Fig. 134.

Now contrive a jet for burning hydrogen from the bottle, Fig. 133, by removing the delivery-tube, and fitting to it a tube bent twice at right angles, as shown in Fig. 136. Draw out the jet at the end of the tube as already directed. As soda glass gives a yellow tinge to hydrogen flame, it is better for having the tip of platinum; this you can do by bending a small piece of platinum foil and putting it into the glass-tube when the end is soft. When it cools, the platinum tip will be fixed tightly. A straight jet about 6 inches long attached to the end of a length of indiarubber tubing is sometimes even more convenient than that we have described.

How To Make Simple Apparatus For Chemical Experime 147

Fig. 135.

How To Make Simple Apparatus For Chemical Experime 148

Fig. 136.

In the next place we will show how you may fit up in series U tubes. First get a good soft cork for each tube; see that they fit well. Then bore each cork to fit the " quill" tubing you must use for the con-nectiona. Heat the tubes and bend them carefully, keeping the bends all in the same plane, or they will look badly when put together. We show such an arrangement in Fig. 137; attach cords at a, bt by which the whole arrangement can be suspended on a stand or frame made for the purpose.

The frame referred to you can make for yourselves. Take a flat piece of board about 6 inches wide. Plane it up nice and smooth; bevel off the upper edge. Then cut off two pieces for uprights, about 10 inches long and inch square; let these into the base-board. Then across the top fix a horizontal piece of the same thickness. Clean it up and stain it; or it may be left plain, for it is equally useful either way.

Set of u tubes.

Fig. 137. - Set of u tubes.

Put in some tacks or hooks in the top piece at the points in which you wish to suspend the apparatus.

A few square blocks are useful for raising above the level of the table, or blocking up any items of apparatus. They can be made in sets 4 or 5 inches square, and of thicknesses varying from inch to 4 inches thick.

One or two other items of apparatus may be mentioned here, and an easy method of making them.

The first we will give is how to blow a bulb at the end of a tube. First, one end of the tube must be closed. If the tube be a small one, this is easily done by holding one end in the gas-flame till it is melted; it will then run together and close the end. If the tube is of large bore, it must be closed by softening a part near to the end so that it can be drawn out, and then twisted while it is soft, and thus closed.

Having succeeded in closing the tube, heat the closed end, rotating it by twisting it between the hands all the time. When the tube is quite soft, put the open end to the mouth, remove the other from the flame, and then blow gently down the tube till a bulb of the required size is formed. Do not allow it to cool too quickly. This is assisted by allowing the bulb to remain some time in the smoky part of the flame.

How To Make Simple Apparatus For Chemical Experime 150

Fig. 138.

A piece of glass-tubing of large bore may be joined to a piece of smaller bore, by drawing in a small length of the larger to the size of the smaller; then melt both ends, bringing them together when quite soft.

Sometimes a hole is needed in the side of a glass tube. This requires care. If the tube be a small one, it is best done after closing the ends by melting them together. When closed and the ends are cold, bring a small blow-pipe flame on to the part of the tube at which the hole is required. The air within the closed tube will get very hot and endeavour to get out of the tube, and will do so by forcing a hole through the softest and hottest part of the tube. When cool, trim off the edge of the hole with a file. If the tube is larger it can be closed at one end with a good cork. Play upon the point at which the hole is required with the blow-pipe flame till the glass is soft. Then blow hard down the tube; a bulb will be formed at the heated spot. When cool, take off the bulb by means of the file, clean down the edges, and you will have what you require. The process is shown at Fig. 138, a.

A platinum wire may be fitted into glass readily, because the glass and the metal expand very nearly at the same rate, so that the platinum does not get loose. For getting the coloured flame when testing salts it is useful to have a platinum wire fitted into a stem of glass, which may be a tube or a solid piece. Soften the end into which the wire is to be fixed; press the wire in while the glass is soft. Then hold in the blow-pipe flame so that the glass may close well round the wire, and let it cool slowly. You will have such a contrivance as shown in Fig. 138, b.

By practice you will be able to form very many more appliances than we have given here, and make for yourself several pieces of apparatus sketched in your book on Chemistry. But all require care and patience. The skill with which you will be able to manipulate glass will increase very much by practice; and we are sure that the few hours practice in making even the little fittings and arrangements we have pointed out will give you great satisfaction, and, we hope, encouragement.

Good and successful glass-blowing such as is required for complicated pieces of apparatus is rarely acquired by the amateur, unless he gives an immense amount of time to it.