THE ANALYST. 109 APPARATUS, ETC. A New Vacuum Regulator. J. W. Holterman. (Cheylt. Zeit., 1908, 32, 8.) -The use of the regulator here shown reduces to a minimum the effect of variations in the water-pressure when a water-pump is used to create a vacuum. It consists of nine glass manometer tubes fixed in a stand and connected by means of rubber tubing, and a tenth manometer tube which is movable. On the other side of this tube is a small washing-flask, the inner tube of which is drawn out to a fine point, whilst the other tube contains cotton-wool to filter the air as it enters. The manometers are charged with the requisite measnred quantity of water, and the apparatus connected with the pump and the distillation apparatus. With the aid of this apparatus it is possible to distil i i z Z~CCCPLO for a whole day with no greater variations in pressure than 0.25 mm.in the height of the mercury. I t isessential, however, that the opening of the small tube in the flask shall be of the right size, so that the air bubbles may follow one another in the smallest possible time throughout the apparatus. Variations in the atmospheric pressure may be compensated by altering the position of the movable manometer tube. Still better results may be obtained by the use of petroleum or olive oil (especially the latter) in place of water in the apparatus, but mercury is unsuitable110 THE ANALYST. owing to its becoming oxidised, and to its possessing a considerable surface tension which is greatly influenced by impurities. C. A. M. An Accurate Form of Gas Analysis Apparatus.William A. Bone and Richard V. Wheeler. (Jourit. SOC. Ch,ent. Ind., 1908, 27, 10-l2.)-The authors’ research apparatus (see Proc. Cliem. SOC., 1898, 154) has been adapted to meet the general requirements of accurate commercial work, and in its modified form is prscticnlly universally applicable in the examination of gaseous mixtures. The I apparatus comprises three parts : (1) A water-jacketed combination of measuring and pressure tubes, A, B, communicating with the reservoir, D, and connecting also with the special sampling tube, I<; (2) an absorption vessel, F, standing in a mercury trough; and (3) an explosion-tube, E, connected with its own mercury reservoir, If. All the connections are of capillary bore, and the whole of the apparatus, including all the connections between -4, E , and E’, is filled with niercury before the analysis is commenced.The sample is introduced into I<, or under the wide-open end of the absorption vessel, F. The glass taps should be kept lubricated with a solution of rubber in vas- eline, and the whole apparatus washed out with dilute acid after each analysis. The principle of memurewent followed in the apparatus is the measurement of the pressure of the gas, in mm. of mercury, at constant volume. For this purpose the gas is brought to a certain “constant volume” mark in the measuring-tube, d, and its pressure as registered on the tube B noted. Each of the series of ‘‘ constant volume ” marks on A corresponds with a100 mm. pressure markonB, SO that the actual pressure is obtained by subtracting from the reading the numbers 0, 100, or 200, etc., according to the volume inark selected in the analysis.The tubes A, I’THE ANALYST. 11 1 are made in one piece and are surrounded by a water-jacket, and their inner surfaces are kept moist with 1-ery dilute sulphuric acid (1 in 20), in case the measuring-tube is accidentally fouled by alkali. The wetting of these tubes with the flame liquid eliminates the influence of water-vapour on the measurements, the pressures thus representing thosc of the dry gas. The tap at the end of B, which allows of the vacuum being easily made in the tube, is connected with the latter by means of stout pressure tubing, giving a tight joint and suEcient elasticity to prevent fracture of the tube in case the mercury is allowed to run up too quickly.The measurement of pressure at a constant volunie has the advantages of allowing of the use of smaller volumes of gas tor analysis-q., 5 to 10 C.C. of gas can be made to have a pressure of 100 mni., and this can be read off directly to within 0.2 mm.-and the measurements are independent of barometric pressure, and unaffected by the tension of aqueous vapour. The length of the pressure-tube I' (700 mm.) allows of the proper dilution of the " explosive mixture." Dilute gases (producer-gas, etc.) may be examined in an apparatus having a tube, I;, of, say, 400 mm. and a correspondingly reduced explosion- tube, E , but this would be quite unsuited for the examination of richer gases. All the absorptions are carried out in the vessel F, only a small volume of the reagent being necessary, and this being discarded after once using.To introduce the absorp- tion reagent, and the water or dilute sulphuric acid between each successive addition, 3 to 3 c.c. of the solution are delivered from a suitable pipette into F from under the surface of the mercury in the trough, any bubble of air being drawn out by the capillary three-way tap through its lower branch, which conimunicates with a pump. X bottle is interposed between the latter and the vessel F, to serve as a trap for the mercury or the reagent after use. The insertion of a tap between the pump and the bottle renders only one exhaustion necessary a t the beginning of the analysis, and the reagents and washings can be successively withdrawn from the absorption vessel.The necessary operations can be carried out without disturbing any of the connections, and the apparatus is thus rapid in its working. The analysis of a producer-gas recluires forty-five minutes, and that of a sample of coal-gas about one hour. &4. 1%. T. Porous Materials as Substitutes for Stopcocks in Work with Gases. A. Stock. (Be].. dcrtt. Cl~ciir. Gcs., 190'7, 40, 4956-4959.)-The author describes apparatus in which glass stopcocks are replaced by plugs of porous clay. These plugs are made by calcination of a mixture of clay, waterglass, and gum ; the pores are very uniform ; the plugs resist the action of dilute acids and boiling water, and possess the great advantage of being fixed firmly in glass tubes by simple fusion of the latter without the use of any cement.The principle on which these plugs are used was first enunciated by Pryts ( - 1 1 1 ~ t l . Phys., 1905, 18, 617). I t may be under- stood from the following example : Given a glass tube A , with a porous plug fixed a short distance below its upper end, this tube may be closed by a layer of mercury poured upon the porous plug. If now another tube, 11, fitted with a similar porous plug flush with its lower end, be pushed through the mercury in A until the two porous plugs touch each other, gaseous connection is established between the two112 THE ANALYST. tubes. A may then be evacuated by a pump connected with B, and is perfectly sealed when B is lifted out of the mercury, the arrangement acting exactly as a stop- cock. Such valves are useful on air-pumps, particularly on water-air pumps, as automatic back-pressure valves. J. F. B. Soda-Lime Apparatus for Elementary Analyses and Carbon Dioxide Estimations. M. Dennstedt. (C'hem. Zeit., 1908, 32, 77.)-The apparatus shomii in the figure con- sists of two cylinders uniting in a circular base with flat bottom. The cylinder through which the gas enters the vessel passes nearly to the bottom, and ends in a constriction, whilst the remainder of the apparatus is filled with granulated soda-lime. The weight of the vessel does not exceed 40 t o 50 grams when empty, or 100 grams when charged. It is advisable to intersperse a little glass wool with the soda-lime, which should be loosely packed. c. A. 31.