Blow pipe

A very delicate and useful piece of apparatus, which is leadily made with the blow-pipe, is Perkins modification of Sprengel s pyknometer. It is especially adapted for small quantities of liquid and for the moie volatile ones. The apparatus (Fig. 46) consists of a U l ube to hold from 2 to 10 c.c., drawm out at each end into a fine capillary. The one capillaiy limb, a, is bent outwards and is furnished with a small bulb the other, b, is bent at a right angle with the first. On the limb a, between the bulb and the top of the U-tnbe a mark is etched. The... 

In outside collectors, wliich arc iiomially top-access systems, inspection of the bag itself is difficult however, location of tlie broken bag or bags can noniially be found by looking for dust accmiiulation on top of tlie tube sheet, on the miderside of tlie lop-access door, or on a blow pipe". ... 

Run the metal melted or deposited during one passage of an electrode, torch or blow-pipe. 

A spirit burner. .., blow-pipe, one platinum crucible, one platinum sheet and 3-4 platinum wires, a test tube stand with 10-12 test tubes, several beakers and flasks, one porcelain dish and a pair of porcelain crucibles, several glass filter funnels in various sizes, a wash-bottle, several rods and watch glasses, one agate mortar, several iron spoons, a pair of steel or brass pincers, a filtration stand made of wood and one iron tripod stand. 

This tube is drawn out in the flame of a blow-pipe from glass tubing 4-8 mm. wide and is then drawn out again to sufficient fineness in a micro-flame. To make sure before use that the capillary is not closed, the tip is submerged in ether in a small test tube and air is blown in from the mouth. The bubbles should emerge separately and slowly. Capillaries for distillation in a high vacuum should emit air bubbles only on powerful blowing, and then with difficulty. 

The heating liquid is pure concentrated sulphuric acid, with which the bulb of the flask is three-quarters filled. The substance, in powder form, is introduced into a small, thin-walled capillary tube. Such tubes are made as follows from test tubes (preferably from damaged tubes which must, however, be clean and dry ). The tubes are rotated in the flame of the blow-pipe till soft and then drawn out rapidly already after short practice the student can strike the correct diameter, which should be 1 0-1 -5 mm. internally. Suitable portions of the drawn-out material are cut off with scissors. It is convenient to cut double lengths (about 12 cm.), so that by sealing each length in the middle (micro-burner) two melting-point tubes are obtained ready for use. 

Prepare the copper oxide-lead chromate as follows Spread a thin layer of coarse copper oxide over a small iron plate, heat from above with a blow pipe until the glow is as bright as possible and sprinkle with a thin layer of finely powdered lead chromate. The chromate melts at once and spreads over the copper oxide forming a firmly adherent layer and causing the strips of copper oxide to stick together a little. Now turn the cake over and treat the under side in the same way. When the mass has cooled break it up gently in a mortar and remove powder and unduly large pieces with a sieve. 

Sealing the Tube.—In addition to compressed air use oxygen from a cylinder connected to the blow-pipe when sealing the hard glass tube. 

If granulated tin is not available it may be prepared by melting block-tin over a blow-pipe in a long-handled iron spoon provided with a spout, and then pouring the metal drop by drop from a height of 2-3 feet into a bucket filled with water. 

Shortly before 2.00 some 175 tonnes of metal had been run into the first torpedo and the iron stream diverted to the second ladle. Some 10 to 15 minutes later the blow pipe at the No. 3 tuyere position started to bum down on the side facing on to No. 2 tuyere hearth cooler. The burning developed rapidly with intense flame and sparks despite efforts by the furnace keeper to cool the pipe by spraying it with water. 

Within a few minutes of the blow pipe starting to bum down progressive action was being taken by the furnace crew to bring the furnace off blast so that a new pipe could be fitted. 

Gahn was a man of broad interests who often laid aside the Philosophical Transactions or his blow-pipe to read aloud, near the sewing-table in the next room, now a poem by Kellgren, Fianzen, Fru Lenngren, Leopold, or Voltaire, now a comedy by Molibre or Holberg or to exhibit a litde mechanical or optical masterpiece or to study the instruments for some household art and present a method of improving diem (44). 

Before the blow-pipe the sulphate decrepitates, and then melts in the oxidising flame it fuses into a transparent globule, which on hardening turns milk-white in the inner flame it effervesces, owing to the evolution of sulphurous acid, and is quickly reduced to the metallic state. Samples of this mineral afforded to Klaproth the annexed composition. 

A common test for zinc and aluminium is to heat together before the blow-pipe the salt suspected to contain the metal with cobalt nitrate it is probable that the green colour produced by zinc is due to the formation of a cobalt zincate, Co(Zn02), and the blue colour shown by alumina to a similar body, Co(A102)2. 

The apparatus essential to the modern chemical philosopher is much less bulky and expensive than that used by the ancients. An air pump, an electrical machine, a voltaic battery (all of which may be upon a small scale), a blow-pipe apparatus, a bellows and forge, a mercurial and water gas apparatus, cups and basins of platinum and glass, and the common reagents of chemistry, are what are required. All the implements absolutely necessary may be carried in a small trunk and some of the best and most refined researches of modern chemists have been made by means of an apparatus which might with ease be contained in a small travelling carriage, and the expense of which is only a few pounds. 

Ferric oxide, pseudomorphous with magnetite, may be obtained by heating magnetite crystals m the blow-pipe flame for several hours oxidation takes place, the crystals retaining their original form almost unaltered, but losing their magnetic properties.9... 

Dry Tests.—Iron salts, when moistened with hydrochloric acid and heated on a loop of platinum wire in a Bunsen flame, emit a shower of sparks. When heated on charcoal with sodium carbonate in the blowpipe flame, the compound is converted into a dark-coloured residue. If potassium cyanide is added to the sodium carbonate and iron compound, and the whole heated on charcoal in the inner flame of the blow-pipe, metallic iron is obtained as a grey, magnetic powder. 

If a little of the iron compound is heated with borax on platinum wire in the outer blow-pipe flame, on cooling, a yellow transparent bead is obtained, which becomes bottle-green upon heating in the inner or reducing flame of the blow-pipe, in consequence of reduction to the ferrous condition.2... 

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