36 THE ANALYST. APPARATUS, ETC. Apparatus for absorbing Acid Vapours given off during the Assay of Gold, Silver, etc. Dard. (Anu. Chiin. anal., 1907, 12, 425-42G.)-The apparatus, which is to be placed in the chimney through which the acid vapours pass, consists of 8, lead-lined box of hard wood having a perforated bottorri and filled with pieces of marble. The lead is turned over, and dips into a gutter made around the chimney; the gutter contains water and forms a water-seal, forcing the gases to pass through the box, where they are absorbed by the pieces of marble. A. G. L, f f i by the-use of this mixture, The oven is heated by a burner in the usual way ; when the alcoholic mixture boils, the vapours passing up the tube c (Fig. 2) are condensed in a condenser fitted to the top of the tube a, and fall back into this tube.During this time the tap d is turned so that the condensed liquid does not return to the oven (see Fig. l), but is conducted When sufficiant condensed liquid 9 FIG. 1. FIG. 2. through the opening h to avessel outside the oveu. 3---+- -11 quently, a wide range of temperature may be attained Apparatus for obtaining Constant Temper- atures in Drying Ovens. J. Habermann. (Zeit. aizal. Clicin., 1907, 46, 574-578.)--The apparatus is constructed of glass, and has the foriii shown in the figures. It is fitted, by means of the cork 9, into an opening at the top of the drying oven. The jacket of the latter is filled with a mixture of two liquids; in an illustration given a mixture of amyl and ethyl alcohols is employed.Amy1 alcohol, mixed with 1 per cent. of alcohol, boils at 120" C. ; with 2 per cent., at 100" C. ; and with 10 per cent., at 84" C. ; conse- has been run off to cause the mixture in the jacket to give the required temperature to the oven (as is ascertained by a thermometer inserted through another opening in the top of the oven), the tap is turned so that vapours condensing subsequently are returned through the tube b to the jacket of the oven. w. P. s. Collodion Membranes. S. L. Bigelow and A. Gemberling. ( JOZLIYZ. Amer. Cheiiz. Soc., 1907, 29, 1576-1589.)-Collodion membranes for dialysis may be easily made by NOVY'S method. A hole 1 or 2 mm. in diameter is blown in the bottom of a glass tube. This hole is then closed by touching it repeatedly with a cork carrying some collodion, but without allowing any of the latter to enter the tube.The tube is next coated with collodion by rotating it whilst just touching the surface of a collodion solution. As soon as the coating has set, and does not stick to the finger, the tube is plunged into water, and water is poured into the interior. The proper moment for this immersion is important, but is soon learnt by experience. TheTHE ANALYST- 37 membrane obtained should neither be too brittle nor adhere to the glass too firmly. Experiments made with sacs prepared in this way showed that collodion membranes B dialyse more quickly than parchment paper, but not so quickly as gold- beater's skin. At constant temperature, the quantity of water passing through collodion membranes is nearly a linear function of the pressure ; at 25" C.a change of 1 mm. in pressure causes a change equal to about 0.6 per cent. of the quantity of water passing with a pressure of 150 mni. With constant pressure, the quantity of water passing is not a linear function of the temperature, but an increase of 20" to 30" C. approxi- mately doubles the rate of flow, The membranes last from one to three months. A. G. L. Simple Gas Generator for Analytical Operations, James McC, Sanders. (Proc. Chcm, SOC., 1907, 23, 232.)-This apparatus consists of a glass tube open at one end, B (see figure), and having a tube of very small bore fused into the other end, C. For the pre- paration of sulphuretted hydrogen, for example, the ferrous sulphide is placed in the space A of the tube, a little dilute acid run in, and the mouth B of the tube closed by the finger, when the gas escapes at C through the fine tube.The apparatus may thus be introduced into a test-tube or other vessel, and employed as a stirrer at the same time. I n operations necessitating the heating of the apparatus it is allowed to touch the bottom of the vessel in which it is placed, and the heat then applied to the outer vessel. For quantitative work a larger form of appa- ratus is used, and the mouth of the tube closed with a cork. A. R. T. Apparatus for Use in Testing Sub- stances for Phosphorus. J. Habermann. (Zeit. a?inl. Chem., 1907, 46, 580-581.) - Nitecherlich's process for the detection of phosphorus in suspected cases of poisoning has the disadvantage that the distillation frequently produces an extremely disagreeable odour. To avoid the latter, the author has devised the piece of apparatus shown in the illustration. The distillation flask is attached to the tube c, the condensed vapours fall from the condenser b into the flask C, whilst volatile compounds distilling over, pass from the flask C through the tube j into the device g, whence they are carried away with the waste water from the condenser. w. P. s.