APPARATUS, ETC. 477 APPARATUS, ETC. Apparatus for the Rapid Testing of Substanees used for Newtralising Noxious Gases. E. Kohn-Abrest. (Compt. rend., 1915, 161, 310-313.)-The apparatus employed for testing the efficacy of respirator charges consists of a, bottle, F, of about 4 litres capacity containing the gas to be tested at a known dilution. This is connected with the tube T, containing cotton-wool impregnated with the absorbing substance.The tube T i g also connected with a glass bulb, A , of about 250 C.C. capacity, having three tubulures, each controlled by a, stopcock. The bulb A is evacuated by means of a pump through the stopcock 5, until the mercury in the manometer M indicates a vacuum of 10 to 12 mm. The gas is then aspirated, at a rate corresponding to that of moderate breathing, by opening the taps.2 and 3, the gas passing through the charge in the tube 57, and being collected in the bulb A. The connections are closed while a slightly reduced pressure still exists in the bulb. Reagents are then introduced into A to determine the efficiency of the absorption. Working with chlorine, it was found that at a dilution of 1 per 1,000.the cotton-wool alqne was sufficient to remove all the chlorine, and no appreciable difference could be detected in the behaviour of the varioue absorbing chemicals at concentrations below 1 per cent. of chlorine. With higher concentrations, a, saturated solution of sodium carbonate was considerably more effective than one of478 ABSTRACTS OF CHEMICAL PAPERS bicarbonate, and the former should be used in preference to the latter, in conjunction with sodium thiosulphate. A 30 per cent.solution of potassium iodide is a very effective agent for absorbing chlorine gas at high concentrations. Glycerol is used for preventing evaporation ; it also tends to make the absorption of chlorine more regular. J. F. B. Mano-nitrometer for the Analysis of Nitrocellu- lose, Nitrating Acids, etc.V. Planchon. (Ann. Chim. anal., 1915, 20, 189-197.)-The estimation of nitrates with the ordinary nitrometer is subject to errors which can scarcely be reduced below 1 per cent.; among the incon- veniences attending the method may be mentioned : The very small quantity of sample taken for the estimation; the difficulty of adjnsting the gas to atmospheric pressure for reading ; the uncertainty of the temperature of the gas inside the tube ; the necessity for an arbitrary correction for the solubility of the gas in the sulphuric acid; the presence of air dissolved in the acid at the same time as the nitro- cellulose; the effect of the violence and duration of the shaking on the results obtained. These difficulties are avoided or rninimised by the use of the ‘‘ mano-nitrometer ” (see Fig.), in which the gas is developed in an evacuated vessel from a larger quantity of the sample and measured by the increase of pressure recorded.The apparatus consists of a reaction bottle, P, with a stopper, B, bored so as to communicate with two delivery tubes; one of these has a tap, P, and is connected with a vacuum pump- the other is connected with the upper end of the barometric tube T by the rubber tube X ; the bottle and stopper are held in close contact by the clamp ‘v and a rubber washer.A millimetre scale and vernier, moved by the milled head C, and fixed in any position by the screw S, are fitted to the support of the barometric tube. The reaction bottle is charged with mercury, sulphuric acid and the substance to be analysed, and the whole apparatus evacuated by connecting with the pump.The scale is clamped with the zero adjusted to the height of the mercury in the tube and the pump-connection closed. The bottle is shaken until no further fall in the column oE mercury is noticed, and is then immersed in a vessel of cold water until the position of the mercury is steady.This is read off by means of the vernier, and the tempsrature, t, of the water-bath is noted. If F = the fall of the column of mercury in mm., C = the total gas-space in the apparatus at the time of reading, and P = the weight of substance taken, the number of C.C. of gas 760 (1 + 0*00366S). evolved per 1 grm. of substance is expressed by the formula - p x CXF 1 The capacity of the apparatus is found from the difference in weight of the bottle, clamp and connecting tubes empty and filled with water, plus the capacity of the barometric tube down to its lowest measure.A table can then be constructedAPPARATUS, ETC. 479 showing the capacity for any position of the mercury in the tube, and the volume of the reagents used is deducted. For the analysis of nitrocellulose in an apparatus of about 700 C.C.capacity, the usual quantities of reagents taken are: 50 C.C. of sulphuric acid (measured), 15 C.C. of mercury (weighed, 204 grms.), and 2.5 grms. of nitrocellulose (sp. gr. 1.5). Sulphuric acid of commercial strength (93 to 97 per cent.) should b9 used, variations within these limits having no appreciable effect. All the sources of error noted with the ordinary nitrometer are considerably reduced by working under vacuum ; the air is removed from the solution before the reaction and the solubility of the nitric oxide in the per cent.is attainable with ordinary care. acid is negligible. An accuracy of 0.5 J. F. B. Receivers for Fractional Distillation under Dimin- ished Pressure. M. T. Bogert. (J.I d . and Eng. Chem., 1915, 7, 785-786.)-Two slightly different pieces of apparatus are figured in the original. The single illustra- tion reproduced here is nearly self-explanatory. The receiver is graduated in c.cs. The connection to the con- denser is at B, that to the pump at P. F and Hare plain cocks, but D is a three-way cock, by means of which the ultimate receiver (a, flask, separator, or other convenient vessel attached to E by means of a, rubber bung) can be put into connec.tion with the pump or with the outer air.Connection with the pump is neccessary when drawing off fractions from A . To prevent liquid being drawn over to the pump from the outlet stem of the receiver, the latter is jacketed, liquid falling through the inner tube G, and air being exhausted by the outer tube E. G. C. J. Weighing Pipette. F. Hall.. ( J . Amer. Chem. SOL, 1915, 37, 2062-2063.)- The pipette consists of a cylindrical body having a short tube provided with a tap at its lower end. The upper stem of the pipette is made of a short length of thick- walled glaw tubing with a bulb blown in it. This bulb fits into a slotted metal hook attached to the arm of the balance. If desired, the pipette may be graduated, and glass caps may be provided for closing the ends when dealing with volatile liquids. w. P. s.