burnt.

A spirit lamp, with flat wick, which, however, must not be too small, may also be employed, if the alcohol be mixed with some compound rich in carbon; say, I part of turpentine or 3 of benzol to 12 parts of the alcohol. Such a lamp gives a high temperature, and does not require trimming so often as an oil lamp,

A candle-flame will serve for most experiments, but is attended by the inconvenience that the candle is con

stantly decreasing in length. Thick stearin candles, the so-called carriage candles, are employed, and the wick is bent in the direction in which the blowpipe flame plays. Gas blowpipes are made, in which the lamp and blow-pipe are combined. The jet tube is surrounded by another tube, and the gas is passed into the space between the two. The air and gas mix near to the open mouths of the two tubes, and the flame produced is oxidizing or reducing according as much or little air is mixed with the

FIG. 8.

gas. Fig. 8 shows a common blowpipe, and Fig. 9 a stand blowpipe with this arrangement.

FIG. 9,

3. Charcoal, platinum, and glass are the principal substances used as supports before the blowpipe.

Of these charcoal is the most important on account of its low heat-conductivity and its reducing power. That

from light woods, such as fir, is the best; it must be well burnt, and should neither smoke nor give off sparks.

It is sawn into pieces about 10 cm. long, 3 cm. wide, and 2 cm. thick, and only that side should be used which shows the rings of growth.

As a substitute for charcoal may be used the so-called plastic-porous charcoal (plastisch-poröse Kohle), which is produced on a large scale. This can also be prepared by working up charcoal powder to a plastic mass with starch paste, moulding into shape, drying, and then heating in a closed crucible to faint redness, in order to decompose the binding material.

As another kind of substitute for charcoal, aluminium plate may be advantageously employed. A piece about 5 inches long, 11⁄2 inches broad, and of the thickness of a sixpenny piece is taken, and one end is bent up so as to form a ledge 3/4 of an inch deep, at a slightly acute angle to the body of the plate. On to this plate a small piece of charcoal, about 1⁄2 an inch square, and rather thicker than a penny-piece, is laid, upon which the substance under investigation is brought. The plate may be cleaned by means of wash leather with bone-ash and water, and lasts for a long time.

Platinum, which in the form of wire is very frequently used, is preferable to charcoal in oxidation tests as it exerts no reducing action, and the colour of beads can be more easily seen. Platinum wire, of the thickness of horse hair, is cut into pieces about 8 cm. long; one end of each piece is then bent into a small loop to serve as support to the flux to be used. Smaller pieces have one end fused into a drawn-out glass tube, which serves as handle. U-shaped loops, which are mainly used, form

spherical beads, whilst O-shaped ones form flat lensshaped beads, which in the case of deeply-coloured beads show the colour better. To have a clean stock of wires on hand they should be kept in a glass filled with water. Platinum foil, which is not very largely employed, is used in pieces of about 50 mm. long by 15 mm. wide. A small platinum spoon is very useful in fusing substances with acid potassium sulphate or nitre. A platinum spiral, from 2 to 3 mm. wide, made by coiling platinum wire around a lead pencil, may be used for the same purpose.

Glass tubes and small glass matrasses are very frequently employed, and should always be kept in stock.

For heating substances in air (roasting) glass tubes about 6 mm. in diameter and 100 mm. long, open at both ends, are used; whilst small matrasses, or glass tubes closed at one end, are employed for heating substances alone, without a current of air.

4. Of other apparatus, the most necessary are:

An agate mortar of from 40 to 50 mm. diameter. Forceps with platinum points, which open by pressure. Steel forceps.

A pair of steel cutting pincers, to cut off fragments from minerals.

A small hammer and anvil; both of hardened steel, and well polished.

A small magnetic needle.

A lens.

A spatula of polished iron.

Coloured glasses: a blue one, coloured by cobalt; a violet one, coloured by manganese; a red one, coloured by suboxide of copper; and a green one, coloured by