134 THE ANALYST. APPARATUS. A Generator for the Continuous Preparation of Gases on a Large Scale in the Laboratory. Rsston Stevenson and W. MoKim Marriotte. (Joum. Amer. Chem. Sot., xxvi., 64.)-The apparatus shown is designed to generate hydrogen chloride gas from com- mercial hydrochloric acid, contained in the reservoir C, and strong sulphuric acid, contained in the flask D, the bottom of which is at the same height as C ; the flask D is heated on a water-bath, 0, the hot acid giving a larger and more rapid yield of gas. The two acids flow, drop by drop, through the tubes M and L, into the tower A , containing broken glass covered by a layer of glass wool. The tube I; should project against the tube M at an angle, so that the sulphnric acid may run down the tube carrying the hydrochloric acid for a lengtsh of about 5 millimetres.The gas generated passes through the tube*X into the safety flask E, from which it passes through 2 into the vessel F, or into a suitable drying-tube. The spent acids, flow through the tube Y into the carboy B, from which the tube Q leads to E, in order to equalize pressure inside the apparatus, and to obtain the remaining gas from the acids. By closing the stop-cocks N , 0, P, R, the flow of gas can be stopped a t any moment. A. G. L.THE ANALYST. 135 A Simple Thermostat for Use i n Connection with the Refkactometric Exrtmination of Oils and Fats. T. E. Thorpe. (Joum. C'hem. SOC., 1904, lxxxv., 357-259.)-The principle of the thermostat and the method of working it will be obvious from the -figure.The apparatus consists essentially of a vessel for gene- rating steam, containing a coil through which the current of water flows, and is heated before passing through the instrument shown in the drawing at Z. The vessel A is 5 centimetres in dia- meter and 5 centimetres deep, contain- ing about 100 C.C. of water. It is sur- mounted by the conical steam-chamber, B, in which the coil, C', is suspended. The diameter of the cover is 10 centi- metres. The coil is made of '' compo " tubing, about 30 centimetres long and 3 millimetres internal diameter. D is a reflux condenser, fitting tightly in the tubulure tl. The arrangement El is for maintaining a constant head of water a t the point of entrance to the coil, to avoid variations of temperature due to fluctuations in the pressure of the water- supply.F, a stout glass tube, serves as a gauge to indicate whether the over- flow and the current of water are run- ning properly. The caoutchouc tube, G, should be thick-walled to avoid loss of heat. A screw-clamp, H , regulates the flow of water through the instrument 2, and the tube, K, carries away the waste- water from the instrument. L is a, burner surrounded by a draught-protector, M, the latter having a hole, m, at its lower part, through which the gas-pipe pasees. Only a few minutes are required to bring the apparatus into action, and B steady current of water may be obtained, not varying more than 0.1" or SO in temperature throughout the day. w. P. s.136 THE ANALYST. New Lsboratory Apparatus. A. Hesse. (Chem. Zeit., xxviii., 18.) --For titratione, beaker and Erlenmeyer flasks with white enamelled bottoms are now made by Max Kaehler and Martini in Berlin.A. G. L. An Instrument for Determining the Degree of Turbidity and Depth Of Colour of Solutions. J. Konig. (Zed. fiir Untersuch. der Nahr. and Q e w s s r n i t t e l , 1904, vii., 129-141.)-The instrument, called a diaphanometer, consists of two - 0 - Eye-piece with red and green glasses I I I Reflection prism fT - - -@ Lummer Brodhun prism Compensator for loss of light in reflection prism Glass for absorbing light r* 1 I I ! I I I 1 Ground-glass plate / ,-/ .! immersion - tubes ; the light transmitted by the solution under examination passes through one tube (the right), the other tube serving as a comparison. The light from both tubes is observed through one eye-piece, each tube lighting one-half the field, after the manner of a half - shadow polarimeter.Discs of red and green glass are supplied to be inserted in the left tube, to cut-down the light until it is about equal to that transmitted through the other tube. A series of discs can also be introduced into the path, between the left-hand tube and its prism ; these cut off from 10 per cent. and up- wards of the transmitted light. The final comparison is made by raising or lowering the right-hand tube. Tables are given for converting the observations into percentages of turbidity or colour for white light, the number obtained actually denoting the percentage of light transmitted by the liquid under observation. window, the diffused light being reflected into the tubes by a ground-glass plate. Direct sunlight should be avoided. Standard glasses or solutions are not needed with the instrument. The strength of solutions of various coloured salts may be The instrument is used in front of approximately determined by this instrument. w. P. s.THE ANALYST. 137 A Back Pressure Valve for Ulse with Filter Pumps. R. N. Kofoid. (Journ. Amer. Chem. SOL, xxvi., 110.)-The body of the valve shown is made of fairly stout glass tubing. The valve itself is of the old Bun- sen type, with a glass rod, of slightly smaller diameter than the rubber tubing, wired on to prevent collapse. used should be soft. A. G. L. The rubber tubing