102. Construction of the oxy-hydrogen blow-pipe.—This useful instrument consists of a cubical vessel, made of tin plate, being from ten to twenty inches in length, breadth and height. The inside is divided into four equal apartments, by two partitions, crossing each other in the centre. The two front apartments are covered at the top, and each of them have a tube fixed in the front side, near the top, with a stopcock. The other apartments are open at the top, and communicate with those in front, by a small aperture near the bottom of each. These apartments being all filled with water, those in front are filled, the one with oxygen, and the other with hydrogen gas, which is done by forcing the gases into them through the tubes in front, which causes the water to recede through the aperture at the bottom, and consequently, part of the water is forced over the top of the other apartments; or rather, may run off through small tubes, fixed for the purpose, near the top, similar to those in front. When the front apartments are filled with the gases, (which may be known by the bubbling in the others) the tubes are stopped, and two leaden pipes are fixed in them, the opposite ends of which, are so placed, that the two streams of gas, when expelled from the gas holders, may come in contact very near the ends of the pipes. When the tubes are open, the pressure of the water will expel the gases, and will consequently settle, and must be replenished, so as to keep the apartments nearly full. When the two streams of gas are ignited at the point of contact, a flame is produced of sufficient intensity to burn gold, silver, copper or tin, with a very brilliant combustion.
103. To make a dry phosphorescent powder.—Take some thick oyster shells, wash them, and calcine by keeping them red hot in an open fire for half an hour: then, select the clearest and whitest parts, and reduce them to powder. Mix three parts of this powder, with one of the flour of sulphur; fill a crucible with this compound, pressing or beating it down as hard and solid as may be, without breaking the crucible. Set the crucible in the fire, and heat it moderately at first, but increase the heat gradually for an hour, in which time it must approach nearly to a white heat. Then let it cool, and again select from the mass, the whitest and purest parts, which must be preserved in a phial with a glass stopper. This powder has the peculiar property of imbibing the rays of the sun in the day time, and emitting them again in the night; or if the phial containing it, be exposed for a few minutes to the direct rays of the sun and then carried into a dark room, light enough will be evolved to render it distinctly visible.
104. Curious experiment of precipitation.—Set five glasses on the table, and nearly fill one of them with a solution of sulphate of iron; and another with a solution of sulphate of copper; a third with a solution of nitrate of bismuth; pour into the fourth, a solution of nitro-muriate of cobalt, and into the fifth a solution of acetate of lead, or sulphate of zinc. These liquid solutions may all be diluted so as to be colourless. Then pour into each glass, a few drops of a colourless solution of prussiate of potass. The contents of the first glass will be instantly changed to a full blue colour; those of the second to a reddish brown; those of the third, to a yellow; the fourth to a green, and the fifth to a white. Thus five distinct colours will be given, by the addition of one colourless solution.
105. To make a beautiful soft glass for jewelry.—Take six ounces of clean fine white sand, three ounces of red lead, three ounces of pure sub-carbonate of potass, one ounce of nitrate of potass, half an ounce of borate of soda, and two drachms of arsenic; mix and pound them all together. Put the compound in a crucible, and set it in a common fire, often stirring it with an iron rod, till it is well melted, and becomes transparent. This compound will liquify very easily without any great heat, if the sand is fine, (which sometimes requires to be ground or pounded in a glass or flint mortar,) and if it be kept melted awhile, will become beautifully transparent, and may be cast or blown in the manner of other glass. This glass may be changed to a red or ruby colour, by adding and fusing together with it, a small quantity of finely powdered precipitate of gold, (gold precipitated from solution in nitro-muriatic acid by the addition of tin.) It may be also changed to blue by the addition of zaffre, (an ore of cobalt,) and magnesia: a green colour may be given by a precipitate of copper; and yellow by calcined iron, and white by calcined bones. This subject is treated of largely in the Handmaid of the Arts, to which, for further information on the subject, the reader is referred.
106. Composition of various kinds of glass.—The best flint glass is composed of 129 lbs. of white sand, 50 lbs. of red lead, 40 lbs. of sub-carbonate of potass, 20 lbs. of nitrate of potass, and 5 oz. of magnesia. The best crown glass is composed of 60 lbs. of white sand, 30 lbs. of sub-carbonate of potass, 15 lbs. of nitrate of potass, 1 lb. of borate of soda and ½ lb. of arsenic. The composition of common green window glass, is 120 lbs. of white sand, 30 lbs. of sub-carbonate of potass, 60 lbs. of wood ashes, 20 lbs. of muriate of soda and 5 lbs. of arsenic. The composition for looking glass plates, is 60 lbs. of clean white sand, 25 lbs. of purified sub-carbonate of potass, 15 lbs. of nitrate of potass, and 7 lbs. of borate of soda. Common green bottle glass is made from 200 lbs. of wood ashes, and 100 lbs. of sand. The materials for making glass, is first reduced to powder; then mixed and exposed to a strong heat, in suitable pots and furnaces, till the whole mass liquifies and becomes thoroughly commixed and transparent.