OF1 for Oxydation-flame; RF1 for Reduction-flame; SPh for Salt A MANUAL OF BLOW-PIPE ANALYSIS. FIRST CHAPTER. AUXILIARY APPARATUS AND REAGENTS. § 1. THE common blow-pipe of gas-fitters, jewellers, &c., is not very well adapted for analytical researches, as the narrow outlet becomes frequently obstructed by the moisture which is exhaled from the lungs and condenses in the tube. To avoid this inconvenience, the long cylindrical tube of the blow-pipe should be furnished at the extremity with a globular or cylindrical chamber for the reception of the condensed water. In this chamber the jet is inserted at a right angle to the tube. Silver is, in many respects, the best material for the construction of a blow-pipe, but has the disadvantage of becoming very hot when used for a long while, so that it becomes almost impossible to hold it with the naked fingers; next to silver stands German silver and brass. For jets, platinum is preferable to all other metals. A mouth-piece of box-wood or ivory is convenient, though not necessary. § 2. Any kind of flame may be used for the blow-pipe, provided it be not too small. Some of the older chemists used common candles in preference, and it must be confessed that, in the majority of cases, the heat produced by the flame of a good sperm candle is quite sufficient. Berzelius recommended an oil lamp with a flat wick, which is now in general use as "Berzelius's Blow-pipe Lamp." I find that a common fluid lamp, with a rather large burner, answers every purpose; it gives a very good heat, and, besides being much cleaner than an oil lamp, admits of a very (21) quick and accurate adjustment of the size of the flame, by means of a little brass cylinder, which is movable, and slides up and down the burner. The heating of substances in glass tubes and matrasses is best performed over a common spirit lamp. § 3. As supports, charcoal, platinum, and glass are principally. used. Wood charcoal is in most cases the best support. It must be well burnt, and not scintillate or smoke; it must leave but little ash; charcoal of light wood, as alder, &c., has been found the best. Platinum is used whenever the reducing action of the charcoal acts injuriously. It is advantageously employed on all occasions where no reduction to the metallic state takes place, since the color of the flux is much better seen on the platinum than on charcoal. It is mostly used in the shape of wire, the end of which is bent so as to form a hook, which serves as support to the flux. As foil, its use is very limited. A little platinum spoon, of from about 12 to 15 m. m. in diameter, is very convenient for fusing substances with bisulphate of potassa or nitre. Glass tubes, open at both ends, are used for calcination, and for testing the presence of substances which are volatile at a high temperature. The tubes should be from 5 to 8 inches long. Of glass tubes, sealed at one end, or little matrasses, an assortment should always be kept on hand, since they are of very frequent use. -§ 4. Of other apparatus, the most necessary are: A mortar of agate or chalcedony, from 1 to 2 inches in width, with pestle of the same material. A forceps of brass or German silver, with platinum points. A little hammer and anvil, both of steel and well polished. A three-cornered file for cutting glass tubes, trying the hardness of minerals, &c. A little magnet. A pocket magnifying glass. A set of watch glasses, which are very convenient for the reception of the assay-piece, the metallic globules, &c. § 5. Of reagents, Carbonate of Soda, Borax, and Salt of Phosphorus, are the most important ones; but there are others, which, though not so extensively used, still are indispensable for the detection of certain substances; those only shall here be mentioned; others, the use of which is very limited, are omitted in this list. Carbonate of Soda: The monocarbonate or the bicarbonate may be indifferently employed; it must be perfectly free from sulphuric acid, for the presence of which it may be tested as shown § 107. The neutral oxalate of potassa and the commercial [fused] cyanide of potassium deserve in many cases the preference, their reducing powers being superior to that of carbonate of soda. Borax: The commercial article is purified by crystallization, the crystals dried and reduced to a coarse powder. Salt of Phosphorus: [double phosphate of soda and ammonia] 100 parts of crystallized common phosphate of soda and 16 parts of sal ammoniac are dissolved in 32 parts of water; the solution is aided by heat, the liquid filtered while hot, and the crystals, which form on cooling, dried between blotting paper. When pure it gives a glass which, on cooling, remains transparent; if this is not the case it must be purified by recrystallization. It is kept as a coarse powder. Bisulphate of Potassa: It is employed in the fused [anhydrous] state as a coarse powder; it must be kept in a bottle provided with a ground glass stopper. Vitrified Boracic Acid: Is employed in the state of a coarse powder. Fluor-spar: Must be deprived of water by ignition; must be perfectly free from boracic acid, which may be tested as described § 61. It is convenient, to keep in a separate bottle a mixture of 1 part of finely powdered fluor-spar with 4 parts of bisulphate of potassa. Nitrate of Cobalt, in solution: It must be pure, free from alkali, and [for many purposes] free from nickel; it is kept in a bottle with . a ground glass stopper, which, very conveniently, is so much elongated as to dip into the liquid. Instead of the nitrate, the oxalate of cobalt may be used, which, being in the shape of powder, is advantageously substituted for the former in travelling. Nitrate or Oxalate of Nickel: It must be perfectly free from cobalt; it is tested with borax, with which it ought to produce a pure brown glass. Oxide of Copper: It is best prepared by heating the nitrate to ignition. Chloride of Silver: It is prepared by precipitating a solution of nitrate of silver with hydrochloric acid, washing the precipitate, and making it into a thick paste with water, which is kept in a small glass-stoppered bottle. This reagent should not be used with platina wire, since the silver fuses with the platina to an alloy; thin iron wire is in this case substituted for the platina. For each experiment a fresh hook should be made. Pure Metallic Lead: It is easily obtained pure by decomposing a solution of the acetate by metallic zinc; the precipitate is repeatedly washed with water and then dried between blotting paper. Metallic Iron: In the shape of thin wire [harpsichord wire]. Metallic Tin: Usually in the shape of foil, which is cut into strips and rolled up tightly. Bone-ash: In the state of very fine powder. Test Paper: Blue and red Litmus Paper, and Brazil Wood Paper. § 6. If the analytical research is strictly confined to blow-pipe operations, the above enumerated reagents are sufficient; but if, as is sometimes advantageously done, some simple operations of the humid method of chemical analysis are called to aid, the list must be somewhat extended. The most important of these reagents, all of which must be kept in bottles with ground glass stoppers, are: Sulphuric Acid, Hydrochloric Acid, Nitric Acid, Oxalic Acid, Hydrate of Potassa, Ammonia, Carbonate of Ammonia, Chloride of Ammonium, Molybdate of Ammonia, Ferrocyanide of Potassium, Ferridcyanide of Potassium, Bichloride of Platinum, Acetate of Lead, Sulphuretted Hydrogen Water, Sulphydrate of Ammonia, Alcohol, Distilled Water. The principal auxiliary apparatus are: Test-tubes and Test-tube Rack, small Porcelain Dishes, small Beaker Glasses, some Glass Funnels and Filtering Stand, Filtering Paper, Platinum Crucible, some Glass Rods and round Glass Plates, for covering beaker glasses, a common Spirit Lamp, and a Spirit Lamp with Argand Burner. |