382 ABSTRACTS OF CHEMICAL PAPERS APPARATUS, ETC. Estimation of the Concentration of Colloidal Solutions with the New Interferometer for Liquids. R. Marc. (Chem. Zeit., 1912, 36, 537.)-The interferometer described by F. Lowe (Phys. Zeitsch., 1910, 11, 1047) was sensitive with true solutions to 0.003 per cent., with a 4-cm. cell; it is found to be nearly as sensitive with solutions of dextrin, albumin, and other colloids.The ageing of such solutions on standing was almost without effect on the concentration 8s determined by the instrument. For small ranges the concentration was found to be nearly enough proportional to the readings to render a calibration curve unnecessary. With colloidal solutions the difficulty of matching the right pairs of lines is increased, and methods for overcoming this are given.As an example of the application of the instrument to concentration determinations in colloidal. solutions, adsorption experi- ments (albumin and dextrin by barium carbonate) are described. The method may be extended to the examination of water : at the waterworks, by examining before and after filtering ; for potable waters, before and after shaking with a substance capable of adsorbing colloids, but not affecting substances in true solution.The method is not usually applicable to dyes. 0. E. M.APPARATUS, ETC. 383 New Apparatus for the Coking Test of Coal. R. Lessing. (J. Soc. Chem. Ind., 1912, 31, 465-467.)-This apparatus is devised to show, more markedly than the usual b 6 crucible method” can, the difference in the coke produced from various coals.The apparatus is also useful for quantitative determinations of the volatile matter, in which respect it gives, generally speaking, results similar to those obtained by the old method. 1. Factors tending to Increase the b b Volatile” Valu,e.-(a) Burning of coke in the more or less oxidising atmosphere ; ( b ) 6‘ spitting ” of coal-dust due to the explosive character of gasification of some coals, or rush of currents produced by the flame. 2.Factors tending to Decrease the ( 6 Kolatile” Value.-(a) Insufficient coking of the coal ; (b) secondary catalytic decomposition of volatile products on the walls of the crucible ; ( c ) decomposition of volatile products by radiation in the waste space of the crucible ; ( d ) deposition of carbon during coking by too rapid primary decomposition of volatile coal sub- stance.These factors are at work concurrently, and may compensate each other, but their presence explains the difliculty of obtaining agreement under slightly altered working conditions. In order to avoid the drawbacks due to the waste space above the coal, and to the excessive amount of heated surface in contact with the gas and vapours in the crucible test, the author uses a cylindrical vessel, as shown in the figure.B is the heating-tube of quartz glass, round which an electric resistance coil of platinum wire is wound. A number of quartz pin-points are fused on this tube to keep the turns of the coil apart. To concentrate the heat where required, the wire is first wound to a coil about 3 mm.in diameter, and this coil is then wound round the heating-tube. The re- acting vessel B is a flanged quartz tube about 10 mm. in internal diameter, fitting loosely into the heating-tube. (Platinum tubes may be used instead of quartz tubes.) One grm. of the powdered sample of coal is placed in this tube B, and a third quartz tube C, fitting closely into the reacting chamber B, is placed on top of the coal before the commencement of the test.The pressure on the coal may be altered if desired by filling the piston-tube C with varying quantities of quartz powder. The outer tube A is permanently fixed in an insulating material, such aB kieselguhr. Suitable resistance is provided according to the voltage of the supply current, end a rheostat is combined with the furnace itself, SO that the temperature can be controlled.When the current is turned on, the different stages of carbonisation can be observed as the temperature rises; moisture goes off quickly, as a rule, some of the occluded gases follow, and, shortly after this, tarry vapours are evolved, increasing in volume according to the coal used for the test, and, finally, the heavier tars and pitchy matter make their appearance, the latter condensing on the cool parts of tube C.The teat takes from five to seven minutes, and the tubes are then allowed to cool, when the tar a t the mouth of B may be burnt off without interfering with the coke. The apparatus brings out the peculiarities of cokes from coals, although in the The sources of error of the crucible test are stated to be-384 ABSTRACTS OF CHEMICAL PAPERS crucible test little or no difference is to be seen.The same kind of coal also gives the same characteristic coke. The paper is illustrated with photographs showing the appearance of the cokes produced by coals in this apparatus, together with their analytical figures. A. R. T. Modification of the Beckmann Apparatus.E. Knecht and J. P. Batey. (J. Chem. SOC., 1912, 103, 1189-1193.)-For the determination of the boiling-points of aqueous solutions of certain sparingly soluble dyestuffs, the ordinary types of Beckmann apparatus failed to give satisfactory results owing to superheating effects caused by cohesion of the liquid on the glass walls of the vessel. The authors were therefore led to devise a method of electrical heating by means of a platinum wire in direct contact with the solution.The apparatus (see figure) consists of a tube with a platinum heating coil inside, and somewhat thicker wires fused through the glass for making the connections. When in use the apparatus is supported in an outer cylindrical glass jacket placed in a wide-mouthed bottle, packed at the bottom and round the neck with cotton-wool.With this arrangement the boiling-point of the liquid was found to remain constant to 0-001" C. In employing this method precautions must be taken to avoid any appreciable electrolytic action. The elec- trolytic effect will depend on the drop in potential across the headng-coil, and when this is reduced below a certain point no electrolysis should take place.In the above apparatus the resistance of the heating-coil at 100" C. was 0.47 ohm; the current used was 6.5 ampitres, hence the drop in potential was only 3 volts. In another apparatus the coil had a resistance of only 0.32 ohm. With a current of 7.5 ampitres, the drop in potential was 2-2 volts. With a 10 per cent. solution of potassium chloride in this apparatus, no chlorate was formed after boiling for half an hour, and the electrolysis of potassium iodide was very small.Measurements of molecular elevations of boiling-point made in this apparatus were in satisfactory agreement with published results. The authors found the molecular weight of tannic acid in aqueous solution to be between 3000 and 4000.Results have also been obtained for various dyestuffs, including benzopurpurine and indigo white. With the electrical heating constant readings are readily obtained without special precautions. J. F. B.APPARATUS, ETC. 385 Drying Oven. J. H. Coste. (J. SOC. Chem. Ind., 1912, 31, 471.)-This oven can be maintained at a constant temperature, and throughout its area a stream of hot air, or other gasof the desired temperature circulates.As shown i n the figure, a horizontal cylindri- cal copper vessel, a, contains a F suitable quantity of a pure liquid, the boiling-point of which is near that of the temperature required. This vessel is heated by a series of gas-jets, and the vapour is con- densed at by and returned. The muffle-shaped drying-chamber, cc, is surrounded by the boiling liquid, or its vapour, with the exception of about one-thirtieth of its ex- ternal surface (the door).Air which bas passed through a flattened I l C C t d d hi tube, dd, lying under, but not in contact with, the drying-chamber, enters it at the bottom of the end in the vapour, and leaves through a slit, communicating with the chimney f, in the door which is fixed tightly against the end of the chamber by m a n s of steam rubber jointing and a screwed hinging bar against the end of the oven. The area of the drying chamber is small, relative to that of the total heated surface. If desired, the air may be dried before it enters the pre-heater at h, or other gases may be used. The drying-chamber will hold six watch-glasses or flat weighing- bottles placed on 8 copper tray, allowing several determinations of water to be simultaneously carried out, and the substances to be dried rapidly attain a tempera- fure within 1" of that of the vapour. A. R. T.