370 ABSTRACTS OF CHEMICAL PAPERS APPARATUS, ETC. Rapid Organic Combustions. 1. Reimer. (J. Anzer. Chem. SOL, 1915, 37, 1636-1638.)-The use of cerium dioxide as contact substance for rapid organic com- bustions has been suggested by Bekk (ANALYST, 1913, 38, 519) in place of the more expensive platinum of Dennstedt. The following modifications are recommended by the author. Instead of the large quantity of asbestos impregnated with cerium dioxide as employed by Bekk, a layer of cerium dioxide asbestos only 3 cm.long is placed in the centre of a combustion-tube of the usual length; following this is a 20 cm. layer of cupric oxide in wire form, held in place by 8 cupric oxide gauze plug. The cupric oxide furnishes oxygen for the burning substance in case the supply of gaseous oxygen is insufficient, or if the vapour of the substance has been carried too fast over the catalyst and prevents the dust of the cerium oxide from being carried forward in the tube.In the back end of the tube is the usual 10 cm. cupric oxide gauze spiral. This serves to break the stream of oxygen and does away with the necessity for the ‘‘ double oxygen ” apparatus of Dennstedt and the glass tube surrounding the boat used by Dennstedt and Bekk.The combustion boat should be placed not more than 2 cm. from the cerium dioxide asbestos, as explosive mixturesAPPARATUS, ETC. 371 of gaes form if there is any considerable space in which the vapours of the sub- stance and oxygen can mix before they come in contact with the catalyst. The method cannot be used for the simultaneous determination of carbon, hydrogen and halogens as can the Bekk method, where no cupric oxide is used.I t is availablefor the analysis of compounds containing nitrogen if a longer empty space is left s t the forward end of the tube for the boats of lead peroxide and care is taken to keep that end of the tube fairly cool. H. F. E. H. Analytical Suetion-Filter.J. Takamine, jun. (J. Amer. Chem. Soc., 1915, 37, 1519-1520.)-A stout glass jar, shaped somewhat like a lipped beaker, with a ground upper edge and a ground glass cover to fit. In the centre of the cover is a tubulure for the accommodation of a cork, Gooch crucible, etc. A side tube for con- nection to the pump is attached to the side of the jar near the top. Halfway down inside axe three projections which support a removable plate.On this plate a small beaker or basin may be set to catch small quantities of filtrate, where it is desired to oollect them without unnecessary dilution, such as would follow from rinsing them out of an ordinary pump flask. By removing the plate a, larger beaker may be introduced into the apparatus, or the lipped jar itself may be treated as a beaker.G. C. J. Gas-Washing Apparatus with Enclosed Filter. E. R. Weaver and J. D. Edwards. (J. I'd. and Eng. Chem., 1915, 7, 534-535.)-Two of the gas-washing appliances figured enclose a filter, by means of which a precipitate, such as barium carbonate or copper acetylide, may be washed without exposure to air. Little description is necessary, but it is pointed out that the absorption-tube (in Figs.1.and 11. the upper horizontal tube; in Fig. 111. the helical tube) should not be too small, 8 to 10 mm. being a suitable diameter for gas rates up to 500 C.C. a minute. The tip372 ABSTRACTS OF CHEMICAL PAPERS of the inlet-tube should be 1 to 2 mm. in diameter, Fig. I. illustrates an apparatus designed to wash gas with a minimum of liquid, and requiring very little pressure behind the gas.The bulbs along the absorption-tube aid absorption, but do not prevent the apparatus from draining completely, These bulbs are omitted from Fig. II., as they would tend to hold precipitates such as this apparatus is designed to collect on the filter above the drain-cock. This filter is of asbestos supported on a perforated plate, and protected by glass beads or another plate from being loosened by the circulating liquid.Washing liquor is introduced through the tap funnel. Fig. 111. illustrates a modification less liable to breakage, and occupying less space. With gas flowing at the rate of 100 C.C. a minute, bubbles remain in the helix seven seconds. G. C. J. Use of the Interferometer for the Analysis of Solutions.L. H. Adams. (J. Amer. Chem. SOL, 1915, 37, 1181-1194.)-1n the interferometer, two beams of light from a single source passing through two rectangular slits are caused to con- verge on a screen, where they produce a system of interference fringes. The inter- position of a transparent medium in the path of one of the bgams causes a shifting of the central bright band to an extent depending on the thickness and refractive index of the medium.When different media are inserted in the paths of the two beams a measure is obtained of the difference in refractive index of the two media, and a far more delicate measure may be obtained of the concentration of a solution than is possible with the simple refractometer, while the correction necessary for the temperature coefficient becomes practically negligible.With simple precautions the concentration of a solution may be determined with an accuracy of 2 parts per million. The optical construction and manipulation of the Zeiss water interferometer are described and illustrated. The interferometer may be used for the examination of solutions in two ways : (1) As a direct reading instrument ; (2) as a zero instrument.In either case the zero reading of the instrument is first obtained by bringing the fringes to coincidence when water or the same solution is contained in both vessels, and this reading is subtracted from the final reading when the contents of the two chambers are different. When following the first method, a series of solutions of the substance of known concentration is made up, and these are compared in one chamber with a sample of the water used for making the solutions in the other chamber, and a calibration curve of concentrations is plotted, with the aid of which unknown solutions may be analysed.In the second method the solution of unknown concentration is compared directly with two known solutions, one of slightly higher, and the other of slightly lower concentration.This method is free from certain sources of error which appear in the first method, where water is used, owing to changes in optical dispersion which cause an apparent shifting of the com- parison band. The sensitiveness and range of the instrument depend on the length of the water-chamber, which is supplied in four sizes, from 5 to 40 mm.in length. With the 40 mm. chamber one division corresponds to 1.5 to 3.0 parts of solute per million for most aqueous solutions, and there are altogether the equivalent of 3,000 divisions ; the greatest differences of concentration whioh can be directly com- pared, therefore, range between 0.45 and 0.9 per cent. An increase of range can beAPPARATUS, ETC.373 obtained by using a shorter water-chamber, with corresponding loss in sensitiveness, or by calibrating the instrument with a standard solution of the salt in plaoe of water. The interferometer was originally designed for the examination of sea- water; it has also been applied to the examination of colloidal solutions and the standardisation of volumetric solutions.I t may be used for the analysis of mixtures of two solid salts by comparing solutims of equal concentration of the mixture, and of one of the components. J. F. B. Substitute for the Twin - Bulb Trap in Toluene - Mercury Thermo- P. B. Davis, (J. Amer. Chem. Soc., 1915, 37, 1198-1199.)-whilst Regulators. toluene, on account of its high coefficient of expansion, is to be preferred to all other liquids for use in thermo-regulators, with mercury for the electrical contact, the usual form of twin-bulb apparatus of this type suffers from certain defects in use and, once set, is not readily adjusted for higher temperatures.The apparatus illustrated has been designed to overcome these defects. I t is simple to construct, compact, and not easily broken. The arrangement (see Fig.) consists of a bulb, a, attached at the bottom of the tube b to the toluene reservoir, which may be of any desired form, Exactly opposite to b is a corresponding tube, c, which carries the capillary and the sealed-in platinum contact.Inside the bulb a the two small tubes e and j are prolongations of c and b respectively, having a length nearly equal to the diameter of the bulb.These tubes are inclined at an angle of about 30" from the perpendicular. The short side- tube d is used in filling the regulator, and is in exact alignment with f. To prepare the apparatus for use, mercury is poured in through the capillary until the bulb a is from half to three- fourths filled. A tube drawn out to a, small diameter is then inserted through d and f into b, and toluene is introduced until the reservoir is filled, also the space in a above the mercury. The tube d is then sealed, and the regulator set for any desired temperature by adding or withdrawing mercury to adjust the contact level in the czapillary. The instrument may be constructed with a range of 50° C., all adjustments being made through the capillary, which should be of 1-5 to 2 mm. bore, according to the b capacity of the toluene reservoir. All danger of the toluene creeping into the capillary is avoided, since the tubes e and f terminate in the same liquid as is con- tained in them. J. F, B.